Acute Effects of High-Intensity Interval Exercise While Wearing a Sauna Suit on Energy Expenditure and Excess Post-exercise Oxygen Consumption.

ABSTRACT: Matthews, ARD, Astorino, TA, Crocker, GH, and Sheard, AC. Acute effects of high-intensity interval exercise while wearing a sauna suit on energy expenditure and excess post-exercise oxygen consumption. J Strength Cond Res 36(9): 2427-2433, 2022-The use of sauna suits has increased because of claims that they enhance weight loss and increase body temperature during exercise. Therefore, the purpose of this study was to examine changes in energy expenditure (EE) and excess post-exercise oxygen consumption (EPOC) in response to high-intensity interval exercise (HIIE) while wearing a sauna suit. Twelve recreationally active men and women age = (28.7 ± 6.0 years) initially completed assessment of resting metabolic rate and maximal oxygen uptake. On two separate days, subjects completed HIIE consisting of ten 1-minute intervals at 85% peak power output, both with and without a sauna suit. Oxygen consumption, heart rate, and core temperature were continuously measured during and 1 hour after exercise. Energy expenditure during (285 ± 57 kcal vs. 271 ± 58 kcal) and post-exercise (123 ± 30 kcal vs. 113 ± 16 kcal) was significantly higher ( p = 0.025) with a sauna suit than without a sauna suit. However, EPOC (6.19 ± 4.46 L of O 2 vs. 4.25 ± 3.36 L of O 2 ; p = 0.05) was not significantly different 1 hour after exercise, and core temperature was similar ( p = 0.62) between conditions. Fat oxidation was significantly increased for 60 minutes after HIIE with a sauna suit ( p = 0.009). Wearing a sauna suit during HIIE elicits greater EE vs. not wearing a sauna suit, but the increase of 23 kcal may not benefit weight loss.

Influence of a 2-km Swim on the Cycling Power-Duration Relationship in Triathletes.

ABSTRACT: Rothschild, J, Sheard, AC, and Crocker, GH. Influence of a 2-km swim on the cycling power-duration relationship in triathletes. J Strength Cond Res 36(5): 1431-1436, 2022-Triathletes must cycle after swimming, and so, it is important to understand how cycling performance may be affected by prior swimming. Therefore, the purpose of this study was to determine the effects of a 2-km swim at a self-selected race-pace intensity on the cycling power-duration relationship. Eighteen trained triathletes (12 M, 6 F; 37.1 ± 10.6 years, V̇o2max 54.8 ± 10.1 ml·kg-1·min-1) performed two 3-minute all-out cycling tests (3MTs) on separate days with one 3 MT immediately after a 2-km swim (swim-bike [SB]) and one without prior swimming (bike-only [BO]). The power-duration relationship was expressed as the total work done (TWD) and subdivided into end-test power (EP) and work done above EP. To assess swimming intensity, heart rate (HR) was continuously monitored during the 2-km swim and blood lactate was assessed on completion of the swim. End-swim lactate was 4.2 ± 1.8 mM, and mean swimming HR was 147 ± 18 b·min-1. The 2-km swim decreased TWD during the 3MT by 6% (BO: 62.8 ± 12.7 kJ; SB: 58.9 ± 13.4 kJ; p = 0.001) though neither EP (BO: 281 ± 65 W; SB: 269 ± 68 W; p = 0.102) nor work done above EP (BO: 12.1 ± 3.8 kJ; SB: 10.5 ± 4.2 kJ; p = 0.096) differed between trials. In conclusion, TWD while cycling decreases after a 2-km race-pace swim. Results from this study suggest that triathletes should determine racing cycling power following a simulated race-pace swim.

Change in Exercise Performance and Markers of Acute Kidney Injury Following Heat Acclimation with Permissive Dehydration.

Implementing permissive dehydration (DEH) during short-term heat acclimation (HA) may accelerate adaptations to the heat. However, HA with DEH may augment risk for acute kidney injury (AKI). This study investigated the effect of HA with permissive DEH on time-trial performance and markers of AKI. Fourteen moderately trained men (age and VO2max = 25 ± 0.5 yr and 51.6 ± 1.8 mL.kg-1.min-1) were randomly assigned to DEH or euhydration (EUH). Time-trial performance and VO2max were assessed in a temperate environment before and after 7 d of HA. Heat acclimation consisted of 90 min of cycling in an environmental chamber (40 °C, 35% RH). Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were assessed pre- and post-exercise on day 1 and day 7 of HA. Following HA, VO2max did not change in either group (p = 0.099); however, time-trial performance significantly improved (3%, p < 0.01) with no difference between groups (p = 0.485). Compared to pre-exercise, NGAL was not significantly different following day 1 and 7 of HA (p = 0.113) with no difference between groups (p = 0.667). There was a significant increase in KIM-1 following day 1 and 7 of HA (p = 0.002) with no difference between groups (p = 0.307). Heat acclimation paired with permissive DEH does not amplify improvements in VO2max or time-trial performance in a temperate environment versus EUH and does not increase markers of AKI.

