Exercise and intestinal polyp development in APCMin mice

PURPOSE: Epidemiological evidence suggests that physical activity protects against colon cancer. We previously used a mouse predisposed to intestinal polyps (APCMin) to evaluate this association and found the suggestion of fewer polyps in exercised males but not females. The present study was designed to further explore the potential exercise x sex interaction on polyp development and to begin to look at potential mechanisms. METHODS: Six-week-old APCMin mice (N = 60 males; 60 females) were randomly assigned to one of two groups by sex: treadmill running at 20 m.min-1, 5% grade, 45 min.d-1, 5 d.wk-1 (EX) or nonrunning controls (CON) (N = 30 per group). EX mice ran in running wheels while in quarantine (weeks 0-3), followed by treadmill running weeks 3-8. Body weights were measured weekly. Urine was collected at 5 wk and fasting blood at 7.5 wk. Body composition was measured, serum was frozen, and polyp number and size were measured at sacrifice. RESULTS: EX resulted in lower body weights (P < 0.01) and reduced fat mass (P < 0.01). Fasting glucose was lower in EX (P < 0.01), and leptin was lower in EX (P = 0.05) compared with CON. EX did not affect serum insulin-like growth factor-1 or urinary corticosterone. Total polyp number and size were not statistically different between groups; however, there were fewer jejunal polyps in EX (3.6 +/- 0.7, mean +/- SE) versus CON males (5.2 +/- 0.8; P = 0.04) and an even larger difference when only the consistent runners were kept in the analysis (2.7 +/- 0.5 in EX; P = 0.01). CONCLUSION: Despite favorable changes in body composition, blood glucose, and leptin, 8 wk of running resulted in only minor changes related to polyp development in male but not female APCMin mice.     

Lower-body negative-pressure exercise and bed-rest-mediated orthostatic intolerance

PURPOSE: Supine, moderate exercise is ineffective in maintaining orthostatic tolerance after bed rest (BR). Our purpose was to test the hypothesis that adding an orthostatic stress during exercise would maintain orthostatic function after BR. METHODS: Seven healthy men completed duplicate 15-d 6 degrees head-down tilt BR using a crossover design. During one BR, subjects did not exercise (CON). During another BR, subjects exercised for 40 min.d(-1) on a supine treadmill against 50-60 mm Hg LBNP (EX). Exercise training consisted of an interval exercise protocol of 2- to 3-min intervals alternating between 41 and 65% (.)VO(2max). Before and after BR, an LBNP tolerance test was performed in which the LBNP chamber was decompressed in 10-mm Hg stages every 3 min until presyncope. RESULTS: LBNP tolerance, as assessed by the cumulative stress index (CSI) decreased after BR in both the CON (830 +/- 144, pre-BR vs 524 +/- 56 mm Hg.min, post-BR) and the EX (949 +/- 118 pre-BR vs 560 +/- 44 mm Hg.min, post-BR) conditions. However, subtolerance (0 to -50 mm Hg LBNP) heart rates were lower and systolic blood pressures were better maintained after BR in the EX condition compared with CON. CONCLUSION: Moderate exercise performed against LBNP simulating an upright 1-g environment failed to protect orthostatic tolerance after 15 d of BR.     

Does endurance training affect orthostatic responses in healthy elderly men?

