Module 4, Lecture 26 - Kinesiol 2C03.docx

Fatigue Overview fatigue → is a decrease in the maximal force and/or power generating capacity is often caused by exercise or physical activity muscle fatigue is not the point of task failure task failure → is when one cannot perform the exercise or the contraction anymore during maxim...

Fatigue Overview fatigue → is a decrease in the maximal force and/or power generating capacity is often caused by exercise or physical activity muscle fatigue is not the point of task failure task failure → is when one cannot perform the exercise or the contraction anymore during maximal contractions, fatigue presents as a decline in force accordingly, the reflected EMG signal magnitude starts high and drops off during submaximal contractions, fatigue presents as a decline in maximal force generating capacity relative intensity (force/power) thus dictates time to failure Fatigue and Contraction Type during isometric contractions, fatigue results in reduced force, a reduced rate of force development (RFD), and reduced rate of force relaxation (RFR) during concentric contractions, fatigue results in reduced force, reduced velocity, and reduced power during eccentric contractions, fatigue results in reduced force, and reduced power velocity may not be under control (reduced?) are more likely to cause ultrastructural damage (i.e. damage to the sarcolemma, T-tubules, z-disks, and the proteins) Ways of Expressing Exercise Intensity isometric contraction → % of MVC weightlifting → % of 1 RM isokinetic contraction (contraction maintained at a given speed) → number of maximal contractions aerobic exercise → % VO2 max VO2 max → is the maximum amount of oxygen one can consume during physical activity or exercise (oxidative phosphorylation is at its maximum) Exercise Intensity and Fatigue - Isometric Contractions the higher the % of MVC, the less time it can be held is a curvilinear relationship occlusion of blood flow at higher intensities of effort increases rate of fatigue (one is no longer able to deliver oxygen or remove wastes from the working fibers as efficiently) the fatigue resistant type I fibers being the predominant fiber at lower intensities also contributes to the curvilinear relationship Exercise Intensity and Fatigue - Weightlifting the higher the % of 1 RM, the less repetitions can be performed is a curvilinear relationship, although not as sharp a curve as the isometric contractions is dynamic and thus allows more blood flow (a small amount of blood is let in every time one moves through their entire range of motion) Exercise Intensity and Fatigue - Isokinetic Contractions after the first few contractions, power decreases as the number of contractions increases the steepness of this decrease increases at first before plateauing at a level called the critical power is assessed by the critical power test whereby the participant will perform contractions repeatedly until there is no further decrease in their percentage of force/power Exercise Intensity and Fatigue - Aerobic Exercise oxygen consumption and exercise intensity increase together in a stepwise pattern before maxing out at the VO2 max as the % of one’s VO2 max increases, time to exhaustion/failure decreases accordingly note: one can exercise at intensities higher than 100% VO2 max by supplementing aerobic power with anaerobic power; presents as a plateau in the relationship this plateau is hard to/not often observed as many people’s exercise intensity maxes out at the VO2 max; is usually only observed in elite athletes Measuring Anaerobic Peak Power anaerobic power is assessed using a wingate test involves a participant pedaling as hard as possible on a magnetic cycle ergometer for 30 seconds at a load set relative to body mass, measuring velocity (rpm) from this data peak power, average power, and the percent decline in power can be determined Assorted Notes fatigue = muscular fatigue fatigue technically starts as soon as the force begins to drop one cannot exercise at intensities above 100% of our maximum voluntary contraction or 100% of our one repetition Max