- Email: [email protected]
REARFOOT NORMS IN A YOUNG, HEALTHY POPULATION
Poster 16, Poster Session 1/Foot. 14:45-15:45, Room 103 & Alley Area
S492
REARFOOT NORMS IN A YOUNG, HEALTHY POPULATION R. Chang1, I.S. Davis2 and J. Hamill1 Department of Kinesiology, University of Massachusetts, Amherst, USA, 2 Department of Physical Therapy, University of Delaware, Newark, USA, email: [email protected] 1
METHODS Fifty healthy college-aged subjects participated: 25 females (21.0 ± 3.2 yr) and 25 males (20.9 ± 4.0 yr). Three-dimensional (3D) kinematics of the right leg and foot were obtained using a 3D motion capture system. At the center of eight circularly positioned infrared cameras (240Hz) was a motorized treadmill positioned over a forceplate (960Hz). Subjects wore running sandals (Bite LLC) and were prepared with anatomical calibration markers (i.e. medial and lateral femoral epicondyle, medial and lateral malleolus, 1st and 5th MTPJ) and rigid marker cluster sets on the lateral leg and posterior calcaneus. For running trials, calibration markers were removed and subjects ran on the treadmill at four speeds: 2.5, 3.0, 3.5, and 4.0 m/s. Marker histories were smoothed and rearfoot angles for the stance phase were decomposed using a Cardan X(sagittal) –y(frontal) –z(transverse) sequence. Five stance phases at each speed for each subject were analyzed. Stance was identified using ground reaction force data. Angles were normalized to standing and to 100 percent stance. The effect of running speed on maximum eversion (EVmax) and total excursion during stance (EVtot) was tested using a repeated measures ANOVA (Į=0.05). A post hoc Tukey procedure was used and effect sizes (d) were calculated. Means were collapsed across speeds that were non-significant (Į>0.05) and when effect sizes were small (d < 0.5). ‘Normal’ was estimated using group means and one standard deviation above was deemed ‘excessive’ [1]. RESULTS AND DISCUSSION The term ‘excessive’ has been used extensively in the literature on the etiology of overuse injuries. It is typically used to represent some ideological quantity as rather than some numerical value. ‘Normal’ and ‘excessive’ were defined here amongst a young healthy sample using a statistical framework. Therefore, the present definition of ‘excessive’ does not imply presence or mechanism of any pathology. Qualitatively, there were no obvious changes in rearfoot kinematics with speed (Figure 1). Statistically, speed influenced both variables (P < 0.01) however, the effect sizes between the significant pairings were very small (d ranged
Journal of Biomechanics 40(S2)
from 0.06 to 0.21). Hence, estimates for ‘normal’ and ‘excessive’ eversion were collapsed across speed (Table 1). 12 2.5 m/s 3.0 m/s 3.5 m/s 4.0 m/s
Inversion ( ° )
10 8 6 4 2 0 Eversion
INTRODUCTION Despite abundant literature on rearfoot motion and running, the terms ‘normal’ and ‘excessive’ eversion remain ill defined. Definitions have been proposed [1] however, small sample sizes, errors related to two dimensional analyses [2] and the validity of external shoe markers [3] are significant obstacles in the generation and reception of normative values. In addition, some disagreement exists as to whether there is an influence of running speed on eversion [4,5]. The primary purpose of this study was to estimate maximum and total eversion using a sample that is larger than usual. The secondary purpose was to determine whether eversion is influenced by running speed.
-2
0
20
40
60
80
100
-4 -6 % Stance
Figure 1. Group mean rearfoot inversion – eversion kinematic profiles (n = 50) during stance at four running speeds. Vertical bars indicate the upper 95% confidence interval at 2.5 m/s. Rearfoot movement patterns and eversion parameters agree with results obtained using heel mounted external rearfoot markers [6] and markers anchored to the calcaneus [3]. When compared to previous norms [1], there is good agreement in EVtot, however previous EVmax values are more extreme (normal: 9.4°; excessive: 13° [1]). Differences are likely due to 2D vs. 3D analyses, footwear type and marker configuration. Table 1. Means ( X ) and 95% confidence intervals (CI) for ‘normal’ and ‘excessive’ eversion. Normal Excessive Variable EVmax (°) EVtot (°)
X 5.1 15.9
95%CI (3.6, 6.6) (14.9 ,16.9)
X 10.5 19.4
95%CI (9.0, 12.0) (18.4, 20.4)
CONCLUSION Estimates for ‘normal’ and ‘excessive’ eversion were proposed for a young, healthy population. The results suggest that eversion is unaffected by running speeds that are between 2.5 – 4.0 m/s. REFERENCES 1. Clarke TE, et al. Sport Shoes and Playing Surfaces, Human Kinetics, 1984. 2. Areblad M, et al. J Biomech, 23, 933-940, 1990. 3. Reinschmidt C, et al. Clin Biomech, 12, 8-16, 1997. 4. Bates BT, et al. Biomechanics VI-B, pp. 30-39, 1978. 5. De Wit B, et al. J Appl Biomech, 16, 169-179, 2000. 6. MacLean C, et al. Clin Biomech, 21, 623-630. ACKNOWLEDGEMENTS We thank Kintec Footlabs Inc. for providing footwear.
XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007
S492
REARFOOT NORMS IN A YOUNG, HEALTHY POPULATION R. Chang1, I.S. Davis2 and J. Hamill1 Department of Kinesiology, University of Massachusetts, Amherst, USA, 2 Department of Physical Therapy, University of Delaware, Newark, USA, email: [email protected] 1
METHODS Fifty healthy college-aged subjects participated: 25 females (21.0 ± 3.2 yr) and 25 males (20.9 ± 4.0 yr). Three-dimensional (3D) kinematics of the right leg and foot were obtained using a 3D motion capture system. At the center of eight circularly positioned infrared cameras (240Hz) was a motorized treadmill positioned over a forceplate (960Hz). Subjects wore running sandals (Bite LLC) and were prepared with anatomical calibration markers (i.e. medial and lateral femoral epicondyle, medial and lateral malleolus, 1st and 5th MTPJ) and rigid marker cluster sets on the lateral leg and posterior calcaneus. For running trials, calibration markers were removed and subjects ran on the treadmill at four speeds: 2.5, 3.0, 3.5, and 4.0 m/s. Marker histories were smoothed and rearfoot angles for the stance phase were decomposed using a Cardan X(sagittal) –y(frontal) –z(transverse) sequence. Five stance phases at each speed for each subject were analyzed. Stance was identified using ground reaction force data. Angles were normalized to standing and to 100 percent stance. The effect of running speed on maximum eversion (EVmax) and total excursion during stance (EVtot) was tested using a repeated measures ANOVA (Į=0.05). A post hoc Tukey procedure was used and effect sizes (d) were calculated. Means were collapsed across speeds that were non-significant (Į>0.05) and when effect sizes were small (d < 0.5). ‘Normal’ was estimated using group means and one standard deviation above was deemed ‘excessive’ [1]. RESULTS AND DISCUSSION The term ‘excessive’ has been used extensively in the literature on the etiology of overuse injuries. It is typically used to represent some ideological quantity as rather than some numerical value. ‘Normal’ and ‘excessive’ were defined here amongst a young healthy sample using a statistical framework. Therefore, the present definition of ‘excessive’ does not imply presence or mechanism of any pathology. Qualitatively, there were no obvious changes in rearfoot kinematics with speed (Figure 1). Statistically, speed influenced both variables (P < 0.01) however, the effect sizes between the significant pairings were very small (d ranged
Journal of Biomechanics 40(S2)
from 0.06 to 0.21). Hence, estimates for ‘normal’ and ‘excessive’ eversion were collapsed across speed (Table 1). 12 2.5 m/s 3.0 m/s 3.5 m/s 4.0 m/s
Inversion ( ° )
10 8 6 4 2 0 Eversion
INTRODUCTION Despite abundant literature on rearfoot motion and running, the terms ‘normal’ and ‘excessive’ eversion remain ill defined. Definitions have been proposed [1] however, small sample sizes, errors related to two dimensional analyses [2] and the validity of external shoe markers [3] are significant obstacles in the generation and reception of normative values. In addition, some disagreement exists as to whether there is an influence of running speed on eversion [4,5]. The primary purpose of this study was to estimate maximum and total eversion using a sample that is larger than usual. The secondary purpose was to determine whether eversion is influenced by running speed.
-2
0
20
40
60
80
100
-4 -6 % Stance
Figure 1. Group mean rearfoot inversion – eversion kinematic profiles (n = 50) during stance at four running speeds. Vertical bars indicate the upper 95% confidence interval at 2.5 m/s. Rearfoot movement patterns and eversion parameters agree with results obtained using heel mounted external rearfoot markers [6] and markers anchored to the calcaneus [3]. When compared to previous norms [1], there is good agreement in EVtot, however previous EVmax values are more extreme (normal: 9.4°; excessive: 13° [1]). Differences are likely due to 2D vs. 3D analyses, footwear type and marker configuration. Table 1. Means ( X ) and 95% confidence intervals (CI) for ‘normal’ and ‘excessive’ eversion. Normal Excessive Variable EVmax (°) EVtot (°)
X 5.1 15.9
95%CI (3.6, 6.6) (14.9 ,16.9)
X 10.5 19.4
95%CI (9.0, 12.0) (18.4, 20.4)
CONCLUSION Estimates for ‘normal’ and ‘excessive’ eversion were proposed for a young, healthy population. The results suggest that eversion is unaffected by running speeds that are between 2.5 – 4.0 m/s. REFERENCES 1. Clarke TE, et al. Sport Shoes and Playing Surfaces, Human Kinetics, 1984. 2. Areblad M, et al. J Biomech, 23, 933-940, 1990. 3. Reinschmidt C, et al. Clin Biomech, 12, 8-16, 1997. 4. Bates BT, et al. Biomechanics VI-B, pp. 30-39, 1978. 5. De Wit B, et al. J Appl Biomech, 16, 169-179, 2000. 6. MacLean C, et al. Clin Biomech, 21, 623-630. ACKNOWLEDGEMENTS We thank Kintec Footlabs Inc. for providing footwear.
XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007