Physical activity buffers fatigue only under low chronic stress

Figures & data

Table 1. Hierarchical linear model predicting momentary fatigue by physical activity, condition, sex and SSCS (n = 33) using restricted maximum likelihood.

Fixed effects	UC	SE	t-ratio
Intercept	1.99	0.13	14.79^a
level 2
Sex	0.05	0.11	0.67
SSCS	0.06	0.01	6.85^a
level 1
Condition	0.48	0.14	3.40^a
Physical activity	<−0.01	<0.01	−0.02
Physical activity × condition	<−0.01	<0.01	−0.14
Cross-level interaction
Physical activity × SSCS	<0.01	<0.01	2.85^b
Random effects	VC	SD	χ²
Intercept	0.13	0.37	136.85^a
Physical activity	<0.01	<0.01	50.90^c
Physical activity × condition	<0.01	<0.01	89.53^a

UC: unstandardized coefficients; SE: standard error; d.f.: degrees of freedom; SD: standard deviation; VC: variance component; SSCS: screening scale for the assessment of chronic stress; condition: 0 – control condition, 1 – examination condition; model controlled for time since awakening,.

^a p < 0.001.

^b p < 0.01.

^c p < 0.05.

Figure 1. Spaghetti plot of average (thick) and subject-specific (dotted) regression lines for momentary fatigue as a function of physical activity counts from the 15 minutes prior to data entry according to chronic stress group (< vs. ≥ a SSCS score of 24, i.e., the threshold of above-average chronic stress); SSCS: Screening Scale for the Assessment of Chronic Stress.

Figure 2. Averaged daily slopes of salivary cortisol (A) and alpha-amylase (B) comparing the control (blank dots) and the exam (filled dots) condition.