Morning fatigue and structured exercise interact to affect non-exercise physical activity of fit and healthy older adults

Abstract

Background: Exercise training is crucial for maintaining physical and mental health in aging populations. However, as people participate in structured exercise training, they tend to behaviorally compensate by decreasing their non-exercise physical activity, thus potentially blunting the benefits of the training program. Furthermore, physical activity of older adults is substantially influenced by physical feelings such as fatigue. Nevertheless, how older people react to day-to-day fluctuations of fatigue and whether fatigue plays a role in non-exercise physical activity compensation is not known. Thus, the purpose of this study was twofold: (1) To explore whether the volume and intensity of habitual physical activity in older adults were affected by morning fatigue. (2) To investigate the effect of attending power and resistance exercise sessions on the levels of non-exercise physical activity later that day and the following day.

Methods: Twenty-eight older adults wore an accelerometer during a 4-week low-volume, low-intensity resistance and power training program with three exercise sessions per week and for 3 weeks preceding and 1 week following the program. During the same period, the participants were prompted every morning, using text messages, to rate their momentary fatigue on a scale from 0 to 10.

Results: Greater morning fatigue was associated with lower volume (p = 0.002) and intensity (p = 0.017) of daily physical activity. Specifically, one point greater on the fatigue scale was associated with 3.2 min (SE 1.0) less moderate-to-vigorous physical activity. Furthermore, attending an exercise session was associated with less moderate-to-vigorous physical activity later that day by 3.7 min (SE 1.9, p = 0.049) compared to days without an exercise session. During the next day, the volume of physical activity was greater, but only in participants with a body mass index up to 23 (p = 0.008).

Conclusions: Following low-volume exercise sessions, fit and healthy older adults decreased their non-exercise physical activity later that day, but this compensation did not carry over into the next day. As momentary morning fatigue negatively affects daily physical activity, we suggest that the state level of fatigue should be monitored during intensive exercise programs, especially in less fit older adults with increased fatigability.

Keywords: Accelerometer; Ecological momentary assessment; Intensity gradient; Physical activity compensation; Within-subject analysis.

Fig. 1

Greater morning fatigue is associated with less physical activity later that day. Legend: The effect of greater morning fatigue by 1 point (on a scale from 0 to 10) on physical activity as a function of age and BMI. a The effect on ACC is moderated both by age and body mass index: the lines represent BMI 22, 27, and 32, respectively; (b) The effect on IG is moderated by age. ACC: average acceleration in milligravitational units (mg) represents the volume of physical activity. IG: intensity gradient represents the intensity of physical activity. BMI: body mass index

Fig. 2

Participation in a training session and physical activity during the next day. Legend: The effect of participation in a training session on physical activity during the next day as a function of body mass index. a The effect on ACC; b The effect on minutes of MVPA. The dashed lines represent two standard errors. ACC: average acceleration in milligravitational units (mg) represents the volume of physical activity. MVPA: minutes of moderate to vigorous physical activity. BMI: body mass index