Oxygen uptake during high-intensity running: response following a single bout of interval training

Elevated oxygen uptake (VO2) during moderate-intensity running following a bout of interval running training has been studied previously. To further investigate this phenomenon, the VO2 response to high-intensity exercise was examined following a bout of interval running. Well-trained endurance runners were split into an experimental group [maximum oxygen uptake, VO2max 4.73 (0.39)l x min(-1)] and a reliability group [VO2max 4.77 (0.26)l x min(-1)]. The experimental group completed a training session (4 x 800 m at 1 km x h(-1) below speed at VO2max, with 3 min rest between each 800-m interval). Five minutes prior to, and 1 h following the training session, subjects completed 6 min 30 s of constant speed, high-intensity running designed to elicit 40% delta (where delta is the difference between VO2 at ventilatory threshold and VO2max; tests 1 and 2, respectively). The slow component of VO2 kinetics was quantified as the difference between the VO2 at 6 min and the VO2 at 3 min of exercise, i.e. deltaVO2(6-3). The deltaVO2(-3) was the same in two identical conditions in the reliability group [mean (SD): 0.30 (0.10)l x min(-1) vs 0.32 (0.13)l x min(-1)]. In the experimental group, the magnitude of the slow component of VO2 kinetics was increased in test 2 compared with test 1 by 24.9% [0.27 (0.14)l x min(-1) vs 0.34 (0.08)l x min(-1), P < 0.05]. The increase in deltaVO2(6-3) in the experimental group was observed in the absence of any significant change in body mass, core temperature or blood lactate concentration, either at the start or end of tests 1 or 2. It is concluded that similar mechanisms may be responsible for the slow component of VO2 kinetics and for the fatigue following the training session. It has been suggested previously that this mechanism may be linked primarily to changes within the active limb, with the recruitment of alternative and/or additional less efficient fibres.     

Acute response of plasma markers of bone turnover to a single bout of resistance training or plyometrics

The time course of changes in plasma bone turnover markers following an acute bout of resistance training (RT) or plyometrics (PLY) has not been well characterized. This study is the first to compare the acute response of bone formation and resorption markers to a single bout of RT or PLY. Using a partially randomized, cross-over study design, 12 recreationally active men, aged 43 ± 5 yr, each completed four exercise trials: RT (Fed/Fasted) and PLY (Fed/Fasted). In addition to the RT and PLY trials, 5 of the original 12 participants also completed a fasted, no-exercise control trial to examine time-of-day variation. For each trial, blood was drawn immediately before exercise (PRE), immediately following exercise, and 15 min, 30 min, 1 h, 2 h, and 24 h following PRE for determination of plasma bone-specific alkaline phosphatase (BAP), osteocalcin (OC), tartrate-resistant acid phosphatase 5b (TRAP5b), COOH-terminal telopeptide of type I collagen (CTX), testosterone, parathyroid hormone, and cortisol. A one-factor repeated-measures ANOVA was performed for each trial to detect changes in bone markers during the 2 h following RT or PLY. TRAP5b transiently decreased during the 2 h following all exercise trials (main effect for time, P < 0.05), but returned to PRE concentrations 2 h postexercise. BAP, CTX, and OC remained unchanged, except for reductions in BAP and CTX following PLY-Fasted and PLY-Fed, respectively. During the control trial, BAP decreased, while TRAP5b, CTX, and OC remained unchanged. In general, plasma hormone concentrations decreased during the 2 h following PLY or RT, and cumulative decreases in TRAP5b during the 2 h following exercise were positively correlated with cumulative decreases in parathyroid hormone. The results of the present study suggest that the timing of the measurement of bone turnover markers relative to the last exercise bout is important for detection of exercise-associated changes in bone turnover markers, as the markers returned to preexercise values within 2 h of RT or PLY.     

