- Email: [email protected]
Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries
THEKNE-02327; No of Pages 6 The Knee xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
The Knee
Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries Karin Mani a,b, William F. Brechue c, Bernd Friesenbichler a, Nicola A. Maffiuletti a,⁎ a b c
Human Performance Lab, Schulthess Clinic, Zurich, Switzerland Institute of Human Movement Sciences and Sport, ETH Zurich, Zurich, Switzerland Department of Physiology, A. T. Still University of Health Sciences, Kirksville, MO, USA
a r t i c l e
i n f o
Article history: Received 19 January 2016 Received in revised form 31 August 2016 Accepted 1 September 2016 Available online xxxx Keywords: Performance-based physical function Foot contact time Muscle strength Knee injuries
a b s t r a c t Background: Conventional one-legged hop tests simply evaluate the total hop distance, thus neglecting important temporal and spatial parameters related to the strategy of execution, such as foot contact time. Aim: To examine the validity and reliability of an instrumented one-legged hop test, the “four hops, three contacts” (4H3C) test, in patients with knee injuries. Methods: The 4H3C test consists of four consecutive one-legged hops, of which individual hop distance and foot contact time are recorded by a validated floor-based photocell system. We examined the test–retest reliability, discriminant validity (involved vs. uninvolved side) and convergent validity (relation with maximal voluntary strength) of consecutive hop distance and foot contact time parameters in 50 patients with unilateral knee injuries. Results: Test–retest reliability was very high for hop distance (intraclass correlation coefficients: 0.91 to 0.97) and high for contact time variables (intraclass correlation coefficients: 0.75 to 0.88). The difference between the involved and the uninvolved side was significant for all hop distance and contact time parameters (p b 0.05). Maximal voluntary strength was correlated to both hop distance (r = 0.67; p b 0.001) and contact time (r = −0.42; p b 0.01) variables. Conclusion: The 4H3C is a valid and reliable test for the evaluation of single hops in patients with knee injuries and may be useful in sport and clinical settings. The interpretation of foot contact time data requires however some caution. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Performance-based measures of physical function are widely used in orthopedics and sports medicine for evaluative, discriminative or predictive purposes [1–3]. For example, these data can be used to quantify the functional deficit consequent to injury and/or surgery [4], assess the effectiveness of a rehabilitation program [5–7], discriminate between different groups of subjects or conditions (e.g., involved vs. uninvolved limb) [8,9] and evaluate the readiness of an individual to return to sport [10,11]. The single, triple or quintuple one-legged hop tests have gained popularity in the clinic because they are easy to administer and do not require expensive equipment [4,7,8,11–14]. However, only the total hop distance is usually quantified, thereby
Abbreviations: 4H3C, four hops three contacts; ACL, anterior cruciate ligament; C1, contact one; C2, contact two; C3, contact three; CI, confidence interval; H1, hop one; H2, hop two; H3, hop three; H4, hop four; ICC, intraclass correlation coefficient; SD, standard deviation; TE, typical error. ⁎ Corresponding author at: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008 Zurich, Switzerland. E-mail address: nicola.maffi[email protected] (N.A. Maffiuletti).
http://dx.doi.org/10.1016/j.knee.2016.09.004 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
2
K. Mani et al. / The Knee xxx (2016) xxx–xxx
neglecting important variables related to the strategy of execution, such as foot contact times and hop distances for the different hops of a series. Therefore, we propose here a novel, instrumented one-legged hop test, called the “four hops, three contacts” (4H3C) test, which involves the use of a valid and accurate floor-based photocell system (Optogait, Microgate, Bolzano, Italy) [9,15]. In comparison to the conventional hop tests [4], the instrumented 4H3C test would allow a more comprehensive assessment of the distance of each of the four consecutive hops together with the three associated foot contact times. This could offer potentially useful insights into the strategy of test execution. For example, quantification of foot contact time may reveal that the foot of the involved limb remains longer on the ground compared to the uninvolved limb, despite a comparable total hop distance for the two sides. Therefore, the aim of this methodological study was to examine the reliability and validity of the 4H3C test in individuals with unilateral knee injuries. Foot contact time and hop distance of single and multiple hops were evaluated for test–retest reliability, discriminant validity (comparison between involved and uninvolved side) and convergent validity (correlation with maximal voluntary strength). 2. Methods The study protocol was approved by the Kantonale Ethikkommission Zürich (reference: KEK-ZH-Nr. 2013-0240), and was carried out at the Schulthess Clinic in Zurich, Switzerland. Written informed consent forms were signed by all subjects prior to enrollment. 2.1. Patients The main inclusion criteria were the presence of one or more of the following knee injuries: anterior cruciate ligament (ACL) tear, tibiofemoral/patellofemoral cartilage damage and medial/lateral meniscus tear. The main exclusion criteria were the current presence of back, knee, hip or ankle pain on either of the two sides, acute musculoskeletal injury and previous open surgery on the uninvolved side. The estimated sample size for test–retest reliability analyses was 46 subjects with a minimally acceptable level of reliability of 0.8 [16]. With regard to possible drop outs, 50 patients with different knee injuries were enrolled in this study (21 women and 29 men, mean age ± SD: 27 ± 6 years, height: 176 ± 9 cm, weight: 74 ± 13 kg, proximal thigh circumference: 53 ± 4 cm, femur length: 47 ± 5 cm, tibia length: 41 ± 4 cm). With respect to knee injury, 27 patients (54%) had an isolated ACL tear, seven (14%) had an isolated cartilage damage, six (12%) had an isolated meniscal tear, and 10 (20%) had a combination of knee injuries (ACL tear, cartilage damage, meniscal tear). With respect to surgery, 24 subjects (48%) had ACL reconstruction (bone-patellar tendon-bone or hamstring autografts), five (10%) had cartilage repair (autologous chondrocyte implantation, autologous matrix-induced chondrogenesis, microfracturing or cartilage shaving), five (10%) had meniscus repair, one (two percent) had ACL reconstruction and meniscus repair and 15 (30%) had no surgery. On average, surgical patients were tested 223 ± 30 days after ACL reconstruction or cartilage repair and 159 ± 55 days after meniscus repair. Non-surgical subjects were tested 573 ± 688 days after the injury. The mean score for the Tegner activity scale [17] at the time of knee injury was 5.9 ± 1.9 (range: 0 to 10). 2.2. Experimental protocol Patients were asked to participate in two identical testing sessions (test and retest, duration: one hour) that were separated by 2 to 7 days. Each session included two main assessments that were conducted unilaterally for the involved and uninvolved side: the 4H3C test for the evaluation of hop distance and foot contact time and an isometric test for the evaluation of lower extremity maximal voluntary strength. Within each test, the uninvolved side was always tested before the involved one [11,13]. Subjects wore their own sport shoes and received consistent verbal encouragement during testing. They were also instructed to avoid exhausting exercise the day before the assessments. 