Dexamethasone improves maximal exercise capacity of individuals susceptible to high altitude pulmonary edema at 4559 m

We have previously demonstrated that prophylactic intake of dexamethasone improves maximal oxygen uptake (Vo(2)max) in high altitude pulmonary edema (HAPE) susceptible subjects 4 to 6 h after a 2-day climb to 4559 m. However, since with this ascent protocol HAPE usually develops after the first night at 4559 m or later, we hypothesized that a continued dexamethasone prophylaxis would result in an even more pronounced improvement of Vo(2)max after an additional night at high altitude. Vo(2)max of 24 HAPE susceptibles was evaluated on a bicycle ergometer at an altitude of 490 m and at 24 h after rapid ascent to 4559 m. Subjects were divided into two groups: The control group (n=14) performed both tests without dexamethasone, whereas the dexamethasone group (n=10) received dexamethasone 8 mg twice a day (b.i.d), starting 24 h prior to ascent. At 4559 m, Vo(2)max was 61% ± 6% of the baseline value in the control group and 70% ± 9% in the dexamethasone group (p=0.025). Similarly, O(2) pulse (Vo(2)/heart rate) was 68% ± 7% and 77% ± 11% of baseline, respectively (p=0.043). Arterial O(2) saturation at maximal exercise did not differ between groups, whereas at rest it was 83% ± 10% in the control group and 91% ± 4% in the dexamethasone group (p=0.009). Dexamethasone prophylaxis increased Vo(2)max of HAPE-susceptible individuals after the first night at 4559 m without affecting arterial O(2) saturation at maximal exercise. This might be explained by a sustained effect of dexamethasone on maximal cardiac output and pulmonary O(2) diffusion, both resulting in enhanced convectional O(2) transport to the locomotor muscles.     

Physiological adjustments of facial cooling during exercise

Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% VO2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10 degrees C, 4.6 M.S-1). Facial cooling at the end of greated maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (VO2 max), maximal heart rate (HR max), rectal temperature (Tre), work load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.     

Maximal lactate steady state is altered in the heat

The aim of this study was to compare the maximal lactate steady state (MLSS) and ventilatory threshold (VT) under different environments (TEMP: 22°C; and HOT: 40°C; 50% RH). 8 male subjects (age 23.9±2.4 years, body mass 75.9±7.3?kg and VO2(max) 47.8±4.9?mL·kg(-1)·min(-1)) performed a series of tests to determine the peak workload (W(peak)), VT and MLSS on a cycle ergometer. W(peak) was higher in the TEMP as compared to the HOT condition (225±9?W vs. 195±8?W, respectively; p<0.05). The workload at MLSS was higher at 22°C (180±11?W) than 40°C (148±11?W; p<0.05), as well as VT at 22°C (156±9?W) was higher than 40°C (128±6?W). Likewise, the blood lactate concentration at MLSS was higher at 22°C (5.60±0.26?mM) than 40°C (4.22±0.48?mM; p<0.05). The mean of heart rate (HR) was not statistically different between TEMP (168±3?bpm) and HOT (173±3?bpm) at MLSS, despite being different at trials between the 25(th) and the 30(th)?min of exercise. The HR at VT was significantly higher in HOT (153±4?bpm) as compared to the TEMP (145±2?bpm). Our results suggest that environmental conditions may influence the determination of MLSS and VT. Moreover, VT was appropriate for estimation of the workload at MLSS in the HOT.     

Intermittent hypobaric hypoxia induces altitude acclimation and improves the lactate threshold

