Cell numbers and in vitro responses of leucocytes and lymphocyte subpopulations following maximal exercise and interval training sessions of different intensities.

In vitro lymphocyte function and the mobilisation of peripheral blood leucocytes was examined in eight trained subjects who undertook an incremental exercise test to exhaustion and a series of interval training sessions. Venous blood samples were obtained before the incremental test, immediately after, and 30, 60, and 120 min after the test. Interval training sessions were undertaken on separate days and the exercise intensities for each of the different sessions were 30%, 60%, 90% and 120% of their maximal work capacity respectively, as determined from the incremental exercise test. There were 15 exercise periods of 1-min duration separated by recovery intervals of 2 min in each session. Venous blood samples were obtained immediately after each training session. Significant increases in lymphocyte subpopulations (CD3+, CD4+, CD8+, CD20+, and CD56+) occurred following both maximal and supramaximal exercise. This was accompanied by a significant decrease in the response of cultures of peripheral blood lymphocytes to Concanavalin A (ConA), a T-cell mitogen. The state of lymphocyte activation in vivo as measured by CD25+ surface antigen was not, however, affected by acute exercise. The total number of lymphocytes, distribution of lymphocyte subpopulations and in vitro lymphocyte response to ConA had returned to pre-exercise levels within half an hour of termination of exercise but serum cortisol concentrations had not begun to fall at this time. There was a significant decrease in the CD4+:CD8+ cell ratio following exercise; this was more the result of increases in CD3-CD8+ cells (CD8+ natural killer cells) than to CD3+CD8+ cells (CD8+ T-lymphocytes). Decreased responsiveness of T-cells to T-cell mitogens, postexercise, may have been the result of decreases in the percentage of T-cells in postexercise mixed lymphocyte cultures rather than depressed cell function. The cause of this was an increase in the percentage of natural killer cells which did not respond to the T-cell mitogen. The results indicated that while a substantial immediate in vitro "immunomodulation" occurred with acute exercise, this did not reflect an immunosuppression but was rather the result of changes in the proportions of reactive cells in mononuclear cell cultures. We have also demonstrated that the degree of the change in distribution of lymphocyte subpopulation numbers and responsiveness of peripheral blood mononuclear cells in in vitro mitogen reactions increased with increasing exercise intensity. Plasma volume changes may have contributed to some of the changes seen in leucocyte population and subpopulation numbers during and following exercise.     

Thermoregulatory responses in humans during exercise after exposure to two different light intensities

The effects after exposure to two different light intensities (dim, 50 lx and bright, 5000 lx) on thermoregulatory responses during exercise in a climatic chamber (27 degrees C, 60% relative humidity) were studied in nine untrained female subjects, aged 19-22 years. The subjects were in either the dim or bright light intensities from 0600 hours to 1200 hours. They were then instructed to exercise on a cycle ergometer at an intensity of 60% maximal oxygen uptake from 1200 hours to 1300 hours in a light intensity of 500 Ix. The main results can be summarized as follows. Firstly, exercise-induced increases of core temperature were significantly smaller, after exposure to the bright than after the dim light intensities, although both tests were performed in the same light intensity. Secondly, body mass loss after exercise was significantly greater after exposure to the bright light intensity. Thirdly, an increase in salivary lactic acid during exercise was significantly lower after the bright intensity. Fourthly although the salivary melatonin level was not different between the two light intensities both before and after the exercise, it increased significantly during exercise only after the bright intensity. These results are discussed in terms of the establishment of a lower set-point in the core temperature after exposure to a bright light intensity.     

Breathing pattern during and after exercise of different intensities

We recently observed rapid shallow breathing during recovery from maximal exercise in some normal subjects. We wondered whether this phenomenon is randomly related to level of exercise or is limited to recovery from very high levels of exercise. We monitored ventilation, tidal volume, and respiratory frequency in seven normal subjects during and after exercise. Each subject exercised on several occasions on separate days. At least two of the tests were maximal (i.e., subject terminated). In the other tests exercise was terminated by the experimenter at different fractions of the highest level attained by the subject. There was no systematic difference between breathing pattern during exercise and recovery in tests where final O2 consumption (VO2) was 45-92% of the subjects' highest VO2. By contrast 13 of 19 studies in which final VO2 was 92-100% of highest VO2 were followed by relative rapid shallow breathing. We conclude that rapid shallow breathing during recovery from exercise is a phenomenon that is limited to very high exercise levels. On consideration of the various mechanisms that may be entertained to explain this phenomenon, we believe that development of pulmonary congestion-interstitial edema at very high levels of exercise is the most consistent with our findings.     

