Likelihood ratio approach for flying time evaluation in standing vertical jump

Abstracts of the 2007 SIAMOC congress / Gait & Posture xxx (2008) xxx–xxx to lordosis (C: 30.2 ± 5.2◦ ; cLBP: 41.0 ± 12.9◦ ). Concerning forward flexion, O group and cLBP group showed limited trunk flexion (C: 118.2 ± 9.3◦ ; O: 107.1 ± 7.5◦ ; cLBP: 99.8 ± 14.6◦ ) and limited dorsal flexion L1D1 (C: 44.1 ± 8.5◦ ; O: 34.5 ± 10.0◦ ; cLBP: 28.2 ± 9.6◦ ). No differences were found in ROM related to lordosis. Concerning the bilateral bending, cLBP group was characterized by a limited trunk inclination (C: 77.8 ± 13.7◦ ; O: 80.7 ± 8.0◦ ; cLBP: 60.7 ± 21.3◦ ), limited dorsal movement (C: 59.2 ± 9.7◦ ; O: 50.5 ± 11.8◦ ; cLBP: 35.5 ± 12.9◦ ), and limited lumbar curve values (C: 46.0 ± 7.0◦ ; O: 43.9 ± 11.3◦ ; cLBP: 29.4 ± 11.8◦ ). Discussion: Obesity seems to influence mostly the upper part of the trunk: the angle related to kyphosis (in forward flexion) and the dorsal curve (in lateral bending) resulted limited both in O and cLBP group. This adaptation induces a limited trunk flexion. The effects related to LBP are more visible in lateral bending, where the cLBP group shows a limitation in lumbar curve inducing a limitation of trunk inclination. In forward flexion, the cLBP group shows an increased lordosis while standing, despite ROM values similar to O and C groups. This trunk strategy may be related to the high incidence of lumbar degenerative pathologies in obese subjects [3].

Reference [1] Davis RB, et al. Hum Mov Sci 1991;10:575–87. [2] Frigo C, et al. Clin Biomech 2003;18:419–25. [3] Larsson UE. Int J Obes Relat Metab Disord 2004;28(February (2)):269–77.

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Table 1 Constant scores (CSs), HFS and MD for the five patients at the end of the assessment Patient ID

P1

P2

P3

P4

P5

CS HFS MD [◦ ]

56 10/10 8.6; 8.1; 4.5

58 10/10 4.9; 5.4; 2.6

53 8/10 1; 9.4; 10.4

62 8/10 −0.1; 2.9; 5.2

60 8/10 −5.4; −3.5; −0.7

Results and discussion: Table 1 reports the CSs and the MD values for each patient during the last assessment. From the data reported it can be concluded that a CS > 53/100 and a HFS > 8/10 do not exclude the existence of compensatory movement, since P1–P4 had a CS > 53/100 and a HFS > 8/10 but showed marked compensatory movements, as proved by the MD values. Moreover, even though P4 and P5 had very close CSs and identical HFSs, they presented different patterns for the compensatory movements: no compensation for P5 while marked for P4. Different patterns were also found comparing P1 and P2 (who showed HFS = 10/10), as well as for P5 and P3 (see Ref. [3] for images). In conclusion, patients with overlapping CSs and identical HFSs do not always present the same compensatory movements. The CS and HF scores considered were chosen since they are typical of patients after 3–5 weeks of active mobilization, i.e. in the second half of rehabilitation. From the results it can be concluded that C should be used with caution to draw conclusions on the recovery of shoulder normal kinematics.

doi:10.1016/j.gaitpost.2007.12.054 Limitations of the constant scale in the assessment of shoulder compensatory strategies P. Garofalo 1,2,∗ , A.G. Cutti 1 , M.V. Filippi 1 , S. Cavazza 3 , A. Davalli 1 , A. Cappello 2 1

INAIL Prosthesis Centre, Vigorso di Budrio (Bo), Italy Department of Electronics, Computer Science and Systems, University of Bologna, Italy 3 Ospedale S. Giorgio, Ferrara, Italy

Reference [1] Pynsent P, et al. Outcome measure in orthopaedics. Butterworth– Heinemann Ltd.; 1994. [2] Cutti AG, et al., Proceedings international shoulder group meeting. 2006. [3] www.inail-starter.org/AnMovEngRep.html.

