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1.
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   

2.
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   

3.
Abstract

This study investigated the effects of oral taurine supplementation on cycling time to exhaustion at a fixed-intensity and thermoregulation in the heat. In a double-blind, randomised crossover design, 11 healthy males participated in a time to exhaustion test in the heat (35°C, 40% RH), cycling at the power output associated with ventilatory threshold, 2?h after ingesting: Taurine (50?mg?kg?1) or placebo (3?mg?kg?1?maltodextrin). Core and mean skin temperature, mean sweat rate, heart rate, rating of perceived exertion (RPE), thermal comfort and thermal sensation were measured during exercise and blood lactate concentration (B[La]) was measured after exercise. Taurine supplementation increased time to exhaustion by 10% (25.16 min vs. 22.43 min, p?=?0.040), end sweat rate by 12.7% (687?nL?min?1 vs. 600?nL?min?1, p?=?0.034) and decreased B[La] by 16.5% (5.75?mmol?L?1 vs. 6.85?mmol?L?1, p?=?0.033). Core temperature was lower in the final 10% of the time to exhaustion (38.5°C vs. 38.1°C, p?=?0.049). Taurine supplementation increased time to exhaustion and local sweating, while decreasing RPE and core temperature in the later stages of exercise, as well as reducing post-exercise B[La]. This study provides the evidence of taurine's role in thermoregulatory processes. These findings have implications for the short-term preparation strategies of individuals exercising in the heat. Based on these findings, a single dose of taurine 2?h prior to training or competition would provide an ergogenic and thermoregulatory effect.  相似文献   

4.
Nine male student games players consumed either flavoured water (0.1 g carbohydrate, Na+ 6 mmol · l?1), a solution containing 6.5% carbohydrate-electrolytes (6.5 g carbohydrate, Na+ 21 mmol · l?1) or a taste placebo (Na+ 2 mmol · l?1) during an intermittent shuttle test performed on three separate occasions at an ambient temperature of 30°C (dry bulb). The test involved five 15-min sets of repeated cycles of walking and variable speed running, each separated by a 4-min rest (part A of the test), followed by 60 s run/60 s rest until exhaustion (part B of the test). The participants drank 6.5 ml · kg?1 of fluid as a bolus just before exercise and thereafter 4.5 ml · kg?1 during every exercise set and rest period (19 min). There was a trial order effect. The total distance completed by the participants was greater in trial 3 (8441 ± 873 m) than in trial 1 (6839 ± 512, P < 0.05). This represented a 19% improvement in exercise capacity. However, the trials were performed in a random counterbalanced order and the participants completed 8634 ± 653 m, 7786 ± 741 m and 7099 ± 647 m in the flavoured water (FW), placebo (P) and carbohydrate-electrolyte (CE) trials, respectively (P = 0.08). Sprint performance was not different between the trials but was impaired over time (FW vs P vs CE: set 1, 2.41 ± 0.02 vs 2.39 ± 0.03 vs 2.39 ± 0.03 s; end set, 2.46 ± 0.03 vs 2.47 ± 0.03 vs 2.47 ± 0.02 s; main

effect time, P < 0.01). The rate of rise in rectal temperature was greater in the carbohydrate-electrolyte trial (rise in rectal temperature/duration of trial, °C · h?1; FW vs CE, P < 0.05; P vs CE, N.S.). Blood glucose concentrations were higher in the carbohydrate-electrolyte than in the other two trials (FW vs P vs CE: rest, 4.4 ± 0.1 vs 4.3 ± 0.1 vs 4.2 ± 0.1 mmol · l?1; end of exercise, 5.4 ± 0.3 vs 6.4 ± 0.6 vs 7.2 ± 0.5 mmol · l?1; main effect trial, P < 0.05; main effect time, P < 0.01). Plasma free fatty acid concentrations at the end of exercise were lower in the carbohydrate-electrolyte trial than in the other two trials (FW vs P vs CE: 0.57 ± 0.08 vs 0.53 ± 0.11 vs 0.29 ± 0.04 mmol · l?1; interaction, P < 0.01). The correlation between the rate of rise in rectal temperature (°C · h?1) and the distance completed was ?0.91, ?0.92 and ?0.96 in the flavoured water, placebo and carbohydrate-electrolyte conditions, respectively (P < 0.01). Heart rate, blood pressure, plasma ammonia, blood lactate, plasma volume and rate of perceived exertion were not different between the three fluid trials. Although drinking the carbohydrate-electrolyte solution induced greater metabolic changes than the flavoured water and placebo solutions, it is unlikely that in these unacclimated males carbohydrate availability was a limiting factor in the performance of intermittent running in hot environmental conditions.  相似文献   