PURPOSE: To investigate the effects and time course of endurance training on the regulation of heart rate (HR), arterial pressure (AP), norepinephrine (NE), and plasma volume (PV) during orthostatic stress in healthy elderly men. METHODS: Thirty-one healthy men (65--75 yr) were randomly allocated into endurance training (N = 20, EX) and control (N = 11, CON) groups. The EX group cycled 3 d x wk(-1) for 30 min at 70% VO(2peak) for 12 wk x VO(2peak) was determined on an electronically braked cycle ergometer, before training and after 4, 8, and 12 wk of endurance training. The immediate (initial 30 s), early steady-state (1 min), and prolonged (5, 10, 15 min) beat-by-beat HR and AP responses during 90 degrees head-up tilt (HUT) were measured at least 3 d after each VO(2peak) test. Spontaneous baroreflex slopes were determined by application of linear regression to sequences of at least three cardiac cycles in which systolic blood pressure (SBP) and R-R interval changed in the same direction. Venous blood was collected during 90 degrees HUT and analyzed for changes in plasma NE concentrations, as well as hematocrit and hemoglobin to determine changes in PV. RESULTS: Endurance training significantly (P < 0.01) increased VO(2peak) (mL x kg(-1) x min(-1)) in EX by 10 +/- 2%. The immediate, early steady-state, and prolonged HR and AP responses and spontaneous baroreflex slopes during 90 degrees HUT were not significantly different (P > 0.05) between EX and CON groups before or after 4, 8, or 12 wk of endurance training. No significant differences (P > 0.05) were observed between EX and CON groups for peak changes in PV during orthostasis before (-15.0 +/- 1.4% vs -11.9 +/- 1.3%) or after 4 (-12.2 +/- 1.0% vs -12.7 +/- 1.4%), 8 (-13.7 +/- 1.2% vs -12.4 +/- 0.7%), and 12 wk (-10.8 +/- 1.6% vs -10.6 +/- 0.6%) of endurance training, suggesting a similar stimulus presented by 90 degrees HUT in both groups. Peak changes in NE concentrations during HUT were similar (P > 0.05) between EX and CON groups before (119 +/- 23 pg x mL(-1) vs 191 +/- 36 pg x mL(-1)) and after 4 (139 +/- 29 pg x mL(-1) vs 146 +/- 25 pg x mL(-1)), 8 (114 +/- 32 pg x mL(-1) vs 182 +/- 41 pg x mL(-1)), and 12 wk (143 +/- 35 pg x mL(-1) vs 206 +/- 42 pg.mL-1) of endurance training. CONCLUSIONS: These data indicate that in healthy elderly men, improvements in VO(2peak) can occur without compromising the regulation of HR, AP, NE, and PV during orthostatic stress.     

Maximal exercise as a countermeasure to orthostatic intolerance after spaceflight

Previous investigators have suggested that maximal exercise performed 24 h before the end of bed rest, a spaceflight analog, restores prebed rest plasma volume, baroreflex responses, and orthostatic tolerance. PURPOSE: In this case report, we examined the effect of a similar exercise protocol 24 h before a Shuttle landing on the orthostatic responses of four crewmembers (EX) after spaceflights of 8-14 d. Four additional crewmembers (CON) served as controls and did not perform exercise during the final day of the flight. METHODS: Each crewmember performed a 10-min stand test approximately 10 d before launch (L-10) and within 1-2 h of landing (R+0). Cardiac stroke volume was measured (Doppler ultrasound) supine and during each min of standing for three EX and three CON subjects. RESULTS: Preflight, all crewmembers completed the stand test and each group had similar heart rate and blood pressure responses. Postflight, all subjects also completed the 10-min stand test. Each group had similarly elevated supine and standing heart rates, elevated diastolic and mean arterial blood pressures, and reduced pulse pressures compared to L-10. However, postflight cardiac output, mean +/- SEM, (EX: 4.5+/-0.6 L x min(-1); CON: 3.1+/-0.3 L x min(-1)) and stroke volume (EX: 43+/-7 mL x beat; CON: 30+/-6 mL x beat) were higher after 10 min standing in the EX subjects compared to CON subjects. CONCLUSIONS: For these four crewmembers, maximal exercise performed 24 h before landing may have helped maintain stroke volume but did not maintain heart rate and blood pressure responses during standing compared to preflight.     

N-acetyl-L-cysteine inhibits exercise-induced lymphocyte apoptotic protein alterations

PURPOSE: To investigate the effect of strenuous exercise and antioxidant administration on pro- and antiapoptotic protein expression in intestinal lymphocytes. METHODS: Female C57BL/6 mice (N = 52) were randomly assigned to receive N-acetyl-L-cysteine (NAC; 1 g.kg(-1)) or saline (SAL) 30 min before treadmill exercise (EX) for 90 min and 2 degrees slope (30 min at 22 m.min(-1), 30 min at 25 m.min(-1), and 30 min at 28 m.min(-1)) and sacrificed immediately (Imm) or 24 h (24 h) after exercise. Control mice were exposed to treadmill noise and vibration without running (nonexercised). Intestinal lymphocytes (IL) were isolated and pro- and antiapoptotic protein expression was evaluated by Western blot analysis. RESULTS: IL protein levels of proapoptotic (caspase 3 and cytosolic cytochrome c) and antiapoptotic (Bcl-2) were significantly different among groups. Relative to nonexercised mice, protein levels of caspase 3 (P < 0.001) and cytosolic cytochrome c (P < 0.005) were significantly elevated, whereas Bcl-2 (P < 0.05) was significantly lower immediately after exercise in mice receiving saline (EX + SAL + Imm) but not in animals receiving NAC (EX + NAC + Imm) or both 24 h postgroups (EX + SAL + 24 h and EX + NAC + 24 h). CONCLUSION: These results suggest that oxidative stress acting through a mitochondrial pathway may play a role in intestinal lymphocyte apoptosis after strenuous exercise.     

