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1.
Effects of swing-weight on swing speed and racket power   总被引：1，自引：0，他引：1  
Measurements are presented of the speed at which six different rods could be swung by four male students. Three of the rods had the same mass but their swing-weight (i.e. moment of inertia) differed by large factors. The other three rods had the same swing-weight but different masses. Our primary objective was to quantify the effects of mass and swing-weight on swing speed. The result has a direct bearing on whether baseball, tennis, cricket and golf participants should choose a heavy or light implement to impart maximum speed to a ball. When swinging with maximum effort, swing speed (V) was found to decrease as swing-weight (Io) increased, according to the relation V = C/Ion, where C is a different constant for each participant and n = 0.27 when Io > 0.03 kg x m2. Remarkably similar results were obtained previously with softball bats (where n = 0.25) and golf clubs (where n = 0.26). Swing speed remained approximately constant as swing mass increased (when keeping swing-weight fixed). The implications for racket power are discussed.  相似文献   

2.
Abstract

The aim of this study was to examine the effectiveness of either a standard care programme (n?=?9) or a 12-week supported exercise programme (n?=?10) on glycaemic control, β-cell responsiveness, insulin resistance, and lipid profiles in newly diagnosed Type 2 diabetes patients. The standard care programme consisted of advice to exercise at moderate to high intensity for 30?min five times a week; the supported exercise programme consisted of three 60-min supported plus two unsupported exercise sessions per week. Between-group analyses demonstrated a difference for changes in low-density lipoprotein cholesterol only (standard care programme 0.01 mmol?·?L?1, supported exercise programme –0.6 mmol?·?L?1; P?=?0.04). Following the standard care programme, within-group analyses demonstrated a significant reduction in waist circumference, whereas following the supported exercise programme there were reductions in glycosylated haemoglobin (6.4 vs. 6.0%; P?=?0.007), waist circumference (101.4 vs. 97.2?cm; P?=?0.021), body mass (91.7 vs. 87.9?kg; P?=?0.007), body mass index (30.0 vs. 28.7?kg?·?m?2; P?=?0.006), total cholesterol (5.3 vs. 4.6 mmol?·?L?1; P?=?0.046), low-density lipoprotein cholesterol (3.2 vs. 2.6 mmol?·?L?1; P?=?0.028), fasting β-cell responsiveness (11.5?×?10?9 vs. 7.0?×?10?9 pmol?·?kg?1?·?min?1; P?=?0.009), and insulin resistance (3.0 vs. 2.1; P?=?0.049). The supported exercise programme improved glycaemic control through enhanced β-cell function associated with decreased insulin resistance and improved lipid profile. This research highlights the need for research into unsupported and supported exercise programmes to establish more comprehensive lifestyle advice for Type 2 diabetes patients.  相似文献   

3.
The aim of the study was to determine whether estimates of the speed–duration relationship are affected using different time-trial (TT) field-based testing protocols, where exhaustive times were located within the generally recommended durations of 2–15?min. Ten triathletes (mean?±?SD age: 31.0?±?5.7?years; height: 1.81?±?0.05?m; body mass: 76.5?±?6.8?kg) performed two randomly assigned field tests to determine critical speed (CS) and the total distance covered above CS (D?). CS and D? were obtained using two different protocols comprising three TT that were interspersed by 60?min passive rest. The TTs were 12, 7, and 3?min in Protocol I and 10, 5, and 2?min in Protocol II. A linear relationship of speed vs. the inverse of time (s?=?D??×?1/t?+?CS) was used to determine parameter estimates. Significant differences were found for CS (p?=?0.026), but not for D? (p?=?0.123). The effect size for CS (d?=?0.305) was considered small, while that for D? was considered moderate (d?=?0.742). CS was significantly correlated between protocols (r?=?0.934; p?D? (r?=?0.053; p?=?0.884). The 95% limits of agreement were ±0.28m?s?1 and ±73.9?m for CS and D?, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations results in different estimates of CS and D?, and thus protocols cannot be used interchangeably. The use of a consistent protocol is therefore recommended, when investigating or monitoring the speed–duration relationship estimates in well-trained athletes.  相似文献   