5.
The aim of the present study was to evaluate the effects of a 12-week home-based strength, explosive and plyometric (SEP) training on the cost of running (Cr) in well-trained ultra-marathoners and to assess the main mechanical parameters affecting changes in Cr. Twenty-five male runners (38.2?±?7.1 years; body mass index: 23.0?±?1.1?kg·m?2; V˙O2max: 55.4?±?4.0 mlO2·kg?1·min?1) were divided into an exercise (EG?=?13) and control group (CG?=?12). Before and after a 12-week SEP training, Cr, spring-mass model parameters at four speeds (8, 10, 12, 14?km·h?1) were calculated and maximal muscle power (MMP) of the lower limbs was measured. In EG, Cr decreased significantly (p?<?.05) at all tested running speeds (?6.4?±?6.5% at 8?km·h?1; ?3.5?±?5.3% at 10?km·h?1; ?4.0?±?5.5% at 12?km·h?1; ?3.2?±?4.5% at 14?km·h?1), contact time (tc) increased at 8, 10 and 12?km·h?1 by mean +4.4?±?0.1% and ta decreased by ?25.6?±?0.1% at 8?km·h?1 (p?<?.05). Further, inverse relationships between changes in Cr and MMP at 10 (p?=?.013; r?=??0.67) and 12?km·h?1 (p?<?.001; r?=??0.86) were shown. Conversely, no differences were detected in the CG in any of the studied parameters. Thus, 12-week SEP training programme lower the Cr in well-trained ultra-marathoners at submaximal speeds. Increased tc and an inverse relationship between changes in Cr and changes in MMP could be in part explain the decreased Cr. Thus, adding at least three sessions per week of SEP exercises in the normal endurance-training programme may decrease the Cr.  相似文献   

6.
Abstract

In this study, we investigated the effect of ingesting carbohydrate alone or carbohydrate with protein on functional and metabolic markers of recovery from a rugby union-specific shuttle running protocol. On three occasions, at least one week apart in a counterbalanced order, nine experienced male rugby union forwards ingested placebo, carbohydrate (1.2 g · kg body mass?1 · h?1) or carbohydrate with protein (0.4 g · kg body mass?1 · h?1) before, during, and after a rugby union-specific protocol. Markers of muscle damage (creatine kinase: before, 258 ± 171 U · L?1 vs. 24 h after, 574 ± 285 U · L?1; myoglobin: pre, 50 ± 18 vs. immediately after, 210 ± 84 nmol · L?1; P < 0.05) and muscle soreness (1, 2, and 3 [maximum soreness = 8] for before, immediately after, and 24 h after exercise, respectively) increased. Leg strength and repeated 6-s cycle sprint mean power were slightly reduced after exercise (93% and 95% of pre-exercise values, respectively; P < 0.05), but were almost fully recovered after 24 h (97% and 99% of pre-exercise values, respectively). There were no differences between trials for any measure. These results indicate that in experienced rugby players, the small degree of muscle damage and reduction in function induced by the exercise protocol were not attenuated by the ingestion of carbohydrate and protein.  相似文献   

7.
Abstract

Individuals with impaired glucose tolerance (IGT) are at greater risk of developing diabetes than in normoglycaemia. The aim of this study was to examine the effects of 12-weeks exercise training in obese humans with IGT. Eleven participants (6 males and 5 females; 49±9 years; mean Body Mass Index (BMI) 32.4 kg · m?2), completed a 12-week brisk walking intervention (30 min per day, five days a week (d · wk?1), at 65% of age-predicted maximal heart rate (HRmax). Anthropometric measurements, dietary intake, pulse wave velocity (PWV, to determine arterial stiffness) and blood pressure (BP) were examined at baseline and post intervention. Fasting blood glucose, glycosylated haemoglobin, insulin, blood lipids, indices of oxidative stress and inflammation (lipid hydroperoxides; superoxide dismutase; multimeric adiponectin concentration and high-sensitivity C-reactive protein) were also determined. Post intervention, PWV (9.08±1.27 m · s?1 vs. 8.39±1.21 m · s?1), systolic BP (145.4±14.5 vs. 135.8±14.9 mmHg), triglycerides (1.52±0.53 mmol . L?1 vs. 1.31±0.54 mmol . L?1), lipid hydroperoxides (1.20±0.47 μM · L?1 vs. 0.79±0.32 μM · L?1) and anthropometric measures decreased significantly (P < 0.05). Moderate intensity exercise training improves upper limb vascular function in obese humans with IGT, possibly by improving triglyceride metabolism, which may subsequently reduce oxidative stress. These changes were independent of multimeric adiponectin modification and alterations in other blood biomarkers.  相似文献   

