Table 3.

Hierarchical multiple regression analyses predicting sleep and psychological functioning at follow-up with baseline scores of sleep and psychological functioning, social and demographic background, self-reported PA, and personal beliefs about sufficient PA as predictor variables.

Predictor	Insomnia (T2)		Sleep quality (T2)		Sleep-onset latency (T2)		Number of awakenings (T2)		Depressive symptoms (T2)		Quality of life (T2)		Perceived stress (T2)		Mental toughness (T2)
	ΔR2	β	ΔR2	β	ΔR2	β	ΔR2	β	ΔR2	β	ΔR2	β	ΔR2	β	ΔR2	β
Step 1	0.307***		0.182***		0.192***		0.116***		0.173***		0.255***		0.303***		0.246***
Baseline level (T1)		0.51***		0.40***		0.43***		0.33***		0.38***		0.48***		0.53***		0.47***
Step 2	0.021***		0.011***		0.007		0.012*		0.012*		0.011*		0.010*		0.007
School (T1)		−0.07*		0.01		−0.06		−0.10**		−0.08**		0.10**		−0.02		0.04
Gender (T1)		−0.06*		0.02		−0.03		−0.03		0.01		−0.03		−0.06		0.01
Age (T1)		0.06*		0.03		0.02		−0.10		0.02		0.04		0.00		0.03
Family financial situation (T1)		0.02		0.08*		0.02		0.00		−0.04		0.01		−0.04		0.05
BMI (T1)		0.06*		−0.04		−0.03		0.02		0.011		−0.03		0.06		−0.02
Step 3	0.001		0.000		0.001		0.003		0.004*		0.002		0.001		0.004*
Self-reported PA (T1)		−0.02		0.01		−0.03		−0.06		−0.06*		0.03		−0.03		0.06*
Step 4	0.004*		0.004*		0.000		0.001		0.007**		0.003*		0.000		0.004*
Personal beliefs about sufficient PA (T1)		−0.07*		0.07*		−0.01		0.03		−0.09**		0.07*		−0.02		0.07*
Total R2	0.333***		0.197***		0.200***		0.122***		0.189***		0.262***		0.314***		0.259***

Note: No significant interactions were found between self-reported PA and personal beliefs about sufficient PA; therefore, no interaction effects between these 2 variables are reported.

*p < 0.05, **p < 0.01, ***p < 0.001.

Abbreviations: BMI = body mass index; PA = physical activity; T1 = baseline; T2 = follow-up.