Effects of leg press training on cycling, leg press, and running peak cardiorespiratory measures

Six males and seven females trained 3 d per wk (30 min at 80 to 85% heart rate reserve) for 20 wk on a leg press apparatus. A progressive exercise test was administered on a cycle ergometer, leg press apparatus, and treadmill before and after training. Before training, peak oxygen consumption (VO2, ml X kg-1 X min-1) during the leg press test was higher for the males (23.9 +/- 1.60, mean +/- SE) compared to the females (19.5 +/- 2.40, P less than or equal to 0.05). Peak VO2 during the cycling (males = 36.6 +/- 2.65, females = 28.5 +/- 2.35) and treadmill (males = 39.8 +/- 2.04, females = 33.2 +/- 2.64) tests was also different between the sexes, and 30 to 40% higher than during the leg press test (P less than or equal to 0.05). Peak heart rate (beats X min-1) was not different between the sexes (P greater than 0.05), yet was 11% lower during the leg press test (165 +/- 3.5) compared to the cycling (184 +/- 2.8) and treadmill (187 +/- 1.3) tests (P less than or equal to 0.05). After training, peak VO2 during the cycling and treadmill tests increased 10 to 15%, compared to 35% during the leg press test (P less than or equal to 0.05). The only change in peak heart rate was a 6% increase during the leg press test (P less than or equal to 0.05). Although peak VO2 on the leg press apparatus was lower than on the cycle ergometer and treadmill, leg press exercise elicited a sufficient stimulus for increasing peak VO2 on the three testing modes.     

Rate and amplitude of adaptation to intermittent and continuous exercise in older men

PURPOSE: This study determined the amplitude and rate of adaptation to 10 wk of continuous (CEx) and intermittent exercise (IEx) in a group of older men when the training intensity and total amount of work completed by each exercise group were the same. METHODS: Ten healthy men were assigned to either a CEx (63 +/- 1 yr) or IEx (65 +/- 1 yr) group while a further five subjects (65 +/- 1 yr) acted as nonexercising controls (CON). The three groups (CEx, IEx, and CON) were matched for age, peak oxygen uptake (VO2peak), and cardiac output (Qpeak) before commencing training. The CEx group trained for 30 min at an intensity corresponding to 70-75% VO2peak, and the IEx group trained for a total exercise time of 30 min using intermittent exercise (60-s exercise, 60-s rest) at the same absolute intensity as the CEx group (CEx 112 +/- 5W; IEx 112 +/- 5W). The exercise groups trained three times per week and completed a similar amount of work during each training session (CEx, 199 +/- 9 kJ; IEx 195 +/- 9 kJ, P = 0.67). RESULTS: The CEx and IEx groups had similar and significant amplitude increases in peak VO2, ventilation (VEpeak), power, Q, and SV after training. Peak VO2, Qpeak, SVpeak, and peak arteriovenous O2 difference for the CON group were unchanged. The change in VO2peak, peak ventilation, and peak power for CEx and IEx groups were best described by a linear model. Moreover, the CEx and IEx groups had the same rate of change in VO2peak (CEx: 0.02 +/- 0.00 L x min(-1) x wk(-1), IEx: 0.02 +/- 0.00 L x min(-1) x wk(-1), P = 0.32), VEpeak (CEx: 2.0 +/- 0.2 L x min(-1) x wk(-1), IEx: 1.2 +/- 0.5 L x min(-1) x wk(-1), P = 0.10), and peak power (CEx: 2.6 +/- 0.4 W x wk(-1), IEx: 2.6 +/- 0.4 W x wk(-1), P = 0.92). CONCLUSION: These results suggest that the amplitude and rate of change of select adaptations in men aged 60-70 yr are independent of the mode of training (i.e., continuous or intermittent exercise) when the absolute training intensity and the total amount of work completed were similar.     

