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1.
High Intensity Interval Training (HIIT) can be performed with different effort to rest time-configurations, and this can largely influence training responses. The purpose of the study was to compare the acute physiological responses of two HIIT and one moderate intensity continuous training (MICT) protocol in young men. A randomised cross-over study with 10 men [age, 28.3?±?5.5years; weight, 77.3?±?9.3?kg; height, 1.8?±?0.1?m; peak oxygen consumption (VO2peak), 44?±?11?mL.kg?1.min?1]. Participants performed a cardiorespiratory test on a treadmill to assess VO2peak, velocity associated with VO2peak (vVO2peak), peak heart rate (HRpeak) and perceived exertion (RPE). Then participants performed three protocols equated by distance: Short HIIT (29 bouts of 30s at vVO2peak, interspersed by 30s of passive recovery, 29?min in total), Long HIIT (3 bouts of 4?min at 90% of vVO2peak, interspersed by 3?min of recovery at 60% of vVO2peak, 21?min in total) and MICT (21?min at 70% of vVO2peak). The protocols were performed in a randomised order with ≥48 h between them. VO2, HRpeak and RPE were compared. VO2peak in Long HIIT was significantly higher than Short HIIT and MICT (43?±?11 vs 32?±?8 and 37?±?8?mL.kg?1.min?1, respectively, P?P?P?2, HR and RPE than Short HIIT and MICT, suggesting a higher demand on the cardiorespiratory system. Short HIIT and MICT presented similar physiologic and perceptual responses, despite Short HIIT being performed at higher velocities.  相似文献   

2.
This study compared the effects of 12-week sprint interval training (SIT), high-intensity interval training (HIIT), and moderate-intensity continuous training (MICT) on cardiorespiratory fitness (V?O2peak), body mass and insulin sensitivity in overweight females. Forty-two overweight women (age 21.2 ± 1.4 years, BMI 26.3 ± 2.5 kg·m?2) were randomized to the groups of SIT (80 × 6-s sprints + 9-s rest), and isoenergetic (300KJ) HIIT (~9 × 4-min cycling at 90% V?O2peak + 3-min rest) and MICT (cycling at 60% V?O2peak for ~ 61-min). Training intervention was performed 3 d·week?1 for 12 weeks. After intervention, all three groups induced the same improvement in V?O2peak (~ +25%, p < 0.001) and a similar reduction in body mass (~ – 5%, p < 0.001). Insulin sensitivity and fasting insulin levels were improved significantly on post-training measures in SIT and HIIT by ~26% and ~39% (p < 0.01), respectively, but remain unchanged in MICT. In contrast, fasting glucose levels were only reduced with MICT (p < 0.01). The three training strategies are equally effective in improving V?O2peak and reducing body mass, however, the SIT is time-efficient. High-intensity training (i.e. SIT and HIIT) seems to be more beneficial than MICT in improving insulin sensitivity.

Abbreviations: BMI: body mass index; CVD: cardiovascular disease; HIEG: hyperinsulinaemic euglycaemic glucose; HIIT: high-intensity interval training; HOMA-IR: homeostasis model assessment of insulin resistance; HR: heart rate; MICT: moderate-intensity continuous training; RPE: ratings of perceived exertion; SIT: sprint interval training; T2D: type 2 diabetes; V?O2peak: peak oxygen consumption  相似文献   


