Is self-regulation key in reducing running-related injuries and chronic fatigue? A randomized controlled trial among long-distance runners

Figures & data

Figure 1. Participant flow.

Table 1. Baseline characteristics of the intervention and control group.

Characteristic	Intervention	Control	Difference testing^a
	(n = 214)	(n = 211)
Age^bc	46.17 ± 11.53	43.13 ± 11.78	t(423) = −2.70, p = .001
Gender (#)	124 men, 90 women	119 men, 92 women	χ²(1) = 0.10, p = .769
Chronic fatigue^b	2.10 ± 0.56	2.13 ± 0.51	t(423) = −0.46, p = .646
RRIs in past 12 months (%)	56.5%	63.0%	χ²(1) = 1.86, p = .172

^aAs a result of randomization, any significant differences are exclusively the result of chance.

^bDefined as mean ± standard deviation.

^cDefined in years.

Table 2. RRIs, fatigue, and dropout across all time points.

	Proportion of injured runners^a		Chronic fatigue^b		Number of runners^c
Group	Control	Intervention	Control	Intervention	Control	Intervention
	(%)	(%)	M (SD)	M (SD)	n (%)	n (%)
T0^d	63.0	56.5	2.13 (0.51)	2.10 (0.56)	211 (0%)	214 (0%)
T1^e	32.4	34.8	2.16 (0.53)	2.11 (0.52)	170 (19%)	135 (37%)
T2^e	32.7	26.8	2.15 (0.54)	2.14 (0.51)	159 (25%)	123 (43%)
T3^e	32.7	26.7	2.17 (0.60)	2.09 (0.53)	156 (26%)	116 (46%)
T4^e	26.0	32.2	2.16 (0.60)	2.09 (0.52)	154 (27%)	118 (45%)
T5^f	32.3	33.6	2.15 (0.59)	2.11 (0.48)	167 (21%)	131 (39%)

^aThe proportion of runners reporting at least one RRI in the previous period. Note that the periods involved differ per time point, hence causing the “drop” at T1.

^bChronic fatigue is expressed as mean (M) and standard deviation (SD) at the respective time points.

^cThe number of participants (n) and the percentage (%) of dropout per group and time point.

^dBaseline.

^eIntervention periods 1–4.

^fFollow-up.

Table 3. Effect of the intervention on RRIs and chronic fatigue following the intention-to-treat principle.

Intention-to-treat	T1	T2	T3	T4	T5
RRIs
OR	1.499	0.848	0.813	2.144	1.488
CrI^a	[0.696, 3.270]	[0.379, 1.935]	[0.360, 1.899]	[0.931, 4.850]	[0.684, 3.277]
Chronic fatigue
Mean difference	−0.027	−0.011	−0.065	−0.055	−0.040
CrI^a	[−0.108, 0.053]	[−0.096, 0.070]	[−0.151, 0.018]	[−0.138, 0.032]	[−0.121, 0.042]

^aThe lower and upper levels of the credibility interval (CrI) were based on the 95% highest density posterior interval.

Table 4. Intervention group allocation effects across risk profiles of long-distance runners.

	Low-risk profile	Medium-risk profile	High-risk profile
Intervention on chronic fatigue
β [95% CI]	0.11 [−0.20, 0.42]	−0.03 [−0.17, 0.12]	−0.15 [−0.49, 0.18]
B [95% CI]	0.22 [−0.40, 0.83]	−0.05 [−0.33, 0.23]	−0.30 [−0.98, 0.38]
p	.488	.715	.374
Intervention on RRIs
β [95% CI]	0.18 [−0.10, 0.46]	0.03 [−0.12, 0.17]	−0.02 [−0.26, 0.23]
B [95% CI]	0.18 [−0.11, 0.47]	0.03 [−0.12, 0.17]	−0.02 [−0.26, 0.22]
p	.209	.733	.879

Note. Any estimates below zero indicated that runners with the associated risk profile responded more favorably to being allocated to the intervention group (e.g., reporting fewer RRIs than the control group) compared to the overall relation between group allocation and outcomes at T5.