2

Introduction: The constant scale (C) [1] is routinely used to assess the level of shoulder impairment during rehabilitation. C rates important issues, such as pain, range of motion and power. However, it does not comprise any item directly intended to follow the recovery of the normal coordination between humerus elevation and shoulder–girdle movements (named hereinafter girdle–humeral rhythm), which is an important aspect of rehabilitation. To fully understand the validity of C in monitoring the rehabilitation process, it is therefore essential to establish the relation between C scores and the compensatory movements affecting the girdle–humeral rhythm. In particular, the aim of this study was to establish if: (1) a C score (CS) higher than 50/100 and a humerus flexion score in C (HFS) higher than 8/10 can exclude the existence of compensatory movement; and (2) patients with overlapping CS and an identical HFS always present the same compensatory movements. Method: Five patients (P1–P5, 57 ± 16 years-old) participated in this study. P1–P4 successfully underwent surgery for rotator cuff-tear and P5 for traumatic shoulder instability. All non-op sides were sound. Every week from the start of the active mobilization, each side of each patient was scored with C and its 3D kinematics was measured with the motion analysis protocol presented in [2]: the assessment ended when the CS overcame 50/100 and the HFS was higher than 8/10. In each motion analysis acquisition, subjects were asked to cyclically flex-extend the humerus in the sagittal plane for 5 times. The coordination plot relating the girdle elevation and the humerus flexion was then obtained for both sides. The affected and sound girdle–humeral rhythm were finally compared intra-subject by computing the mean difference (MD) between the girdle elevation of the sound side and that of the affected side, at 40◦ , 80◦ and 100◦ of humerus flexion (see Ref. [3] for images).

doi:10.1016/j.gaitpost.2007.12.055 Likelihood ratio approach for flying time evaluation in standing vertical jump L. Quagliarella 1,∗ , G. Minervini 2 , N. Sasanelli 1 , L. Fabbiano 2 1

Sezione di Ingegneria Biomedica, Universit`a degli studi di Bari, Bari, Italy Dipartimento di Elettrotecnica ed Elettronica, Politecnico di Bari, Bari, Italy 2

Introduction: In a previous work [1] a new method was presented to evaluate, during coutermovement vertical jumps (CMJ), the flying time (FT) of each limb as well total FT, which can describe subjects plyometric capacity. On that occasion, FT was evaluated through a Peak Detection Method (PDM) specifically developed. Likelihood Ratio Approach (LRA), already used in others biomedical signal analysis [2], is now compared with PDM in order to verify the possibility to increase the reliability of FT evaluation from accelerometric data. Methods: Experimental data, obtained by 45 healthy male subjects (mean age 34.4 ± 8.5 years) who gave their informed consent, were acquired and collected adopting the same equipments and procedures already presented [1,3]. After a 10-min warm-up phase each subject was asked to perform a series of five maximum height CMJ. CMJ acquired signal were divided in three following phases, where landing and take-off instants represented the transition moments among them. Each phase was statistically characterized in order to obtain LRA appraisers. A parametric algorithm, based on Gauss distribution with variable mean, was developed using data obtained from a Training Set (TS), constituted by 15 persons, randomly selected from experimental sample. LRA reliability was evaluated by means of a Verification Set (VS), i.e. the remaining 30 subjects.

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Abstracts of the 2007 SIAMOC congress / Gait & Posture xxx (2008) xxx–xxx

Results: PDM and LRA effectiveness was evaluated by absolute percentage error (APE); considering single jumps, LRA implies a 15% of APE reduction in TS and a 7% reduction in VS. While referring to the most relevant mean APE of each subjects, the highest error decrease of 7% in TS and of 29% in VS. Discussion: LRA seems to be more effective for FT evaluation from accelerometric data compared to PDM. A possible explanation is that while PDM can analyse data only in short time window, LRA can evaluate the global course of the acquired signal.

