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Two studies were conducted to examine the effects of ice slushy ingestion (ICE) and cold water immersion (CWI) on thermoregulatory and sweat responses during constant (study 1) and self-paced (study 2) exercise. In study 1, 11 men cycled at 40–50% of peak aerobic power for 60 min (33.2 ± 0.3C, 45.9 ± 0.5% relative humidity, RH). In study 2, 11 men cycled for 60 min at perceived exertion (RPE) equivalent to 15 (33.9 ± 0.2C and 42.5 ± 3.9%RH). In both studies, each trial was preceded by 30 min of CWI (~22C), ICE or no cooling (CON). Rectal temperature (T re ), skin temperature (T sk ), thermal sensation, and sweat responses were measured. In study 1, ICE decreased T re- T sk gradient versus CON (p = 0.005) during first 5 min of exercise, while CWI increased T re- T sk gradient versus CON and ICE for up to 20 min during the exercise (p0.05). Increased T re -T sk gradient by CWI improved MPO while ICE reduced T re but did not confer any ergogenic effect. Both precooling treatments attenuated the thermal efferent signals until a specific body temperature threshold was reached. © 2019 Choo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This study compared the effect of passive rest (CON) and water immersion at 8.6±0.2°C (CWI9), 14.6±0.3°C (CWI15) and 35.0±0.4°C (thermoneutral water immersion [TWI]) on post-exercise heart rate variability (HRV) indices. In a climate chamber (32.8±0.4°C, 32±5% relative humidity), nine men completed 25 min of cycling at the first ventilatory threshold and repeated 30-second bouts at 90% of peak power followed by a 5-minute recovery treatment in a randomised crossover manner. All water immersion re-established the HRV indices (natural logarithm of the square root of the mean sum squared differences between RR intervals [ln rMSSD], low-frequency [lnLF] and high-frequency power densities [lnHF] and Poincaré plotderived measures [lnSD1 and lnSD2]) to the pre-exercise levels at 60 min post-immersion; however, only CWI9 accelerated parasympathetic reactivation during immersion. CWI9 increased lnLF and lnSD2 during immersion when compared with CON (p<.05). Although CWI9 had a large positive effect size (ES>0.80) on all HRV indices during immersion when compared with CON, between-conditions differences were observed only in lnLF and lnSD2 (p=.017-.023). CWI15 had a large positive ES on ln rMSSD and lnSD1 when compared with CON (both p=.064). Sympathovagal antagonism (i.e., SD ratio<0.15) did not occur during CWI9 and CWI15. Hence, both CWI treatments are effective means of enhancing post-exercise parasympathetic reactivation, but CWI9 is likely to be more effective at increasing post-exercise cardiac vagal tone.

This study investigated the effect of regular postexercise cold water immersion (CWI) on muscle aerobic adaptations to endurance training. Eight males performed 3 sessions/wk of endurance training for 4 wk. Following each session, subjects immersed one leg in a cold water bath (10°C; COLD) for 15 min, while the contralateral leg served as a control (CON). Muscle biopsies were obtained from vastus lateralis of both CON and COLD legs prior to training and 48 h following the last training session. Samples were analyzed for signaling kinases: p38 MAPK and AMPK, peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), enzyme activities indicative of mitochondrial biogenesis, and protein subunits representative of respiratory chain complexes I–V. Following training, subjects' peak oxygen uptake and running velocity were improved by 5.9% and 6.2%, respectively (P < 0.05). Repeated CWI resulted in higher total AMPK, phosphorylated AMPK, phosphorylated acetyl-CoA carboxylase, β-3-hydroxyacyl-CoA-dehydrogenase and the protein subunits representative of complex I and III (P < 0.05). Moreover, large effect sizes (Cohen's d > 0.8) were noted with changes in protein content of p38 (d = 1.02, P = 0.064), PGC-1α (d = 0.99, P = 0.079), and peroxisome proliferator-activated receptor α (d = 0.93, P = 0.10) in COLD compared with CON. No differences between conditions were observed in the representative protein subunits of respiratory complexes II, IV, and V and in the activities of several mitochondrial enzymes (P > 0.05). These findings indicate that regular CWI enhances p38, AMPK, and possibly mitochondrial biogenesis.