3.
Background: High-intensity interval training (HIIT) has been shown to improve cardiometabolic health during supervised lab-based studies but adherence, enjoyment, and health benefits of HIIT performed independently are yet to be understood. We compared adherence, enjoyment, and cardiometabolic outcomes after 8 weeks of HIIT or moderate-intensity continuous training (MICT), matched for energy expenditure, in overweight and obese young adults. Methods: 17 adults were randomized to HIIT or MICT. After completing 12 sessions of supervised training over 3 weeks, participants were asked to independently perform HIIT or MICT for 30 min, 4 times/week for 5 weeks. Cardiometabolic outcomes included cardiorespiratory fitness (VO2 peak), lipids, and inflammatory markers. Exercise enjoyment was measured by the validated Physical Activity Enjoyment Scale. Results: Exercise adherence (93.4?±?3.1% vs. 93.1?±?3.7%, respectively) and mean enjoyment across the intervention (100.1?±?4.3 vs. 100.3?±?4.4, respectively) were high, with no differences between HIIT and MICT (p?>?.05). Similarly, enjoyment levels did not change over time in either group (p?>?.05). After training, HIIT exhibited a greater decrease in low-density lipoprotein cholesterol than MICT (?0.66?mmol?L?1 vs. ?0.03?mmol?L?1, respectively) and a greater increase in VO2 peak than MICT (p?<?.05, +2.6?mL?kg?min?1 vs. +0.4?mL?kg?min?1, respectively). Interleukin-6 and C-reactive protein increased in HIIT (+0.5?pg?mL?1 and +?31.4?nmol?L?1, respectively) and decreased in MICT (?0.6?pg?mL?1 and ?6.7?nmol?L?1, respectively, p?<?.05). Conclusions: Our novel findings suggest that HIIT is enjoyable and has high unsupervised adherence rates in overweight and obese adults. However, HIIT may be associated with an increase in inflammation with short-term exercise in this population.  相似文献   

4.
Abstract

It has been shown that the critical power (CP) in cycling estimated using a novel 3-min all-out protocol is reliable and closely matches the CP derived from conventional procedures. The purpose of this study was to assess the predictive validity of the all-out test CP estimate. We hypothesised that the all-out test CP would be significantly correlated with 16.1-km road time-trial (TT) performance and more strongly correlated with performance than the gas exchange threshold (GET), respiratory compensation point (RCP) and V?O2 max. Ten club-level male cyclists (mean±SD: age 33.8±8.2 y, body mass 73.8±4.3 kg, V?O2 max 60±4 ml·kg?1·min?1) performed a 10-mile road TT, a ramp incremental test to exhaustion, and two 3-min all-out tests, the first of which served as familiarisation. The 16.1-km TT performance (27.1±1.2 min) was significantly correlated with the CP (309±34 W; r=?0.83, P<0.01) and total work done during the all-out test (70.9±6.5 kJ; r=?0.86, P<0.01), the ramp incremental test peak power (433±30 W; r=?0.75, P<0.05) and the RCP (315±29 W; r=?0.68, P<0.05), but not with GET (151±32 W; r=?0.21) or the V?O2 max (4.41±0.25 L·min?1; r=?0.60). These data provide evidence for the predictive validity and practical performance relevance of the 3-min all-out test. The 3-min all-out test CP may represent a useful addition to the battery of tests employed by applied sport physiologists or coaches to track fitness and predict performance in atheletes.  相似文献   

5.
Abstract

The present study aimed to establish whether 2 weeks of high-intensity interval training would have a beneficial effect on aerobic fitness, fat oxidation, blood pressure and body mass index (BMI) in healthy adolescent boys. Ten adolescent boys (15.1 ± 0.3 years, 1.3 ± 0.2 years post-estimated peak height velocity) completed six sessions of Wingate-style high-intensity interval training over a 2-week period. The first session consisted of four sprints with training progressed to seven sprints in the final session. High-intensity interval training had a beneficial effect on maximal O2 uptake (mean change, ±90% confidence intervals: 0.19 L · min?1, ±0.19, respectively), on the O2 uptake at the gas exchange threshold (0.09 L · min?1, ±0.13) and on the O2 cost of sub-maximal exercise (–0.04 L · min?1, ±0.04). A beneficial effect on the contribution of lipid (0.06 g · min?1, ±0.06) and carbohydrate (–0.23 g · min?1, ±0.14) oxidation was observed during sub-maximal exercise, but not for the maximal rate of fat oxidation (0.04 g · min?1, ±0.08). Systolic blood pressure (1 mmHg, ±4) and BMI (0.1 kg · m2, ±0.1) were not altered following training. These data demonstrate that meaningful changes in health outcomes are possible in healthy adolescent boys after just six sessions of high-intensity interval training over a 2-week period.  相似文献   

