Effects of Cooling and Magnesium Supplementation on the Objective and Subjective Outcomes of Acute High-Intensity Rowing

Abstract

Background: Body temperature and level of magnesium in the body can be important factors affecting the level of exercise activities. However, beneficial effects of body cooling and magnesium supplementation on acute high-intensity exercises have not yet been studied in large number of athletes. We hypothesized that cooling interventions and supplementation of magnesium will improve both objective and subjective outcomes of acute high-intensity exercises. Subjects and Methods: Twenty-four athletes with different backgrounds of sports were recruited (n = 24, all males; age 25 ± 4 years; weight 76 ± 10 kg; height 175 ± 5 cm). Indoor rowing was used as acute high-intensity exercise. Subjects were evenly and independently assigned to four groups, namely, (1) Group C: control group, (2) Group HC: hand cooling intervention (HC), (3) Group WBC: whole-body cryotherapy intervention, and (4) Group MgS: magnesium supplementation. Each group had three measurements: before exercise, during acute high-intensity 1000 m open-end rowing, and in the recovery period. During rowing, the power output and speed values were collected at every 200 m. Before and after rowing, the following six parameters were collected; objective outcomes: ammonia (NH3) and lactate (La) of blood plasma, heart rate (HR), whole-body temperature (TW), and subjective outcome: rate of perceived exertion (RPE) by standard questionnaire, and self-rated perception of thermal sensation (TS). Results: HC, MgS and WBC (which significantly lowered TW as compared to other groups (p < 0.05), but it did not elicit significant changes in the measured parameters (such as La, NH3, HR, RPE, rowing power, and rowing speed). In terms of TS, as the subjective outcome, we observed positive effects in response to all three interventions of HC, WBC, and MgS compared to Group C. We also observed a slight, yet significant difference of the RPE between interventions of HC and WBC. Conclusions: Data show that whole-body cryotherapy lowers body temperature and together with magnesium supplementation – without affecting objective outcomes - improve the thermal sensation. Thus, we propose that cooling intervention and magnesium supplementation - in certain conditions - can enhance output of acute high-intensity exercise, especially in warm environment. Abbreviations: HC - hand cooling; WBC - whole-body cryotherapy; La - lactate; NH3 - blood ammonia; HR - heart rate; TS - thermal sensation; RPE - rate of perceived exertion; TW - whole-body temperature