8.
Abstract

The aim of the present study was to examine the relationship between intensities of exercise during match-play of elite-standard soccer referees with those of the players from the same match. Match analysis data were collected (Prozone® Leeds, UK) for 18 elite-standard soccer referees (age 26–49 years) on FA Premier League matches during the 2008/09 English FA Premier League season (236 observations). Running categories for referees and players were as follows: total distance covered (m); high-speed running distance (speed >19.8 km · h?1); and sprinting distance (speed >25.2 km · h?1). Analysis of the distance–time regression coefficients revealed no differences between the referees' and players' within-match rates of change for total distance covered (?0.594 ± 0.394 vs. ?0.713 ± 0.269 m · min?1; P = 0.104), high-speed running (?0.039 ± 0.077 vs. ?0.059 ± 0.030 m · min?1; P = 0.199), and sprinting (?0.003 ± 0.039 vs. ?0.021 ± 0.017 m · min?1; P = 0.114). In addition, there were no differences between across-season rates of change for total distance (–26.756 ± 40.434 vs. ?20.031 ± 25.502 m per match day; P = 0.439) and sprinting (–9.662 ± 7.564 vs. ?8.589 ± 4.351 m per match day; P = 0.542). These results show that elite-standard soccer referees' intensities of exercise during match-play are interrelated with those of the players and thus demonstrate that referees are able to keep pace with the players during FA Premier League matches.  相似文献   

9.
Strenuous physical exercise of the limb muscles commonly results in damage, especially when that exercise is intense, prolonged and includes eccentric contractions. Many factors contribute to exercise-induced muscle injury and the mechanism is likely to differ with the type of exercise. Competitive sports players are highly susceptible to this type of injury. AM3 is an orally administered immunomodulator that reduces the synthesis of proinflammatory cytokines and normalizes defective cellular immune fractions. The ability of AM3 to prevent chronic muscle injury following strenuous exercise characterized by eccentric muscle contraction was evaluated in a double-blind and randomized pilot study. Fourteen professional male volleyball players from the First Division of the Spanish Volleyball League volunteered to take part. The participants were randomized to receive either placebo (n?=?7) or AM3 (n?=?7). The physical characteristics (mean±s) of the placebo group were as follows: age 25.7±2.1 years, body mass 87.2±4.1?kg, height 1.89±0.07?m, maximal oxygen uptake 65.3±4.2?ml?·?kg?1?·?min?1. Those of the AM3 group were as follows: age 26.1±1.9 years, body mass 85.8±6.1?kg, height 1.91±0.07?m, maximal oxygen uptake 64.6±4.5?ml?·?kg?1?·?min?1. All participants were evaluated for biochemical indices of muscle damage, including concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase (CK) and its MB fraction (CK-MB), myoglobin, lactate dehydrogenase, urea, creatinine and γ-glutamyltranspeptidase, both before and 30 days after treatment (over the peak of the competitive season). In the placebo group, competitive exercise (i.e. volleyball) was accompanied by significant increases in creatine kinase (494±51 to 560±53?IU?·?l?1, P?<?0.05) and myoglobin (76.8±2.9 to 83.9±3.1?μg?·?l?1, P?<?0.05); aspartate aminotransferase (30.8±3.0 to 31.1±2.9?IU?·?l?1) and lactate dehydrogenase (380±31 to 376±29?IU?·?l?1) were relatively unchanged after the 30 days maximum effort. AM3 not only inhibited these changes, it led to a decrease from baseline serum concentrations of creatine kinase (503±49 to 316±37?IU?·?l?1, P?<?0.05) and myoglobin (80.1±3.2 to 44.1±2.6?IU?·?l?1, P?<?0.05), as well as aspartate aminotransferase (31.1±3.3 to 26.1±2.7?IU?·?l?1, P?<?0.05) and lactate dehydrogenase (368±34 to 310±3?IU?·?l?1, P?<?0.05). The concentration of CK-MB was also significantly decreased from baseline with AM3 treatment (11.6±1.2 to 5.0±0.7?IU?·?l?1, P?<?0.05), but not with placebo (11.4±1.1 to 10.8±1.4?IU?·?l?1). In conclusion, the use of immunomodulators, such as AM3, by elite sportspersons during competition significantly reduces serum concentrations of proteins associated with muscle damage.  相似文献   