6.
ABSTRACT

High-intensity interval training (HIIT) has been proposed as a time-efficient exercise protocol to improve metabolic health, but direct comparisons with higher-volume moderate-intensity continuous training (MICT) under unsupervised settings are limited. This study compared low-volume HIIT and higher-volume MICT interventions on cardiometabolic and psychological responses in overweight/obese middle-aged men. Twenty-four participants (age: 48.1±5.2yr; BMI: 25.8±2.3kg·m?2) were randomly assigned to undertake either HIIT (10 X 1-min bouts of running at 80–90% HRmax separated by 1-min active recovery) or MICT (50-min continuous jogging/brisk walking at 65–70% HRmax) for 3 sessions/week for 8 weeks (2-week supervised + 6-week unsupervised training). Both groups showed similar cardiovascular fitness (VO2max) improvement (HIIT: 32.5±5.6 to 36.0±6.2; MICT: 34.3±6.0 to 38.2±5.1mL kg?1 min?1, p < 0.05) and %fat loss (HIIT: 24.5±3.4 to 23.2±3.5%; MICT: 23.0±4.3 to 21.5±4.1%, p< 0.05) over the 8-week intervention. Compared to baseline, MICT significantly decreased weight and waist circumference. No significant group differences were observed for blood pressure and cardiometabolic blood markers such as lipid profiles, fasting glucose and glycated haemoglobin. Both groups showed similar enjoyment levels and high unsupervised adherence rates (>90%). Our findings suggest that low-volume HIIT can elicit a similar improvement of cardiovascular fitness as traditional higher-volume MICT in overweight/obese middle-aged men.  相似文献   

7.
This study compares test-retest reliability and peak exercise responses from ramp-incremented (RAMP) and maximal perceptually-regulated (PRETmax) exercise tests during arm crank exercise in individuals reliant on manual wheelchair propulsion (MWP). Ten untrained participants completed four trials over 2-weeks (two RAMP (0–40 W + 5–10 W · min?1) trials and two PRETmax. PRETmax consisted of five, 2-min stages performed at Ratings of Perceived Exertion (RPE) 11, 13, 15, 17 and 20). Participants freely changed the power output to match the required RPE. Gas exchange variables, heart rate, power output, RPE and affect were determined throughout trials. The V?O2peak from RAMP (14.8 ± 5.5 ml · kg?1 · min?1) and PRETmax (13.9 ± 5.2 ml · kg?1 · min?1) trials were not different (P = 0.08). Measurement error was 1.7 and 2.2 ml · kg?1 · min?1 and coefficient of variation 5.9% and 8.1% for measuring V?O2peak from RAMP and PRETmax, respectively. Affect was more positive at RPE 13 (P = 0.02), 15 (P = 0.01) and 17 (P = 0.01) during PRETmax. Findings suggest that PRETmax can be used to measure V?O2peak in participants reliant on MWP and leads to a more positive affective response compared to RAMP.  相似文献   

8.
Abstract

Graded exercise tests are commonly used to assess peak physiological capacities of athletes. However, unlike time trials, these tests do not provide performance information. The aim of this study was to examine the peak physiological responses of female outrigger canoeists to a 1000-m ergometer time trial and compare the time-trial performance to two graded exercise tests performed at increments of 7.5 W each minute and 15 W each two minutes respectively. 17 trained female outrigger canoeists completed the time trial on an outrigger canoe ergometer with heart rate (HR), stroke rate, power output, and oxygen consumption ([Vdot]O2) determined every 15 s. The mean (± s) time-trial time was 359 ± 33 s, with a mean power output of 65 ± 16 W and mean stroke rate of 56 ± 4 strokes · min?1. Mean values for peak [Vdot]O2, peak heart rate, and mean heart rate were 3.17 ± 0.67 litres · min?1, 177 ± 11 beats · min?1, and 164 ± 12 beats · min?1 respectively. Compared with the graded exercise tests, the time-trial elicited similar values for peak heart rate, peak power output, peak blood lactate concentration, and peak [Vdot]O2. As a time trial is sport-specific and can simultaneously quantify sprint performance and peak physiological responses in outrigger canoeing, it is suggested that a time trial be used by coaches for crew selection as it doubles as a reliable performance measure and a protocol for monitoring peak aerobic capacity of female outrigger canoeists.  相似文献   