Oxygen uptake during moderate intensity running: response following a single bout of interval training

Eight male endurance runners [mean ± (SD): age 25 (6) years; height 1.79 (0.06) m; body mass 70.5 (6.0) kg; % body fat 12.5 (3.2); maximal oxygen consumption (V˙O_2max 62.9 (1.7) ml · kg⁻¹ · min⁻¹] performed an interval training session, preceded immediately by test 1, followed after 1 h by test 2, and after 72 h by test 3. The training session was six 800-m intervals at 1 km · h⁻¹ below the velocity achieved at V˙O_2max with 3 min of recovery between each interval. Tests 1, 2 and 3 were identical, and included collection of expired gas, measurement of ventilatory frequency (f _v ), heart rate (f _c), rate of perceived exertion (RPE), and blood lactate concentration ([La⁻]_B) during the final 5 min of 15 min of running at 50% of the velocity achieved at V˙O_2max (50% −V˙O_2max).␣Oxygen uptake (V˙O₂), ventilation (V˙ _E ), and respiratory exchange ratio (R) were subsequently determined from duplicate expired gas collections. Body mass and plasma volume changes were measured preceding and immediately following the training session, and before tests 1–3. Subjects ingested water immediately following the training session, the volume of which was determined from the loss of body mass during the session. Repeated measures analysis of variance with multiple comparison (Tukey) was used to test differences between results. No significant differences in body mass or plasma volume existed between the three test stages, indicating that the differences recorded for the measured parameters could not be attributed to changes in body mass or plasma volume between tests, and that rehydration after the interval training session was successful. A significant (P < 0.05) increase was found from test 1 to test 2 [mean (SD)] for V˙O₂ [2.128 (0.147) to 2.200 (0.140) 1 · min⁻¹], f _c [125 (17) to 132 (16) beats · min⁻¹], and RPE [9 (2) to 11 (2)]. A significant (P < 0.05) decrease was found for submaximal R [0.89 (0.03) to 0.85 (0.04)]. These results suggest that alterations in V˙O₂ during moderate-intensity, constant-velocity running do occur following heavy-intensity endurance running training, and that this is due to factors in addition to changed substrate metabolism towards greater fat utilisation, which could explain only 31% of the increase in V˙O₂. Accepted: 8 December 1997     

The acute response of neutrophil function to a bout of judo training

Intensive exercise training decreases neutrophil functions in athletes. However, no studies to date have investigated the effect of irregular‐interval training, such as is associated with judo training programmes, on neutrophil functions. The purpose of this study was to examine such effects. Thirty‐seven male college judoists participated in this study. Neutrophil oxidative burst activity, phagocytic activity and expression of CD11b and CD16 per cell were measured by ?ow cytometry before and after judo training. Total neutrophil counts increased signi?cantly from 2.98 ± 0.82 to 7.95 ± 1.80 × 10³/µL (p < 0.001). The proportion of neutrophils producing reactive oxygen species (ROS) was increased signi?cantly (p < 0.001). On the other hand, the phagocytic activity decreased after training, as shown by a decrease in the amount of ingested opsonized zymosan per cell (p < 0.001), possibly as a compensatory effect for the increased numbers of ROS‐producing neutrophils. Expression of CD11b and CD16 per cell decreased by 20% and 30%, respectively, after judo training. In conclusion, judo training induced a decrease in phagocytic activity through the lowered expression of CD11b and CD16 on the surface of neutrophils, and increased the oxidative burst activity of neutrophils. Copyright © 2003 John Wiley & Sons, Ltd.     

Autophagic response to a single bout of moderate exercise in murine skeletal muscle

The effect of a single bout of exercise on autopahgy in murine gastrocnemius muscle was investigated. Autophagy is a process for the degradation system of cytoplasmic components, which may help maintain intracellular quality control of cell survival and turnover under normal conditions. The present study investigated the changes of autophagy-related proteins including microtubule-associated protein 1b light chain 3 (LC3), Beclin-1, Atg7 (autophagy-related gene 7), conjugation form of Atg12 to Atg5, lysosome-associated membrane protein (LAMP2a), and muscle-specific RING finger protein-1 (MURF-1) protein level in gastrocnemius muscle after a single bout of treadmill exercise. Mice exercised on a treadmill for 50 min at a speed of 12.3 m/min with a slope of 5°. The animals were sacrificed by cervical dislocation 0, 3, 6, or 12 h after exercise, and muscle samples were collected immediately. Western blot analysis demonstrated that the autophagy marker LC3-II was significantly decreased during the recovery period (3, 6, and 12 h) whereas there was no decrease immediately after exercise (0 h). To identify factors related to this decrease, autophagosome component proteins were examined in murine gastrocnemius muscle. A decrease in Beclin-1, Atg7, and LAMP2a during recovery period was concomitant with the decreased level of LC3-II. Additionally, MuRF-1 expression was significantly increased after a single bout of exercise. This study is the first to demonstrate autophasic related protein expression after a single bout of treadmill exercise and our results suggest that a single bout of treadmill exercise attenuates the autophagic response in murine skeletal muscle.     