10.
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   

11.
The aim of this study was to examine neuromuscular variables contributing to differences in force loss after participants were exposed to the same relative bout of eccentric exercise. Thirty-six males performed 50 maximal eccentric contractions of the elbow flexors and were stratified into high responders (n?=?10) and low responders (n?=?10) based on force loss 36 h after exercise. Maximal voluntary isometric contractions (MVCs) and electromyography (EMG) were measured at baseline and 36 h after exercise. During eccentric exercise, mean peak torque, mean end-range torque from the final 25% of each trial and total angular impulse were computed over 25 contractions in each of two bouts. The slope of the change in these values for each 25 eccentric contractions was calculated for each participant using linear regression. At baseline, MVC was not different between groups (low responders: 97.0?±?9.6 N?·?m; high responders: 82.7?±?6.4 N?·?m; P?=?0.08). High responders demonstrated a 68% (range 62-78%) reduction in MVC and low responders a 39% (29-48%) reduction after exercise. Peak torque, end-range torque and total angular impulse were 13%, 40% and 33% higher, respectively, in the low than in the high responders (peak torque: P?=?0.0002; end-range torque: P?<?0.0001; total angular impulse: P?<?0.001). The rate of decline in peak torque slope was greater in high than in low responders (P?=?0.044). In conclusion, lower peak torque, end-range torque and total angular impulse during eccentric contractions and a greater peak torque slope may identify high responders to eccentric exercise.  相似文献   

12.
The aims of this study were: (1) to identify the exercise intensity that corresponds to the maximal lactate steady state in adolescent endurance-trained runners; (2) to identify any differences between the sexes; and (3) to compare the maximal lactate steady state with commonly cited fixed blood lactate reference parameters. Sixteen boys and nine girls volunteered to participate in the study. They were first tested using a stepwise incremental treadmill protocol to establish the blood lactate profile and peak oxygen uptake ([Vdot]O2). Running speeds corresponding to fixed whole blood lactate concentrations of 2.0, 2.5 and 4.0?mmol?·?l?1 were calculated using linear interpolation. The maximal lactate steady state was determined from four separate 20-min constant-speed treadmill runs. The maximal lactate steady state was defined as the fastest running speed, to the nearest 0.5?km?·?h?1, where the change in blood lactate concentration between 10 and 20?min was?<0.5?mmol?·?l?1. Although the boys had to run faster than the girls to elicit the maximal lactate steady state (15.7 vs 14.3?km?·?h?1, P?<0.01), once the data were expressed relative to percent peak [Vdot]O2 (85 and 85%, respectively) and percent peak heart rate (92 and 94%, respectively), there were no differences between the sexes (P?>0.05). The running speed and percent peak [Vdot]O2 at the maximal lactate steady state were not different to those corresponding to the fixed blood lactate concentrations of 2.0 and 2.5?mmol?·?l?1 (P?>0.05), but were both lower than those at the 4.0?mmol?·?l?1 concentration (P?<0.05). In conclusion, the maximal lactate steady state corresponded to a similar relative exercise intensity as that reported in adult athletes. The running speed, percent peak [Vdot]O2 and percent peak heart rate at the maximal lactate steady state are approximated by the fixed blood lactate concentration of 2.5?mmol?·?l?1 measured during an incremental treadmill test in boys and girls.  相似文献   

