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Background. Fatigue affects self-reported functioning in older persons. Balance and gait problems increase fall risk. The effect of physical fatigue in the elderly population in general, and on balance control during walking in particular is not well known. This study investigates how a repeated sit-to-stand task affects gait control in older persons.
Methods. Twenty-two persons (mean age 78 years) took part in a fatigue group (FG), and 22 persons (mean age 80 years) in a matched control group (CG). Participants walked back and forth on a walkway at different walking speeds. Gait data were adjusted for pretest-posttest differences in walking speed. The FG participants were physically fatigued by a repeated sit-to-stand task. Trunk data were obtained by a triaxial accelerometer and foot level data by an electronic walkway.
Results. There were no group differences in preferred gait speed (p =.96) or in step length (p =.47) following the fatiguing task, but there were significant increases in step width (p =.023) and in mediolateral trunk acceleration amplitude (p =.038) in the FG group. Step-length variability (p =.004) and interstride trunk acceleration variability in the vertical direction (p =.002) increased, and tended to increase in the anteroposterior direction (p =.10) and to decrease in the mediolateral direction (p =.10) in the FG only.
Conclusion. Gait changes following a physical fatiguing task agree with changes previously found in older persons at risk of falling, suggesting that physical fatigue may represent a risk factor for falls in elderly persons
To investigate the effects of muscle fatigue on force sense at the ankle joint, 10 young healthy adults were asked to perform an isometric contra-lateral force ankle-matching task in two experimental conditions of: (1) no-fatigue and (2) fatigue of the plantar–flexor muscles. Measures of the overall accuracy and the variability of the force matching performances were determined using the absolute error and the variable error, respectively. Results showed less accurate and less consistent force matching performances in the fatigue than no fatigue condition, as indicated by decreased absolute and variable errors, respectively. The present findings evidence that muscle fatigue degrades force sense at the ankle joint.
The effects of running in an exerted state on lower extremity kinematics and joint timing.
Dierks TA, Davis IS, Hamill J. J Biomech. 2010 Jul 19.
Runners rarely run to the point of maximum fatigue or exhaustion. However, no studies have investigated how the level of exertion associated with a typical running session influences running mechanics. The purpose of this study was to investigate the effects that running in an exerted state had on the kinematics and joint timing within the lower extremity of uninjured, recreational runners. Twenty runners performed a prolonged treadmill run at a self-selected pace that best represented each runner's typical training run. The run ended based on heart rate or perceived exertion levels that represented a typical training run. Kinematics and joint timing between the foot, knee, and hip were analyzed at the beginning and end of the run. Increases were primarily observed at the end of the run for the peak angles, excursions, and peak velocities of eversion, tibial internal rotation, and knee internal rotation. No differences were observed for knee flexion, hip internal rotation, or any joint timing relationship. Based on these results, runners demonstrated subtle changes in kinematics in the exerted state, most notably for eversion. However, runners were able to maintain joint timing throughout the leg, which may have been a function of the knee. Thus, uninjured runners normally experience small alterations in kinematics when running with typical levels of exertion. It remains unknown how higher levels of exertion influence kinematics with joint timing and the association with running injuries, or how populations with running injuries respond to typical levels of exertio
We aimed to describe the changes in footprint characteristics after 2 types of resistance training sessions performed at different intensities. 18 young subjects (8 men and 10 women) volunteered for the study. All of them performed 2 different resistance training sessions, one with light loads (LS) and the other with heavy loads (HS). Their footprint was recorded and analysed before and after exercise. Lengths, widths, and areas of the footprint (rearfoot, midfoot, and forefoot) were measured. Almost all the variables significantly increased after both sessions. The greatest changes were found in the midfoot (area, LS: 10.4%; HS: 8.1%, P<0.0005; width, LS: 7.5%, P=0.002, and HS: 8%, P<0.0005). However, there were no significant differences between post-exercise data from both sessions. The variable that showed the smallest changes was the foot length (LS: 0.3%, P=0.023; HS: -0.4%, P=0.549). A resistance training session led to increases in most of the dimensions of the footprint, regardless of the magnitude of the loads handled. The greatest changes were found in the midfoot, indicating that the foot was flatter after exercise, and the foot changed more in width than in length.
Load carriage and muscular fatigue are two major stressors experienced by military recruits during basic training. The purpose of this study was to assess the influences of load carriage and muscular fatigue on ground reaction forces and ground reaction loading rates during walking. Eighteen healthy males performed the following tasks in order: unloaded and unfatigued walking, loaded and unfatigued walking, fatiguing exercise, loaded and fatigued walking, and unloaded and fatigued walking. The fatiguing exercise consisted of a series of metered step-ups and heel raises with a 16-kg rucksack. Loaded walking tasks were performed with a 32-kg rucksack. Two-way repeated measures analysis of variances were used to determine the effects of fatigue and load carriage on ground reaction forces and loading rates. Muscular fatigue has a significant influence on peak vertical ground reaction force and loading rate (p < 0.01). Load carriage has a significant influence on peak ground reaction forces and loading rates (p < 0.001). As both muscular fatigue and load carriage lead to large increases of ground reaction forces and loading rates, the high incidence of lower extremity overuse injuries in the military may be associated with muscular fatigue and load carriage.