Physical performance and cardiovascular responses to an acute bout of heavy resistance circuit training versus traditional strength training

Circuit training effectively reduces the time devoted to strength training while allowing an adequate training volume to be achieved. Nonetheless, circuit training has traditionally been performed using relatively low loads for a relatively high number of repetitions, which is not conducive to maximal muscle size and strength gain. This investigation compared physical performance parameters and cardiovascular load during heavy-resistance circuit (HRC) training to the responses during a traditional, passive rest strength training set (TS). Ten healthy subjects (age, 26 +/- 1.6 years; weight, 80.2 +/- 8.78 kg) with strength training experience volunteered for the study. Testing was performed once weekly for 3 weeks. On day 1, subjects were familiarized with the test and training exercises. On the subsequent 2 test days, subjects performed 1 of 2 strength training programs: HRC (5 sets x (bench press + leg extensions + ankle extensions); 35-second interset rest; 6 repetition maximum [6RM] loads) or TS (5 sets x bench press; 3-minute interset rest, 6RM loads). The data confirm that the maximum and average bar velocity and power and the number of repetitions performed of the bench press in the 2 conditions was the same; however, the average heart rate was significantly greater in the HRC compared to the TS condition (HRC = 129 +/- 15.6 beats x min(-1), approximately 71% maximum heart rate (HRmax), TS = 113 +/- 13.1 beats x min(-1), approximately 62% HRmax; P < 0.05). Thus, HRC sets are quantitatively similar to traditional strength training sets, but the cardiovascular load is substantially greater. HRC may be an effective training strategy for the promotion of both strength and cardiovascular adaptations.     

Thioredoxin induction of peripheral blood mononuclear cells in mice in response to a single bout of swimming exercise

Thioredoxin (TRX) is a stress-inducible protein with diverse intracellular functions, which is expressed under conditions of oxidative stress. Exercise is known to cause oxidative stress by the generation of oxygen radicals from various biological pathways. The purpose of this study was to determine the level of TRX induction of cellular extracts prepared from peripheral blood mononuclear cells after a 30-min swimming exercise in mice. Plasma corticosterone concentration, considered to be a marker for exercise-induced various stress, rose significantly (p < 0.05) 0.5 h after exercise and rapidly dropped down following recovery. The carbonyl proteins as a marker of oxidative stress were significantly (p < 0.05) higher after 6 and 12 h of recovery in cytosolic extracts. The cytoplasm and nucleus TRX expressions were slightly higher to resting values after 12 and 24 h of recovery. The nucleus TRX expression was significantly (p < 0.05) higher after 24 h of recovery. These findings demonstrate that exercise-induced oxidative stress may be associated with increased intracellular TRX expression after 12 and/or 24 h after exercise in peripheral blood mononuclear cells. It is implied that this delayed and prolonged over-expression of TRX may play some roles in response to exercise-induced oxidative stress.     

The effects of yoga training and a single bout of yoga on delayed onset muscle soreness in the lower extremity

The purpose of this study was to determine the effects of yoga training and a single bout of yoga on the intensity of delayed onset muscle soreness (DOMS). 24 yoga-trained (YT; n = 12) and non-yoga-trained (CON; n = 12), matched women volunteers were administered a DOMS-inducing bench-stepping exercise. Muscle soreness was assessed at baseline, 24, 48, 72, 96, and 120 hours after bench-stepping using a Visual Analog Scale (VAS). Groups were also compared on body awareness (BA), flexibility using the sit-and-reach test (SR), and perceived exertion (RPE). Statistical significance was accepted at p 相似文献   

Gender differences in insulin action after a single bout of exercise.