2.2.1. Assessment of 4H3C parameters Following a general warm-up that included five minutes of stationary cycling at one watt per kilogram of body weight, subjects were asked to complete the 4H3C test. The 4H3C test protocol is similar to the one originally described by Noyes et al. [4] with the exception of the number of hops (four vs. three), the measurement tool (photocells vs. tape measure) and the inclusion of additional outcomes. A validated floor-based photocell system (Optogait, Microgate, Bolzano, Italy) was used to measure hop distances and foot contact times of single and multiple hops (Fig. 1A). Accordingly, H1 was defined as the distance of the first hop, H2 as the sum of the distance of the first and second hop, and so on for H3 and H4 (Fig. 1B). In the same way, C1 was defined as the foot contact time between the first and second hop, C2 as the contact time between the second and third hop, and C3 as the contact time between the third and fourth hop (Fig. 1B). Ten transmitting and 10 receiving bars (each with a length of one meter) were placed in parallel along a virtual corridor of 10 m, with a lateral distance of approximately one meter between transmitting and receiving units. Each one-meter transmitting unit (sampling frequency: one kilohertz) contains 96 light emitting diodes that are positioned three millimeters from ground level at one-centimeter intervals. A webcam connected to the Optogait system and positioned one meter behind the starting point was used to control feet and body positions during testing. At the beginning of the test, subjects were asked to stand on the starting line with the tested foot, while the untested foot was lifted off the ground, and then to perform four consecutive hops on the same leg with the instruction to “hop as far as possible four times”. Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
K. Mani et al. / The Knee xxx (2016) xxx–xxx
3
They were also asked to swing their upper limbs naturally and to stand still for at least one second upon landing after the forth hop. Trials in which the movement was not fluent enough and/or in which subjects lost balance and touched the ground with the untested foot were not considered. For each side, subjects completed one (or more) quasi-maximal familiarization trial, followed by three maximal trials. Rest periods of 30 s were interspersed between the different trials. For each side, the mean value of the three maximal trials was retained. 2.2.2. Assessment of maximal voluntary strength The test protocol used in this study is very similar to the one originally described by Marcora and Miller [18]. Briefly, lower extremity maximal voluntary strength was measured isometrically by means of a S-shaped load cell (Vishay Precision Group, Malvern, USA) mounted on a conventional horizontal leg press machine (Technogym, Gambettola, Italy). The load cell was secured with chains and rod ends to the frame of the leg press, so that it was in series with the sliding axis of the machine. The force signal was fed directly from the load cell into a 16-bit A/D converter (Biopac Systems, Goleta, USA), then into a computer sampling at one kilohertz using AcqKnowledge software (Biopac Systems). Subjects were tested in the supine position, with the foot of the tested limb on the vertical plate of the leg press, the shank parallel to the floor, and the knee flexed 45° (as verified with a manual goniometer during the actual contractions). Subjects were carefully instructed to concomitantly extend their hip, knee and ankle joints by building up force progressively and then to push as hard as possible for 3 to 5 s. We quantified maximal voluntary strength as the highest force attained during the contraction. Trials in which no plateau was observed around maximal strength and/or in which a visible countermovement was discerned on the initial phase of the contraction were not considered. Data from two subjects were excluded because of a technical problem and back pain during the assessments. For each side, subjects completed one (or more) quasi-maximal familiarization trial, followed by three maximal trials. Rest periods of 30 s were interspersed between the different trials. For each side, the mean value of the three maximal trials was retained. 2.3. Statistical analyses All results are presented as mean ± standard deviation (SD). Test–retest reliability of the 4H3C parameters were assessed with two-tailed paired t-tests (bias), intraclass correlation coefficients (ICC(3,1)) and typical errors with 95% confidence interval (CI) [19]. We considered ICCs over 0.90 as very high, between 0.70 and 0.89 as high and between 0.50 and 0.69 as moderate [20]. Discriminant validity was assessed with two-tailed paired t-tests (involved vs. uninvolved side). Convergent validity was examined
Figure 1. (A) 4H3C test set-up showing the receiving and transmitting bars of the floor-based photoelectric system, the personal computer and the starting line. (B) 4H3C outcomes: H1 refers to the distance of the first hop, H2 to the distance of the first and second hop (sum of H1 and H2), and so on for H3 (sum of H1, H2 and H3) and H4 (sum of H1, H2, H3 and H4); C1 refers to the foot contact time between the first and second hop, C2 to the contact time between the second and third hop, and C3 to the contact time between the third and fourth hop.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
4
K. Mani et al. / The Knee xxx (2016) xxx–xxx
by correlating 4H3C parameters with maximal voluntary strength using Pearson's correlation coefficients with 95% CI. We considered correlation coefficients over 0.90 as nearly perfect, between 0.70 and 0.89 as very large, between 0.50 and 0.69 as large, and between 0.30 and 0.49 as moderate [19]. The significance level was set at p b 0.05 for all the analyses. 3. Results Test–retest reliability results of hop distance and foot contact time data are presented in Tables 1 and 2, respectively. A significant difference between test and retest (bias) was observed for five out of eight hop distance parameters while all foot contact time variables showed a significant bias. ICCs were very high for all hop distance parameters (range: 0.91 to 0.97) and high for foot contact time variables (range: 0.75 to 0.88). Typical errors were considerably lower for hop distance (range: 3.5 to 5.2%) than for foot contact time parameters (range: 7.3 to 10.9%). The difference between the involved and the uninvolved side (discriminant validity) was significant for all hop distance parameters at both test and retest and for all foot contact time parameters at retest (Table 1). Hop distances were significantly shorter while foot contact times were significantly longer for the involved than for the uninvolved side (p b 0.05). Convergent validity results are presented in Table 3. Correlation coefficients between hop distance parameters and maximal voluntary strength were positive and large for both the involved (r = 0.66 to 0.67) and the uninvolved side (r = 0.58 to 0.61). Correlation coefficients between foot contact time parameters and maximal voluntary strength were negative and moderate for both the involved (r = |0.40 to 0.42|) and the uninvolved side (r = |0.41 to 0.46|). 4. Discussion The main findings of the present methodological study were that the novel, instrumented one-legged test showed good test– retest reliability, discriminant validity and convergent validity for hop distance and foot contact time parameters in patients with knee injuries. As a general observation, both reliability and validity estimates were better for hop distance than for foot contact time parameters. The attractiveness of the 4H3C test compared to pre-existing single and multiple hop tests [4,8,11–14] is the possibility to evaluate foot contact time and hop distance of single and multiple hops in addition to the crude assessment of total hop distance (universally obtained by means of a tape measure). This is particularly relevant for sport activities requiring short foot contact times (e.g., in several track and field disciplines) but also for gaining useful insights into the individual strategy of test execution. For example, this could reveal otherwise-undetected irregularities in spatiotemporal hop parameters during the course of a test trial. Moreover, hop distance and foot contact time parameters are measured with high spatial and temporal resolution (10 mm and 1/1000 s, respectively) by means of a validated photocell system, which results in an objective and