Training enhances vascular relaxation after chemotherapy-induced vasoconstriction

PURPOSE: Although evidence is accumulating that suggests regular moderate physical activity improves physiological and psychological well-being of cancer patients undergoing chemotherapy, the mechanisms involved remain unclear. Therefore, the purpose of this study was to determine if exercise training improves endothelium-dependent vasodilation after exposure to the chemotherapeutic agent 5-fluorouracil (5-FU). METHODS: Rats were injected with N-methyl-N-nitrosourea (MNU) and assigned to either exercise (EX; treadmill running, 20-25 m.min(-1) grade, 30 min.d(-1), 5 d.wk(-1) for 8 wk) or sedentary (SED) groups. After the exercise training period, aortic rings were obtained and used to assess contractile and relaxation characteristics. In addition, endothelial nitric oxide synthase (eNOS) protein content and eNOS enzyme activity was determined. RESULTS: Exercise training resulted in increased maximal endothelium-dependent vasorelaxation to acetylcholine (ACh, 1 x 10(-5) M) (SED, 56 +/- 3%; exercise, 71 +/- 5%; P < 0.05) after norepinephrine-induced (1 x 10(-7) M) vasoconstriction. Exposure of aortic rings from each group to increasing concentrations of 5-FU (7 x 10(-5) x 10 M(-3)) resulted in vasoconstriction. Rings obtained from exercise-trained animals demonstrated enhanced vasorelaxation to ACh (1 x 10(-5) M) after 5-FU-induced vasoconstriction compared with rings obtained from SED animals (P < 0.05). In addition, exercise training enhanced eNOS protein content and eNOS activity. CONCLUSION: Exercise training enhances endothelium-dependent vasorelaxation after 5-FU-induced vasoconstriction, and this may be due, at least in part, to an increase in aortic eNOS protein content and activity. Such exercise-induced adaptations may help alleviate chemotherapy-related fatigue observed in cancer patients.     

Supine LBNP exercise maintains exercise capacity in male twins during 30-d bed rest

INTRODUCTION: Exercise capacity is reduced after both short- and long-duration exposures to microgravity. Previously, we have documented that supine treadmill exercise within lower-body negative pressure (LBNP(ex)) maintains upright exercise responses in men after 5 and 15 d of bed rest, as a simulation of microgravity. PURPOSE: The purpose of this study was to determine whether LBNP(ex) would protect against loss of upright exercise capacity (VO2peak) and sprint performance during a longer-duration bed rest. METHODS: Eight sets of male twins participated in 30 d of bed rest. Within each twin pair, one was randomly assigned to a control group (CON) who performed no exercise, and the other was assigned to an exercise group (EX) that performed a 40-min interval (40-80% pre-bed rest VO2peak) LBNP(ex) (55 +/- 4 mm Hg) protocol, plus 5 min of resting LBNP, 6 d.wk(-1). LBNP produced footward force equivalent to 1.0-1.2 body weight. Before and after bed rest, subjects completed an upright graded exercise test to volitional fatigue and a sprint test of 30.5 m. RESULTS: After bed rest, VO2peak was decreased significantly in the CON subjects (-23 +/- 4%, P < 0.01) but was maintained in the EX subjects (-3 +/- 3%). Sprint time was increased in the CON subjects (24 +/- 8%, P < 0.05) but was maintained in the EX group (8 +/- 2%). CONCLUSIONS: This exercise countermeasure protocol may help prevent microgravity-induced deconditioning during long-duration space flight.     

Influence of short-term endurance exercise training on heart rate variability

PURPOSE: To examine the influence of 2 wk (eight sessions) of endurance training on cardiac autonomic modulation, as measured by heart rate variability (HRV). METHODS: Twenty-four males (mean age: 23.1 yr) were randomized to an exercise (EX; N = 12) or control group (CT; N = 12). EX trained for eight sessions (4x wk-1, 40 min, 80-85% HRreserve) on a cycle ergometer. ECG tracings were collected during 5 min of paced breathing (12 breaths x min-1 (PB)), 5 min of spontaneous breathing (SB1), 5 min of 70 degrees head-up tilt (TILT), and a second 5-min period of spontaneous breathing (SB2). Data were collected before (test 1), during (tests 2-4), and 48 h after (test 5) the 2-wk period. HRV was reported as the standard deviation of RR intervals, and as natural logarithm of the normalized units (NU) of high- and low-frequency power (lnHF and lnLF). RESULTS: EX exhibited a significant increase in peak oxygen consumption (8%). During PB and TILT conditions, ANOVA revealed a group x time interaction such that EX exhibited lower lnLFNU and lnLF/lnHF during test 5 compared with test 1. CONCLUSION: These data suggest that eight endurance exercise-training sessions performed over 2 wk enhance the relative vagal modulation of the heart during PB and TILT, but not during SB.     

