The ideal exercise time of day (ETOD) remains elusive regarding simultaneous effects on health and performance outcomes, especially in women. The timing to schedule a work out remains a controversial topic, with some investigators favoring morning exercise to enhance muscle adaptations and fuel utilization whereas, others have shown afternoon/evening exercise is most favorable to improve muscle function. In either case, research exploring potential effects of exercise time of day (ETOD) on training-induced adaptations remains to be fully chartered within multiple domains of “real-life” applicability, warranting examination.
Over the last decade, increasing attention has focused on healthy lifestyle routines that are multimodal (i.e., resistance, high intensity intervals, stretching/flexibility, and endurance training). Prior research has demonstrated that training programs which combine resistance and endurance exercises are more effective in improving body composition than either training modality alone. In addition to traditional resistance and endurance exercise, other routines are gaining in popularity, including stretching exercises such as yoga, tai chi, Pilates, and interval sprint training. The American College of Sports Medicine (ACSM) has historically recommended moderate intensity physical aerobic activity but also includes resistance, flexibility, and neuromotor training exercises, though more recent guidelines suggest that inclusion of higher intensity interval training may result in more favorable cardiometabolic adaptations than traditional moderate-intensity aerobic training protocols.
But what is the best time to exercise? In women, researchers found that both AM and PM exercise significantly reduced total body fat, along with abdominal and hip fat. However, the magnitude of improvement was significantly greater in AM exercisers for the reduction of abdominal fat and blood pressure, along with increased lower body muscle power. Meanwhile, evening exercise significantly enhanced muscular performance, which included greater gains in upper body muscle strength, power, endurance and improved mood. These findings provide support for exercise-trained women to perform a multi-model exercise training regimen (RISE) in the morning to optimize total body and abdominal fat loss, lowering of blood pressure, and increasing lower body muscular power, whereas exercise in the evening may provide improvements in upper body muscular performance, and possibly mood enhancement.
Meanwhile, in men, total body fat mass and abdominal and hip fat decreased for both AM and PM participants. However, evening exercise increased fat oxidation and reduced systolic blood pressure, HDL cholesterol and fatigue. For exercise-trained men, multi-modal evening exercise may be more advantageous to reduce blood pressure and fatigue, as well as to maximally stimulate fat oxidation.
Thus, women and men respond differently to Exercise Time of Day (ETOD), and therefore, careful attention should be used in matching physical performance, cardiometabolic, and psychological mood state goals with the scheduling of multi-modal exercise training to optimize results. Exercising at the same time of day, regardless of whether it is during the morning, afternoon, or evening, may help with achieving higher levels of physical activity.
In conclusion, a morning work out for women, enhances total and abdominal fat loss, reduces blood pressure, and increases lower body muscle power, whereas, evening exercise greatly increases upper body muscle strength, power, and endurance, and enhances overall mood. For men, evening exercise lowers systolic blood pressure and fatigue, and stimulates fat oxidation compared to early morning exercise.