Repeated passive stretching: acute effect on the passive muscle moment and extensibility of short hamstrings

OBJECTIVE: To examine the response of short hamstring muscles to repeated passive stretching. DESIGN: A repeated measures design. SETTING: A university laboratory for human movement analysis in a department of rehabilitation. SUBJECTS: Students (7 men, 10 women) from the Department of Human Movement Sciences. MAIN OUTCOME MEASURES: The lift force, range of motion, pelvic-femoral angle, first sensation of pain, and electromyogram of the hamstrings were measured. RESULTS: Comparison of the data of the test group (n = 17) after five successive passive stretch tests by means of an instrumental straight-leg raising test showed no significant change of the variables passive muscle stiffness and extensibility (p>.05). CONCLUSION: The acute effect of repeated passive stretching of short hamstring muscles is negligible. With an instrumental straight-leg raising test, the relevant muscle variables can be examined noninvasively

Speed dependence of averaged EMG profiles in walking

Electromyogram (EMG) profiles strongly depend on walking speed and, in pathological gait, patients do not usually walk at normal speeds. EMG data was collected from 14 muscles in two groups of healthy young subjects who walked at five different speeds ranging from 0.75 to 1.75 ms(-1). We found that average EMG profiles varied in a predictable way with speed. The average EMG profile for each muscle at any speed could be estimated in a simple way from two functions, one constant and one proportionally increasing with walking speed. By taking into account the similarity among profiles within functional groups, the number of basic functions could be reduced further. Any average EMG profile among the 14 leg muscles studied at all speeds in the measured range could be predicted from six constant and ten speed-dependent basic patterns. These results can be interpreted in terms of a central pattern generator for human walking. Copyright 2002 Elsevier Science B.V

Detection of non-standard EMG profiles in walking

The amplitude of an EMG and the temporal pattern can be used when considering if an EMG profile is normal or not. In the method described in this paper a gain factor of the complete EMG profile was determined and then the profile normalised with this gain factor. This normalised individual profile was then compared with a standard profile, predicted on the basis of walking speed. Deviating profiles were identified when they fell outside the upper and lower 95% limits range for the average profiles of 14 leg muscles. The amount of deviation from the normal profile can be quantified with the normalised mean square difference D2. Gain factors varied over a factor of 4 within a group of 10 normal subjects. For a normal population D2 was below 1. Most muscles had consistent profiles but some patterns could be discerned which showed marked variability among muscles and subjects

Comparative roll-over analysis of prosthetic feet

A prosthetic foot is a key element of a prosthetic leg, literally forming the basis for a stable and efficient amputee gait. We determined the roll-over characteristics of a broad range of prosthetic feet and examined the effect of a variety of shoes on these characteristics. The body weight of a person acting on a prosthetic foot during roll-over was emulated by means of an inverted pendulum-like apparatus. Parameters measured were the effective radius of curvature, the forward travel of the center of pressure, and the instantaneous radius of curvature of the prosthetic feet. Finally, we discuss how these parameters relate to amputee gait

Obstacle crossing in lower limb amputees

OBJECTIVE: To study limitations in function and adjustment strategies in lower limb amputees during obstacle crossing. DESIGN: Observational cohort study. SUBJECTS: Transfemoral and transtibial amputees and able-bodied control subjects. METHODS: In a motion analysis laboratory unimpeded and obstacle crossing runs were performed. The subjects stepped over an obstacle of 0.1m height and thickness and 1m width. Outcome measures were gait velocity, hip, knee and ankle joint angles and leading limb preference. RESULTS: Whereas able-bodied and transtibial subjects demonstrated an increase in knee flexion during obstacle crossing compared to unimpeded walking, in transfemoral amputees the opposite was seen, namely a decrease in knee flexion. The lack of knee strategy in transfemoral amputees was compensated by circumduction at the hip on the prosthetic side and plantar flexion of the non-affected ankle. Transtibial amputees preferred to cross the obstacle with the prosthetic limb first, while transfemoral amputees preferred the non-affected limb. CONCLUSION: The different leading limb strategy in transfemoral and transtibial amputees could be explained by the restricted flexion and propulsion properties of the prosthetic knee. Training of obstacle crossing tasks during rehabilitation and improvement of prosthetic design may contribute to safe obstacle crossing