4.
Mouth rinsing using a carbohydrate (CHO) solution has been suggested to improve physical performance in fasting participants. This study examined the effects of CHO mouth rinsing during Ramadan fasting on running time to exhaustion and on peak treadmill speed (Vpeak). In a counterbalanced crossover design, 18 sub-elite male runners (Age: 21?±?2 years, Weight: 68.1?±?5.7?kg, VO2max: 55.4?±?4.8?ml/kg/min) who observed Ramadan completed a familiarization trial and three experimental trials. The three trials included rinsing and expectorating a 25?mL bolus of either a 7.5% sucrose solution (CHO), a flavour and taste matched placebo solution (PLA) for 10?s, or no rinse (CON). The treatments were performed prior to an incremental treadmill test to exhaustion. Three-day dietary and exercise records were obtained on two occasions and analysed. Anthropometric characteristics were obtained and recorded for all participants. A main effect for mouth rinse on peak velocity (Vpeak) (CHO: 17.6?±?1.5?km/h; PLA: 17.1?±?1.4?km/h; CON: 16.7?±?1.2?km/h; P?ηp2?=?0.49) and time to exhaustion (CHO: 1282.0?±?121.3?s; PLA: 1258.1?±?113.4?s; CON: 1228.7?±?98.5?s; P?=?.002, ηp2?=?0.41) was detected, with CHO significantly higher than PLA (P?P?P?>?.05). Energy availability from dietary analysis, body weight, and fat-free mass did not change during the last two weeks of Ramadan (P?>?.05). This study concludes that carbohydrate mouth rinsing improves running time to exhaustion and peak treadmill speed under Ramadan fasting conditions.  相似文献   

5.
This study was designed to develop a single-stage submaximal treadmill jogging (TMJ) test to predict VO2max in fit adults. Participants (N?=?400; men?=?250 and women?=?150), ages 18 to 40 years, successfully completed a maximal graded exercise test (GXT) at 1 of 3 laboratories to determine VO2max. The TMJ test was completed during the first 2 stages of the GXT. Following 3 min of walking (Stage 1), participants achieved a steady-state heart rate (HR) while exercising at a comfortable self-selected submaximal jogging speed at level grade (Stage 2). Gender, age, body mass, steady-state HR, and jogging speed (mph) were included as independent variables in the following multiple linear regression model to predict VO2max (R?=?0.91, standard error of estimate [SEE]?=?2.52 mL?·?kg?1?·?min?1): VO2max (mL?·?kg?1?·?min?1)?=?58.687?+?(7.520 × Gender; 0?=?woman and 1?=?man)?+?(4.334 × mph) ? (0.211 × kg) ? (0.148 × HR) ? (0.107 × Age). Based on the predicted residual sum of squares (PRESS) statistics (RPRESS?=?0.91, SEE PRESS?=?2.54 mL?·?kg?1?·?min?1) and small total error (TE; 2.50 mL?·?kg?1?·?min?1; 5.3% of VO2max) and constant error (CE; ?0.008 mL?·?kg?1?·?min?1) terms, this new prediction equation displays minimal shrinkage. It should also demonstrate similar accuracy when it is applied to other samples that include participants of comparable age, body mass, and aerobic fitness level. This simple TMJ test and its corresponding regression model provides a relatively safe, convenient, and accurate way to predict VO2max in fit adults, ages 18 to 40 years.  相似文献   

