Grant: Discovery Grants Program - Individual

Since my first publication as master's student 32 years ago, I have averaged more than 10 publications/year (last 15 years; approximately 20 publications/year), with a primary focus on neuromuscular responses to activity. This proposal will continue to build on these contributions to the scientific and professional fields. Whereas, my earlier work focused on the effects and mechanisms underlying physical muscle fatigue, my recent work and present proposal includes psycho-physiological responses and mechanisms. Due to COVID we could not complete initial projects on performance empathy (action observation), but we presently have two investigations ongoing. Performance empathy refers to the physiological and performance responses of an individual after observing another individual performing fatiguing work. Our initial results have shown that the observer experiences performance impairments possibly due to a subconscious pacing strategy. Other action observation research using non-fatiguing, short duration activities have reported performance enhancements. We have seen anticipatory increases in heart rate, blood pressure, galvanic skin responses and electromyographic (EMG) signals. We hope to add high density EMG, electroencephalography, reflex measures (i.e., H-reflex) and corticospinal excitability measures in addition to performance measures (e.g., peak force, endurance, power, movement control). A further interesting area that we are pursuing (two investigations completed) is the effect of muscle fatigue and multi-tasking (motor outputs and sensory inputs) upon time perception. The ability to estimate time is very important in daily work (especially with military, and health professionals), sport, and fitness activities. We found that isometric contractions at 10%, 60%, and 100% of maximal voluntary isometric contractions (MVIC) disrupt timing estimates over 30-seconds with no additive impairments from sensory inputs such as watching a monitor and no significant difference between healthy, active, younger, and older participants. Our research on non-local muscle fatigue (NLMF: unilaterally fatigue one limb and impairments occur in a non-exercised muscle) over the past decade has highlighted that NLMF is unlikely to occur with single, short duration muscle contractions but is evident with prolonged contractions. NLMF effects were not moderated by study design (between vs. within-participant), homologous vs. heterologous effects, upper or lower body effects, training status, sex, age, or fatigue protocol intensity Furthermore, unilaterally stretching one muscle can have global effects with range of motion improvements in other non-stretched muscles, which were not modified by trained state, sex, or stretching intensity. We still need to determine the duration of these NLMF effects, effect of mental vs. physical fatigue further non-local flexibility effects and mechanisms as well as possible additive effects of physical and mental fatigue.