Physiological responses to glycerol ingestion during exercise

To study selected cardiovascular, thermoregulatory, and hormonal responses to the consumption of glycerol solutions during exercise, nine subjects cycled for 90 min at 50% peak O2 uptake in a 30 degree C, 45% relative humidity environment. Beverages tested included a 10% glycerol solution (G), a 6% carbohydrate-electrolyte beverage (CE), the 6% carbohydrate-electrolyte beverage plus 4% glycerol (CEG), and a water placebo (WP) ingested at regular intervals during the first 60 min of exercise. The beverages were administered in counterbalanced order with subjects serving as their own controls. Ingestion of the glycerol solutions resulted in an increase in plasma osmolality and attenuation of the decrease in plasma volume associated with the WP treatment (P less than 0.05). Plasma renin activity was highest with WP (P less than 0.05), and G was associated with increased antidiuretic hormone levels (P less than 0.05). Ratings of perceived thirst were lowest for CEG and G, and the frequency of gastrointestinal distress was greatest for G (P less than 0.05). However, no differences among beverage treatments were observed for heart rate, esophageal temperature, sweat rate, ratings of perceived exertion, or changes in cortisol and aldosterone levels. These data indicate that there are no substantial metabolic, hormonal, cardiovascular, or thermoregulatory advantages to the consumption of solutions containing 4 or 10% glycerol during exercise.     

Physiological responses to interval training sessions at velocities associated with VO2max

Previous research has indicated that short-duration, high-intensity work intervals performed at velocities associated with maximal oxygen uptake (vVO2max) combined with active recovery intervals may be effective in eliciting improvements in endurance performance. This study was designed to characterize selected physiological responses to short-duration (< or = 60 seconds) interval work performed at velocities corresponding to 100% of vVO2max. Twelve men participated in 3 randomized trials consisting of treadmill running using work (W)/recovery (R) intervals of 15 seconds W/15 seconds R (15/15); 30 seconds W/15 seconds R (30/15); and 60 seconds W/15 seconds R (60/15). Work intervals were performed at 100% of vVO2max, whereas R intervals were performed at 50% of vVO2max. A fourth trial consisting of continuous work (C) at 100% of vVO2max was also performed. All subjects completed the 15/15 and 30/15 trials; however, only 5 of the 12 completed the 60/15 trial. The percentage of VO2max (mean +/- SD) during 15/15 (71.6 +/- 4.2%) was significantly lower (p < or = 0.05) than the percentages during 30/15 (84.6 +/- 4.0%), 60/15 (89.2 +/- 4.2%), or C (87.9 +/- 5.0%). Similar results were found for heart rate and perceived exertion. Blood lactate concentrations following exercise were significantly lower (p < or = 0.05) in 15/15 (7.3 +/- 2.4 mmol x L(-1)) than in the other trials. No significant differences (p > 0.05) existed among 30/15 (11.5 +/- 1.8 mmol x L(-1)), 60/15 (12.5 +/- 1.8 mmol x L(-1)) or C (12.1 +/- 1.8 mmol x L(-1)). High intensity, short-duration 2:1 W/R intervals appear to produce responses that may benefit both aerobic and anaerobic energy system development. A 4:1 W/R ratio may be an upper limit for individuals in the initial phases of interval training.     