6.
Abstract

The aim of this study was to examine the effects of active versus passive recovery on blood lactate disappearance and subsequent maximal performance in competitive swimmers. Fourteen male swimmers from the University of Virginia swim team (mean age 20.3 years, s = 4.1; stature 1.85 m, s = 2.2; body mass 81.1 kg, s = 5.6) completed a lactate profiling session during which the speed at the lactate threshold (VLT), the speed at 50% of the lactate threshold (VLT.5), and the speed at 150% of the lactate threshold (VLT1.5) were determined. Participants also completed four randomly assigned experimental sessions that consisted of a 200-yard maximal-effort swim followed by 10 min of recovery (passive, VLT.5, VLT, VLT1.5) and a subsequent 200-yard maximal effort swim. All active recovery sessions resulted in greater lactate disappearance than passive recovery (P < 0.0001 for all comparisons), with the greatest lactate disappearance associated with recovery at VLT (P = 0.006 and 0.007 vs. VLT.5 and VLT1.5 respectively) [blood lactate disappearance was 2.1 mmol · l?1 (s = 2.0), 6.0 mmol · l?1 (s = 2.6), 8.5 mmol · l?1 (s = 1.8), and 6.1 mmol · l?1 (s = 2.5) for passive, VLT.5, VLT, and VLT1.5 respectively]. Active recovery at VLT and VLT1.5 resulted in faster performance on time trial 2 than passive recovery (P = 0.005 and 0.03 respectively); however, only active recovery at VLT resulted in improved performance on time trial 2 (TT2) relative to time trial 1 (TT1) [TT2?TT1: passive +1.32 s (s = 0.64), VLT.5+1.01 s (s = 0.53), VLT?1.67 s (s = 0.26), VLT1.5?0.07 s (s = 0.51); P < 0.0001 for VLT). In conclusion, active recovery at the speed associated with the lactate threshold resulted in the greatest lactate disappearance and in improved subsequent performance in all 14 swimmers. Our results suggest that coaches should consider incorporating recovery at the speed at the lactate threshold during competition and perhaps during hard training sessions.  相似文献   

7.
Running downhill, in comparison to running on the flat, appears to involve an exaggerated stretch-shortening cycle (SSC) due to greater impact loads and higher vertical velocity on landing, whilst also incurring a lower metabolic cost. Therefore, downhill running could facilitate higher volumes of training at higher speeds whilst performing an exaggerated SSC, potentially inducing favourable adaptations in running mechanics and running economy (RE). This investigation assessed the efficacy of a supplementary 8-week programme of downhill running as a means of enhancing RE in well-trained distance runners. Nineteen athletes completed supplementary downhill (?5% gradient; n?=?10) or flat (n?=?9) run training twice a week for 8 weeks within their habitual training. Participants trained at a standardised intensity based on the velocity of lactate turnpoint (vLTP), with training volume increased incrementally between weeks. Changes in energy cost of running (EC) and vLTP were assessed on both flat and downhill gradients, in addition to maximal oxygen uptake (?O2max). No changes in EC were observed during flat running following downhill (1.22?±?0.09 vs 1.20?±?0.07?Kcal?kg?1?km?1, P?=?.41) or flat run training (1.21?±?0.13 vs 1.19?±?0.12?Kcal?kg?1?km?1). Moreover, no changes in EC during downhill running were observed in either condition (P?>?.23). vLTP increased following both downhill (16.5?±?0.7 vs 16.9?±?0.6?km?h?1 , P?=?.05) and flat run training (16.9?±?0.7 vs 17.2?±?1.0?km?h?1, P?=?.05), though no differences in responses were observed between groups (P?=?.53). Therefore, a short programme of supplementary downhill run training does not appear to enhance RE in already well-trained individuals.  相似文献   

