Cardio-respiratory responses to moderately heavy aerobic exercise during the Ramadan fasts

OBJECTIVE: The aim of this study was to quantify the magnitude of the cardiovascular and respiratory changes that occur during the month of Ramadan in response to moderately heavy aerobic physical exertion.

METHODS: Eighteen sedentary Kuwaiti adult males were tested under thermo-neutral conditions during a spring-like month of Ramadan and one month thereafter.

RESULTS: There were no significant changes in maximal exercise capacity, treadmill walking efficiency, percentage VO2 max, in body weight and composition associated with Ramadan fasting or one month after. Cardiac (heart rate) and ventilatory responses to moderately intense bouts of sub-maximal aerobic exercise (70% of VO2 max) were actually slightly (<5%) but significantly (P<0.05) reduced, while exercise systolic but not diastolic pressure increased slightly (6%) by the end of Ramadan.

CONCLUSION: Hormonal changes associated with dehydration or fasting, abstention from consumption of substances with negative inotropy and changes in circadian rhythms during Ramadan may be responsible for these mild changes in cardiorespiratory responses to exercise. Such changes had no negative effect on the physical aerobic performance of these subjects while exercising at moderately heavy intensity under thermally neutral conditions, during the month of Ramadan. Reduced ventilation during exercise may reflect a limited glycolytic capacity by the end of Ramadan.