Effects of a single exercise bout on insulin action were compared in men (n = 10) and women (n = 10). On an exercise day, subjects cycled for 90 min at 85% lactate threshold, whereas on a rest (control) day, they remained semirecumbent. The period of exercise, or rest, was followed by a 3-h hyperinsulinemic-euglycemic clamp (30 mU.m(-2).min(-1)) and indirect calorimetry. Glucose kinetics were measured isotopically by using an infusion of [6,6-2H2]glucose. Glucose infusion rate (GIR) during the clamp on the rest day was not different between the genders. However, GIR on the exercise day was significantly lower in men compared with women (P = 0.01). This was mainly due to a significantly lower glucose rate of disappearance in men compared with women (P = 0.05), whereas no differences were observed in the endogenous glucose rate of appearance. Nonprotein respiratory quotient (NPRQ) increased significantly during the clamp from preclamp measurements in men and women on the rest day (P < 0.01). Exercise abolished the increase in NPRQ seen during the clamp on the rest day and tended to decrease NPRQ in men. Our results indicate the following: 1) exercise abolishes the usual increase in NPRQ observed during a hyperinsulinemic-euglycemic clamp in both genders, 2) men exhibit relatively lower whole body insulin action in the 3-4 h after exercise compared with women, and 3) gender differences in insulin action may be explained by a lower glucose rate of disappearance in the men after acute exercise. Together, these data imply gender differences in insulin action postexercise exist in peripheral tissues and not in liver.     

Evidence for altered alpha-adrenoreceptor responsiveness after a single bout of maximal exercise.

We studied hemodynamic responses to alpha- and beta-receptor agonists in eight men to test the hypothesis that adrenoreceptor responsiveness is altered within 24 h of the performance of maximal exercise. Adrenoreceptor responsiveness was tested under two experimental conditions (with and without maximal exercise). Adrenoreceptor tests were performed 24 h after each subject performed graded upright cycle ergometry to volitional exhaustion. The 2 test days (experimental conditions) were separated by at least 1 wk, and the order of exercise and no-exercise conditions was counterbalanced. Steady-state graded infusions of phenylephrine (PE) and isoproterenol (Iso) were used to assess alpha- and beta-adrenoreceptor responsiveness, respectively. Slopes calculated from linear regressions between Iso and PE doses and changes in heart rate, blood pressure, and leg vascular resistance for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. The slope of the relationship between heart rate and Iso with maximal exercise was 1773 +/- 164 beats x microm-1x kg-1x min-1 compared with 1987 +/- 142 beats x microg-1x kg-1x min-1 without exercise (P = 0.158), whereas the slopes of the relationship between vascular resistance to Iso were -438 +/- 123 peripheral resistance units (PRU) x microg-1x kg-1x min-1 with maximal exercise and -429 +/- 105 x microg-1x kg-1 x min-1 without exercise (P = 0.904). Maximal exercise was associated with greater (P < 0.05) vascular resistance (15.1 +/- 2.8 PRU x microg-1 kg-1x min-1) and mean arterial blood pressure (15.8 +/- 2.1 mmHg. microg-1x kg-1x min-1) responses to PE infusion compared with no exercise (9.0 +/- 2.0 PRU x microg-1 kg-1 x min-1 and 10.9 +/- 2.0 mmHg. microg-1x kg-1x min-1, respectively). These results provide evidence that a single bout of maximal exercise increases alpha1-adrenoreceptor responsiveness within 24 h without affecting beta-cardiac and vascular adrenoreceptor responses.     

Effects of aerobic training on heart rate dynamics in sedentary subjects.

This study was designed to assess the effects of moderate- and high-volume aerobic training on the time domain and on spectral and fractal heart rate (HR) variability indexes. Sedentary subjects were randomized into groups with moderate-volume training (n = 20), high-volume training (n = 20), and controls (n = 15). The training period was 8 wk, including 6 sessions/wk at an intensity of 70-80% of the maximum HR, lasting for 30 min/session in the moderate-volume group and 60 min/session in the high-volume group. Time domain, frequency domain, and short-term fractal scaling measures of HR variability were analyzed over a 24-h period. Mean HR decreased from 70 +/- 7 to 64 +/- 8 beats/min and from 67 +/- 5 to 60 +/- 6 beats/min (P < 0.001 for both) for the moderate- and high-volume training groups, respectively. The normalized high-frequency spectral component increased in both groups (P < 0.05). The normalized low-frequency component decreased significantly (P < 0.05), resulting in a marked decrease in low frequency-to-high frequency ratio in both groups. In addition, short-term scaling exponent decreased in both groups (P < 0.001). There were no significant differences in the changes of HR variability indexes between groups. Aerobic training in sedentary subjects results in altered autonomic regulation of HR toward vagal dominance. A moderate training volume is a sufficient intervention to induce these beneficial effects.     