8.
Analysing the centre of pressure (COP) and centre of gravity (COG) could reveal stabilising strategies used by golfers throughout the golf swing. This study identified and compared golfers’ COP and COG patterns throughout the golf swing in medial–lateral (ML) and anterior–posterior (AP) directions using principal component analysis (PCA) and examined their relationship to clubhead velocity. Three-dimensional marker trajectories were collected using Vicon motion analysis and force plate data from two Kistler force plates for 22 low-handicap golfers during drives. Golfers’ COG and COP were expressed as a percentage distance between their feet. PCA was performed on COG and COP in ML and AP directions. Relationships between principal component (PC) scores were examined using Pearson correlation and regression analysis used to examine the relationship with clubhead velocity. ML COP movements varied in magnitude (PC1), rate of change and timing (PC2 and PC3). The COP and COG PC1 scores were strongly correlated in both directions (ML: r?=?0.90, P?<?.05; AP: r?=?0.81, P?<?.05). Clubhead velocity, explained by three PCs (74%), related to timing and rate of change in COPML near downswing (PC2 and PC3) and timing of COGML late backswing (PC2). The relationship between COPML and COGML PC1 scores identified extremes of COP and COG patterns in golfers and could indicate a golfer’s dynamic balance. Golfers with earlier movement of COP to the front foot (PC2) and rate of change (PC3) patterns in ML COP, prior to the downswing, may be more likely to generate higher clubhead velocity.  相似文献   

9.
Aim: The aim of this study was to examine the relationship between ventilatory adaptation and performance during altitude training at 2700?m. Methods: Seven elite cyclists (age: 21.2?±?1.1?yr, body mass: 69.9?±?5.6?kg, height 176.3?±?4.9?cm) participated in this study. A hypoxic ventilatory response (HVR) test and a submaximal exercise test were performed at sea level prior to the training camp and again after 15 d at altitude (ALT15). Ventilation (VE), end-tidal carbon-dioxide partial pressure (PETCO2) and oxyhaemoglobin saturation via pulse oximetry (SpO2) were measured at rest and during submaximal cycling at 250?W. A hill climb (HC) performance test was conducted at sea level and after 14 d at altitude (ALT14) using a road of similar length (5.5–6?km) and gradient (4.8–5.3%). Power output was measured using SRM cranks. Average HC power at ALT14 was normalised to sea level power (HC%). Multiple regression was used to identify significant predictors of performance at altitude. Results: At ALT15, there was a significant increase in resting VE (10.3?±?1.9 vs. 12.2?±?2.4?L·min?1) and HVR (0.34?±?0.24 vs. 0.71?±?0.49?L·min?1·%?1), while PETCO2 (38.4?±?2.3 vs. 32.1?±?3.3?mmHg) and SpO2 (97.9?±?0.7 vs. 94.0?±?1.7%) were reduced (P?VE at altitude as significant predictors of HC% (adjusted r2?=?0.913; P?=?0.003). Conclusions: Ventilatory acclimatisation occurred during a 2 wk altitude training camp in elite cyclists and a higher HVR was associated with better performance at altitude, relative to sea level. These results suggest that ventilatory acclimatisation is beneficial for cycling performance at altitude.  相似文献   

10.
Abstract

Previous studies on the kinematics of the golf swing have mainly focused on group analysis of male golfers of a wide ability range. In the present study, we investigated gross body kinematics using a novel method of analysis for golf research for a group of low handicap female golfers to provide an understanding of their swing mechanics in relation to performance. Data were collected for the drive swings of 16 golfers using a 12-camera three-dimensional motion capture system and a stereoscopic launch monitor. Analysis of covariance identified three covariates (increased pelvis–thorax differential at the top of the backswing, increased pelvis translation during the backswing, and a decrease in absolute backswing time) as determinants of the variance in clubhead speed (adjusted r 2 = 0.965, P < 0.05). A significant correlation was found between left-hand grip strength and clubhead speed (r = 0.54, P < 0.05) and between handicap and clubhead speed (r = ?0.612, P < 0.05). Flexibility measures showed some correlation with clubhead speed; both sitting flexibility tests gave positive correlations (clockwise: r = 0.522, P < 0.05; counterclockwise: r = 0.711, P < 0.01). The results suggest that there is no common driver swing technique for optimal performance in low handicap female golfers, and therefore consideration should be given to individual swing characteristics in future studies.  相似文献   

