Vitamin C status and perception of effort during exercise in obese adults adhering to a calorie-reduced diet.
OBJECTIVE
Moderate energy restriction and exercise are recommended for effective weight loss. Obese individuals oxidize less fat and report a higher perceived exertion during exercise, characteristics that may negatively influence exercise behavior. Because vitamin C status has been linked to fatigability, we compared the effects of vitamin C supplementation on self-reported fatigue and on the respiratory exchange ratio and the Ratings of Perceived Exertion scale during moderate exercise in healthy obese adults adhering to a hypocaloric diet.


METHODS
Twenty adults (4 men and 16 women) were stratified and randomly assigned to receive 500 mg of vitamin C (VC) or placebo (CON) daily for 4 wk while adhering to a vitamin C-controlled, calorie-restricted diet. Feelings of general fatigue as assessed by the Profile of Mood States questionnaire were recorded on a separate day from the exercise session at weeks 0 and 4. Participants walked on a treadmill at an intensity of 50% predicted maximal oxygen consumption for 60 min at weeks 0 and 4, and heart rate, respiratory exchange ratio, and Ratings of Perceived Exertion were recorded.


RESULTS
After 4 wk, the two groups lost similar amounts of weight (≈ 4 kg), and the respiratory exchange ratio was not altered by group. Heart rate and the Ratings of Perceived Exertion during exercise were significantly decreased in the VC versus the CON group (-11 versus -3 beats/min, P = 0.022, and -1.3 versus +0.1 U, P = 0.001, respectively), and the general fatigue score was decreased 5.9 U for the VC group versus a 1.9 U increase for the CON group (P = 0.001).


CONCLUSIONS
These data provide preliminary evidence that vitamin C status may influence fatigue, heart rate, and perceptions of exertion during moderate exercise in obese individuals.
Department of Health Promotion and Human Development, University of Wisconsin, Stevens Point, Wisconsin, USA.
Corey J
CJ
Huck
Carol S
CS
Johnston
Bonnie L
BL
Beezhold
Pamela D
PD
Swan
D000328:Adult; D001205:Ascorbic Acid / Q000008:administration & dosage*; D031204:Caloric Restriction; D019587:Dietary Supplements; D005080:Exercise Test / Q000523:psychology; D005081:Exercise Therapy / Q000523:psychology*; D005221:Fatigue / Q000503:physiopathology / Q000523:psychology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009752:Nutritional Status; D009765:Obesity / Q000178:diet therapy* / Q000503:physiopathology / Q000523:psychology* / Q000628:therapy; D010465:Perception; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D061217:Weight Reduction Programs
D001205:Ascorbic Acid