A reduction in body temperature is considered to be the primary mechanism by which cold water immersion (CWI) enhances short-term (h) recovery and improves exercise capacity in the heat. However, improvement in exercise performance may be optimised at a given cooling magnitude. Water temperature and immersion duration influence the magnitude of cooling in the core body, muscle and skin. Given the role of blood flow in convective heat flux, substrate delivery and metabolic waste clearance, it is important to understand the influence of different water temperatures on compartmental distribution of limb blood flow during CWI. Therefore, the purpose of this study was to compare blood flow changes in the common femoral artery, vastus lateralis muscle, and thigh skin induced by 5 min of post-exercise water immersion at 8°C, 14°C, 35°C or passive rest. In a randomised manner, nine recreationally active men performed exhaustive cycling in a climate control chamber (32.8 ± 0.4°C and 32 ± 5%rh), followed by 5 min of water immersion at 8.6 ± 0.2°C (WI8), 14.6 ± 0.3°C (WI14), 35.0 ± 0.4°C (WI35) or passive rest (CON). The exercise task involved 25 min of cycling at a power output equivalent to first ventilatory threshold, followed by high-intensity intermittent cycling (30 s at 90% of peak power output to 30 s at 70 W). Measurement of blood flow in thigh skin (laser Doppler flowmetry), vastus lateralis muscle (near infrared spectroscopy), and common femoral artery (Doppler ultrasound), heart rate, mean arterial pressure, skin, muscle, rectal, and mean body temperatures were obtained prior to exercise and up to 60 min post-immersion. Both WI14 and WI8 reduced mean body, calf and thigh skin, and muscle temperatures, compared with WI35 and CON (p0.05). Relative to pre-immersion, differences were observed in the magnitude of reduction between skin, muscle, and common femoral blood flow. Decreases in muscle and skin blood flow were similar (p>0.05), but to a lesser extent when compa

Choo, H. C., Nosaka, K., Peiffer, J. J., Ihsan, M., & Abbiss, C. R. (2018). Ergogenic effects of precooling with cold water immersion and ice ingestion: A meta-analysis. European journal of sport science, 18(2), 170-181. doi:here.

Choo, H. C., Peiffer, J. J., Pang, J. W., Tan, F. H., Aziz, A. R., Ihsan, M., ... Abbiss, C. R. (2020). Effect of regular precooling on adaptation to training in the heat. European Journal of Applied Physiology, 120, 1143-1154. https://doi.org/10.1007/s00421-020-04353-1

Ihsan, M., Tan, F., Sahrom, S., Choo, H. C., Chia, M., & Aziz, A. R. (2017). Pre-game perceived wellness highly associates with match running performances during an international field hockey tournament. European Journal of Sport Science, 17(5), 593-602. Available here

Choo, H. C., Peiffer, J. J., Lopes-Silva, J. P., Mesquita, R. N. O., Amano, T., Kondo, N., & Abbiss, C. R. (2019). Effect of ice slushy ingestion and cold water immersion on thermoregulatory behavior. PLoS ONE, 14(2). Available here

Choo, H. C., Nosaka, K., Peiffer, J. J., Ihsan, M., Yeo, C. C., & Abbiss, C. R. (2018). Effect of water immersion temperature on heart rate variability following exercise in the heat. Kinesiology, 50, 67-74. Available here

Lopes-Silva, J. P., Choo, H. C., Franchini, E., & Abbiss, C. R. (2019). Isolated ingestion of caffeine and sodium bicarbonate on repeated sprint performance: A systematic review and meta-analysis. Journal of Science and Medicine in Sport, 22, 962-972. Available here

Choo, H. C., Nosaka, K., Peiffer, J. J., Ihsan, M., Yeo, C. C., & Abbiss, C. R. (2017). Reliability of laser Doppler, near-infrared spectroscopy and Doppler ultrasound for peripheral blood flow measurements during and after exercise in the heat. Journal of Sports Sciences, 35(17), 1715-1723. Available here

Choo, H. C., Nosaka, K., Peiffer, J. J., Ihsan, M., Yeo, C. C. and Abbiss, C. R. (2017), Peripheral blood flow changes in response to postexercise cold water immersion. Clinical Physiology and Functional Imaging. 38(1), 46-55. Available here