11.
Abstract

Hypoxic training methods are increasingly being used by researchers in an attempt to improve performance in normoxic ambients. Moreover, previous research suggests that resistance training in hypoxia can cause physiological and muscle adaptations. The primary aim of this study was to compare the effects of 8 weeks of high-intensity resistance circuit-based (HRC) training in hypoxia on body composition and strength performance. The secondary aim was to examine the effects of HRC on metabolic parameters. Twenty-eight male participants were randomly assigned to either hypoxia (Fraction of inspired oxygen [FIO2]?=?15%; HRChyp: n?=?15; age: 24.6?±?6.8 years; height: 177.4?±?5.9?cm; weight: 74.9?±?11.5?kg) or normoxia [FIO2]?=?20.9%; HRCnorm: n?=?13; age: 23.2?±?5.2 years; height: 173.4?±?6.2?cm; weight: 69.4?±?7.4?kg) groups. Training sessions consisted of two blocks of three exercises (Block 1: bench press, leg extension and front pull down; Block 2: deadlift, elbow flexion and ankle extension). Each exercise was performed at six repetition maximum. Rest periods lasted for 35-s between exercises, 3-min between sets and 5-min between blocks. Participants exercised twice weekly for 8 weeks, and body composition, strength and blood tests were performed before and after the training program. Lean body mass and bone mineral density significantly increased over time in the HRChyp (p?<?.005; ES?=?0.14 and p?<?.014; ES?=?0.19, respectively) but not in the HRCnorm after training. Both groups improved their strength performance over time (p?<?.001), but without group effect differences. These results indicate that simulated hypoxia during HRC exercise produced trivial effects on lean body mass and bone mineral density compared to normoxia.  相似文献   

12.
Abstract

Previous investigations have revealed that in well-trained middle-distance runners, oxygen uptake (VO2) does not attain maximal values (VO2max) in exhaustive treadmill trials where the VO2 demand exceeds VO2max. To date, this shortfall in the VO2 attained has been demonstrated in trials as short as 2 min in duration. In this study, we investigated whether a reduction in exhaustive test duration influences the VO2 attained during running on a treadmill. Six middle-distance runners participated in the study, completing an exhaustive 400 m and 800 m trial. These trials, together with a progressive test to determine VO2max, were completed in a counterbalanced order. Oxygen uptakes attained during the 400 m and 800 m trials were compared to examine the influence of exhaustive test duration. A plateau in VO2 was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The mean speed, duration, and resulting distance in the constant-speed exhaustive trials were 25.8 km · h?1 (s=1.2), 55.8 s (s=2.3), and 400.2 m (s=20.2) for the 400 m trial, and 24.3 km · h?1 (s=0.8), 108.4 s (s=21.2), and 730.1 m (s=129.1) for the 800 m trial, respectively. A paired-samples t-test revealed a significantly different (P=0.018)%VO2max was attained for the 400 m (85.7%, s=3.0) and 800 m (89.1%, s=5.0) trials. In conclusion, VO2 did not reach VO2max during the exhaustive constant-speed 400 m and 800 m trials, but the test duration does influence the%VO2max achieved. Specifically, the VO2 attained becomes progressively further below VO2max as trial duration is reduced, such that 89% and 86% VO2max is achieved in exhaustive 800 m and 400 m constant-speed trials, respectively.  相似文献   