Effect of a single bout of resistance exercise on postprandial glucose and insulin response the next day in healthy, strength-trained men

Postprandial blood glucose and insulin levels are both risk factors for developing obesity, type-2 diabetes, and coronary heart diseases. To date, research has shown that a single bout of moderate- to high-intensity aerobic exercise performed 相似文献   

Exercise-induced oxidative stress in elderly subjects: the effect of red orange supplementation on the biochemical and cellular response to a single bout of intense physical activity

Abstract

Aging is characterized by an impaired capacity to maintain the redox balance both in physiological and pathological situations associated with an increased production of reactive oxygen species. Since the extent of this phenomenon may be influenced by an antioxidants-rich diet, we investigated the effect of supplementation with fresh red orange juice (ROJ) on biochemical and cellular biomarkers of oxidative stress in healthy, trained elderly women after a single bout of exhaustive exercise (EE). To this purpose, a sample of 22 females, 15 (69.0 ± 5.1 years) taking the ROJ supplementation and 7 (68.1 ± 2.7 years) as Control group, was constituted. Blood samples were collected immediately before, 30 minutes, and 24 hr after a single bout of EE, at baseline and after 4 weeks. Our results demonstrate that markers of DNA damage or apoptosis were not affected by EE both in Control and ROJ group, and by ROJ, whereas, exercise temporarily affected the redox balance in both groups. Controls didn't change their response to EE after the experimental period, but experimental group after ROJ supplementation had lower EE-induced MDA, consumed less ascorbic acid, and had less activation of the hypoxanthine/xanthine system, i.e., they seemed to be protected from hypoxia/reoxygenation mechanisms.     

Effects of suckling frequency and breed on productive performance,follicular dynamics and postpartum interval in beef cows

One experiment was conducted to determine the influence of suckling frequency (restricted suckling (RS) versus ad libitum suckling (AS)) and breed (Brown Swiss versus Pirenaica) on productive performance, follicular dynamics and postpartum cyclicity resumption in beef cows. Twenty-four spring-calving cows (12 Brown Swiss and 12 Pirenaica) were used. After calving cows were assigned, within breed, to the two suckling frequencies (RS versus AS). During the postpartum period, cows were fed 100% of the daily energy estimated requirements. The study was conducted from calving to either day 90 postpartum or to detection of the second ovulation whenever it came later. The pattern of follicular development was monitored daily by transrectal ultrasonography, and blood samples were collected three times a week to analyse progesterone concentrations by RIA. Body condition score at calving was 2.5 (from 1 to 5). Productive parameters were not significantly affected by suckling frequency. Pirenaica cows gained more weight (P<0.001), while Brown Swiss cows had higher milk yield (P<0.001) and thus their calves grew faster (P<0.05). In the present moderate conditions of nutrition, either suckling frequency or breed did not affect follicular dynamics (on average there were 6.5 follicles in emergence, growth rate of dominant follicle (DF) was 1.3mm per day and maximum diameter of dominant follicle was 13.9mm). There were gradual increases in maximum diameter and growth rate of dominant follicle related to the proximity of the ovulatory waves, and they were defined by third order polynomial equations. Postpartum anoestrous interval (PPI) was markedly affected by the interaction between suckling frequency and breed (P<0.001): ad libitum suckling prolonged significantly the interval from calving to first ovulation in Brown Swiss cows (31.8 day versus 82.7 day, in RS and AS groups, respectively, P<0.05), but not in Pirenaica cows (43.5 day versus 32.6 day, in RS and AS groups, respectively, not statistically significant). It is concluded that in moderate pre- and postpartum nutritional conditions Brown Swiss cows were more susceptible to the suppressor effect of ad libitum suckling on postpartum anoestrous interval than Pirenaica cows, although this breed difference did not seem to be mediated by differences in energy balance or in ovarian follicular dynamics.     

