Exercise intensity

Ranges aie given foi those activities which may vary considerably from one place of work or leisure to another, or when performed by different people. Some occupational and leisure time activities ate difficult to evaluate because of differences in exercise intensity and body position. To convert W to kcal/h, divide by 1.162. 

Denis, C., Linossier, M.-T, Dormois, D., Cottier-Perrin, M., Geyssant, A., and Lacour, J,-R. (1989). Effects of endurance training on hyperammonaemia during a 45-min constant exercise intensity. Eur. J. Appi Physiol. 59, 268-272. 

This categorization of relative whole body intensity is also valuable in distinguishing between high intensity and submaximal exercise. Exercise intensities or power outputs at or above 100% VO2 max are generally considered high intensity. These intensities require muscle contractions that generate -40-100% of the force... 

Figure 7. Muscle glycogen utilization rates at various exercise intensities expressed as a percentage of VO2 max. VL, vastus lateralis SOL, soleus CAST, gastrocnemius. Redrawn from Costill etal.(1971), Hermansen etal. (1967), Saltin and Karlsson (1971), and Sherman et al. (1981).

Muscles are capable of contracting for very long periods of time when the exercise intensity is below 60% VO2 max. For example, endurance times of 3—5 hours at 50% and over eight hours at or below 40% VO2 max are reported. There are many instances in the workplace where individuals work at intensities averaging 20-40% VO2 max for an eight hour shift. 

During NCR a clear reduction of IMCL in both muscles was observed (about 20%, spectra not shown), which was even more prominent after M (about 50-60%, Fig. 28a). In contrast to this, IMCL were nearly unchanged after HM (Fig. 28b). The mean reduction of IMCL in all subjects is given in Fig. 28c. The studies show that decline of IMCL levels depends on exercise intensity, as a marked decrease in IMCL after exercise of similar duration is only observable at lower aerobic workloads (NCR vs. HM). IMCL reduction also depends on exercise duration, as shown by the greater decline after the marathon run (M = 225 min) compared to the non-competitive exercise bout (NCR =106 min). 

Martin B, Haney R. Self-selected exercise intensity is unchanged by sleep loss. Eur J Appl Physiol 1982 49 79-86. 

ATP yield/mole oxygen CHO > fat Relative Exercise Intensity... 

ADP monitored simultaneously in human gastrocnemius and soleus during three different exercise intensities, 20%, 30%, and 40% of maximum (bars), with rest periods in between and recovery at the end of the protocol. To standardize the data, PCr and ATP are expressed as the ratios of each to the sum of easily MRS-measurable phosphate metabolites [PCr] + [ATP] + [Pi], while ADP is given in molar units, since it is calculated from the CPK equilibrium. Left panels in A, B, and C indicate representative MRS data. Right panels show plots of work intensity (% maximum ATP turnover rate) as the independent parameter and metabolite concentrations at the end of each work bout are plotted as dependent parameters (on the vertical axes). (Modified from Allen et al., 1997.)... 

Mole, P.A., Y. Chung, K. Tran, N. Sailasuta, R. Hurd, and T. Jue (1999). Myoglobin desaturation with exercise intensity in human gastrocnemius muscle. Am. J. Physiol. 277 R173-R180. 

In summary, all mammals possess a large fraction of hlgh-oxl-datlve muscle. The ordered pattern of motor unit recruitment Involves these high oxidative muscle fibers before the low-oxldatlve fibers, as exercise Intensity progresses from mild, to moderate, to severe. This progression favors an enhanced exercise performance at submaxlmal exercise Intensities, since the slow and fast—twitch red fibers are capable of repeated contractions for long periods of time. 

Figure 2. The Influence of exercise intensity (treadmill running) on muscle cytochrome c content in the rat. Red vastus = fast-twitch red fiber section Soleus = slow-twitch red fiber section White vastus = fast-twitch white fiber section. "Reproduced with permission from Ref. 44. Copyright 1982, American Physiological Society. "...

Dudley, G. A., Abraham, W. M. and Terjung, R. L. (1982) Influence of exercise Intensity and duration on biochemical adaptations in skeletal muscle. J. Appl. Physiol. Resplrat. Environ. Exercise Physiol. 53 844-50. 

Subsequently, Dohm et al. (24) demonstrated an increased production of carbon dioxide from leucine during exercise. They found a 50 increase in CO2 production in muscle tissue from trained rats. The study by Dohm et al. (24) utilized a motor-driven treadmill with an eight degree incline and ran the animals at 35 meters per minute for 60 minutes per day, 6 days per week. These experimental conditions produce an exercise intensity of 75-80 of V02i ax program was used for 6 to 8 weeks. 

At low cirabient temperatures a greater portion of the metabolic heat production (depending upon exercise intensity and clothing) is dissipated by convection and radiation and a minor portion by evaporation of sweat and respiratory water. As ambient temperature rises, the portion of heat dissipated by convection and radiation decreases progressively in concert with a proportional increase in the rate of sweating and evaporative heat loss. The coordination of the rate of heat loss between conduction, radiation, and evaporation is so precise that, for ambient dry-bulb temperatures between 5 C and 29 C, the equilibrium level of core (rectal) temperature is related directly to the intensity of the exercise load and is independent of environmental temperature (25). 

Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle. J. Appl. Physiol. 53, 844-850. 

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