Date of Completion


Embargo Period



Aging, Semi-reclined Cycling, Muscle Activity, Electromyography, Kinematics, Muscle Fatigue, Lower-Extremity

Major Advisor

Pouran D. Faghri

Associate Advisor

Douglas J. Adams

Associate Advisor

Bryan Buchholz

Associate Advisor

Hariharan Swaminathan

Associate Advisor

Jaci L. VanHeest and Nicholas Warren

Field of Study

Biomedical Engineering


Doctor of Philosophy

Open Access

Campus Access


The aging process has been observed to impair the structure and function of skeletal muscles over time. However, physical activity (e.g., cycling) is known to minimize the physiological and functional effects caused by a sedentary lifestyle in old age. Therefore, a better understanding of lower-extremity muscle activations and joint kinematics between young and older adults during cycling could help rehabilitation professionals to prescribe more effective exercise programs for older populations and those with compromised musculoskeletal systems.

The purpose of this work was to provide a better understanding of the lower limb muscles (rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GT)) and joints’ characteristics during cycling between young adults (i.e., early 20s in age) and older adults (i.e., early 50s in age). Further comparison was made between the two groups during submaximal, prolonged cycling to examine the progression of muscle fatigue by using the frequency content of the muscles’ EMG signals. This was done with the intention of proposing a cycling protocol –based on the ACSM guidelines– that can be utilized as a safe physical activity protocol for older individuals.

Findings indicate that changes in workload affect the lower-extremity muscular activity and coordination. Older participants appear to use a different strategy, compared to young, in recruiting their lower-extremity muscles to perform at higher cycling workloads. It is recommended that rehabilitation professionals consider these differences and recognize that the stimulus required to promote positive change in older skeletal muscles might be different from what works for young adults. Future research should evaluate such changes specific to these populations. Furthermore, the proposed prolonged submaximal cycling protocol did not exhibit significant levels of sustained muscle fatigue in any of the age groups. This finding confirms that the protocol is a safe physical activity alternative for older individuals, similar to those who participated in this study, and future research is required to evaluate its effectiveness as part of rehabilitation or exercise interventions for said population.