Influence of Fatigue and Speed on Electromyographic Activity of Lower Extremity Muscles During Selected Weight Bearing Exercises Commonly Used for Fitness and Rehabilitation

It is generally accepted that the effectiveness of an exercise can be controlled not only by the weight or resistance applied but also by doing an exercise that would better target the desired muscle. Information regarding selected lower extremity muscle activity during specific exercise and the influence of fatigue and speed on muscular activation may enhance exercise prescription for all parties involved. Specifically, selection of specific training or rehabilitation exercises may be guided by increased awareness of specific muscle activation patterns during common exercises. Methods and Measures: Healthy subjects between 18 - 35 years old will be recruited from the community by a sample of convenience and word of mouth. Potential participants will report to the Institute for Human Performance. The potential participants will be asked to complete all documentation including informed consent, and health screening questionnaire. The qualified participants will be familiarized with the set up and specific exercises. If eligible, surface EMG recordings will be collected from the back extensors, gluteal muscles (buttocks), hamstrings (posterior thigh), quadriceps (anterior thigh), and gastrocnemius (calf) during squat and lunges exercises. For data analysis, a within subject measures analysis will be conducted using general linear models. Specifically, we will use paired t-tests and an analysis of variance (ANOVA). When applicable, post-hoc tests will be used to uncover differences among the groups of subjects on descriptor variables such as age, height, weight, rate of perceived exertion, and maximal and sub-maximal voluntary muscle performance variables (i.e. EMG amplitude, frequency). The statistical significance level will be set at alpha = 0.05 for all analyses performed.