9.
Purpose: Critical power (CP) from the 3-min test was compared to the power outputs associated with thresholds determined from gas exchange parameters that have been used to demarcate the exercise-intensity domains including the respiratory compensation point (RCP), gas exchange threshold (GET), and ventilatory threshold (VT). Method: Twenty-eight participants performed an incremental-cycle ergometer test to exhaustion. The VT was determined from the relationship between the ventilatory equivalent for oxygen uptake (V˙E/V˙O2) versus V˙O2 and the GET was determined using the V-slope method (V˙CO2 vs. V˙O2). The RCP was identified from the V˙E-versus-V˙CO2 relationship. CP was the average power output during the last 30 s of the 3-min all-out test. Linear regression was used to determine the power outputs associated with the RCP, GET, and VT, as well as the V˙O2 associated with CP. Mean differences among the associated power outputs, percent V˙O2 peak, and percent peak power output for the GET, VT, RCP, and CP were analyzed using separate one-way repeated-measures analyses of variance. Results: There were no significant differences between CP (187 ± 47 W) and the power output associated with RCP (190 ± 49 W) or between the power outputs associated with GET (139 ± 37 W) and VT (145 ± 37 W). The power outputs associated with GET and VT, however, were significantly less than were those at CP and associated with RCP. Conclusions: These findings suggest CP and RCP demarcate the heavy from severe exercise-intensity domain and result from a different mechanism of fatigue than that of GET and VT, possibly hyperkalemia.  相似文献   

10.
This study investigated the effect cadence has on the estimation of critical power (CP) and the finite work capacity (W?) during the 3-minute all-out cycling test. Ten participants completed 8 tests: 1) an incremental test to calculate gas exchange threshold (GET), maximal aerobic power (MAP) and peak oxygen uptake (V?O2peak), 2–4) three time-to-exhaustion tests at 80, 100 and 105% MAP to calculate CP and W?, 5–7) four 3-minute all-out tests to calculate end power (EP) and work done above EP (WEP) using cadences ranging from preferred ?5 to preferred +10 rev·min?1 to set the fixed resistance. Significant differences were seen between CP and EP-preferred (267.5 ± 22.6 W vs. 296.6 ± 26.1 W, P < 0.001), CP and EP?5 (267.5 ± 22.6 W vs. 303.6 ± 24.0 W, P < 0.001) and between CP and EP+5 (267.5 ± 22.6 W vs. 290.0 ± 28.0 W, P = 0.002). No significant differences were seen between CP and EP+10 (267.5 ± 22.6 W vs. 278.1 ± 30.9 W, P = 0.331). Significant differences were seen between W? and WEP at all tested fixed resistances. EP is reduced when cycling at higher than preferred cadences, providing better estimates of CP.  相似文献   

11.
This case study reports the results of a 12-year (2005–2016) follow-up study of two Olympic champion rowers. The rowers were prospective athletes at the junior level when the study began, and we monitored their relevant physiological and performance data annually. Our findings indicated that their V?O2max gradually increased up to about 22 years of age and leveled off at a value of approximately 7 l·min?1 with minimal fluctuations thereafter. However, the variables that directly influence the V?O2max changed. There was an age-related decline in maximal heart rate of about 0.5 beats·year?1, while oxygen pulse, which serves as an indirect measure of stroke volume, correspondingly increased by about 1 ml O2·beat?1 per year, allowing the athletes to maintain exceptional V?O2max values. Maximal minute power of the studied rowers, derived each year from their ramp-wise tests, closely resembled the mean power output sustained during the 2000-m all-out tests on a rowing ergometer. A 12-year improvement of 28% and 33% occurred for the mean power output sustained over 2000 and 6000-m on a rowing ergometer, respectively. The findings contribute to the body of knowledge on athletes representing the true elites of their respective sports.  相似文献   