controlled evaluation of a series of one-legged hops. In the present study, we considered a series of four hops in order to measure at least three consecutive foot contact times, however the number of hops (and thus of foot contacts) can be modulated depending on the study needs. The evaluation of measurement properties, such as validity and reliability for the instrumented test proposed here, is essential before it can be used legitimately for clinical and/or research purposes. As far as total hop distance is considered (i.e., H4), our test–retest reliability data confirm the findings obtained previously for single, triple and quintuple hop distance [2,7,10,13,21– 23], with ICCs ranging from 0.80 to 0.98 and standard errors of the mean (analogous to our typical errors) ranging from 0.11 to 0.23 m. As a new finding, the ICCs of the 4H3C test were very high for hop distance and high for foot contact time parameters in the large group of patients with knee injuries we tested (sample size was low in the above-cited reliability studies). Importantly, ICCs and typical errors for both the involved and the uninvolved side were comparable regardless of the number of hops (from Table 1 Hop distance data by session and side (n = 50). Test
Retest
ICC (95% CI)
%TE (95% CI)
H1 Involved (m) Uninvolved (m)
1.33 ± 0.29 1.46 ± 0.26†
1.32 ± 0.26 1.43 ± 0.26⁎,†
0.94 (0.90–0.97) 0.91 (0.85–0.95)
5.2 (4.3–6.5) 5.0 (4.2–6.3)
H2 Involved (m) Uninvolved (m)
2.86 ± 0.62 3.14 ± 0.57†
2.88 ± 0.60 3.14 ± 0.58†
0.97 (0.94–0.98) 0.96 (0.93–0.98)
3.9 (3.2–4.9) 3.6 (3.0–4.5)
H3 Involved (m) Uninvolved (m)
4.53 ± 1.02 4.97 ± 0.94†
4.62 ± 1.01⁎ 5.05 ± 0.97⁎,†
0.96 (0.94–0.98) 0.96 (0.93–0.98)
4.1 (3.4–5.1) 3.5 (2.9–4.3)
H4 Involved (m) Uninvolved (m)
6.40 ± 1.51 7.04 ± 1.34†
6.57 ± 1.50⁎ 7.21 ± 1.44⁎,†
0.96 (0.93–0.98) 0.96 (0.91–0.98)
4.1 (3.4–5.1) 3.7 (3.1–4.6)
Mean data ± SD. CI: confidence interval; H1: hop one; H2: hop two; H3: hop three; H4: hop four; ICC: intraclass correlation coefficient; TE: typical error. ⁎ Significant difference between test and retest (p b 0.05). † Significant difference between involved and uninvolved (p b 0.05).
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
K. Mani et al. / The Knee xxx (2016) xxx–xxx
5
Table 2 Foot contact time data by session and side (n = 50). Test
Retest
ICC (95% CI)
%TE (95% CI)
C1 Involved (s) Uninvolved (s)
0.36 ± 0.08 0.36 ± 0.07
0.35 ± 0.08⁎ 0.33 ± 0.07⁎,†
0.88 (0.79–0.93) 0.78 (0.56–0.89)
7.3 (6.0–9.2) 8.2 (6.8–10.2)
C2 Involved (s) Uninvolved (s)
0.34 ± 0.09 0.34 ± 0.09
0.33 ± 0.09⁎ 0.31 ± 0.06⁎,†
0.80 (0.67–0.89) 0.76 (0.50–0.88)
10.9 (9.1–13.7) 10.3 (8.6–12.9)
C3 Involved (s) Uninvolved (s)
0.34 ± 0.08 0.34 ± 0.08
0.32 ± 0.08⁎ 0.31 ± 0.06⁎,†
0.87 (0.74–0.93) 0.75 (0.37–0.89)
7.6 (6.3–9.5) 9.2 (7.7–11.6)
Mean data ± SD. C1: contact one; C2: contact two; C3: contact three; CI: confidence interval; ICC: intraclass correlation coefficient; TE: typical error. ⁎ Significant difference between test and retest (p b 0.05). † Significant difference between involved and uninvolved (p b 0.05).
H1 to H4), and the same was true for contact times (from C1 to C3). This demonstrates that test–retest reliability of hop distance and foot contact time parameters was similar between the first and last hop of a series. However, a systematic bias was observed for several parameters and more particularly so for contact time, which confirms that additional practice and a potential learning effect can modify the 4H3C test results. These results are in line with previous findings obtained with the triple hop test for distance [7]. Our discriminant validity results were quite consistent and compelling because all hop distance parameters were significantly shorter on the involved side on both test and retest sessions, and vice versa for foot contact time parameters (the involved side had longer contact times), but only at retest. These findings confirm the presence of a functional impairment on the involved side, and further demonstrate that the 4H3C test has the potential to detect significant differences between conditions when a real difference in fact exists. Thus, this test can be used with confidence in cross-sectional studies for discriminating between different groups of subjects. Nevertheless, the validity of foot contact time seems to only be acceptable if a separate familiarization session is included before the actual assessments, contrary to hop distance parameters. Hop distance and foot contact time parameters of both sides were respectively positively and negatively correlated to lower extremity maximal voluntary strength in our group of patients. Thus, the highest strength values were observed in those individuals with the longest hop distances and shortest contact times, and vice versa. This suggests that maximal voluntary strength is a determinant of the 4H3C performance in patients with knee injuries, particularly with respect to hop distance parameters (correlation coefficients were markedly lower, though significant, for foot contact time). Hypothetically, a stronger correlation should exist between contact time and explosive strength/power (as opposed to maximal strength), but this was not verified experimentally in the current investigation. Previous studies reported mixed results in regard to the relationship between hop distance and muscle strength [10,14,24], probably because an open-chain single-joint action was mainly considered as opposed to the more functional closed-chain multi-joint contraction modality used in our study. As already observed for reliability results, the correlation coefficients for convergent validity were comparable regardless of the number of hops for all the parameters, and validity estimates were markedly better for hop distance (large correlations) than for foot contact time parameters (moderate correlations). It is worth mentioning that all contact time variables (C1–C3) showed large variability, both within (test to retest) but also between subjects, most likely as a consequence of different hopping strategies (e.g., dynamic postural control). Some patients had long contact times, probably as a means of safely stabilizing their body during the support phase of the one-legged hop, such as following a jump-landing task [25]. Other patients had very short foot contact times and no marked stabilization phase that was often associated with short hop distances. While this inevitably affected validity estimates for foot contact time, it may reflect unique information concerning reduced motor function. As a possible solution to minimize the observed variability in foot contact time, we propose that, instead of instructing subjects to “jump as far as possible” (as it was done here and elsewhere [4,8,11,13,14]), the instruction “jump as far and fast as possible” should be used to avoid different strategies. This will probably
Table 3 Correlations between 4H3C data and maximal voluntary strength (n = 50). Involved
H1 H2 H3 H4 C1 C2 C3
Uninvolved
r (95% CI)
p
r (95% CI)
p
0.66 (0.47–0.79) 0.66 (0.47–0.79) 0.67 (0.47–0.80) 0.67 (0.49–0.80) −0.42 (|0.16–0.63|) −0.42 (|0.16–0.63|) −0.40 (|0.14–0.61|)
b0.001 b0.001 b0.001 b0.001 0.002 0.002 0.004
0.58 (0.36–0.74) 0.57 (0.35–0.73) 0.59 (0.38–0.75) 0.61 (0.41–0.76) −0.41 (|0.15–0.62|) −0.46 (|0.20–0.65|) −0.45 (|0.20–0.65|)
b0.001 b0.001 b0.001 b0.001 0.003 b0.001 b0.001
C1: contact one; C2: contact two; C3: contact three; H1: hop one; H2: hop two; H3: hop three; H4: hop four.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
6
K. Mani et al. / The Knee xxx (2016) xxx–xxx
help in identifying otherwise-undetected irregularities in both spatial and temporal parameters during the course of a one-legged hop test. A limitation of this study was that the recruited patients with knee injuries had quite heterogeneous diagnoses and characteristics and no attempt was made to conduct sub-analyses according to injury type, severity or gender (because of low sample size). However, simple comparisons of reliability and validity scores between pre-operative, post-operative and conservatively-treated patients according to diagnoses and gender did not show any significant differences between the subgroups.