The physiological responses to short-term intermittent exposure to hypoxia in a hypobaric chamber were evaluated. The exposure to hypoxia was compatible with normal daily activity. The ability of the hypoxia program to induce hematological and ventilatory adaptations leading to altitude acclimation and to improve physical performance capacity was tested. Six members of a high-altitude expedition were exposed to intermittent hypoxia and low-intensity exercise (in cycle-ergometer) in the INEFC-UB hypobaric chamber over 17 d, 3-5 h x d(-1), at simulated altitude of 4,000 m to 5,500 m. Following this hypoxia exposure program, significant increases were found in packed cell volume (41 to 44.6%; p<0.05), red blood cells count (4.607 to 4.968 10(6) cells x microL(-1); p<0.05), and hemoglobin concentration (14.8 to 16.4 g x dL(-1); p<0.05), thus implying an increase in the blood oxygen transport capacity. Significant differences in exercise blood lactate kinetics and heart rate were also observed. The lactate vs. exercise load curve shifted to the right and heart rate decreased, thus indicating an improvement of aerobic endurance. These results were associated with a significant increase in the ventilatory anaerobic threshold (p<0.05). Significant increases (p<0.05) in pulmonary ventilation, tidal volume, respiratory frequency, O2 uptake, CO2 output and ventilatory equivalents to oxygen (VE/Vo2) and carbon dioxide (VE/co2) were observed at the ventilatory threshold and within the transitional zone of the curves. We conclude that short-term intermittent exposure to moderate hypoxia, in combination with low-intensity exercise in a hypobaric chamber, is sufficient to improve aerobic capacity and to induce altitude acclimation.     

Changes in ventilatory threshold at high altitude: effect of antioxidants

PURPOSE: To investigate the effects of prolonged hypoxia and antioxidant supplementation on ventilatory threshold (VT) during high-altitude (HA) exposure (4300 m). METHODS: Sixteen physically fit males (25 +/- 5 yr; 77.8 +/- 8.5 kg) performed an incremental test to maximal exertion on a cycle ergometer at sea level (SL). Subjects were then matched on VO2peak, ventilatory chemosensitivity, and body mass and assigned to either a placebo (PL) or antioxidant (AO) supplement group in a randomized, double-blind manner. PL or AO (12 mg of beta-carotene, 180 mg of alpha-tocopherol acetate, 500 mg of ascorbic acid, 100 mug of selenium, and 30 mg of zinc daily) were taken 21 d prior to and for 14 d at HA. During HA, subjects participated in an exercise program designed to achieve an energy deficit of approximately 1400 kcal.d(-1). VT was reassessed on the second and ninth days at HA (HA2, HA9). RESULTS: Peak power output (Wpeak) and VO2peak decreased (28%) in both groups upon acute altitude exposure (HA2) and were unchanged with acclimatization and exercise (HA9). Power output at VT (WVT) decreased from SL to HA2 by 41% in PL, but only 32% in AO (P < 0.05). WVT increased in PL only during acclimatization (P < 0.05) and matched AO at HA9. Similar results were found when VT was expressed in terms of % Wpeak and % VO2peak. CONCLUSIONS: VT decreases upon acute HA exposure but improves with acclimatization. Prior AO supplementation improves VT upon acute, but not chronic altitude exposure.     

The effects of physical fitness and body composition on oxygen consumption and heart rate recovery after high-intensity exercise

The aim of this study was to investigate the potential relationship between excess post-exercise oxygen consumption (EPOC), heart rate recovery (HRR) and their respective time constants (tvo2 and t HR) and body composition and aerobic fitness (VO2max) variables after an anaerobic effort. 14 professional cyclists (age=28.4±4.8 years, height=176.0±6.7 cm, body mass=74.4±8.1 kg, VO2max=66.8±7.6 mL·kg - 1·min - 1) were recruited. Each athlete made 3 visits to the laboratory with 24 h between each visit. During the first visit, a total and segmental body composition assessment was carried out. During the second, the athletes undertook an incremental test to determine VO2max. In the final visit, EPOC (15-min) and HRR were measured after an all-out 30 s Wingate test. The results showed that EPOC is positively associated with % body fat (r=0.64), total body fat (r=0.73), fat-free mass (r=0.61) and lower limb fat-free mass (r=0.55) and negatively associated with HRR (r= - 0.53, p<0.05 for all). HRR had a significant negative correlation with total body fat and % body fat (r= - 0.62, r= - 0.56 respectively, p<0.05 for all). These findings indicate that VO2max does not influence HRR or EPOC after high-intensity exercise. Even in short-term exercise, the major metabolic disturbance due to higher muscle mass and total muscle mass may increase EPOC. However, body fat impedes HRR and delays recovery of oxygen consumption after effort in highly trained athletes.     