13.
This study examined the effects of different work?–?rest durations during 40?min intermittent treadmill exercise and subsequent running performance. Eight males (mean?±?s: age 24.3?±?2.0 years, body mass 79.4?±?7.0?kg, height 1.77?±?0.05?m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O2max) was attained with passive recovery between each one. The work?–?rest ratio was constant at 1:1.5 with trials involving short (6:9?s), medium (12:18?s) or long (24:36?s) work?–?rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O2max. After 40?min, mean exercise intensity was greater during the long (68.4?±?9.3%) than the short work?–?rest trial (54.9?±?8.1% [Vdot]O2max; P?<?0.05). Blood lactate concentration at 10?min was higher in the long and medium than in the short work?–?rest trial (6.1?±?0.8, 5.2?±?0.9, 4.5?±?1.3?mmol?·?l?1, respectively; P?<?0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work?–?rest trials (P <?0.05). Plasma glucose concentration was higher in the long and medium than in the short work?–?rest trial after 40?min of exercise (5.6?±?0.1, 6.6?±?0.2 and 5.3?±?0.5?mmol?·?l?1, respectively; P?<?0.05). No differences were observed between trials for performance time (72.7?±?14.9, 63.2?±?13.2, 57.6?±?13.5?s for the short, medium and long work?–?rest trial, respectively; P = 0.17), although a relationship between performance time and 40?min plasma glucose was observed (P?<?0.05). The results show that 40?min of intermittent exercise involving long and medium work?–?rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work?–?rest duration.  相似文献   

14.
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   

15.
The purpose of this study was to develop an age-generalized regression model to predict maximal oxygen uptake (VO2max) based on a maximal treadmill graded exercise test (GXT; George, 1996) George, J. D. 1996. Alternative approach to maximal exercise testing and VO2max prediction in college students. Research Quarterly for Exercise and Sport, 67: 452–457. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. Participants (N?=?100), ages 18–65 years, reached a maximal level of exertion (mean?±?standard deviation [SD]; maximal heart rate [HRmax]?=?185.2?±?12.4 beats per minute (bpm); maximal respiratory exchange ratio [RERmax]?=?1.18?±?0.05; maximal rating of perceived exertion (RPEmax)?=?19.1?±?0.7) during the GXT to assess VO2max (mean?±?SD; 40.24?±?9.11 mL·kg?1·min?1). Multiple linear regression generated the following prediction equation (R?=?.94, standard error of estimate [SEE]?=?3.18 mL·kg?1·min?1, %SEE?=?7.9): VO2max (mL·kg?1·min?1)?=?13.160?+?(3.314 × gender; females?=?0, males?=?1) ? (.131 × age) ? (.334 × body mass index (BMI))?+?(5.177 × treadmill speed; mph)?+?(1.315 × treadmill grade; %). Cross validation using predicted residual sum of squares (PRESS) statistics revealed minimal shrinkage (Rp ?=?.93 and SEE p ?=?3.40 mL·kg?1·min?1); consequently, this model should provide acceptable accuracy when it is applied to independent samples of comparable adults. Standardized β-weights indicate that treadmill speed (.583) was the most effective at predicting VO2max followed by treadmill grade (.356), age (?.197), gender (.183), and BMI (?.148). This study provides a relatively accurate regression model to predict VO2max in relatively fit men and women, ages 18–65 years, based on maximal exercise (treadmill speed and grade), biometric (BMI), and demographic (age and gender) data.  相似文献   

16.
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17.
Physical inactivity is a major contributor to low-grade systemic inflammation. Most of the studies characterizing interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) release from exercising legs have been done in young, healthy men, but studies on inactivity in older people are lacking. The impact of 14 days of one-leg immobilization (IM) on IL-6 and TNF-α release during exercise in comparison to the contralateral control (CON) leg was investigated. Fifteen healthy men (age 68.1?±?1.1?year (mean?±?SEM); BMI 27.0?±?0.4 kg·m2; VO2max 33.3?±?1.6 ml·kg?1·min?1) performed 45?min of two-leg dynamic knee extensor exercise at 19.5?±?0.9 W. Arterial and femoral venous blood samples from the CON and the IM legs were collected every 15?min during exercise, and thigh blood flow was measured with ultrasound Doppler. Arterial plasma IL-6 concentration increased with exercise (rest vs. 45?min, main effect p?p?p?=?.085, effect size 0.28) higher in the IM leg compared to the CON leg (288 (95% CI: 213–373) vs. 220 (95% CI: 152–299) pg·min?1, respectively). There was no release of TNF-α in either leg and arterial concentrations remained unchanged during exercise (p?>?.05). In conclusion, exercise induces more pronounced IL-6 secretion in healthy older men. Two weeks of unilateral immobilization on the other hand had only a minor influence on IL-6 release. Neither immobilization nor exercise had an effect on TNF-α release across the working legs in older men.  相似文献   

