Cardiopulmonary Demand of 16-kg Kettlebell Snatches in Simulated Girevoy Sport.

Chan, M, MacInnis, MJ, Koch, S, MacLeod, KE, Lohse, KR, Gallo, ME, Sheel, AW, and Koehle, MS. Cardiopulmonary demand of 16-kg kettlebell snatches in simulated Girevoy Sport. J Strength Cond Res 34(6): 1625-1633, 2020-Kettlebell lifting has become popular both as a strength and conditioning training tool and as a sport in and of itself: Girevoy Sport (GS). Although several kettlebell multimovement protocols have been analyzed, little research has attempted to quantify the aerobic stimulus of the individual events in GS, which could better inform kettlebell-related exercise prescription. The purpose of this study was to quantify the cardiopulmonary demand, assessed primarily by oxygen consumption (V[Combining Dot Above]O2) and heart rate (HR), of continuous high-intensity kettlebell snatches-under conditions relevant to GS-and to compare this demand with a more traditional graded rowing ergometer maximal exercise test. Ten male participants (age = 28.4 ± 4.6 years, height = 185 ± 7 cm, body mass = 95.1 ± 14.9 kg) completed (a) a graded-exercise test on a rowing ergometer to determine maximal oxygen consumption (V[Combining Dot Above]O2max) and maximal heart rate (HRmax) and (b) a graded-exercise test consisting of continuous 16-kg kettlebell snatches to determine peak oxygen consumption (V[Combining Dot Above]O2peak) and peak heart rate (HRpeak) during a simulated GS snatch event. Subjects achieved a V[Combining Dot Above]O2max of 45.7 ± 6.7 ml·kg·min and HRmax of 177 ± 8.3 b·min on the rowing ergometer. The kettlebell snatch test produced a V[Combining Dot Above]O2peak of 37.6 ± 4.4 ml·kg·min (82.7 ± 6.5% V[Combining Dot Above]O2max) and a HRpeak of 174 ± 10 b·min (98.0 ± 3.4% HRmax). These findings suggest that GS kettlebell snatches with 16-kg can provide an adequate aerobic stimulus to improve cardiorespiratory fitness in those with a V[Combining Dot Above]O2max of ≤51 ml·kg·min, according to aerobic training recommendations from the American College of Sports Medicine.

Acute Beetroot Juice Supplementation Does Not Improve Cycling Performance in Normoxia or Moderate Hypoxia.

Beetroot juice (BR) has been shown to lower the oxygen cost of exercise in normoxia and may have similar effects in hypoxia. We investigated the effect of BR on steady-state exercise economy and 10-km time trial (TT) performance in normoxia and moderate hypoxia (simulated altitude: ~2500 m). Eleven trained male cyclists (VO 2peak ≥ 60 ml · kg(-1) · min(-1)) completed four exercise trials. Two hours before exercise, subjects consumed 70 mL BR (~6 mmol nitrate) or placebo (nitrate-depleted BR) in a randomized, double-blind manner. Subjects then completed a 15-min self-selected cycling warm-up, a 15-min steady-state exercise bout at 50% maximum power output, and a 10-km time trial (TT) in either normoxia or hypoxia. Environmental conditions were randomized and single-blind. BR supplementation increased plasma nitrate concentration and fraction of exhaled nitric oxide relative to PL (p < .05 for both comparisons). Economy at 50% power output was similar in hypoxic and normoxic conditions (p > .05), but mean power output was greater in the normoxic TT relative to the hypoxic TT (p < .05). BR did not affect economy, steady-state SpO2, mean power output, or 10-km TT completion time relative to placebo in either normoxia or hypoxia (p > .05 in all comparisons). In conclusion, BR did not lower the oxygen cost of steady-state exercise or improve exercise performance in normoxia or hypoxia in a small sample of well-trained male cyclists.

Methods to Estimate V˙O2max upon Acute Hypoxia Exposure.