Reference [1] Quagliarella L, et al. Flying time evaluation in standing vertical jump by measurement of ankle acceleration. Gait Posture 2006;24(S1):S56–7. [2] Micera S, et al. An algorithm for detecting the onset of muscle contraction by EMG signal processing. Med Eng Phys 1998;20:211–5. [3] Quagliarella L, et al., Biomedical signal analysis by a low-cost accelerometer measurement system. In: Instrumentation and measurement technology conference, 2006. IMTC 2006. Proceedings of the IEEE April 2006. 2006. p. 2236–9. doi:10.1016/j.gaitpost.2007.12.056 Stance posture changes in early Parkinson’s disease are detectable with a wearable inertial device M. Mancini 1,2,∗ , C. Zampieri 1 , P. Carlson-Kuhta 2 , F.B. Horak 2 , L. Chiari 1 1 Department of Electronics, Computer Science and Systems, University of Bologna, Italy 2 Neurological Sciences Institute, Oregon Health & Science University, Beaverton, OR, USA

Introduction: Natural sway and corrective surface reactive forces during stance are important signs of postural function and can be quantified with force plates. A preliminary study showed that is possible to use wearable inertial devices instead of force plates to quantify spontaneous body sway in young subjects. While several studies have shown that subjects with

advanced Parkinson’s disease (PD) exhibit abnormalities in sway parameters during quiet standing, just a few studies investigated postural changes associated with early symptoms of PD. We hypothesized that inertial devices could provide sensitive measures of postural function in early PD. Materials and methods: We examined six PD (67 ± 7 years) and seven healthy, age matched control subjects (65 ± 8 years). PD subjects were newly diagnosed (H&Y ≤ II) and were not taking any medications, yet. Subjects wore two MTX Xsens (49A33G15) sensors, mounted by means of Velcro belts on the posterior trunk, at the level of L5 and C7. Two-minutes trials were performed with subjects staying on a force platform (AMTI) in a comfortable position with arm crossed. Three conditions were evaluated: eyes open (EO), eyes closed (EC), eyes closed with cognitive task (ECC). Data were acquired and synchronized at 50 Hz. Three sway parameters were computed on COP and acceleration signals in the transverse plane: root mean square distance (RMS), mean velocity (Mvelo), and frequency containing 95% of the power (f95). ANOVAs were used to test statistical differences between groups and across conditions. Results and discussion: Major findings, partly shown in Fig. 1, tell us that: (1) COP, as a projected measure of postural sway, mostly reflects the behaviour of body center of mass, closely related to L5; (2) postural sway, though, is an inherently multisegmental phenomenon, and accelerations at L5 and C7 may reflect different components of a postural stabilization strategy; (3) with respect to control subjects, patients with early PD display a larger variability of the accelerations (quantified by RMS) at L5 but not at C7, indicating that the efficacy of head but not lower trunk stabilization is preserved; (4) patients with early PD already sway their upper and lower trunk in a much more ’scattered’ way than control subjects, as reflected by the large increase in f95; (5) the smoothness of lower and upper trunk displacements (quantified by Mvelo of acceleration, i.e. jerk) is clearly compromised, at L5 more than it is at C7; (6) no differences it is at C7; (6) no differences in the chosen accelerations measures were observed across different conditions in this experiment; on the other side it seems that even simple conditions as EO and EC, without the need of a concurrent cognitive task, may be clear enough to make evident the changes in body sway accompanying the early stage of PD. Our results confirm that postural control is affected in early PD, and that wearable inertial sensors could be useful for monitoring patients’ progression in the home environment. Acknowledgement: Supported by the Kinetics Foundation. doi:10.1016/j.gaitpost.2007.12.057

Fig. 1. Results of the posture analysis.

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