Gender-Specific Usage of Intramyocellular Lipids and Glycogen during Exercise

Sep 24, 2005Medicine and science in sports and exercise

Differences between men and women in muscle fat and sugar use during exercise

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Abstract

In a 3-hour endurance exercise, intramyocellular lipid (IMCL) depletion was significantly higher in males compared with females.

Average fat oxidation rates were similar between genders, while carbohydrate oxidation was significantly higher in males.
Both males and females depleted their IMCL and glycogen stores significantly during the exercise.
Males had significantly higher IMCL levels at rest and experienced greater depletion of IMCL during exercise compared to females.
Glycogen storage and utilization were comparable between genders.
The similar overall energy contribution from fat and carbohydrates suggests that exercise duration may influence substrate utilization.

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PURPOSE: Gender-specific differences in substrate utilization during exercise have been reported, typically such that women rely more on fat than men. This study investigated whether gender differences exist in the utilization of intramyocellular lipids (IMCL) and glycogen.

METHODS: IMCL and glycogen, as well as total fat and carbohydrate (CHO) oxidation were measured in nine males and nine females before, during, and after an endurance exercise. The trained subjects exercised on a bicycle ergometer at 50% maximal workload for 3 h. IMCL and glycogen were determined in the thigh by magnetic resonance spectroscopy. Oxygen uptake (VO(2)) and carbon dioxide production were determined by open circuit spirometry to calculate total fat and CHO oxidation. Relative power output, percent of maximum heart rate, VO(2peak), and respiratory exchange ratio were the same.

RESULTS: Average fat oxidation was the same, whereas CHO oxidation was significantly higher in males compared with females. The relative contribution of these fuels to total energy used were similar in males and females. Males and females depleted IMCL and glycogen significantly (P < 0.001) during the 3-h exercise. IMCL levels at rest (P < 0.05) and its depletion during exercise (P < 0.001) were significantly higher in males compared with females, whereas glycogen was stored and used in the same range by both genders.

CONCLUSION: During this 3-h exercise, energy supplies from fat and CHO were similar in both genders, and males as well as females reduced their IMCL stores significantly. The larger contribution of IMCL during exercise in males compared with females could either be a result of gender-specific substrate selection, or different long-term training habit.

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Gender-Specific Usage of Intramyocellular Lipids and Glycogen during Exercise

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