King Grub
2011-05-25, 08:31
Migrating birds have been able to sustain an energy expenditure (EE) that is five times their basal metabolic rate (BMR). While humans can readily reach these levels, it is not yet clear what levels can be sustained for several days.
PURPOSE:
(1) To determine the upper limits of human EE and whether or not those levels can be sustained without inducing catabolism of body tissues, and (2) to determine whether initial body weight is related to the levels that can be sustained.
METHODS:
We compiled data on documented EE as measured by doubly labeled water during high levels of physical activity (minimum of 5 consecutive days). We calculated the physical activity level (PAL) of each individual studied (PAL= total EE/BMR) from the published data. Correlations were run to examine the relationship between initial body weight and body weight lost with both total EE and PAL.
RESULTS:
The upper-most limit of EE was a peak PAL of 6.94 that was sustained for 10 consecutive days of a 95-day race. Only two studies reported PALs above 5.0, however, significant decreases in body mass were found in each study (0.45 to 1.39kg/week of weight loss). To test whether initial weight affects the ability to sustain high PALs, we found a significant positive correlation between TEE and initial body weight (r=0.46, p<0.05), but no correlation between PAL and body weight (r=0.27, ns).
CONCLUSION:
Some elite humans are able to sustain PALs above 5.0 for a minimum of 10 days. Although significant decreases in body weight occur at this level, catabolic of body tissue may be preventable in situations with proper energy intake. Further, initial body weight does not appear to affect the sustainability of PALs.
Med Sci Sports Exerc. 2011 May 20. Maximal Sustained Levels of Energy Expenditure in Humans during Exercise.
PURPOSE:
(1) To determine the upper limits of human EE and whether or not those levels can be sustained without inducing catabolism of body tissues, and (2) to determine whether initial body weight is related to the levels that can be sustained.
METHODS:
We compiled data on documented EE as measured by doubly labeled water during high levels of physical activity (minimum of 5 consecutive days). We calculated the physical activity level (PAL) of each individual studied (PAL= total EE/BMR) from the published data. Correlations were run to examine the relationship between initial body weight and body weight lost with both total EE and PAL.
RESULTS:
The upper-most limit of EE was a peak PAL of 6.94 that was sustained for 10 consecutive days of a 95-day race. Only two studies reported PALs above 5.0, however, significant decreases in body mass were found in each study (0.45 to 1.39kg/week of weight loss). To test whether initial weight affects the ability to sustain high PALs, we found a significant positive correlation between TEE and initial body weight (r=0.46, p<0.05), but no correlation between PAL and body weight (r=0.27, ns).
CONCLUSION:
Some elite humans are able to sustain PALs above 5.0 for a minimum of 10 days. Although significant decreases in body weight occur at this level, catabolic of body tissue may be preventable in situations with proper energy intake. Further, initial body weight does not appear to affect the sustainability of PALs.
Med Sci Sports Exerc. 2011 May 20. Maximal Sustained Levels of Energy Expenditure in Humans during Exercise.