Immersion with menthol improves recovery between 2 cycling exercises in hot and humid environment

Abstract

Endurance exercise performance is impaired in a hot and humid environment. This study compared the effects of cold water immersion, with (CMWI) and without (CWI) menthol, on the recovery of cycling performance. Eight heat-acclimatized cyclists (age, 24.1 ± 4.4 years; mass, 65.3 ± 5.2 kg) performed 2 randomized sessions, each consisting of a 20-min cycling trial (T1) followed by 10 min of immersion during recovery and then a second 20-min cycling trial (T2). Mean power output and perceived exertion (RPE) were recorded for both trials. Rectal (T) and skin temperatures were measured before and immediately after T1, immersion, and T2. Perceived thermal sensation (TS) and comfort were measured immediately after T1 and T2. Power output was significantly improved in T2 compared with T1 in the CMWI condition (+15.6%). Performance did not change in the CWI condition. After immersion, T was lower in CWI (-1.17 °C) than in CMWI (-0.6 °C). TS decreased significantly after immersion in both conditions. This decline was significantly more pronounced in CMWI (5.9 ± 1 to 3.6 ± 0.5) than in CWI (5.6 ± 0.9 to 4.4 ± 1.2). In CMWI, RPE was significantly higher in T1 (6.57 ± 0.9) than in T2 (5.14 ± 1.25). However, there was no difference in TC. This study suggests that menthol immersion probably (i) improves the performance of a repeated 20-min cycling bout, (ii) decreases TS, and (iii) impairs thermoregulation processes.

Menthol can be safely applied to improve thermal perception during physical exercise: a meta-analysis of randomized controlled trials

“…By screening on title and abstract, further 72 records were excluded from the analysis because (1) the required outcome parameters were not reported, (2) menthol-treated or control group was absent, (3) not only healthy participants were recruited, and (4) no original data was reported. The full texts of 22 articles were reviewed in detail, from which 17 papers provided eligible data for qualitative and quantitative analyses 13,14,17,18,[20][21][22][23][24][25][26][27][28][29][30][31]41 . All included studies had randomized, crossover design and included data from a total of 177 athletes.…”

“…The majority of the studies was conducted in males, except for an article which included participants of both sexes 31 and possibly another one which did not report the sex ratio in the sample 26 . In 12 trials, the participants were refrained from strenuous exercise, alcohol and caffeine intake before the experiments 13,14,[20][21][22][23]25,[27][28][29][30]41 , two studies included unspecified training limitations 18,24 , and three articles did not report any limitations 17,26,31 .…”

“…The TS-decreasing effect of menthol differed significantly (p < 0.001) between the two subgroups. We also analysed whether the menthol-induced improvements in TS and TC are associated with an increased power output (an indicator of exercise intensity) during physical exercise and found that the power output remained higher in the menthol-treated groups compared to controls in all of the individual studies 18,28,30 , and accordingly, their overall average was also higher by a WMD of 31.52 W (95% CI, 22.52 to 40.53 W) ( Fig. 4).…”

“…There were inter-study differences in the design of the analysed studies regarding, for example, the sample population, the menthol administration route and dose, the exercise protocol, and the measurement of the outcome parameters. For example, the assessment of power output differed in the three analysed studies 18,28,30 . The study with the biggest effect size showed a significant improvement in power output 18 , whereas power output did not differ statistically between the menthol-treated and control groups in either of the studies with smaller effect size 57,58 .…”

“…For example, the assessment of power output differed in the three analysed studies 18,28,30 . The study with the biggest effect size showed a significant improvement in power output 18 , whereas power output did not differ statistically between the menthol-treated and control groups in either of the studies with smaller effect size 57,58 . Based on the risk of bias assessment, we found that blinding was not feasible in many studies, because of the characteristic odour of menthol.…”