5. Conclusion The novel instrumented 4H3C test presented in this study was both valid and reliable for the evaluation of single and multiple hop distance and foot contact time parameters in patients with knee injuries. A recent systematic review recognized an urgent need for standardizing the methodology of one-legged hop tests in clinical practice [26]. We believe this new test has the potential to provide a more controlled and comprehensive assessment of hop performance compared to the conventional one-legged hop tests for distance.
Conflicts of interest None.
Funding None.
References [1] Katayama M, Higuchi H, Kimura M, Kobayashi A, Hatayama K, Terauchi M, et al. Proprioception and performance after anterior cruciate ligament rupture. Int Orthop 2004;28:278–81. [2] Maulder P, Cronin J. Horizontal and vertical jump assessment: reliability, symmetry, discriminative and predictive ability. Phys Ther Sport 2005;6:74–82. [3] Neeter C, Gustavsson A, Thomee P, Augustsson J, Thomee R, Karlsson J. Development of a strength test battery for evaluating leg muscle power after anterior cruciate ligament injury and reconstruction. Knee Surg Sports Traumatol Arthrosc 2006;14:571–80. [4] Noyes FR, Barber SD, Mangine RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med 1991;19:513–8. [5] Impellizzeri FM, Rampinini E, Maffiuletti N, Marcora SM. A vertical jump force test for assessing bilateral strength asymmetry in athletes. Med Sci Sports Exerc 2007;39:2044–50. [6] Petschnig R, Baron R, Albrecht M. The relationship between isokinetic quadriceps strength test and hop tests for distance and one-legged vertical jump test following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 1998;28:23–31. [7] Reid A, Birmingham TB, Stratford PW, Alcock GK, Giffin JR. Hop testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction. Phys Ther 2007;87:337–49. [8] Barber SD, Noyes FR, Mangine RE, McCloskey JW, Hartman W. Quantitative assessment of functional limitations in normal and anterior cruciate ligamentdeficient knees. Clin Orthop Relat Res 1990;204–214. [9] Glatthorn JF, Gouge S, Nussbaumer S, Stauffacher S, Impellizzeri FM, Maffiuletti NA. Validity and reliability of Optojump photoelectric cells for estimating vertical jump height. J Strength Cond Res 2011;25:556–60. [10] Hamilton RT, Shultz SJ, Schmitz RJ, Perrin DH. Triple-hop distance as a valid predictor of lower limb strength and power. J Athl Train 2008;43:144–51. [11] Schmitt LC, Paterno MV, Hewett TE. The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 2012;42:750–9. [12] Grindem H, Logerstedt D, Eitzen I, Moksnes H, Axe MJ, Snyder-Mackler L, et al. Single-legged hop tests as predictors of self-reported knee function in nonoperatively treated individuals with anterior cruciate ligament injury. Am J Sports Med 2011;39:2347–54. [13] Gustavsson A, Neeter C, Thomee P, Silbernagel KG, Augustsson J, Thomee R, et al. A test battery for evaluating hop performance in patients with an ACL injury and patients who have undergone ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 2006;14:778–88. [14] Newton RU, Gerber A, Nimphius S, Shim JK, Doan BK, Robertson M, et al. Determination of functional strength imbalance of the lower extremities. J Strength Cond Res 2006;20:971–7. [15] Lienhard K, Schneider D, Maffiuletti NA. Validity of the Optogait photoelectric system for the assessment of spatiotemporal gait parameters. Med Eng Phys 2012; 35:500–4. [16] Walter SD, Eliasziw M, Donner A. Sample size and optimal designs for reliability studies. Stat Med 1998;17:101–10. [17] Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985;43–9. [18] Marcora S, Miller MK. The effect of knee angle on the external validity of isometric measures of lower body neuromuscular function. J Sports Sci 2000;18:313–9. [19] Hopkins WG. Measures of reliability in sports medicine and science. Sports Med 2000;30:1–15. [20] Munro BH. Statistical Methods for Health Care Research. Lippincott Williams & Wilkins; 2005. [21] Bolgla LA, Keskula DR. Reliability of lower extremity functional performance tests. J Orthop Sports Phys Ther 1997;26:138–42. [22] Munro AG, Herrington LC. Between-session reliability of four hop tests and the agility T-test. J Strength Cond Res 2011;25:1470–7. [23] Ross MD, Langford B, Whelan PJ. Test–retest reliability of 4 single-leg horizontal hop tests. J Strength Cond Res 2002;16:617–22. [24] Selistre LFA, Cintra GC, Aleixo RD, Rosa SMMG. Relationship between extensor torque and H:Q ratio with triple hop distance in professional soccer players. Rev Bras Med Esporte 2012;18:390–3. [25] Webster KA, Gribble PA. Time to stabilization of anterior cruciate ligament-reconstructed versus healthy knees in National Collegiate Athletic Association Division I female athletes. J Athl Train 2010;45:580–5. [26] Hegedus EJ, McDonough S, Bleakley C, Cook CE, Baxter GD. Clinician-friendly lower extremity physical performance measures in athletes: a systematic review of measurement properties and correlation with injury, part 1. The tests for knee function including the hop tests. Br J Sports Med 2015;49:642–8.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
Contents lists available at ScienceDirect
The Knee
Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries Karin Mani a,b, William F. Brechue c, Bernd Friesenbichler a, Nicola A. Maffiuletti a,⁎ a b c
Human Performance Lab, Schulthess Clinic, Zurich, Switzerland Institute of Human Movement Sciences and Sport, ETH Zurich, Zurich, Switzerland Department of Physiology, A. T. Still University of Health Sciences, Kirksville, MO, USA
a r t i c l e
i n f o
Article history: Received 19 January 2016 Received in revised form 31 August 2016 Accepted 1 September 2016 Available online xxxx Keywords: Performance-based physical function Foot contact time Muscle strength Knee injuries
a b s t r a c t Background: Conventional one-legged hop tests simply evaluate the total hop distance, thus neglecting important temporal and spatial parameters related to the strategy of execution, such as foot contact time. Aim: To examine the validity and reliability of an instrumented one-legged hop test, the “four hops, three contacts” (4H3C) test, in patients with knee injuries. Methods: The 4H3C test consists of four consecutive one-legged hops, of which individual hop distance and foot contact time are recorded by a validated floor-based photocell system. We examined the test–retest reliability, discriminant validity (involved vs. uninvolved side) and convergent validity (relation with maximal voluntary strength) of consecutive hop distance and foot contact time parameters in 50 patients with unilateral knee injuries. Results: Test–retest reliability was very high for hop distance (intraclass correlation coefficients: 0.91 to 0.97) and high for contact time variables (intraclass correlation coefficients: 0.75 to 0.88). The difference between the involved and the uninvolved side was significant for all hop distance and contact time parameters (p b 0.05). Maximal voluntary strength was correlated to both hop distance (r = 0.67; p b 0.001) and contact time (r = −0.42; p b 0.01) variables. Conclusion: The 4H3C is a valid and reliable test for the evaluation of single hops in patients with knee injuries and may be useful in sport and clinical settings. The interpretation of foot contact time data requires however some caution. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Performance-based measures of physical function are widely used in orthopedics and sports medicine for evaluative, discriminative or predictive purposes [1–3]. For example, these data can be used to quantify the functional deficit consequent to injury and/or surgery [4], assess the effectiveness of a rehabilitation program [5–7], discriminate between different groups of subjects or conditions (e.g., involved vs. uninvolved limb) [8,9] and evaluate the readiness of an individual to return to sport [10,11]. The single, triple or quintuple one-legged hop tests have gained popularity in the clinic because they are easy to administer and do not require expensive equipment [4,7,8,11–14]. However, only the total hop distance is usually quantified, thereby