高原环境对阿莫西林药代参数的影响研究

目的探讨急进高原后大鼠体内阿莫西林药代动力学参数的变化。方法Wistar大鼠于平原地区和急进高原后灌胃给药,分别于给药前（0h）及给药后0．33、0．66、1、1．5、2、3、4、6、8、12、24h采血,采用LC—MS／MS方法测定血药浓度,并分别计算蛋白结合率和药代动力学参数。结果急进高原组血浆蛋白结合率（45．oo％）与平原组血浆蛋白结合率（36．31％）相比显著升高,药一时曲线下面积从（11616．40±1071．92）μg·L^-1·h增大到（47879．24±9417．18）μg·L^-1·h,急进高原后体内平均驻留时间延长,峰浓度增大,清除率降低。结论统计学分析结果显示急进高原后,阿莫西林在大鼠体内药代动力学参数发生显著变化,为进一步研究人体药代动力学提供实验基础和参考依据。     

Comparison of exercise responses of males and females during acute exposure to hypobaria

Seventeen male and 20 female college students were tested on a bicycle ergometer in a hypobaric chamber to determine whether both sexes had similar submax and max exercise responses to acute hypoxia. Initial testing was at a terrestrial altitude of 1576 m, to which the subjects were acclimated; subsequent tests were at simulated altitudes of 2743 m and 3962 m. Analysis of covariance showed that inspired V was the only variable during submaximal work (50% max) to exhibit a significant difference in altitude response between males and females; women had a smaller increase than men. During max work, V and O2 pulse increased less in women. At 2743 m, max VO2 decreased more in females whereas, at 3962 m, no difference was noted. It was concluded that during both submaximal and maximal work with acute altitude exposure, women would demonstrate smaller relative increases in ventilation than would men.     

Cardiac output differences in males and females during mild cycle ergometer exercise.

To study sex differences in cardiac output during submaximum exercise, eight male and eight female subjects were matched on max Vo2 (1 min-1 and ml kg-1 min-1). Each subject performed one, eight minute submaximum bicycle ergometer test at 35% of Vo2max (300 kpm min-1). At a steady state mean Vo2 of 0.96 1 min-1, cardiac output was determined. Significant differences between men and women were observed (p less than .05) in cardiac output, stroke volume and (a-v) O2 difference. The males had a lower cardiac output (1.75 1 min-1) and stroke volume (17.2 ml beat-1) and a higher (a-v) O2 difference (2.01 vol %). When these variables were expressed independent of lean body weight the above differences were non-significant. It was suggested that cardiac output differences between the sexes during mild exercise are due, in part, to differences in lean body weight.     

急进高原前后战士无氧阈的调查研究

报道60名新兵空运进驻3680m 前后通气无氧阈(ATGE)测定结果。受试者进入高原初期,负荷运动达无氧阈时,负荷功率和摄氧量均降低,心率升高;达最大负荷运动时,负荷功率,摄氧量和心率均降低,通气量升高。进驻高原前后各参数均存在显著性差异(P<0.01)。研究认为,ATGE 是很有价值而可靠的心肺功能评价指标,尤以 ATGE(负荷功率)最为敏感,其次为 ATGE(Vo2)。     

平原人进驻海拔4370m高原后无氧阈的改变

本文观察了14名平原人进驻高原后气体交换无氧阈(AT_(GE))的改变。从中看到,达海拔4370m 高原后第3、5、7和14天,与到高原前比,AT_(GE)分别下降36.5%、32.4%、40.0%和39.0%(P<0.01),并十分接近在此海拔高度上最大氧耗量下降的经验值(34.0%)。平原人达高原后AT_(GE)下降的百分比与入高原前AT_(GE)呈正相关(r=0.851),P<0.01),在平原AT_(GE)较高者,达高原后AT_(GE)下降较多。还在同地观察了8名久居一年的平原人的AT_(GE),与平原对照值比,仍减少25.4%。上述结果表明,平原人进驻高原后,AT_(GE)明显下降,在短时间里尚不能恢复到平原时水平。AT_(GE)作为高原劳动能力评价指标是有应用意义的。     

Effect of acute hypoxia on maximal oxygen uptake and maximal performance during leg and upper-body exercise in Nordic combined skiers