Effects of short-term exercise training on plasminogen activator inhibitor (PAI-1)

PURPOSE: To observe the effects of exercise training on plasminogen activator inhibitor, type-1 (PAI-1), tissue plasminogen activator (tPA), and associated metabolic variables in sedentary men and women. METHODS: A randomized, controlled experimental design was used to examine the influence of 10 d of moderate-intensity exercise training on measures of fibrinolysis. Sixteen men and 16 women between the ages of 50 and 70 yr were randomly assigned to exercise (EX) and control groups (CON) that were balanced for gender and hormone replacement therapy. Blood samples were collected on days 1, 2, 11, and 12 for measurement of plasma PAI-1, tPA, insulin, glucose, and triglyceride. Subjects in EX performed 50 min of treadmill walking at an intensity corresponding to 65% of heart rate reserve each day for 10 consecutive days. RESULTS: There were no significant changes in PAI-1, tPA, or associated metabolic variables between EX and CON during the intervention period. Within EX subjects, those with higher body fatness had a significant decrease in insulin and triglyceride compared with those with lower body fatness. However, no changes in fibrinolytic measures were observed within these subgroups. CONCLUSIONS: Short-term exercise training does not change PAI-1 levels in normal, asymptomatic men and women. In addition, modest decreases in insulin and triglyceride in individuals with elevated body fatness do not result in changes in PAI-1 after short-term training. It appears likely that decreases in PAI-1 with exercise training require decreases in adiposity and/or marked changes in metabolic variables.     

Clenbuterol diminishes aerobic performance in horses

PURPOSE: The purpose of this 8-wk study was to examine the effect of therapeutic levels of clenbuterol on aerobic performance and hemodynamics associated with exercise. METHODS: Twenty-three unfit Standardbred mares were divided into four experimental groups, clenbuterol (2.4 microg x kg(-1) body weight twice daily) plus exercise (20 min at 50% O2max; CLENEX; N = 6), clenbuterol only (CLEN; N = 6), exercise only (EX; N = 5), and control (CON; N = 6). All horses performed an incremental exercise test (GXT) to measure maximal oxygen consumption (O2max), blood lactate concentration, total plasma protein concentration, and hematocrit. Plasma volume, heart rate, right ventricular pressure (RVP), and pulmonary artery pressure (PAP) were measured before and after the treatment/training. Each horse also performed an exercise capacity test (ECT) in which they ran at their pretreatment O2max speed until exhausted. RESULTS: There were no significant changes in blood lactate, total protein, or hematocrit for any group during either the GXT or ECT. CLENEX decreased (P < 0.05) O2max (-6.2%) and velocity to O2max (-10.0%), whereas both CLENEX and CLEN decreased (P < 0.05) in time to exhaustion (-20.5+/-4.7 and -20.9 +/- 5.6%). EX alone increased (P < 0.05) O2max (+6.5%), velocity to O2max (+10.0%), velocity to produces lactate concentration of 4 mmol (+13.5%), and time to exhaustion (+32.3 +/- 15.0%). Plasma volume was altered (P < 0.05) in CLENEX (-10%) and EX (+27%) but not in CLEN. Posttest recovery HR was higher (P < 0.05) at 2 min post-GXT in the CLENEX, CLEN, and CON compared with their pretest values; RVP remained elevated at 2 min of recovery in the CLEN and CON groups; however, in the EX, recovery HR and RVP had returned to pre-GXT levels by 2 min of recovery. CONCLUSIONS: These data suggest that the combined effect of therapeutic levels of clenbuterol and training decrease aerobic performance and that the resultant reduction in plasma volume may affect improvements in cardiovascular function during recovery normally seen with exercise training.     