Abbreviations: 4H3C, four hops three contacts; ACL, anterior cruciate ligament; C1, contact one; C2, contact two; C3, contact three; CI, confidence interval; H1, hop one; H2, hop two; H3, hop three; H4, hop four; ICC, intraclass correlation coefficient; SD, standard deviation; TE, typical error. ⁎ Corresponding author at: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008 Zurich, Switzerland. E-mail address: nicola.maffi[email protected] (N.A. Maffiuletti).
http://dx.doi.org/10.1016/j.knee.2016.09.004 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
2
K. Mani et al. / The Knee xxx (2016) xxx–xxx
neglecting important variables related to the strategy of execution, such as foot contact times and hop distances for the different hops of a series. Therefore, we propose here a novel, instrumented one-legged hop test, called the “four hops, three contacts” (4H3C) test, which involves the use of a valid and accurate floor-based photocell system (Optogait, Microgate, Bolzano, Italy) [9,15]. In comparison to the conventional hop tests [4], the instrumented 4H3C test would allow a more comprehensive assessment of the distance of each of the four consecutive hops together with the three associated foot contact times. This could offer potentially useful insights into the strategy of test execution. For example, quantification of foot contact time may reveal that the foot of the involved limb remains longer on the ground compared to the uninvolved limb, despite a comparable total hop distance for the two sides. Therefore, the aim of this methodological study was to examine the reliability and validity of the 4H3C test in individuals with unilateral knee injuries. Foot contact time and hop distance of single and multiple hops were evaluated for test–retest reliability, discriminant validity (comparison between involved and uninvolved side) and convergent validity (correlation with maximal voluntary strength). 2. Methods The study protocol was approved by the Kantonale Ethikkommission Zürich (reference: KEK-ZH-Nr. 2013-0240), and was carried out at the Schulthess Clinic in Zurich, Switzerland. Written informed consent forms were signed by all subjects prior to enrollment. 2.1. Patients The main inclusion criteria were the presence of one or more of the following knee injuries: anterior cruciate ligament (ACL) tear, tibiofemoral/patellofemoral cartilage damage and medial/lateral meniscus tear. The main exclusion criteria were the current presence of back, knee, hip or ankle pain on either of the two sides, acute musculoskeletal injury and previous open surgery on the uninvolved side. The estimated sample size for test–retest reliability analyses was 46 subjects with a minimally acceptable level of reliability of 0.8 [16]. With regard to possible drop outs, 50 patients with different knee injuries were enrolled in this study (21 women and 29 men, mean age ± SD: 27 ± 6 years, height: 176 ± 9 cm, weight: 74 ± 13 kg, proximal thigh circumference: 53 ± 4 cm, femur length: 47 ± 5 cm, tibia length: 41 ± 4 cm). With respect to knee injury, 27 patients (54%) had an isolated ACL tear, seven (14%) had an isolated cartilage damage, six (12%) had an isolated meniscal tear, and 10 (20%) had a combination of knee injuries (ACL tear, cartilage damage, meniscal tear). With respect to surgery, 24 subjects (48%) had ACL reconstruction (bone-patellar tendon-bone or hamstring autografts), five (10%) had cartilage repair (autologous chondrocyte implantation, autologous matrix-induced chondrogenesis, microfracturing or cartilage shaving), five (10%) had meniscus repair, one (two percent) had ACL reconstruction and meniscus repair and 15 (30%) had no surgery. On average, surgical patients were tested 223 ± 30 days after ACL reconstruction or cartilage repair and 159 ± 55 days after meniscus repair. Non-surgical subjects were tested 573 ± 688 days after the injury. The mean score for the Tegner activity scale [17] at the time of knee injury was 5.9 ± 1.9 (range: 0 to 10). 2.2. Experimental protocol Patients were asked to participate in two identical testing sessions (test and retest, duration: one hour) that were separated by 2 to 7 days. Each session included two main assessments that were conducted unilaterally for the involved and uninvolved side: the 4H3C test for the evaluation of hop distance and foot contact time and an isometric test for the evaluation of lower extremity maximal voluntary strength. Within each test, the uninvolved side was always tested before the involved one [11,13]. Subjects wore their own sport shoes and received consistent verbal encouragement during testing. They were also instructed to avoid exhausting exercise the day before the assessments. 2.2.1. Assessment of 4H3C parameters Following a general warm-up that included five minutes of stationary cycling at one watt per kilogram of body weight, subjects were asked to complete the 4H3C test. The 4H3C test protocol is similar to the one originally described by Noyes et al. [4] with the exception of the number of hops (four vs. three), the measurement tool (photocells vs. tape measure) and the inclusion of additional outcomes. A validated floor-based photocell system (Optogait, Microgate, Bolzano, Italy) was used to measure hop distances and foot contact times of single and multiple hops (Fig. 1A). Accordingly, H1 was defined as the distance of the first hop, H2 as the sum of the distance of the first and second hop, and so on for H3 and H4 (Fig. 1B). In the same way, C1 was defined as the foot contact time between the first and second hop, C2 as the contact time between the second and third hop, and C3 as the contact time between the third and fourth hop (Fig. 1B). Ten transmitting and 10 receiving bars (each with a length of one meter) were placed in parallel along a virtual corridor of 10 m, with a lateral distance of approximately one meter between transmitting and receiving units. Each one-meter transmitting unit (sampling frequency: one kilohertz) contains 96 light emitting diodes that are positioned three millimeters from ground level at one-centimeter intervals. A webcam connected to the Optogait system and positioned one meter behind the starting point was used to control feet and body positions during testing. At the beginning of the test, subjects were asked to stand on the starting line with the tested foot, while the untested foot was lifted off the ground, and then to perform four consecutive hops on the same leg with the instruction to “hop as far as possible four times”. Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
K. Mani et al. / The Knee xxx (2016) xxx–xxx
3