12.
To examine the reliability for peak responses of oxygen consumption (VO2peak) in relative (ml · kg-1 · min-1) and absolute (L/min-1) measures, as well as peak heart rate (HRpeak) during deep water running (DWR), 26 participants (12 women, 14 men) completed two DWR maximal graded exercise tests. To estimate the validity of the peak responses during DWR, a comparison to a treadmill running (TMR) graded exercise test (GXT) was completed. Test order was randomized. The DWR GXT utilized a system of weights and pulleys to increase intensity of exercise. Reliability of the DWR test for the total group was estimated using a repeated measures one-way analysis of variance (ANOVA) for VO2peak (ml · kg-1 · min-1, R = .96; L/min-1, R = .97) and HRpeak (R = .90). There were no significant differences (p > .05) between the two DWR tests for men or women for the means of VO2peak in relative units (men: 50.5 vs. 52.0 ml · kg-1 · min-1; women: 37.1 vs. 36.8 ml · kg-1 · min-1), or absolute units (men: 4.1 vs. 4.1 L/min-1; women: 2.2 vs. 2.2 L/min-1), or HR (men: 174 vs. 175 beats per minute (bpm); women: 181 vs. 183 bpm). There was a significant correlation between the average of the two DWR tests and TMR for the total group for VO2peak for relative (r = .88, p = .001) and absolute (r = .93, p = .001) measures as well as HRpeak (r = .64, p = .001). Peak responses during the DWR protocol were judged to be reliable. Also, the correlation for the variables between DWR and TMR indicates a positive relation between peak responses. The correlation suggests validity of predicting TMR peak responses from DWR peak responses; however, this conclusion may be questionable due to the low sample size and the large systemic differences between tests. Finally, HRpeak and VO2peak were lower during DWR than TMR for both men and women.  相似文献   

13.
To characterise timing of movements and evaluate performance effects of technique alterations in V2 ski skating, 13 elite male cross-country skiers (age, 23 ± 2 years; stature, 182 ± 6 cm; body mass, 76 ± 8 kg; V2 V?O2max, 79.3 ± 4.4 mL · kg?1 · min?1) were tested four times during the preparation and competition phase on a roller ski treadmill. Each test consisted of submaximal intensities of exercise for determination of oxygen cost followed by one 1000-m performance test. Hip movement (from accelerometer data) and joint angles (2D video) were determined for high-intensity exercise (6° and 3.5 m · s?1; ~ 97–100% of V?O2peak). Each ski thrust consisted of three phases: gliding phase (18–50% of cycle time), poling phase (50–70% of cycle time), and kick phase (70–78% of cycle time). Flexion/extension of the hip initiated all phases, followed by the respective joints in legs and arms. Mixed-model analysis, adjusting for systematic time-point effects, identified that both reduced vertical hip acceleration and increased cycle time gave a small likely reduction in oxygen cost and 1000-m time. In conclusion, well-developed hip movement is a key characteristic of the V2 technique for elite-standard skiers’ long-term performance development.  相似文献   

14.
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15.
Abstract

The aims of this study were two-fold: (1) to consider the criterion-related validity of the multi-stage fitness test (MSFT) by comparing the predicted maximal oxygen uptake ([Vdot]O2max) and distance travelled with peak oxygen uptake ([Vdot]O2peak) measured using a wheelchair ergometer (n = 24); and (2) to assess the reliability of the MSFT in a sub-sample of wheelchair athletes (n = 10) measured on two occasions. Twenty-four trained male wheelchair basketball players (mean age 29 years, s = 6) took part in the study. All participants performed a continuous incremental wheelchair ergometer test to volitional exhaustion to determine [Vdot]O2peak, and the MSFT on an indoor wooden basketball court. Mean ergometer [Vdot]O2peak was 2.66 litres · min?1 (s = 0.49) and peak heart rate was 188 beats · min?1 (s = 10). The group mean MSFT distance travelled was 2056 m (s = 272) and mean peak heart rate was 186 beats · min?1 (s = 11). Low to moderate correlations (ρ = 0.39 to 0.58; 95% confidence interval [CI]: ?0.02 to 0.69 and 0.23 to 0.80) were found between distance travelled in the MSFT and different expressions of wheelchair ergometer [Vdot]O2peak. There was a mean bias of ?1.9 beats · min?1 (95% CI: ?5.9 to 2.0) and standard error of measurement of 6.6 beats · min?1 (95% CI: 5.4 to 8.8) between the ergometer and MSFT peak heart rates. A similar comparison of ergometer and predicted MSFT [Vdot]O2peak values revealed a large mean systematic bias of 15.3 ml · kg?1 · min?1 (95% CI: 13.2 to 17.4) and standard error of measurement of 3.5 ml · kg?1 · min?1 (95% CI: 2.8 to 4.6). Small standard errors of measurement for MSFT distance travelled (86 m; 95% CI: 59 to 157) and MSFT peak heart rate (2.4 beats · min?1; 95% CI: 1.7 to 4.5) suggest that these variables can be measured reliably. The results suggest that the multi-stage fitness test provides reliable data with this population, but does not fully reflect the aerobic capacity of wheelchair athletes directly.  相似文献   