Determining the Optimal Workrate for Cycle Ergometer Verification Phase Testing in Males with Obesity.

The aim of the present study was to assess the validity of verification phase (VP) testing and a 3 min all-out test to determine critical power (CP) in males with obesity. Nine young adult males with a body mass index (BMI) ≥ 30 kg·m-2 completed a cycle ergometer ramp-style VO2max test, four randomized VP tests at 80, 90, 100, and 105% of maximum wattage attained during the ramp test, and a 3 min all-out test. There was a significant main effect for VO2max across all five tests (p = 0.049). Individually, 8 of 9 participants attained a higher VO2max (L/min) during a VP test compared to the ramp test. A trend (p = 0.06) was observed for VO2max during the 90% VP test (3.61 ± 0.54 L/min) when compared to the ramp test (3.37 ± 0.39 L/min). A significantly higher VO2max (p = 0.016) was found in the VP tests that occurred below 130% of CP wattage (N = 15, VO2max = 3.76 ± 0.52 L/min) compared to those that were above (N = 21, VO2max = 3.36 ± 0.41 L/min). Our findings suggest submaximal VP tests at 90% may elicit the highest VO2max in males with obesity and there may be merit in using % of CP wattage to determine optimal VP intensity.

Does sex mediate the affective response to high intensity interval exercise?

High intensity interval exercise (HIIE) is identified as an alternative to moderate intensity continuous exercise (MICE) due to its similar effects on outcomes including maximal oxygen uptake and glycemic control. Nevertheless, its widespread implementation in adults is questioned because acute HIIE elicits more aversive responses (negative affective valence) than MICE which may make it impractical to perform long-term. Differences in muscle mass, fiber type, and substrate utilization exist between men and women that alter physiological responses which may cause differences in affective valence, yet the effect of sex on this outcome is unresolved. This study compared changes in affective valence between active men and women (mean age = 24.0 ±â€¯4.8 yr) performing HIIE and sprint interval exercise (SIE) on a cycle ergometer. Affect (+5 to -5), rating of perceived exertion (RPE 1-10), and blood lactate concentration (BLa) were measured before and throughout exercise, and enjoyment was assessed post-exercise. Results showed that women exhibit more positive affect (p < .05) during HIIE and SIE than men (0.6-1.8 units higher values). In addition, women exhibited lower BLa (p = .003) than men during SIE (11.8 ±â€¯2.4 mM vs. 14.9 ±â€¯3.1 mM). In contrast, there was no effect of sex on RPE (p = .32 and p = .54) or enjoyment (p = .24 and p = .37) in response to HIIE or SIE. Practitioners should consider the sex of their clients when assessing change in affective valence induced by interval-based exercise.

Mitochondrial efficiency and exercise economy following heat stress: a potential role of uncoupling protein 3.

Heat stress has been reported to reduce uncoupling proteins (UCP) expression, which in turn should improve mitochondrial efficiency. Such an improvement in efficiency may translate to the systemic level as greater exercise economy. However, neither the heat-induced improvement in mitochondrial efficiency (due to decrease in UCP), nor its potential to improve economy has been studied. Determine: (i) if heat stress in vitro lowers UCP3 thereby improving mitochondrial efficiency in C2C12 myocytes; (ii) whether heat acclimation (HA) in vivo improves exercise economy in trained individuals; and (iii) the potential improved economy during exercise at altitude. In vitro, myocytes were heat stressed for 24 h (40°C), followed by measurements of UCP3, mitochondrial uncoupling, and efficiency. In vivo, eight trained males completed: (i) pre-HA testing; (ii) 10 days of HA (40°C, 20% RH); and (iii) post-HA testing. Pre- and posttesting consisted of maximal exercise test and submaximal exercise at two intensities to assess exercise economy at 1600 m (Albuquerque, NM) and 4350 m. Heat-stressed myocytes displayed significantly reduced UCP3 mRNA expression and, mitochondrial uncoupling (77.1 ± 1.2%, P < 0.0001) and improved mitochondrial efficiency (62.9 ± 4.1%, P < 0.0001) compared to control. In humans, at both 1600 m and 4350 m, following HA, submaximal exercise economy did not change at low and moderate exercise intensities. Our findings indicate that while heat-induced reduction in UCP3 improves mitochondrial efficiency in vitro, this is not translated to in vivo improvement of exercise economy at 1600 m or 4350 m.