Immunological changes after a single bout of moderate-intensity exercise in a hot environment

This study was aimed to evaluate the possible changes caused by a single bout of moderate-intensity exercise in a hot environmental temperature on the immune function and on inflammatory markers. A total of 22 young male adults (VO_2max, 55.4±3.6 ml·kg^?1·min^?1) volunteered to participate in an exercise session of 60 minutes on a treadmill ergometer at moderate speed (60% of the maximum aerobic speed) in hot environmental conditions (35°C and humidity 60%). Total leukocyte numbers, lymphocyte subsets (CD8+, CD4+, CD3+, NK and CD19+), cytokine production capacity by peripheral blood mononuclear cells (PBMCs) (IL-2, IL-4, IL-5, IL-10, IFN-γ and TNF-α) as well as the concentration of several inflammation related proteins (ceruloplasmin, C-reactive protein (CRP), complement factors C3 and C4) were evaluated before and after exercise. The results show that leukocyte and neutrophil absolute values increased (P<0.001) after the exercise period. In contrast, eosinophil values decreased (P<0.05) after the exercise. In addition, ceruloplasmin, C3 and C4 values (P<0.05) increased after exercise. No changes in T lymphocyte subsets, cytokine production, or CRP were observed. These data confirm previous studies suggesting that a 60 min exercise in a hot environment is enough to cause a physiologic adaptation to these special conditions leading to an increase of non-specific immune cells and promoting inflammatory processes. On the other hand, PCR values, lymphocyte subsets and the capacity of cytokine production by PBMC were not changed in a relatively short bout of exercise under these conditions in contrast with previous studies.     

Effects of creatine supplementation on performance and training adaptations

Creatine has become a popular nutritional supplement among athletes. Recent research has also suggested that there may be a number of potential therapeutic uses of creatine. This paper reviews the available research that has examined the potential ergogenic value of creatine supplementation on exercise performance and training adaptations. Review of the literature indicates that over 500 research studies have evaluated the effects of creatine supplementation on muscle physiology and/or exercise capacity in healthy, trained, and various diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5–7 days) has typically been reported to increase total creatine content by 10–30% and phosphocreatine stores by 10–40%. Of the approximately 300 studies that have evaluated the potential ergogenic value of creatine supplementation, about 70% of these studies report statistically significant results while remaining studies generally report non-significant gains in performance. No study reports a statistically significant ergolytic effect. For example, short-term creatine supplementation has been reported to improve maximal power/strength (5–15%), work performed during sets of maximal effort muscle contractions (5–15%), single-effort sprint performance (1–5%), and work performed during repetitive sprint performance (5–15%). Moreover, creatine supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Although not all studies report significant results, the preponderance of scientific evidence indicates that creatine supplementation appears to be a generally effective nutritional ergogenic aid for a variety of exercise tasks in a number of athletic and clinical populations.     

Effects of training with a dynamic moment of inertia bat on swing performance

The purpose of this study was to investigate the effects of the 8-week dynamic moment of inertia (DMOI) bat training on swing velocity, batted-ball speed, hitting distance, muscle power, and grip force. The DMOI bat is characterized in that the bat could be swung more easily by reducing the moment of inertia at the initial stage of swing without decreasing the bat weight and has a faster swing velocity and lower muscle activity. Seventeen varsity baseball players were randomly assigned to the DMOI bat training group (n = 9) and the normal bat training group (n = 8). The training protocol was 7 swings each set, 5-8 sets each time, 3 times each week, and 8 weeks' training period. The results showed that the swing training with the DMOI bat for 8 weeks significantly increased swing velocity by about 6.20% (96.86 ± 8.48 vs. 102.82 ± 9.93 km·h(-1)), hitting distance by about 6.69% (80.06 ± 9.16 vs. 84.99 ± 7.26 m), muscle power of the right arm by about 12.04% (3.34 ± 0.41 vs. 3.74 ± 0.61 m), and muscle power of the left arm by about 8.23% (3.36 ± 0.46 vs. 3.61 ± 0.39 m) (p < 0.05). Furthermore, the DMOI bat training group had a significantly better change percentage in swing velocity, hitting distance, and grip force of the left hand than did the normal bat training group (p < 0.05). The findings suggested that the swing training with the DMOI bat has a positive benefit on swing performance and that the DMOI bat could be used as a new training tool in baseball.