Effect of repeated post-resistance exercise cold or hot water immersion on in-season inflammatory responses in academy rugby players: a randomised controlled cross-over design

Abstract

Purpose: Uncertainty exists if post-resistance exercise hydrotherapy attenuates chronic inflammatory and hormone responses. The effects of repeated post-resistance exercise water immersion on inflammatory and hormone responses in athletes were investigated.

Methods: Male, academy Super Rugby players (n = 18, 19.9 ± 1.5 y, 1.85 ± 0.06 m, 98.3 ± 10.7 kg) participated in a 12-week programme divided into 3 $\times$ 4-week blocks of post-resistance exercise water immersion (either, no immersion control [CON]; cold [CWI]; or hot [HWI] water immersion), utilising a randomised cross-over pre-post design. Fasted, morning blood measures were collected prior to commencement of first intervention block, and every fourth week thereafter. Linear mixed-effects models were used to analyse main (treatment, time) and interaction effects.

Results: Repeated CWI (p = 0.025, g = 0.05) and HWI (p < 0.001, g = 0.62) reduced creatine kinase (CK), compared to CON. HWI decreased (p = 0.013, g = 0.59) interleukin (IL)-1ra, compared to CON. HWI increased (p < 0.001-0.026, g = 0.06-0.17) growth factors (PDGF-BB, IGF-1), compared to CON and CWI. CWI increased (p = 0.004, g = 0.46) heat shock protein-72 (HSP-72), compared to HWI.

Conclusion: Post-resistance exercise CWI or HWI resulted in trivial and moderate reductions in CK, respectively, which may be partly due to hydrostatic effects of water immersion. Post-resistance exercise HWI moderately decreased IL-1ra, which may be associated with post-resistance exercise skeletal muscle inflammation influencing chronic resistance exercise adaptive responses. Following post-resistance exercise water immersion, CWI increased HSP-72 suggesting a thermoregulatory response indicating improved adaptive inflammatory responses to temperature changes, while HWI increased growth factors (PDGF-BB, IGF-1) indicating different systematic signalling pathway activation. Our data supports the continued use of post-resistance exercise water immersion recovery strategies of any temperature during in-season competition phases for improved inflammatory adaptive responses in athletes.

Keywords: Hydrotherapy; Inflammation; Recovery; Strength training; Team sports.

Fig. 1

Study design overview

Fig. 2

Training intervention schedule overview. Resistance exercise day 1 (Table 1), and day 2 (Table 2), was performed each Monday, and Wednesday respectively, prior to the post-exercise treatment intervention strategy (i.e., CON, CWI or HWI)

Fig. 3

Mean ± SD thermal sensation response over time (min post-immersion) pre- (0 min) and per-immersion (1-, 7.5- and 15-min post-immersion) intervention strategy following whole body resistance exercise with either CON (line with unfilled circle n = 17), CWI (hyphen with filled square n = 17), or HWI (hyphen with filled circle n = 15) intervention. Significant main effects were observed for treatment (p < 0.001), time (p < 0.001), and treatment × time interaction effect (p < 0.001) with Tukey-adjusted p-values reporting differences for individual treatment × time pair-wise comparisons at 1-, 7.5- and 15-min following CWI, and HWI, compared to CON condition; ***: p < 0.001 versus CON at pre-immersion baseline; ###:p < 0.001 versus CON within time-point

Fig. 4

Mean (± 95% C.I.) muscle damage, heat shock protein and anti-inflammatory response pre- (white bar) versus post-intervention (grey bar), and mean (± 95% C.I.) pre- minus post-intervention delta ($\mathrm{\Delta }$) (black bar, and individual data points) for CK (panels A, B), HSP-72 (panels C, D) and IL-1ra (panels E, F) following whole body resistance exercise with either control (CON, n = 17), cold (CWI, n = 17) or hot (HWI, n = 15) water immersion as treatment. Significant main effects for treatment were observed in CK (where CON > CWI, p = 0.025, g = 0.05; and CON > HWI, p < 0.001, g = 0.62) and HSP-72 (where CWI > HWI, p = 0.004, g = 0.46); Significant main effects for treatment were observed in IL-1ra (where CON > HWI, p = 0.013, g = 0.59); *: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001

Fig. 5

Mean (± 95% C.I.) growth factor responses pre- (white bar) versus post-intervention (grey bar), and mean (± 95% C.I.) pre- minus post-intervention delta ($\mathrm{\Delta }$) (black bar, and individual data points) for IGF-1 (panels A, B) and PDGF-BB (panels C, D) following whole body resistance exercise with either control (CON, n = 17), cold (CWI, n = 17) or hot (HWI, n = 15) water immersion as treatment. Significant main effects for treatment were observed in IGF-1 (where HWI > CON, p = 0.001, g = 0.06; and HWI > CWI, p < 0.001, g = 0.11) and PDGF-BB (where HWI > CON, p = 0.026, g = 0.17); *: p ≤ 0.05, ***: p ≤ 0.001

Fig. 6

Mean and individual (open circles) hormone responses pre- (white bar) versus post-intervention (grey bar), and mean (± 95% C.I.) pre- minus post-intervention delta (black bar) for testosterone (panel A, B), cortisol (panel C, D) and TC ratio (panel E, F) following whole body resistance exercise with either control (CON, n = 17), cold (CWI, n = 17) or hot (HWI, n = 15) water immersion as treatment. Significant main effects for treatment were observed in testosterone (where HWI > CON, p = 0.012); *: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001, ****: p ≤ 0.0001