They were also asked to swing their upper limbs naturally and to stand still for at least one second upon landing after the forth hop. Trials in which the movement was not fluent enough and/or in which subjects lost balance and touched the ground with the untested foot were not considered. For each side, subjects completed one (or more) quasi-maximal familiarization trial, followed by three maximal trials. Rest periods of 30 s were interspersed between the different trials. For each side, the mean value of the three maximal trials was retained. 2.2.2. Assessment of maximal voluntary strength The test protocol used in this study is very similar to the one originally described by Marcora and Miller [18]. Briefly, lower extremity maximal voluntary strength was measured isometrically by means of a S-shaped load cell (Vishay Precision Group, Malvern, USA) mounted on a conventional horizontal leg press machine (Technogym, Gambettola, Italy). The load cell was secured with chains and rod ends to the frame of the leg press, so that it was in series with the sliding axis of the machine. The force signal was fed directly from the load cell into a 16-bit A/D converter (Biopac Systems, Goleta, USA), then into a computer sampling at one kilohertz using AcqKnowledge software (Biopac Systems). Subjects were tested in the supine position, with the foot of the tested limb on the vertical plate of the leg press, the shank parallel to the floor, and the knee flexed 45° (as verified with a manual goniometer during the actual contractions). Subjects were carefully instructed to concomitantly extend their hip, knee and ankle joints by building up force progressively and then to push as hard as possible for 3 to 5 s. We quantified maximal voluntary strength as the highest force attained during the contraction. Trials in which no plateau was observed around maximal strength and/or in which a visible countermovement was discerned on the initial phase of the contraction were not considered. Data from two subjects were excluded because of a technical problem and back pain during the assessments. For each side, subjects completed one (or more) quasi-maximal familiarization trial, followed by three maximal trials. Rest periods of 30 s were interspersed between the different trials. For each side, the mean value of the three maximal trials was retained. 2.3. Statistical analyses All results are presented as mean ± standard deviation (SD). Test–retest reliability of the 4H3C parameters were assessed with two-tailed paired t-tests (bias), intraclass correlation coefficients (ICC(3,1)) and typical errors with 95% confidence interval (CI) [19]. We considered ICCs over 0.90 as very high, between 0.70 and 0.89 as high and between 0.50 and 0.69 as moderate [20]. Discriminant validity was assessed with two-tailed paired t-tests (involved vs. uninvolved side). Convergent validity was examined
Figure 1. (A) 4H3C test set-up showing the receiving and transmitting bars of the floor-based photoelectric system, the personal computer and the starting line. (B) 4H3C outcomes: H1 refers to the distance of the first hop, H2 to the distance of the first and second hop (sum of H1 and H2), and so on for H3 (sum of H1, H2 and H3) and H4 (sum of H1, H2, H3 and H4); C1 refers to the foot contact time between the first and second hop, C2 to the contact time between the second and third hop, and C3 to the contact time between the third and fourth hop.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
4
K. Mani et al. / The Knee xxx (2016) xxx–xxx
by correlating 4H3C parameters with maximal voluntary strength using Pearson's correlation coefficients with 95% CI. We considered correlation coefficients over 0.90 as nearly perfect, between 0.70 and 0.89 as very large, between 0.50 and 0.69 as large, and between 0.30 and 0.49 as moderate [19]. The significance level was set at p b 0.05 for all the analyses. 3. Results Test–retest reliability results of hop distance and foot contact time data are presented in Tables 1 and 2, respectively. A significant difference between test and retest (bias) was observed for five out of eight hop distance parameters while all foot contact time variables showed a significant bias. ICCs were very high for all hop distance parameters (range: 0.91 to 0.97) and high for foot contact time variables (range: 0.75 to 0.88). Typical errors were considerably lower for hop distance (range: 3.5 to 5.2%) than for foot contact time parameters (range: 7.3 to 10.9%). The difference between the involved and the uninvolved side (discriminant validity) was significant for all hop distance parameters at both test and retest and for all foot contact time parameters at retest (Table 1). Hop distances were significantly shorter while foot contact times were significantly longer for the involved than for the uninvolved side (p b 0.05). Convergent validity results are presented in Table 3. Correlation coefficients between hop distance parameters and maximal voluntary strength were positive and large for both the involved (r = 0.66 to 0.67) and the uninvolved side (r = 0.58 to 0.61). Correlation coefficients between foot contact time parameters and maximal voluntary strength were negative and moderate for both the involved (r = |0.40 to 0.42|) and the uninvolved side (r = |0.41 to 0.46|). 4. Discussion The main findings of the present methodological study were that the novel, instrumented one-legged test showed good test– retest reliability, discriminant validity and convergent validity for hop distance and foot contact time parameters in patients with knee injuries. As a general observation, both reliability and validity estimates were better for hop distance than for foot contact time parameters. The attractiveness of the 4H3C test compared to pre-existing single and multiple hop tests [4,8,11–14] is the possibility to evaluate foot contact time and hop distance of single and multiple hops in addition to the crude assessment of total hop distance (universally obtained by means of a tape measure). This is particularly relevant for sport activities requiring short foot contact times (e.g., in several track and field disciplines) but also for gaining useful insights into the individual strategy of test execution. For example, this could reveal otherwise-undetected irregularities in spatiotemporal hop parameters during the course of a test trial. Moreover, hop distance and foot contact time parameters are measured with high spatial and temporal resolution (10 mm and 1/1000 s, respectively) by means of a validated photocell system, which results in an objective and controlled evaluation of a series of one-legged hops. In the present study, we considered a series of four hops in order to measure at least three consecutive foot contact times, however the number of hops (and thus of foot contacts) can be modulated depending on the study needs. The evaluation of measurement properties, such as validity and reliability for the instrumented test proposed here, is essential before it can be used legitimately for clinical and/or research purposes. As far as total hop distance is considered (i.e., H4), our test–retest reliability data confirm the findings obtained previously for single, triple and quintuple hop distance [2,7,10,13,21– 23], with ICCs ranging from 0.80 to 0.98 and standard errors of the mean (analogous to our typical errors) ranging from 0.11 to 0.23 m. As a new finding, the ICCs of the 4H3C test were very high for hop distance and high for foot contact time parameters in the large group of patients with knee injuries we tested (sample size was low in the above-cited reliability studies). Importantly, ICCs and typical errors for both the involved and the uninvolved side were comparable regardless of the number of hops (from Table 1 Hop distance data by session and side (n = 50). Test