16.
Abstract

The single-stage treadmill walking test of Ebbeling et al. is commonly used to predict maximal oxygen consumption ([Vdot]O2max) from a submaximal effort between 50% and 70% of the participant's age-predicted maximum heart rate. The purpose of this study was to determine if this submaximal test correctly predicts [Vdot]O2max at the low (50% of maximum heart rate) and high (70% of maximum heart rate) ends of the specified heart rate range for males and females aged 18 – 55 years. Each of the 34 participants completed one low-intensity and one high-intensity trial. The two trials resulted in significantly different estimates of [Vdot]O2max (low-intensity trial: mean 40.5 ml · kg?1 · min?1, s = 9.3; high-intensity trial: 47.5 ml · kg?1 · min?1, s = 8.8; P < 0.01). A subset of 22 participants concluded their second trial with a [Vdot]O2max test (mean 47.9 ml · kg?1 · min?1, s = 8.9). The low-intensity trial underestimated (mean difference = ?3.5 ml · kg?1 · min?1; 95% CI = ?6.4 to ?0.6 ml · kg?1 · min?1; P = 0.02) and the high-intensity trial overestimated (mean difference = 3.5 ml · kg?1 · min?1; 95% CI = 1.1 to 6.0 ml · kg?1 · min?1; P = 0.01) the measured [Vdot]O2max. The predictive validity of Ebbeling and colleagues' single-stage submaximal treadmill walking test is diminished when performed at the extremes of the specified heart rate range.  相似文献   

17.
This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power–duration relationship (W′) are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W′ during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V?O2max]: 58 ± 7 ml · kg?1 · min?1) completed preliminary tests to determine the V?O2–power output relationship and V?O2max. Subsequently, AOD and W′ were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT. There were no differences between tests for duration, work, or average power output (P ≥ 0.05). AOD was greater in the CWR test (4.18 ± 0.95 vs. 3.68 ± 0.98 L; P = 0.004), whereas W′ was greater in 3MT (9.55 ± 4.00 vs. 11.37 ± 3.84 kJ; P = 0.010). AOD and W′ were significantly correlated in both CWR (P < 0.001, r = 0.654) and 3MT (P < 0.001, r = 0.654). In conclusion, despite positive correlations between AOD and W′ in CWR and 3MT, between-test differences in the magnitude of AOD and W′, suggest that both measures have different underpinning mechanisms.  相似文献   

18.
Purpose: To determine if: (i) mean power output and enjoyment of high-intensity interval training (HIIT) are enhanced by virtual-reality (VR)-exergaming (track mode) compared to standard ergometry (blank mode), (ii) if mean power output of HIIT can be increased by allowing participants to race against their own performance (ghost mode) or by increasing the resistance (hard mode), without compromising exercise enjoyment.

Methods: Sixteen participants (8 males, 8 females, VO2max: 41.2?±?10.8 ml?1·kg?1·min?1) completed four VR-HIIT conditions in a partially-randomised cross-over study; (1a) blank, (1b) track, (2a) ghost, and (2b) hard. VR-HIIT sessions consisted of eight 60 s high-intensity intervals at a resistance equivalent to 70% (77% for hard) maximum power output (PMAX), interspersed by 60 s recovery intervals at 12.5% PMAX, at a self-selected cadence. Expired gases were collected and VO2 measured continuously. Post-exercise questionnaires were administered to identify differences in indices related to intrinsic motivation, subjective vitality, and future exercise intentions.

Results: Enjoyment was higher for track vs. blank (difference: 0.9; 95% CI: 0.6, 1.3) with no other differences between conditions. There was no difference in mean power output for track vs. blank, however it was higher for track vs. ghost (difference: 5 Watts; CI: 3, 7), and hard vs. ghost (difference: 19 Watts; 95% CI: 15, 23).