13.
Fat mass is inversely associated with vitamin D status, and athletes with the most adipose tissue may have the greatest risk for insufficient (25(OH)D 20–32?ng?mL?1) or deficient (25(OH)D??1) status. The effects of fat and lean mass on 25(OH)D change in response to vitamin D supplementation have yet to be elucidated in athletes. In addition, vitamin D has a known role in bone health yet a link between short-term changes in 25(OH)D and bone turnover in indoor athletes have not yet been described. Thirty-two collegiate swimmers and divers (19 male, 13 female; 19 (1) years) participated in a 6-month randomized controlled trial and consumed either 4000?IU?d?1 of vitamin D3 (n?=?19) or placebo (PLA; n?=?13). Anthropometry and blood collection of 25(OH)D, bone-specific alkaline phosphatase (B-ALP) and N-terminal telopeptide (NTx) occurred at three time points. Dual-energy X-ray absorptiometry measured body composition analysis at baseline and endpoint. In the vitamin D group, BMI was negatively correlated with 6-month 25(OH)D change (R?=??0.496; P?=?.03) and a stronger predictor of 25(OH)D change (P?=?.04) than ultraviolet B exposure and fat mass change. Athletes in the high bone turnover group showed significantly greater losses of 25(OH)D over 6-months compared to athletes in the low bone turnover group (P?=?.03). These results suggest athletes within the normal BMI category experience a diminished response to 4000?IU?d?1 of vitamin D3 supplementation, and periods of high bone turnover may be an additional risk factor for developing compromised vitamin D status in athletes.  相似文献   

14.
The aims of this study were (i) to determine whether significant three-dimensional (3D) trunk kinematic differences existed between a driver and a five-iron during a golf swing; and (ii) to determine the anthropometric, physiological, and trunk kinematic variables associated with clubhead speed. Trunk range of motion and golf swing kinematic data were collected from 15 low-handicap male golfers (handicap = 2.5 ± 1.9). Data were collected using a 10-camera motion capture system operating at 250 Hz. Data on clubhead speed and ball velocity were collected using a real-time launch monitor. Paired t-tests revealed nine significant (p ≤ 0.0019) between-club differences for golf swing kinematics, namely trunk and lower trunk flexion/extension and lower trunk axial rotation. Multiple regression analyses explained 33.7–66.7% of the variance in clubhead speed for the driver and five-iron, respectively, with both trunk and lower trunk variables showing associations with clubhead speed. Future studies should consider the role of the upper limbs and modifiable features of the golf club in developing clubhead speed for the driver in particular.  相似文献   

15.
ABSTRACT

Purpose: The association between an overlooked classical Lactate Threshold (LT), named “Minimum Lactate Equivalent” (LEmin), with Maximal Lactate Steady State (MLSS) has been recently described with good MLSS prediction results in endurance-trained runners. This study aimed to determine the applicability of LEmin to predict MLSS in lower aerobic-conditioned individuals compared to well-established blood lactate-related thresholds (BLTs). Method: Fifteen soccer players [velocity at MLSS (MLSSV) 13.2 ± 1.0 km·h?1; coefficient of variation (CV) 7.6%] conducted a submaximal discontinuous incremental running test to determine BLTs and 3–6 constant velocity running tests to determine MLSSV. Results: LEmin did not differ from conventional LTs (p > .05) and was 24% lower than MLSS (p < .001; ES: 3.26). Among LTs, LEmin best predicted MLSSV (r = 0.83; p < .001; SEE = 0.59 km·h?1). There was no statistical difference between MLSS and estimated MLSS using LEmin prediction formula (p = .99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.58 km·h?1 and ±1.13 km·h?1, respectively. LEmin best predicted MLSSV (r = 0.92; p < .001; SEE = 0.54 km·h?1) in the pooled data of soccer players and endurance-trained runners of the previous study (n = 28; MLSSV range 11.2–16.5 km·h?1; CV 9.8%). Conclusion: Results support LEmin to be one of the best single predictors of MLSS. This study is the sole study providing specific operational regression equations to estimate the impractical gold standard MLSSV in soccer players by means of a BLT measured during a submaximal single-session test.  相似文献   

