Millet, Guillaume Y.Samozino, PierreLopes Krüger, Renata2019-08-262019-08-262019-08-20Lopes Krüger, R. (2019). Effects of Fatigue on Neuromuscular Function and Mechanical Properties in Young and Elderly Populations (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/110787Neuromuscular (NM) fatigue is defined as an exercise-related decrease in maximal power or isometric force. However, in the past 20 years, most studies have assessed isometric force only. The evaluation of dynamic measures provides important additional information to the fatigue-induced changes in NM function, especially when exploring age-related changes in fatigability. The few studies that explored dynamic measures of NM fatigue have assessed power output during single-joint movements. Therefore, measures of force production capacity (maximal power, velocity and torque) during multi-joint lower limb movements are unknown. The purpose of this thesis was to examine the effects of different intensities/durations of cycling exercises on torque-velocity properties and NM function in aging and young populations. The specific objectives were: (i) to assess kinetics of central and peripheral fatigue and recovery immediately after different cycling exercises in young individuals; (ii) to compare dynamic vs. isometric measures of NM fatigue following cycling and during recovery in young individuals; and (iii) to explore age-related differences in dynamic and isometric measures (including central and peripheral components of fatigue) of NM fatigue induced by cycling. Thanks to an innovative ergometer, NM fatigue was assessed with a minimal delay (10 s) through dynamic measures of force production capacity during 7-s cycling sprints and maximal isometric force. Our findings showed that: (i) NM fatigue is indeed determined by the exercise intensity/duration and previous studies that investigated NM fatigue with a delay (~ 3 min) might have misinterpreted fatigue amplitude and etiology as well as the course of recovery; (ii) isometric and dynamic measures behave differently after fatigue and so they are not interchangeable as they do not share the same physiological mechanisms; and (iii) younger individuals are as fatigable (for the Wingate and moderate-intensity exercise) or more fatigable (for severe-intensity exercise) than older subjects when considering isometric and dynamic measurements of NM fatigue and peripheral fatigue is greater in younger individuals after the severe- and moderate-intensity exercises, but not following the Wingate. This thesis provides the first comprehensive evaluation of age-related NM fatigue due to dynamic exercises with large muscle mass, i.e. exercises often performed in daily-life and rehabilitation activities.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.AgingNeuromuscular fatiguePower outputIsometric forceEducation--Healthdoctoral thesis10.11575/PRISM/36869