We examined the effect of normobaric hypoxia (3200 m) on maximal oxygen uptake (VO2max) and maximal power output (Pmax) during leg and upper-body exercise to identify functional and structural correlates of the variability in the decrement of VO2max (DeltaVO2max) and of maximal power output (DeltaPmax). Seven well trained male Nordic combined skiers performed incremental exercise tests to exhaustion on a cycle ergometer (leg exercise) and on a custom built doublepoling ergometer for cross-country skiing (upper-body exercise). Tests were carried out in normoxia (560 m) and normobaric hypoxia (3200 m); biopsies were taken from m. deltoideus. DeltaVO2max was not significantly different between leg (-9.1+/-4.9%) and upper-body exercise (-7.9+/-5.8%). By contrast, Pmax was significantly more reduced during leg exercise (-17.3+/-3.3%) than during upper-body exercise (-9.6+/-6.4%, p<0.05). Correlation analysis did not reveal any significant relationship between leg and upper-body exercise neither for DeltaVO2max nor for DeltaPmax. Furthermore, no relationship was observed between individual DeltaVO2max and DeltaPmax. Analysis of structural data of m. deltoideus revealed a significant correlation between capillary density and DeltaPmax (R=-0.80, p=0.03), as well as between volume density of mitochondria and DeltaPmax (R=-0.75, p=0.05). In conclusion, it seems that VO2max and Pmax are differently affected by hypoxia. The ability to tolerate hypoxia is a characteristic of the individual depending in part on the exercise mode. We present evidence that athletes with a high capillarity and a high muscular oxidative capacity are more sensitive to hypoxia.     

Is ventilatory anaerobic threshold a good index of endurance capacity?

This study was undertaken to assess whether ventilatory anaerobic threshold (T vent) reflected endurance capacity (EC) in sports medical control. Fifteen subjects performed two cycle ergometer tests. The first was a maximal exercise test, which consisted of increasing the load 20 W/min until exhaustion. During this test, the gas exchange anaerobic threshold was determined and VO2 max was measured. The second was an endurance exercise test, which consisted of asking the subject to work, as long as possible, a load representing 80% of his maximal aerobic power. During this test, we measured endurance time (ET). The statistical analysis showed the lack of relationship between VO2 max and ET and the linear correlations between VO2 T vent ml/min/kg and ET min (r = 0.521, P less than 0.05), VO2 T vent l/min and ET min (r = 0.524, P less than 0.05), and T vent % VO2 max and ET (r = 0.738, P less than 0.01). These results establish that ventilatory anaerobic threshold actually reflects endurance capacity. This relation can be explained referring to the muscle energetic metabolism during exercise. Therefore, T vent should be determined systematically in addition to VO2 max during maximal exercise tests to better evaluate physical fitness.     

Comparison of metabolic, temperature, heart rate and ventilatory responses to exercise at extreme ambient temperatures (0 degrees and 35 degrees C.).

Eight male subjects exercised on a bicycle ergometer for one half to one hour at loads demanding 52 to 59% of Vo2max on two separate occasions, once with ambient temperature held at 0 degrees C and once in a 35 degrees C environment. Throughout exercise and during recovery in a 25 degrees C environment, measurements were made of oxygen consumption, ventilation, heart rate, muscle-rectal-skin temperatures, and blood lactic acid. In the hot condition significant increases in heart rate, blood lactates, sweat loss, muscle, rectal and skin temperature responses were observed. At 0 degrees C Vo2 was significantly elevated during exercise over that in the 35 degrees C condition. Despite the elevated Vo2 response in the cold, higher body temperatures measured in the heat were associated with a significantly higher (P less than .025) recovery Vo2 (x = 866 ml), which was of the magnitude predicted by the van't Hoff-Arrhenius relationship.     