16.
Purpose: This study investigated the physiological effects of wearing a mouthguard during submaximal treadmill exercise. Method: Twenty-four recreationally active males (Mage = 21.3 ± 2.4 years, Mheight = 1.78 ± 0.06 m, Mweight = 81.9 ± 10.6 kg, Mbody mass index = 25.8 ± 3.4 kg·m?2) performed incremental, continuous exercise at 2, 4, 6, and 8 mph (3.2, 6.4, 9.7, 12.9 kph) for 5 min at each speed on a motor-driven treadmill on 2 separate occasions in a randomized, crossover, counterbalanced design while wearing or not wearing a self-adaptable “boil and bite” mouthguard. Respiratory rate (RR), tidal volume (VT), ventilation (VE), oxygen consumption (VO2), respiratory exchange ratio (RER), and heart rate (HR) data were averaged during the last 60 s of each exercise stage; blood lactate (LA) was measured before exercise and 3 min and 10 min following exercise. Results: Repeated-measures analysis of variance revealed that mouthguard use failed to alter the response of RR, VT, VE, VO2, RER, and HR to treadmill exercise (p > .05), although each variable did increase in magnitude as a result of increasing treadmill speed (p < .001). Although increasing to above resting values at both 3 min and 10 min (p < .001) after cessation of exercise, LA levels also displayed no differences with mouthguard use (p > .05). Conclusion: Despite predictable increases in respiratory, metabolic, and cardiovascular variables in response to incremental exercise, the presence of a mouthguard failed to affect the magnitude or nature of these physiological responses.  相似文献   

17.
ABSTRACT

This study examined changes in enjoyment, affective valence, and rating of perceived exertion (RPE) in obese women performing two regimes of high intensity interval training (HIIT) differing in structure and volume. Nineteen obese and inactive women (age and body mass index?=?37.5?±?10.5?yr and 39.0?±?4.3?kg/m2) were randomized to 6?wk of traditional (TRAD, n?=?10) or periodized interval training (PER, n?=?9) which was performed on a cycle ergometer during which structure changed weekly. Two supervised sessions per week were performed in a lab, and one session per week was performed unsupervised. During every lab-based session, perceptual responses including enjoyment, affective valence, and RPE were acquired. Data showed a groupXtraining interaction for enjoyment (p?=?0.02) which was lower by 10–25 units during PER versus TRAD. In addition, there was a groupXtimeXtraining interaction for RPE (p?=?0.01). RPE did not change in response to TRAD yet varied during PER, with lower RPE values exhibited during brief supramaximal bouts (6.3?±?0.9) compared to longer intervals (7.3?±?1.2). Both regimes showed reductions in affective valence during training, with the lowest values equal to 1.5?±?1.6 in TRAD and ?0.2?±?1.6 in PER. Compared to TRAD, more aversive responses were shown in PER throughout training by 0.4–2.0 units. Data show lower enjoyment and more aversive responses to higher-volume bouts of interval training, which suggests that shorter bouts may be perceived more favourably by obese women.  相似文献   

18.
Purpose: To investigate the effect of sodium bicarbonate (NaHCO3) on performance and estimated energy system contribution during simulated taekwondo combat. Methods: Nine taekwondo athletes completed two experimental sessions separated by at least 48?h. Athletes consumed 300?mg/kg body mass of NaHCO3 or placebo (CaCO3) 90?min before the combat simulation (three rounds of 2 min separated by 1 min passive recovery), in a double-blind, randomized, repeated-measures crossover design. All simulated combat was filmed to quantify the time spent fighting in each round. Lactate concentration [La?] and rating of perceived exertion (RPE) were measured before and after each round, whereas heart rate (HR) and the estimated contribution of the oxidative (WOXI), ATP (adenosine triphosphate)-phosphocreatine (PCr) (WPCR), and glycolytic (W[ La? ]) systems were calculated during the combat simulation. Results: [La?] increased significantly after NaHCO3 ingestion, when compared with the placebo condition (+14%, P?=?0.04, d?=?3.70). NaHCO3 ingestion resulted in greater estimated glycolytic energy contribution in the first round when compared with the placebo condition (+31%, P?=?0.01, d?=?3.48). Total attack time was significantly greater after NaHCO3 when compared with placebo (+13%, P?=?0.05, d?=?1.15). WOXI, WPCR, VO2, HR and RPE were not different between conditions (P?>?0.05). Conclusion: NaHCO3 ingestion was able to increase the contribution of glycolytic metabolism and, therefore, improve performance during simulated taekwondo combat.  相似文献   