INTRODUCTION: Altitude and an individual's V˙O2max contribute to a decrease in V˙O2max under hypoxic conditions. The purpose of this study was to update previous reviews with recent research in order to quantitatively determine the individual and interacting effects of altitude and baseline V˙O2max on V˙O2max upon acute exposure to hypoxia while developing a statistical model to predict an individual's V˙O2max under hypoxic conditions. METHODS: Meta-regression was conducted on 105 independent groups of participants (n = 958 subjects from 80 different studies). A series of regression models was tested. The final model included altitude, baseline V˙O2max, Alt2, baseline V˙O2max2, and the interaction of altitude with baseline V˙O2max. RESULTS: A curvilinear model provided the best fit for metadata, explaining almost 80% of the variance in the null model. Nonlinear effects of Alt2 (ß = -0.078; 95% confidence interval, -0.15 to -0.002) and baseline V˙O2max2 (ß = -0.003; 95% confidence interval, -0.004 to -0.001) showed that V˙O2max decreases as altitude increases and that the decrease is greater in individuals with higher aerobic capacities. The interaction of these effects (ß = -0.028; 95% confidence interval, -0.042 to -0.015) also showed that the effects of altitude were augmented with higher baseline aerobic capacities. Furthermore, the predictions of the model were fairly accurate in predicting individual decreases in V˙O2max (root-mean-squared error, 3.9 mL·kg(-1)·min(-1)). CONCLUSIONS: These data provide a robust quantitative framework for the curvilinear and interacting effects of altitude and baseline V˙O2max in determining an individual's effective V˙O2max at altitude. This predictive model is useful for a priori power calculations, design of future experimental studies, and prediction of aerobic capacity declines in applied settings.

Acute mountain sickness is not repeatable across two 12-hour normobaric hypoxia exposures.

OBJECTIVE: The purposes of this experiment were to determine the repeatability of acute mountain sickness (AMS), AMS symptoms, and physiological responses across 2 identical hypoxic exposures. METHODS: Subjects (n = 25) spent 3 nights at simulated altitude in a normobaric hypoxia chamber: twice at a partial pressure of inspired oxygen (PIO2) of 90mmHg (4000 m equivalent; "hypoxia") and once at a PIO2 of 132 mmHg (1000 m equivalent; "sham") with 14 or more days between exposures. The following variables were measured at hours 0 and 12 of each exposure: AMS severity (ie, Lake Louise score [LLS]), AMS incidence (LLS ≥3), heart rate, oxygen saturation, blood pressure, and the fraction of exhaled nitric oxide. Oxygen saturation and heart rate were also measured while subjects slept. RESULTS: The incidence of AMS was not statistically different between the 2 exposures (84% vs 56%, P > .05), but the severity of AMS (ie, LLS) was significantly lower on the second hypoxic exposure (mean [SD], 3.1 [1.8]) relative to the first hypoxic exposure (4.8 [2.3]; P < .001). Headache was the only AMS symptom to have a significantly greater severity on both hypoxic exposures (relative to the sham exposure, P < .05). Physiological variables were moderately to strongly repeatable (intraclass correlation range 0.39 to 0.86) but were not associated with AMS susceptibility (P > .05). CONCLUSIONS: The LLS was not repeatable across 2 identical hypoxic exposures. Increased familiarity with the environment (not acclimation) could explain the reduced AMS severity on the second hypoxic exposure. Headache was the most reliable AMS symptom.

Twin studies in altitude and hypoxia research.

Humans exhibit high individual variation in response to acute hypoxia exposure. A number of published studies have used a classic 'twin study' model, comparing responses within pairs of monozygotic and dizygotic twins, to separate genetic from environmental contributions to the variation in altitude acclimatization. Available data suggest that some aspects of acclimatization have a heritable component. Most prominent is the hypoxic ventilatory response (HVR), which was repeatedly shown to be heritable in a number of age groups spanning infancy to adulthood (F-ratio range: 2.03 to 5.26). The ventilatory response to hypercapnia appears to only be heritable when tested in hypoxic conditions, providing additional evidence for a genetic component to the HVR (F-ratio range: 0.31, 6.92). A number of studies reported an estimate of heritability for more general hypoxic responses, such as heart rate, blood pressure, and blood gases; however, many of these studies relied on relatively small sample sizes and used inaccurate estimates of heritability and thus provided inconclusive evidence to elucidate the source of variation. Future genetic inquiries into the basis of variation in altitude acclimatization might benefit from further use of the classic twin study model: these experiments could identify the specific endophenotypes of altitude acclimatization that are heritable and therefore promising candidates for subsequent molecular studies, such as candidate-gene or genome-wide association studies.