Physiological and behavioral responses of horses during police training

Mounted police horses have to cope with challenging, unpredictable situations when on duty and it is essential to gain insight into how these horses handle stress to warrant their welfare. The aim of the study was to evaluate physiological and behavioral responses of 12 (six experienced and six inexperienced) police horses during police training. Horses were evaluated during four test settings at three time points over a 7-week period: outdoor track test, street track test, indoor arena test and smoke machine test. Heart rate (HR; beats/min), HR variability (HRV; root means square of successive differences; ms), behavior score (BS; scores 0 to 5) and standard police performance score (PPS; scores 1 to 0) were obtained per test. All data were statistically evaluated using a linear mixed model (Akaike's Information criterium; t > 2.00) or logistic regression (P < 0.05). HR of horses was increased at indoor arena test (98 ± 26) and smoke machine test (107 ± 25) compared with outdoor track (80 ± 12, t = 2.83 and t = 3.91, respectively) and street track tests (81 ± 14, t = 2.48 and t = 3.52, respectively). HRV of horses at the indoor arena test (42.4 ± 50.2) was significantly lower compared with street track test (85.7 ± 94.3 and t = 2.78). BS did not show significant differences between tests and HR of horses was not always correlated with the observed moderate behavioral responses. HR, HRV, PPS and BS did not differ between repetition of tests and there were no significant differences in any of the four tests between experienced and inexperienced horses. No habituation occurred during the test weeks, and experience as a police horse does not seem to be a key factor in how these horses handle stress. All horses showed only modest behavioral responses, and HR may provide complimentary information for individual evaluation and welfare assessment of these horses. Overall, little evidence of stress was observed during these police training tests. As three of these tests (excluding the indoor arena test) reflect normal police work, it is suggested that this kind of police work is not significantly stressful for horses and will have no negative impact on the horse's welfare.     

Plasma testosterone and catecholamine responses to physical exercise of different intensities in men

Plasma testosterone, noradrenaline, and adrenaline concentrations during three bicycle ergometer tests of the same total work output (2160 J X kg-1) but different intensity and duration were measured in healthy male subjects. Tests A and B consisted of three consecutive exercise bouts, lasting 6 min each, of either increasing (1.5, 2.0, 2.5 W X kg-1) or constant (2.0, 2.0, 2.0 W X kg-1) work loads, respectively. In test C the subjects performed two exercise bouts each lasting 4.5 min, with work loads of 4.0 W X kg-1. All the exercise bouts were separated by 1-min periods of rest. Exercise B of constant low intensity resulted only in a small increase in plasma noradrenaline concentration. Exercise A of graded intensity caused an increase in both catecholamine levels, whereas, during the most intensive exercise C, significant elevations in plasma noradrenaline, adrenaline and testosterone concentrations occurred. A significant positive correlation was obtained between the mean value of plasma testosterone and that of adrenaline as well as noradrenaline during exercise. It is concluded that both plasma testosterone and catecholamine responses to physical effort depend more on work intensity than on work duration or total work output.     

Hormonal and inflammatory responses to different types of sprint interval training

We evaluated the effect of different types of sprint interval sessions on the balance between anabolic and catabolic hormones and circulating inflammatory cytokines. Twelve healthy elite junior handball players (17-25 years) participated in the study. Exercise consisted of increasing distance (100 m, 200 m, 300 m, 400 m) and decreasing distance (400 m, 300 m, 200 m, 100 m) sprint interval runs on a treadmill (at random order), at a constant work rate of 80% of the personal maximal speed (calculated from the maximal speed of a 100 m run). The total rest period between the runs in the different interval sessions were similar. Blood samples were collected before, after each run, and after 1-hour recovery. Both types of sprint interval trainings led to a significant (p < 0.05) increase in lactate and the anabolic factors growth hormone, insulin-like growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), and testosterone levels. Both types of sprint interval sessions led to a significant (p < 0.05) increase in the circulating pro- and anti-inflammatory mediators IL-1, IL-6, and IL1ra. IL-6 remained elevated in both sessions after 1-hour recovery. Area under the curve was significantly greater (p < 0.05) for lactate and growth hormone (GH) in the decreasing distance session. In contrast, rate of perceived exertion was higher in the increasing distance session, but this difference was not statistically significant (p = 0.07). Changes in anabolic-catabolic hormones and inflammatory mediators can be used to gauge the training intensity of anaerobic-type exercise. Changes in the GH-IGF-I axis and testosterone level suggest exercise-related anabolic adaptations. Increases in inflammatory mediators may indicate their important role in muscle tissue repair after anaerobic exercise. The decreasing distance interval was associated with a greater metabolic (lactate) and anabolic (GH) response but not with a higher rate of perceived exertion. Coaches and athletes should be aware of these differences, and as a result, of a need for specific recovery adaptations after different interval training protocols.     