19.
Abstract

The aim of this study was to examine the effect of menstrual cycle phase on 2000-m rowing ergometry performance. Since high concentrations of oestrogen, indicative of the mid-luteal phase of the menstrual cycle, tend to decrease glycogen utilization and reduce blood lactate concentration, it was predicted that time taken to complete a 2000-m rowing trial would be shorter in the mid-luteal phase. Ten eumenorrhoeic, recreationally trained, female volunteers (mean age 33.0 years, s=7.1) completed 2000-m time trials on a Concept 2 rowing ergometer, in both the mid-follicular and mid-luteal phases of their menstrual cycle. In each phase, a 3-min incremental rowing protocol was used to determine a blood lactate concentration of 4 mmol · l?1 (T lac-4mM) and maximum oxygen consumption (VO2max); a five-stroke maximal test was used to establish maximal power. Order of testing was randomized for menstrual cycle phase. Variables (T lac-4mM, VO2max, maximal power) were correlated with speed in the 2000-m time trials, and the effect of menstrual cycle phase on these variables was examined. A blood lactate concentration of 4 mmol · l?1 occurred at a significantly higher mean exercise intensity (mid-luteal vs. mid-follicular: 169.1 W, s=39.1 vs. 159.0 W, s=38.3; P=0.033), heart rate (179 beats · min?1, s=9 vs. 173 beats · min?1, s=11; P=0.0047), and oxygen consumption (2.64 litres · min?1, s=0.66 vs. 2.42 litres · min?1, s=0.62; P=0.04) in the mid-luteal phase than in the mid-follicular phase. There was no significant difference (P=0.11) in 2000-m time trial speed according to menstrual cycle phase. In conclusion, although T lac-4mM differed due to menstrual cycle phase, 2000-m rowing performance was unaffected. Further research into the effects of menstrual cycle on rowing performance of a longer duration, among a more homogenous group of females, is recommended.  相似文献   

20.
The purpose of this study was to investigate the use of a single 3-min all-out maximal effort to estimate anaerobic capacity (AC) through the lactate and excess post-exercise oxygen consumption (EPOC) response methods (AC[La?]+EPOCfast) on a cycle ergometer. Eleven physically active men (age?=?28.1?±?4.0?yrs, height?=?175.1?±?4.2?cm, body mass?=?74.8?±?11.9?kg and ?O2max?=?40.7?±?7.3?mL?kg?1?min?1), participated in the study and performed: i) five submaximal efforts, ii) a supramaximal effort at 115% of intensity of ?O2max, and iii) a 3-min all-out maximal effort. Anaerobic capacity was estimated using the supramaximal effort through conventional maximal accumulated oxygen deficit (MAOD) and also through the sum of oxygen equivalents from the glycolytic (fast component of excess post-exercise oxygen consumption) and phosphagen pathways (blood lactate accumulation) (AC[La?]+EPOCfast), while during the 3-min all-out maximal effort the anaerobic capacity was estimated using the AC[La?]+EPOCfast procedure. There were no significant differences between the three methods (p?>?0.05). Additionally, the anaerobic capacity estimated during the 3-min all-out effort was significantly correlated with the MAOD (r?=?0.74; p?=?0.009) and AC[La?]+EPOCfast methods (r?=?0.65; p?=?0.029). Therefore, it is possible to conclude that the 3-min all-out effort is valid to estimate anaerobic capacity in physically active men during a single cycle ergometer effort.  相似文献   

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