Retest
ICC (95% CI)
%TE (95% CI)
H1 Involved (m) Uninvolved (m)
1.33 ± 0.29 1.46 ± 0.26†
1.32 ± 0.26 1.43 ± 0.26⁎,†
0.94 (0.90–0.97) 0.91 (0.85–0.95)
5.2 (4.3–6.5) 5.0 (4.2–6.3)
H2 Involved (m) Uninvolved (m)
2.86 ± 0.62 3.14 ± 0.57†
2.88 ± 0.60 3.14 ± 0.58†
0.97 (0.94–0.98) 0.96 (0.93–0.98)
3.9 (3.2–4.9) 3.6 (3.0–4.5)
H3 Involved (m) Uninvolved (m)
4.53 ± 1.02 4.97 ± 0.94†
4.62 ± 1.01⁎ 5.05 ± 0.97⁎,†
0.96 (0.94–0.98) 0.96 (0.93–0.98)
4.1 (3.4–5.1) 3.5 (2.9–4.3)
H4 Involved (m) Uninvolved (m)
6.40 ± 1.51 7.04 ± 1.34†
6.57 ± 1.50⁎ 7.21 ± 1.44⁎,†
0.96 (0.93–0.98) 0.96 (0.91–0.98)
4.1 (3.4–5.1) 3.7 (3.1–4.6)
Mean data ± SD. CI: confidence interval; H1: hop one; H2: hop two; H3: hop three; H4: hop four; ICC: intraclass correlation coefficient; TE: typical error. ⁎ Significant difference between test and retest (p b 0.05). † Significant difference between involved and uninvolved (p b 0.05).
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
K. Mani et al. / The Knee xxx (2016) xxx–xxx
5
Table 2 Foot contact time data by session and side (n = 50). Test
Retest
ICC (95% CI)
%TE (95% CI)
C1 Involved (s) Uninvolved (s)
0.36 ± 0.08 0.36 ± 0.07
0.35 ± 0.08⁎ 0.33 ± 0.07⁎,†
0.88 (0.79–0.93) 0.78 (0.56–0.89)
7.3 (6.0–9.2) 8.2 (6.8–10.2)
C2 Involved (s) Uninvolved (s)
0.34 ± 0.09 0.34 ± 0.09
0.33 ± 0.09⁎ 0.31 ± 0.06⁎,†
0.80 (0.67–0.89) 0.76 (0.50–0.88)
10.9 (9.1–13.7) 10.3 (8.6–12.9)
C3 Involved (s) Uninvolved (s)
0.34 ± 0.08 0.34 ± 0.08
0.32 ± 0.08⁎ 0.31 ± 0.06⁎,†
0.87 (0.74–0.93) 0.75 (0.37–0.89)
7.6 (6.3–9.5) 9.2 (7.7–11.6)
Mean data ± SD. C1: contact one; C2: contact two; C3: contact three; CI: confidence interval; ICC: intraclass correlation coefficient; TE: typical error. ⁎ Significant difference between test and retest (p b 0.05). † Significant difference between involved and uninvolved (p b 0.05).
H1 to H4), and the same was true for contact times (from C1 to C3). This demonstrates that test–retest reliability of hop distance and foot contact time parameters was similar between the first and last hop of a series. However, a systematic bias was observed for several parameters and more particularly so for contact time, which confirms that additional practice and a potential learning effect can modify the 4H3C test results. These results are in line with previous findings obtained with the triple hop test for distance [7]. Our discriminant validity results were quite consistent and compelling because all hop distance parameters were significantly shorter on the involved side on both test and retest sessions, and vice versa for foot contact time parameters (the involved side had longer contact times), but only at retest. These findings confirm the presence of a functional impairment on the involved side, and further demonstrate that the 4H3C test has the potential to detect significant differences between conditions when a real difference in fact exists. Thus, this test can be used with confidence in cross-sectional studies for discriminating between different groups of subjects. Nevertheless, the validity of foot contact time seems to only be acceptable if a separate familiarization session is included before the actual assessments, contrary to hop distance parameters. Hop distance and foot contact time parameters of both sides were respectively positively and negatively correlated to lower extremity maximal voluntary strength in our group of patients. Thus, the highest strength values were observed in those individuals with the longest hop distances and shortest contact times, and vice versa. This suggests that maximal voluntary strength is a determinant of the 4H3C performance in patients with knee injuries, particularly with respect to hop distance parameters (correlation coefficients were markedly lower, though significant, for foot contact time). Hypothetically, a stronger correlation should exist between contact time and explosive strength/power (as opposed to maximal strength), but this was not verified experimentally in the current investigation. Previous studies reported mixed results in regard to the relationship between hop distance and muscle strength [10,14,24], probably because an open-chain single-joint action was mainly considered as opposed to the more functional closed-chain multi-joint contraction modality used in our study. As already observed for reliability results, the correlation coefficients for convergent validity were comparable regardless of the number of hops for all the parameters, and validity estimates were markedly better for hop distance (large correlations) than for foot contact time parameters (moderate correlations). It is worth mentioning that all contact time variables (C1–C3) showed large variability, both within (test to retest) but also between subjects, most likely as a consequence of different hopping strategies (e.g., dynamic postural control). Some patients had long contact times, probably as a means of safely stabilizing their body during the support phase of the one-legged hop, such as following a jump-landing task [25]. Other patients had very short foot contact times and no marked stabilization phase that was often associated with short hop distances. While this inevitably affected validity estimates for foot contact time, it may reflect unique information concerning reduced motor function. As a possible solution to minimize the observed variability in foot contact time, we propose that, instead of instructing subjects to “jump as far as possible” (as it was done here and elsewhere [4,8,11,13,14]), the instruction “jump as far and fast as possible” should be used to avoid different strategies. This will probably
Table 3 Correlations between 4H3C data and maximal voluntary strength (n = 50). Involved
H1 H2 H3 H4 C1 C2 C3
Uninvolved
r (95% CI)
p
r (95% CI)
p
0.66 (0.47–0.79) 0.66 (0.47–0.79) 0.67 (0.47–0.80) 0.67 (0.49–0.80) −0.42 (|0.16–0.63|) −0.42 (|0.16–0.63|) −0.40 (|0.14–0.61|)
b0.001 b0.001 b0.001 b0.001 0.002 0.002 0.004
0.58 (0.36–0.74) 0.57 (0.35–0.73) 0.59 (0.38–0.75) 0.61 (0.41–0.76) −0.41 (|0.15–0.62|) −0.46 (|0.20–0.65|) −0.45 (|0.20–0.65|)
b0.001 b0.001 b0.001 b0.001 0.003 b0.001 b0.001
C1: contact one; C2: contact two; C3: contact three; H1: hop one; H2: hop two; H3: hop three; H4: hop four.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004
6
K. Mani et al. / The Knee xxx (2016) xxx–xxx
help in identifying otherwise-undetected irregularities in both spatial and temporal parameters during the course of a one-legged hop test. A limitation of this study was that the recruited patients with knee injuries had quite heterogeneous diagnoses and characteristics and no attempt was made to conduct sub-analyses according to injury type, severity or gender (because of low sample size). However, simple comparisons of reliability and validity scores between pre-operative, post-operative and conservatively-treated patients according to diagnoses and gender did not show any significant differences between the subgroups.
