Muscle co-activation and ground reaction forces during stair walking in old and young women
Year: 2006
Type: dissertation
Study design: Observational Study
Abstract: Force production and co-activation of different leg muscles are essential elements of the moving strategy in performing daily living tasks such as stair walking.The purpose of this study was to investigate the magnitude and timing in muscular antagonist co-activation of leg muscles in relation to vertical ground reaction force (GRF) in old (age=65-82, n=19) and young (age=23-29, n=10) women.The study is part of a larger intervention study that is being carried out in Odense, Denmark.The differences in muscular antagonist co-activation and in the shape of GRF curve during ascent at maximum velocity (AMV) and at self selected velocity (ASV) and during descent at self selected velocity (DSV) on a nine-step staircase were studied.A force plate was mounted on the fifth step.EMG activity was measured from the agonist muscles vastus lateralis (VL) and medialis (VM), rectus femoris (RF), soleus (Sol), gastrocnemius lateralis (GasLat) and from antagonist muscles biceps femoris (BFcl), semitendinosus (ST) and tibialis anterior (TA).The statistical analyses applied were an unpaired two-tailed t-test, analysis of covariance, Pearson correlation analysis (r), and linear regression.The maximum values (N/kg) of GRF for the old subjecs were 135 ±23 (AMV), 112 ±11 (ASV), 148 ±24 (DSV) and for the young subjects 192 ±16, 117 ±13, 160 ±14, respectively.During AMV, both groups showed a single-peak GRF waveform.In contrast, a double peak GRF waveform was observed during ASV in both young and old subjects.Large variations in GRF were observed during DSV, with one, two or many smaller peak waveforms for both groups.However, there were differences between the old and young subjects in the different phases of the vertical GRF curve during stair ascent and descent.Compared to young subjects, old individuals demonstrated elevated antagonist muscle coactivation in the thigh during AMV in entire stance phase (p=0.010) and loading slope (p=0.024),during ASV in entire stance phase (p=0.013) and mid stance phase (p=0.011), and during DSV in entire stance phase (p=0.034), the first force peak (p=0.039),loading phase (p=0.002) and in the loading slope (p=0.001).For the calf co-activation, there were no significant differences between old and young subjects during AMV.During ASV old subjects had elevated co-activaton in the first peak (p=0.026) and young subjects in the unloading phase (p<0.001), and in the second peak during DSV.Time parameters of step cycle showed old subjects to be slower, their step cycle duration and complete stance phase to be longer than in young subjects.The long complete stance phase and step cycle duration were associated with low GRF parameters for the old subjects when ascending (r=-.561--.924, p<0.001-0.05)and for the young subjects when descending the stairs (r= -.645 --.759, p<0.01-0.05).The differences in antagonist muscle co-activation may be caused by older subjects compensating for a loss in maximal muscle strength, therefore adopting a joint walking strategy that involves elevated joint stiffness, achieved by means of elevated agonist-antagonist muscle co-activation.Further, the present data indicate that old subjects operate nearer to their maximum physiological capacity while ascending and descending stairs, and perhaps therefore muscle co-activation is elevated to perform the task safely.To elucidate these notions more closely, further studies with larger groups of ageing men and women are needed, preferentially including measurements with multiple force plates and more varied stepping velocities.
Author: Ulpu Hämäläinen
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2285376593