Conclusions: These findings demonstrate that VR-exergaming is an effective intervention to increase enjoyment during a single bout of HIIT in untrained individuals. The presence of a ghost may be an effective method to increase exercise intensity of VR-HIIT.  相似文献   

19.
Abstract

The main aim of this study was to determine whether the use of an imposed or freely chosen crank rate would influence submaximal and peak physiological responses during arm crank ergometry. Fifteen physically active men participated in the study. Their mean age, height, and body mass were 25.9 (s = 6.2) years, 1.80 (s = 0.10) m, and 78.4 (s = 6.1) kg, respectively. The participants performed two incremental peak oxygen consumption ([Vdot]O2peak) tests using an electronically braked ergometer. One test was performed using an imposed crank rate of 80 rev · min?1, whereas in the other the participants used spontaneously chosen crank rates. The order in which the tests were performed was randomized, and they were separated by at least 2 days. Respiratory data were collected using an on-line gas analysis system, and fingertip capillary blood samples (～20 μl) were collected for the determination of blood lactate concentration. Heart rate was also recorded throughout the tests. Time to exhaustion was measured and peak aerobic power calculated. Submaximal data were analysed using separate two-way repeated-measures analyses of variance, while differences in peak values were analysed using separate paired t-tests. Variations in spontaneously chosen crank rate were assessed using a one-way analysis of variance with repeated measures. Agreement between the crank rate strategies for the assessment of peak values was examined by calculating intra-class correlation coefficients (ICC) and 95% limits of agreement (95% LoA). While considerable between-participant variations in spontaneously chosen crank rate were observed, the mean value was not different (P > 0.05) from the imposed crank rate of 80 rev · min?1 at any point. No differences (P > 0.05) were observed for submaximal data between crank strategies. Furthermore, mean peak minute power [158 (s = 20) vs. 158 (s = 18) W], time to exhaustion [739 (s = 118) vs. 727 (s = 111) s], and [Vdot]O2peak[3.09 (s = 0.38) vs. 3.04 (s = 0.34) l · min?1] were similar for the imposed and spontaneously chosen crank rates, respectively. However, the agreement for the assessment of [Vdot]O2peak (ICC = 0.78; 95% LoA = 0.04 ± 0.50 l · min?1) between the cranking strategies was considered unacceptable. Our results suggest that either an imposed or spontaneously chosen crank rate strategy can be used to examine physiological responses during arm crank ergometry, although it is recommended that the two crank strategies should not be used interchangeably.  相似文献   

20.
This study examined effects of 4 weeks of caffeine supplementation on endurance performance. Eighteen low-habitual caffeine consumers (<75 mg · day?1) were randomly assigned to ingest caffeine (1.5–3.0 mg · kg?1day?1; titrated) or placebo for 28 days. Groups were matched for age, body mass, V?O2peak and Wmax (P > 0.05). Before supplementation, all participants completed one V?O2peak test, one practice trial and 2 experimental trials (acute 3 mg · kg?1 caffeine [precaf] and placebo [testpla]). During the supplementation period a second V?O2peak test was completed on day 21 before a final, acute 3 mg · kg?1 caffeine trial (postcaf) on day 29. Trials consisted of 60 min cycle exercise at 60% V?O2peak followed by a 30 min performance task. All participants produced more external work during the precaf trial than testpla, with increases in the caffeine (383.3 ± 75 kJ vs. 344.9 ± 80.3 kJ; Cohen’s d effect size [ES] = 0.49; P = 0.001) and placebo (354.5 ± 55.2 kJ vs. 333.1 ± 56.4 kJ; ES = 0.38; P = 0.004) supplementation group, respectively. This performance benefit was no longer apparent after 4 weeks of caffeine supplementation (precaf: 383.3 ± 75.0 kJ vs. postcaf: 358.0 ± 89.8 kJ; ES = 0.31; P = 0.025), but was retained in the placebo group (precaf: 354.5 ± 55.2 kJ vs. postcaf: 351.8 ± 49.4 kJ; ES = 0.05; P > 0.05). Circulating caffeine, hormonal concentrations and substrate oxidation did not differ between groups (all P > 0.05). Chronic ingestion of a low dose of caffeine develops tolerance in low-caffeine consumers. Therefore, individuals with low-habitual intakes should refrain from chronic caffeine supplementation to maximise performance benefits from acute caffeine ingestion.  相似文献   

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