SPATIO-TEMPORAL AND TIME DOMAIN KINETIC PARAMETER VARIABILITY CHANGES WITH AGE

Changes in kinematic parameters and variability in gait cycle duration with age have been associated with adaptations and/or degeneration of the human balance control system and the automated stepping mechanism. We postulated that the degeneration of the control system as related to age will be reflected in variability of selected parameters of the ground reaction force vector that are independent from the gait stride speed. To test this hypothesis we obtained quantitative measures of spatio-temporal parameters and ground reaction forces (GRF) of 45 healthy subjects 21-91 years of age. The variability in cadence and selected vertical and anteroposterior GRF parameters was found to increase significantly with age. These findings are discussed in terms of adaptations for safer gait in the elderly and/or degeneration due to aging

Similarities and Differences of the Soleus and Gastrocnemius H-reflexes during Varied Body Postures, Foot Positions, and Muscle Function: Multifactor Designs for Repeated Measures

<p>Abstract</p> <p>Background</p> <p>Although the soleus (Sol), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles differ in function, composition, and innervations, it is a common practice is to investigate them as single H-reflex recording. The purpose of this study was to compare H-reflex recordings between these three sections of the triceps surae muscle group of healthy participants while lying and standing during three different ankle positions.</p> <p>Methods</p> <p>The Sol, MG and LG muscles' H-reflexes were recorded from ten participants during prone lying and standing with the ankle in neutral, maximum dorsiflexion, and maximum plantarflexion positions. Four traces were averaged for each combination of conditions. Three-way ANOVAs (posture X ankle position X muscle) with planned comparisons were used for statistical comparisons.</p> <p>Results</p> <p>Although the H-reflex in the three muscle sections differed in latency and amplitude, its dependency on posture and ankle position was similar. The H-reflex amplitudes and maximum H-reflex to M-response (H/M) ratios were significantly 1) lower during standing compared to lying with the ankle in neutral, 2) greater during standing with the ankle in plantarflexion compared to neutral, and 3) less with the ankle in dorsiflexion compared to neutral during lying and standing for all muscles (<it>p </it>≤ .05).</p> <p>Conclusion</p> <p>Varying demands are required for muscles activated during distinctly different postures and ankle movement tasks.</p