5. Conclusion The novel instrumented 4H3C test presented in this study was both valid and reliable for the evaluation of single and multiple hop distance and foot contact time parameters in patients with knee injuries. A recent systematic review recognized an urgent need for standardizing the methodology of one-legged hop tests in clinical practice [26]. We believe this new test has the potential to provide a more controlled and comprehensive assessment of hop performance compared to the conventional one-legged hop tests for distance.
Conflicts of interest None.
Funding None.
References [1] Katayama M, Higuchi H, Kimura M, Kobayashi A, Hatayama K, Terauchi M, et al. Proprioception and performance after anterior cruciate ligament rupture. Int Orthop 2004;28:278–81. [2] Maulder P, Cronin J. Horizontal and vertical jump assessment: reliability, symmetry, discriminative and predictive ability. Phys Ther Sport 2005;6:74–82. [3] Neeter C, Gustavsson A, Thomee P, Augustsson J, Thomee R, Karlsson J. Development of a strength test battery for evaluating leg muscle power after anterior cruciate ligament injury and reconstruction. Knee Surg Sports Traumatol Arthrosc 2006;14:571–80. [4] Noyes FR, Barber SD, Mangine RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med 1991;19:513–8. [5] Impellizzeri FM, Rampinini E, Maffiuletti N, Marcora SM. A vertical jump force test for assessing bilateral strength asymmetry in athletes. Med Sci Sports Exerc 2007;39:2044–50. [6] Petschnig R, Baron R, Albrecht M. The relationship between isokinetic quadriceps strength test and hop tests for distance and one-legged vertical jump test following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 1998;28:23–31. [7] Reid A, Birmingham TB, Stratford PW, Alcock GK, Giffin JR. Hop testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction. Phys Ther 2007;87:337–49. [8] Barber SD, Noyes FR, Mangine RE, McCloskey JW, Hartman W. Quantitative assessment of functional limitations in normal and anterior cruciate ligamentdeficient knees. Clin Orthop Relat Res 1990;204–214. [9] Glatthorn JF, Gouge S, Nussbaumer S, Stauffacher S, Impellizzeri FM, Maffiuletti NA. Validity and reliability of Optojump photoelectric cells for estimating vertical jump height. J Strength Cond Res 2011;25:556–60. [10] Hamilton RT, Shultz SJ, Schmitz RJ, Perrin DH. Triple-hop distance as a valid predictor of lower limb strength and power. J Athl Train 2008;43:144–51. [11] Schmitt LC, Paterno MV, Hewett TE. The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 2012;42:750–9. [12] Grindem H, Logerstedt D, Eitzen I, Moksnes H, Axe MJ, Snyder-Mackler L, et al. Single-legged hop tests as predictors of self-reported knee function in nonoperatively treated individuals with anterior cruciate ligament injury. Am J Sports Med 2011;39:2347–54. [13] Gustavsson A, Neeter C, Thomee P, Silbernagel KG, Augustsson J, Thomee R, et al. A test battery for evaluating hop performance in patients with an ACL injury and patients who have undergone ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 2006;14:778–88. [14] Newton RU, Gerber A, Nimphius S, Shim JK, Doan BK, Robertson M, et al. Determination of functional strength imbalance of the lower extremities. J Strength Cond Res 2006;20:971–7. [15] Lienhard K, Schneider D, Maffiuletti NA. Validity of the Optogait photoelectric system for the assessment of spatiotemporal gait parameters. Med Eng Phys 2012; 35:500–4. [16] Walter SD, Eliasziw M, Donner A. Sample size and optimal designs for reliability studies. Stat Med 1998;17:101–10. [17] Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985;43–9. [18] Marcora S, Miller MK. The effect of knee angle on the external validity of isometric measures of lower body neuromuscular function. J Sports Sci 2000;18:313–9. [19] Hopkins WG. Measures of reliability in sports medicine and science. Sports Med 2000;30:1–15. [20] Munro BH. Statistical Methods for Health Care Research. Lippincott Williams & Wilkins; 2005. [21] Bolgla LA, Keskula DR. Reliability of lower extremity functional performance tests. J Orthop Sports Phys Ther 1997;26:138–42. [22] Munro AG, Herrington LC. Between-session reliability of four hop tests and the agility T-test. J Strength Cond Res 2011;25:1470–7. [23] Ross MD, Langford B, Whelan PJ. Test–retest reliability of 4 single-leg horizontal hop tests. J Strength Cond Res 2002;16:617–22. [24] Selistre LFA, Cintra GC, Aleixo RD, Rosa SMMG. Relationship between extensor torque and H:Q ratio with triple hop distance in professional soccer players. Rev Bras Med Esporte 2012;18:390–3. [25] Webster KA, Gribble PA. Time to stabilization of anterior cruciate ligament-reconstructed versus healthy knees in National Collegiate Athletic Association Division I female athletes. J Athl Train 2010;45:580–5. [26] Hegedus EJ, McDonough S, Bleakley C, Cook CE, Baxter GD. Clinician-friendly lower extremity physical performance measures in athletes: a systematic review of measurement properties and correlation with injury, part 1. The tests for knee function including the hop tests. Br J Sports Med 2015;49:642–8.
Please cite this article as: Mani K, et al, Validity and reliability of a novel instrumented one-legged hop test in patients with knee injuries, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.004