Accuracy of polar S410 heart rate monitor to estimate energy cost of exercise

PURPOSE: The purpose of this study was to examine the accuracy of the Polar S410 for estimating gross energy expenditure (EE) during exercise when using both predicted and measured VO2max and HRmax versus indirect calorimetry (IC). METHODS: Ten males and 10 females initially had their VO2max and HRmax predicted by the S410, and then performed a maximal treadmill test to determine their actual values. The participants then performed three submaximal exercise tests at RPE of 3, 5, and 7 on a treadmill, cycle, and rowing ergometer for a total of nine submaximal bouts. For all submaximal testing, the participant had two S410 heart rate monitors simultaneously collecting data: one heart rate monitor (PHRM) utilized their predicted VO2max and HRmax, and one heart rate monitor (AHRM) used their actual values. Simultaneously, EE was measured by IC. RESULTS: In males, there were no differences in EE among the mean values for the AHRM, PHRM, and IC for any exercise mode (P > 0.05). In females, the PHRM significantly overestimated mean EE on the treadmill (by 2.4 kcal x min(-1)), cycle (by 2.9 kcal x min(-1)), and rower (by 1.9 kcal x min(-1)) (all P < 0.05). The AHRM for females significantly improved the estimation of mean EE for all exercise modes, but it still overestimated mean EE on the treadmill (by 0.6 kcal x min(-1)) and cycle (by 1.2 kcal x min(-1)) (P < 0.05). CONCLUSION: When the predicted values of VO2max and HRmax are used, the Polar S410 HRM provides a rough estimate of EE during running, rowing, and cycling. Using the actual values for VO2max and HRmax reduced the individual error scores for both genders, but in females the mean EE was still overestimated by 12%.     

Cardio-respiratory responses to rowing ergometry and treadmill exercise soon after myocardial infarction

PURPOSE: The aim of this study was to compare the cardio-respiratory differences between rowing ergometry and treadmill exercise in beta-blocked men participating in exercise rehabilitation soon after myocardial infarction (postMI). METHODS: Eleven males all receiving beta-blockade medication were measured for oxygen consumption (VO2), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) at individualized submaximal exercise target heart rates (THR) during 6 min of exercise on each of a motorized treadmill and a rowing ergometer 2-6 wk (4.9 +/- 1.4) postMI. RESULTS: The mean THR of the group, predetermined from an exercise ECG stress test, was 107 +/- 16 beats x min(-1). No significant difference was found between rowing versus treadmill VO2 (19.4 +/- 3.2 vs 19.7 +/- 4.2 mL x kg(-1) x min(-1); P = 0.53) or RPE (12.6 +/- 1 vs 12.7 +/- 1; P = 0.72). RER was significantly greater (P = 0.02) during rowing (0.99 +/- 0.07) compared with treadmill exercise (0.94 +/- 0.07). CONCLUSION: Exercising at a specified submaximal THR during rowing versus treadmill exercise in beta-blocked men participating in very early cardiac rehabilitation represents the same VO2 and RPE. A significantly greater RER was, however, apparent during rowing compared with treadmill exercise; thus, agreement was shown with previous studies on healthy individuals where rowing ergometry was less metabolically efficient than treadmill exercise. The results suggest that establishing a THR from a standard treadmill stress test soon after MI is not only suitable for walking/treadmill exercise but also in setting exercise intensity for rowing ergometry.     

Gender differences in viral infection after repeated exercise stress

Fatiguing exercise can increase susceptibility to respiratory infection after intranasal inoculation with herpes simplex virus-1 (HSV-1) in male mice. Although gender differences in susceptibility to certain pathogens do exist, it is unknown whether female mice will respond differently than males in response to strenuous exercise and HSV-1 infection. PURPOSE: To test the effects of gender on susceptibility to HSV-1 respiratory infection after repeated exhaustive exercise. METHODS: Male (N = 86) and female (N = 89) CD-1 mice (approximately 60 d old) were randomly assigned to exercise (Ex) or control (C) groups. Exercise consisted of 3 d of treadmill running at 36 m x min(-1) at 8% grade until volitional fatigue (135 +/- 5min). Fifteen minutes after the last bout of exercise, Ex and C mice were inoculated intranasally with a standard dose (LD30) of HSV-1. Mice were monitored for 21 d for morbidity (time to sickness and symptom severity) and mortality. RESULTS: Run time to fatigue was significantly longer in females than males (P = 0.027). Significant gender differences in susceptibility to infection were found after exercise stress. In males, exercise stress resulted in increased morbidity (66%, P < 0.05) and mortality (30%, P < 0.05) whereas in females, exercise stress only resulted in increased morbidity (66%, P < 0.05). CONCLUSION: Results suggest that although males and females have similar morbidity rates after infection and exercise stress, females recover to a greater extent and are ultimately better protected from death.     