18.
The aim of this study was to determine the effects of caffeine ingestion on a ‘preloaded’ protocol that involved cycling for 2?min at a constant rate of 100% maximal power output immediately followed by a 1-min ‘all-out’ effort. Eleven male cyclists completed a ramp test to measure maximal power output. On two other occasions, the participants ingested caffeine (5?mg?·?kg?1) or placebo in a randomized, double-blind procedure. All tests were conducted on the participants' own bicycles using a Kingcycle? test rig. Ratings of perceived exertion (RPE; 6–20 Borg scale) were lower in the caffeine trial by approximately 1 RPE point at 30, 60 and 120?s during the constant rate phase of the preloaded test (P?<0.05). The mean power output during the all-out effort was increased following caffeine ingestion compared with placebo (794±164 vs 750±163?W; P?=?0.05). Blood lactate concentration 4, 5 and 6?min after exercise was also significantly higher by approximately 1?mmol?·?l?1 in the caffeine trial (P?<0.05). These results suggest that high-intensity cycling performance can be increased following moderate caffeine ingestion and that this improvement may be related to a reduction in RPE and an elevation in blood lactate concentration.  相似文献   

19.
The aim of the present study was to examine the effect of ingesting 75?g of glucose 45?min before the start of a graded exercise test to exhaustion on the determination of the intensity that elicits maximal fat oxidation (Fatmax). Eleven moderately trained individuals ( V?O2max: 58.9±1.0?ml?·?kg?1?·?min?1; mean±sx¯ ), who had fasted overnight, performed two graded exercise tests to exhaustion, one 45?min after ingesting a placebo drink and one 45?min after ingesting 75?g of carbohydrate in the form of glucose. The tests started at 95?W and the workload was increased by 35?W every 3?min. Gas exchange measures and heart rate were recorded throughout exercise. Fat oxidation rates were calculated using stoichiometric equations. Blood samples were collected at rest and at the end of each stage of the test. Maximal fat oxidation rates decreased from 0.46±0.06 to 0.33±0.06?g?·?min?1 when carbohydrate was ingested before the start of exercise (P?<0.01). There was also a decrease in the intensity which elicited maximal fat oxidation (60.1±1.9% vs 52.0±3.4% V?O2max) after carbohydrate ingestion (P?<0.05). Maximal power output was higher in the carbohydrate than in the placebo trial (346±12 vs 332±12?W) (P?<0.05). In conclusion, the ingestion of 75?g of carbohydrate 45?min before the onset of exercise decreased Fatmax by 14%, while the maximal rate of fat oxidation decreased by 28%.  相似文献   

20.
Abstract

This study investigated the influence of dehydration during soccer-type intermittent exercise on isokinetic and isometric muscle function. Eight soccer players performed two 90-min high-intensity intermittent shuttle-running trials without (NF) or with (FL) fluid ingestion (5 ml · kg?1 before and 2 ml · kg?1 every 15 min). Isokinetic and isometric strength and muscular power of knee flexors and knee extensors were measured pre-exercise, at half-time and post-exercise using isokinetic dynamometry. Sprint performance was monitored throughout the simulated-soccer exercise. Isokinetic knee strength was reduced at faster (3.13 rad · s?1; P = 0.009) but not slower (1.05 rad · s?1; P = 0.063) contraction speeds with exercise; however, there was no difference between FL and NF. Peak isometric strength of the knee extensors (P = 0.002) but not the knee flexors (P = 0.065) was significantly reduced with exercise with no difference between FL and NF. Average muscular power was reduced over time at both 1.05 rad · s?1 (P = 0.01) and 3.14 rad · s?1 (P = 0.033) but was not different between FL and NF. Mean 15-m sprint time increased with duration of exercise (P = 0.005) but was not different between FL and NF. In summary, fluid ingestion during 90 min of soccer-type exercise was unable to offset the reduction in isokinetic and isometric strength and muscular power of the knee extensors and flexors.  相似文献   

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