Effects of preexercise feedings on endurance performance

Eight male and female students were studied during exercise to exhaustion on a bicycle ergometer at 80 and 100% of Vo2max following the ingestion of water (W), 75 g of glucose (G) or a liquid meal (M) (10 g protein, 12.5 g fat, 15 g CHO). When compared to the endurance ride (80% Vo2max) in the W treatment, endurance performance time was reduced by 19%, (p less than .05) (53.2 to 43.2 min) as a result of the preexercise glucose feeding (Trial G). No difference in performance at 80% Vo2max was found between the W and M trials. The preexercise feedings had no effect on exercise time to exhaustion at 100% Vo2max. During the G and M trials at 80% Vo2max, most of the subjects demonstrated a transient decline in serum glucose (less than 3.5 mM). After 30-40 min. of exercise, however, serum glucose returned to normal and was seldom low at the time of exhaustion. Serum free fatty acids (FFA) were depressed throughout the G trial. The results of these experiments indicate impaired lipid mobilization following CHO ingestion. The present data support our earlier findings (11) which demonstrate that glucose feedings 30-45 minutes before endurance exercise increase the rate of CHO oxidation and impede the mobilization of FFA, thereby reducing exercise time to exhaustion.     

摄取NaHCO_3对渐增负荷运动时血浆胺和乳酸浓度的影响

本研究的目的是调查在渐增负荷运动中，血浆胺和血浆乳酸浓度是否受细胞外液碱中毒的影响，以及乳酸阈（ＬＴ）和通气闲（ＶＴ）也是否受其影响；８名受试者采用功率自行车进行渐增负荷运动，直至力竭。同时测定吸氧量（ＶＯ２）、通气量（ＶＥ）、血浆乳酸、血浆胺、血液ｐＨ、ＨＣＯ３－及心率（ＨＲ）。受试者在两种条件下进行实验：（１）每公斤体重摄取０．３ａＮａＨＣＯｄ３（碱中毒组：Ａ）；（２）摄取安慰胶囊组（Ｐ）。运动前后的血液ｐＨ和ＨＣＯ３－均有显著性差异。Ａ组与Ｐ组相比较，运动负荷时间及ＶＯ２ｍａｘ无显著性差异（ｐ＞０．０５）。Ｐ组ＬＴ时的ＶＯ２与ＶＴ相比较，无显著性差异（ｐ＞０．０５），但Ａ组ＬＴ时的ＷＯ２与ＶＴ相比较，却有显著性差异（ｐ＜０．０５）。Ａ组和Ｐ组ＶＴ时的ＶＯ２相比较，无显著性差异（ｐ＞０．０５），但两组ＬＴ时的ＶＯ２相比较，有显著性差异（ｐ＜０．０５。Ａ组ＬＴ明显低于Ｐ组，反映了在运动中大量乳酸由肌肉进入血液。Ａ组和Ｐ组的血浆胺阈（ＡＭＴ）相比较，无显著性差异（ｐ＞０．０５），研究证明细胞外碱中毒影响ＬＴ而不影响ＡＭＴ，使ＬＴ和ＶＴ分离，从而影响ＬＴ的确定。     

Short‐term cardiorespiratory adaptation to high altitude in children compared with adults

As short‐term cardiorespiratory adaptation to high altitude (HA) exposure has not yet been studied in children, we assessed acute mountain sickness (AMS), hypoxic ventilatory response (HVR) at rest and maximal exercise capacity (CPET) at low altitude (LA) and HA in pre‐pubertal children and their fathers. Twenty father–child pairs (11 ± 1 years and 44 ± 4 years) were tested at LA (450 m) and HA (3450 m) at days 1, 2, and 3 after fast ascent (HA1/2/3). HVR was measured at rest and CPET was performed on a cycle ergometer. AMS severity was mild to moderate with no differences between generations. HVR was higher in children than adults at LA and increased at HA similarly in both groups. Peak oxygen uptake (VO₂peak) relative to body weight was similar in children and adults at LA and decreased significantly by 20% in both groups at HA; maximal heart rate did not change at HA in children while it decreased by 16% in adults (P < 0.001). Changes in HVR and VO₂peak from LA to HA were correlated among the biological child–father pairs. In conclusion, cardiorespiratory adaptation to altitude seems to be at least partly hereditary. Even though children and their fathers lose similar fractions of aerobic capacity going to high altitude, the mechanisms might be different.     

The effect of normoxic or hypobaric hypoxic endurance training on the hypoxic ventilatory response.