Effects of training duration on substrate turnover and oxidation during exercise

Phillips, S. M., H. J. Green, M. A. Tarnopolsky, G. J. F. Heigenhauser, R. E. Hill, and S. M. Grant. Effects of training duration on substrate turnover and oxidation during exercise. J. Appl. Physiol. 81(5):2182-2191, 1996.Adaptations in fat and carbohydrate metabolismafter a prolonged endurance training program were examined using stableisotope tracers of glucose([6,6-²H₂]glucose),glycerol([²H₅]glycerol),and palmitate([²H₂]palmitate).Active, but untrained, males exercised on a cycle for 2 h/day[60% pretraining peak O₂consumption (O_{2 peak}) = 44.3 ± 2.4 ml ^· kg^{1 ·} min¹]for a total of 31 days. Three cycle tests (90 min at 60% pretraining O_{2 peak}) wereadministered before training (PRE) and after 5 (5D) and 31 (31D) daysof training. Exercise increased the rate of glucose production(R_a) and utilization(R_d) as well as the rate oflipolysis (glycerol R_a) and freefatty acid turnover (FFA R_a/R_d).At 5D, training induced a 10% (P < 0.05) increase in total fat oxidation because of an increase inintramuscular triglyceride oxidation (+63%,P < 0.05) and a decreased glycogenoxidation (16%, P < 0.05).At 31D, total fat oxidation during exercise increased a further 58%(P < 0.01). The pattern of fatutilization during exercise at 31D showed a reduced reliance on plasmaFFA oxidation (FFA R_d) and agreater dependence on oxidation of intramuscular triglyceride, whichincreased more than twofold (P < 0.001). In addition, glucose R_aand R_d were reduced at all timepoints during exercise at 31D compared with PRE and 5D. We concludethat long-term training induces a progressive increase in fatutilization mediated by a greater oxidation of fats from intramuscularsources and a reduction in glucose oxidation. Initial changes arepresent as early as 5D and occur before increases in muscle maximalmitochondrial enzyme activity [S. M. Phillips, H. J. Green, M. A. Tarnopolsky, G. J. F. Heigenhauser, and S. M. Grant.Am. J. Physiol. 270 (Endocrinol. Metab. 33):E265-E272, 1996].

     

Substrate metabolism during different exercise intensities in endurance-trained women.

We have studied eight endurance-trained women at rest and during exercise at 25, 65, and 85% of maximal oxygen uptake. The rate of appearance (R(a)) of free fatty acids (FFA) was determined by infusion of [(2)H(2)]palmitate, and fat oxidation rates were determined by indirect calorimetry. Glucose kinetics were assessed with [6,6-(2)H(2)]glucose. Glucose R(a) increased in relation to exercise intensity. In contrast, whereas FFA R(a) was significantly increased to the same extent in low- and moderate-intensity exercise, during high-intensity exercise, FFA R(a) was reduced compared with the other exercise values. Carbohydrate oxidation increased progressively with exercise intensity, whereas the highest rate of fat oxidation was during exercise at 65% of maximal oxygen uptake. After correction for differences in lean body mass, there were no differences between these results and previously reported data in endurance-trained men studied under the same conditions, except for slight differences in glucose metabolism during low-intensity exercise (Romijn JA, Coyle EF, Sidossis LS, Gastaldelli A, Horowitz JF, Endert E, and Wolfe RR. Am J Physiol Endocrinol Metab 265: E380-E391, 1993). We conclude that the patterns of changes in substrate kinetics during moderate- and high-intensity exercise are similar in trained men and women.     

不同强度有氧运动对大鼠脂代谢的影响

通过对不同强度有氧运动时大鼠脂代谢相关指标进行测试,发现规律的、周期性的、适宜的有氧运动对维持机体健康有益.     

Electromyogram power spectrum during dynamic contractions at different intensities of exercise

During dynamic contractions performed on a cycle ergometer, we studied the influence of motor unit (MU) recruitment on the electromyographic (EMG) spectral content by exerting mechanical power of different intensities, which was chosen to remain below the maximal aerobic power (VO2max). The spectral parameters: EMG total power (PEMG), mean (MPF) and median (MED) power frequencies, which are the most representative of the EMG spectral content, were calculated according to the EMG activity of the vastus medialis muscle (VM) and soleus muscle (SOL) of the right leg. For VM and SOL, PEMG increased linearly with exerted power demonstrating an enhancement of MU recruitment. Moreover these relationships were less scattered when exerted power was expressed as a percentage of VO2max. Changes in MPF and MED with varying exercise intensities were different from one subject to another. For a set of subjects, MPF and MED were found to be independent of exerted power. Although VM and SOL muscles are different in fibre type composition, similar results were obtained for both EMG activities. We have concluded that for dynamic contractions performed at different intensities below VO2max, the recruitment of the MU has a poor effect on the EMG spectral content whatever the predominant type of fibre.     

