ISSN:
1439-6327
Keywords:
Contraction time
;
Exertion
;
Fatigue
;
Relaxation time
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The contractile properties of the quadriceps muscle were measured in seven healthy male subjects before, during and after prolonged cycling to exhaustion. Special efforts were made to obtain measurements immediately after exercise. The exercise intensity corresponded to about 75% of estimated maximal O2 uptake and time to exhaustion was mean 85 (SEM 9) min. At the end of the cycling heart rate and perceived exertion for the legs were 94% and 97% of maximal values, respectively. Maximal voluntary isometric force (MVC) had decreased after 5 min of exercise to a mean 91 (SEM 4)% of the pre-exercise value (P 〈 0.05) and decreased further to a mean 82 (SEM 6) and mean 66 (SEM 5)% after 40-min cycling and at exhaustion, respectively. A new finding was that during recovery reversal of MVC occurred in different phases where the half recovery time of the initial rapid phase was about 2 min. The MVC was a mean 80 (SEM 2)% of the pre-exercise value after 30 min and was not affected by superimposed electrical stimulation. Maximal voluntary concentric and eccentric forces decreased to 74% and 80% o of initial values at exhaustion (P 〈 0.05). The kinetics of isometric contraction expressed as the time between 5% and 50% of tension (rise time) and the time between 95% and 50% of tension (relaxation time) were not significantly affected by the prolonged cycling. The electromechanical delay measured as the time between the first electrical stimulus and 5% of tension decreased from a mean 32 (SEM 1) ms at rest to a mean 26.6 (SEM 0.6) ms at fatigue (P 〈 0.05). It is concluded that prolonged exhausting cycling results in reduced force-generating capacity during isometric, concentric and eccentric conditions. The absence of a slowing of relaxation and the incomplete reversal of MVC after 30 min of recovery indicate that the mechanism(s) of fatigue during prolonged exercise involve other components than those involved during high intensity exercise.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00854977