Cross-sectional studies in endurance athletes have demonstrated a diminished hypoxic ventilatory response (HVR) compared with mountaineers or sedentary controls. Conversely, short-term altitude acclimatization may increase the HVR. The longitudinal effect of training, either at sea level or altitude, on HVR has not been previously reported. We therefore studied 21 untrained men and women before and after 5 wk of cycle ergometer training at either sea level or 2,500 m. HVR was determined using the steady-state method (16). Minute ventilation (VE) was measured with a Tissot spirometer during the last minute of 5 min breathing room air, 8% and 12% O2, administered in random order. CO2 was added at the mouth in an effort to maintain end-tidal CO2 at baseline levels. Oxyhemoglobin saturation was measured directly from arterial blood with a hemoximeter (OSM 3). HVR was defined as the positive slope of the line relating VE to O2 saturation in l.min-1%-1. One group of subjects trained at sea level at 70% maximal oxygen uptake (VO2max; N = 7). A second group trained at 2,500 m in a hypobaric chamber, at the same relative exercise intensity (i.e., 70% altitude VO2max) or same absolute intensity (same power output) as group 1 (N = 14). Both groups trained on a bicycle ergometer for 45 min.d-1, 5 d.wk-1 for 5 wk.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of high- and low-intensity exercise training on aerobic capacity and blood lipids

Sixteen non-obese, non-smoking males, ages 20-30 yr, were assigned to one of two training groups, exercising on a cycle ergometer 3 d/wk for 18 wk: high-intensity (H; N = 7; 80-85% Vo2max, 25 min/session) or low-intensity (L; N = 9; 45% VO2max, 50/min/session). Data were obtained at 3-wk intervals for Vo2max, body weight, percent body fat, and 12-h fasting blood levels of cholesterol (CHOL), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). The average post-training increase in VO2max for group H (0.56 l X min-1, 8.5 ml X min-1 X kg-1) was not significantly (P greater than 0.05) greater than for group L (0.45 l X min-1, 6.5 ml X min-1 X kg-1). Significant reductions in percent body fat occurred in both groups, amounting to an average fat loss of approximately 1.35 kg. No statistically significant changes in CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, or HDL-C/LDL-C occurred in either group. However, changes in HDL-C after 18 wk of training were inversely correlated (r = -0.57, P less than 0.05) with pre-training levels. We conclude that 1) the minimum exercise training-intensity threshold for improving aerobic capacity is at least 45% Vo2max; 2) 18 wk of high- or low-intensity exercise training is ineffective in significantly altering CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, and HDL-C/LDL-C in young male subjects with low blood lipid levels, and 3) exercise training-induced changes in HDL-C are dependent upon initial pre-training levels.     

Gross efficiency and energy expenditure in kayak ergometer exercise

We purposed to study energy expenditure, power output and gross efficiency during kayak ergometer exercise in 12 elite sprint kayakers. 6 males (age 24.2±4.8 years, height 180.4±4.8 cm, body mass 79.7±8.5 kg) and 6 females (age 24.3±4.5 years, height 164.5±3.9 cm, body mass 65.4±3.5 kg), performed an incremental intermittent protocol on kayak ergometer with VO2 and blood lactate concentration assessment, a non-linear increase between power output and energy expenditure being observed. Paddling power output, energy expenditure and gross efficiency corresponding to VO2max averaged 199.92±50.41 W, 75.27±6.30 ml.kg - 1.min - 1, and 10.10±1.08%. Male kayakers presented higher VO2max, power output and gross efficiency at the VO2max, and lower heart rate and maximal lactate concentration than females, but no differences were found between genders regarding energy expenditure at VO2max. Aerobic and anaerobic components of energy expenditure evidenced a significant contribution of anaerobic energy sources in sprint kayak performance. Results also suggested the dependence of the gross efficiency on the changes in the amount of the aerobic and anaerobic contributions, at heavy and severe intensities. The inter-individual variance of the relationship between energy expenditure and the corresponding paddling power output revealed a relevant tracking for females (FDγ=0.73±0.06), conversely to the male group (FDγ=0.27±0.08), supporting that some male kayakers are more skilled in some paddling intensities than others.