Effect of exercise training at different intensities on fat metabolism of obese men.

The present study investigated the effect of exercise training at different intensities on fat oxidation in obese men. Twenty-four healthy male obese subjects were randomly divided in either a low- [40% maximal oxygen consumption (VO(2 max))] or high-intensity exercise training program (70% VO(2 max)) for 12 wk, or a non-exercising control group. Before and after the intervention, measurements of fat metabolism at rest and during exercise were performed by using indirect calorimetry, [U-(13)C]palmitate, and [1,2-(13)C]acetate. Furthermore, body composition and maximal aerobic capacity were measured. Total fat oxidation did not change at rest in any group. During exercise, after low-intensity exercise training, fat oxidation was increased by 40% (P < 0.05) because of an increased non-plasma fatty acid oxidation (P < 0.05). High-intensity exercise training did not affect total fat oxidation during exercise. Changes in fat oxidation were not significantly different among groups. It was concluded that low-intensity exercise training in obese subjects seemed to increase fat oxidation during exercise but not at rest. No effect of high-intensity exercise training on fat oxidation could be shown.     

Dynamics of cardiorespiratory function in Standardbred horses during different intensities of constant-load exercise

Summary Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake ( max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% max, the oxygen consumption ( ) increased to mean values of approximately 130 ml/kg·min, which represents a 40-fold increase above resting . At the low and moderate work rates, showed no significant change from 30 s to 300 s of exercise. At the high work rate, the mean at 30 s was 80% of the value at 300 s. The HR showed no significant change over time at the moderate work rate but differing responses at the low and high work rates. At the low work rate, the mean HR decreased from 188 beats/min at 30 s to 172 beats/min at 300 s exercise, whereas at the high work rate the mean HR increased from 204 beats/min at 30 s to 221 beats/min at 300 s exercise. No changes in acid base status occurred during exercise at the low work rate. At the moderate work rate, a mild metabolic acidosis occurred which was nonprogressive with time, whereas the high work rate resulted in a progressive metabolic acidosis with a base deficit of 16 mmol/l by 300 s exercise. It is concluded that the kinetics of gas exchange during exercise are more rapid in the horse than in man, despite the relatively greater change in in the horse when going from rest to high intensity exercise.Symbols and abbreviations E minute ventilation - V _T tidal volume - oxygen uptake - carbon dioxide output - oxygen pulse - ventilatory equivalent for oxygen - ventilatory equivalent for carbon dioxide - R respiratory exchange ratio - HR heart rate - SBC standard bicarbonate - STPD standard temperature and pressure dry - BTPS body temperature and pressure saturated - arterial oxygen content - arteriovenous oxygen content difference - Rf respiratory frequency     

Effects of intensity and duration of exercise on muscular responses to training of thoroughbred racehorses.

This study examined the effects of the intensity and duration of exercise on the nature and magnitude of training adaptations in muscle of adolescent (2-3 yr old) racehorses. Six thoroughbreds that had been pretrained for 2 mo performed six consecutive conditioning programs of varying lactate-guided intensities [velocities eliciting blood lactate concentrations of 2.5 mmol/l (v2.5) and 4 mmol/l (v4), respectively] and durations (5, 15, 25 min). Pre- and posttraining gluteus muscle biopsies were analyzed for myosin heavy chain content, fiber-type composition, fiber size, capillarization, and fiber histochemical oxidative and glycolytic capabilities. Although training adaptations were similar in nature, they varied greatly in magnitude among the different training protocols. Overall, the use of v4 as the exercise intensity for 25 min elicited the most consistent training adaptations in muscle, whereas the minimal training stimulus that evoked any significant change was identified with exercises of 15 min at v2.5. Within this range, muscular adaptations showed significant trends to be proportional to the exercise load of specific training programs. Taken together, these data suggest that muscular adaptations to training in horses occur on a continuum that is based on the exercise intensity and duration of training. The practical implications of this study are that exercises for 15 to 25 min/day at velocities between v2.5 and v4 can improve in the short term (3 wk) the muscular stamina in thoroughbreds. However, exercises of 5-15 min at v4 are necessary to enhance muscular features related to strength (hypertrophy).