Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Determinants of critical power (CP, the theoretical maximal rate of non-fatiguing work) and anaerobic work capacity (AWC, a finite energetic reserve from intra-muscular sources) were determined in young (n = 13, 24.5 y) and elderly men (n = 12, 70.7 y). The purposes of the four studies were to: (1a) determine and compare CP and AWC in young and elderly men; (1b) determine if CP does represent a true maximal rate of non-fatiguing work; (2) determine thigh component cross-sectional areas (CSA) and volumes; (3) determine the strength and strength/CSA ratios of the knee extensors and knee flexors; and (4) identify determinants of CP and AWC.;The first study showed that CP (115 vs 177 watts) and AWC (8.1 vs 13.6 kJ) were significantly reduced in elderly men. Temporal profiles of cardiorespiratory and metabolic variables monitored during prolonged (24 minutes) cycle exercise at CP indicated that CP elicited a significantly greater VO{dollar}\sb2{dollar} in the elderly men (91.5% vs 85.2% of VO{dollar}\sb2{dollar}max) and that CP did not represent a true rate of non-fatiguing work in either young or elderly men.;The computed tomography scans used in the second study indicated that subcutaneous and intramuscular fat in the thigh were significantly increased in the elderly men, while the quadriceps and hamstring muscle CSA and volumes were decreased in comparison to the young men.;The third study showed that elderly men were weaker (22-32%) in both concentric isometric and isokinetic (120{dollar}\sp\circ{dollar}/s) knee flexion and extension. Isometric strength:CSA ratios were not different between the two groups, but the isokinetic ratios of the elderly men were significantly decreased, suggesting that their decline in isokinetic strength was greater than could be accounted for by their decrease in muscle CSA.;Finally, the fourth study indicated that while CP was correlated with measures of muscle CSA and volume, it was most strongly related to VO{dollar}\sb2{dollar}max and maximal power output in both young and elderly men.;These studies have identified determinants of CP and AWC and suggest a possible age-related effect on muscle strength and size, but not on the ability of elderly men to perform high intensity exercise for prolonged durations.



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