Aerobic demands of the dance simulation game

The purpose of this study was to assess the intensity and energy cost of dance simulation in relation to the American College of Sports Medicine (ACSM) recommendations on the quantity and quality of exercise for developing and maintaining cardiorespiratory fitness, and to assess its safety. Forty subjects (21 males and 19 females, age 17.5 +/- 0.7 years) had their heart rate (HR) and oxygen consumption (.VO(2)) measured during maximal treadmill exercise and during a dance simulation game at a self-selected level of difficulty. They were monitored for injuries during and after the study. The results showed a mean HR of 137 beats x min(-1) (139 beats x min(-1) for males and 136 beats x min(-1) for females) and a mean .VO(2) of 24.6 ml x kg(-1) x min(-1) (25.3 ml x kg(-1) x min(-1) for males and 23.8 ml x kg(-1) x min(-1) for females) during the dance simulation game test, with an estimated energy expenditure of 480 W (550 W for males and 410 W for females). The dance intensity only just meets the minimum ACSM guidelines, so dancer-players will need to play for extended periods to improve or maintain cardiorespiratory fitness or to lose weight. No injuries occurred during 201 hours of dance time.     

Effects of acute aerobic exercise on high-molecular-weight adiponectin

INTRODUCTION: Few studies have reported the response of high-molecular-weight (HMW) adiponectin to acute aerobic exercise. PURPOSE: The purpose of this study was to investigate the influence of acute aerobic exercise on HMW adiponectin in healthy men. METHODS: Eight healthy men (age, 24.9 +/- 1.8 yr; BMI, 21.9 +/- 0.5 kg x m) participated in this study. They performed two trials. Trial 1 [exercise trial (EX)] consisted of 60-min stationary cycle exercise (50% peak oxygen uptake) followed by 30-min rest. Trial 2 [control trial (CON)] was 90-min rest. Blood samples were drawn to assess hormones (catecholamine and insulin), metabolites (free fatty acid [FFA], glycerol, and glucose), and total and HMW adiponectin concentration. RESULTS: There were significant trial x group interactions in serum FFA and glycerol concentrations (P < 0.05). Serum FFA and glycerol concentrations were higher in EX than in CON (P < 0.05). There were significant trial x group interactions in plasma insulin and glucose concentration (P < 0.05). Plasma insulin and glucose concentrations were lower in EX than in CON (P < 0.05). Total adiponectin, HMW adiponectin concentration, and the ratio of HMW to total adiponectin concentration, however, were unchanged during aerobic exercise and postexercise. Also, those changes did not differ between EX and CON. CONCLUSION: Our results indicate that total adiponectin and HMW adiponectin concentrations are not regulated by the change of hormones or metabolites during acute moderate-intensity aerobic exercise and postexercise in healthy young men.     

Influence of continuous and interval training on oxygen uptake on-kinetics

PURPOSE: To examine the relative effectiveness of moderate-intensity continuous training and high-intensity interval training on pulmonary O2 uptake (VO2) kinetics at the onset of moderate- and severe-intensity cycle exercise in previously sedentary subjects. METHODS: Twenty-three healthy subjects (11 males; mean +/- SD age 24 +/- 5 yr; VO2peak 34.3 +/- 5.5 mL x kg(-1) x min(-1)) were assigned to one of three groups: a continuous training group that completed three to four sessions per week of 30-min duration at 60% VO2peak (LO); an interval training group that completed three to four sessions per week involving 20 x 1-min exercise bouts at 90% VO2peak separated by 1-min rest periods (HI); or a control group (CON). Before and after the 6-wk intervention period, all subjects completed a series of step exercise tests to moderate and severe work rates during which pulmonary VO2 was measured breath-by-breath. RESULTS: ANOVA revealed that continuous and interval training were similarly effective in reducing the phase II VO2 time constant during moderate (LO: from 31 +/- 8 to 23 +/- 5 s; HI: from 32 +/- 9 to 21 +/- 4 s; both P < 0.05; CON: from 30 +/- 6 to 29 +/- 7 s; NSD) and severe exercise (LO: from 35 +/- 6 to 24 +/- 7 s; HI: from 32 +/- 11 to 24 +/- 7 s; both P < 0.05; CON: from 27 +/- 7 to 25 +/- 5 s; NSD) and in reducing the amplitude of the VO2 slow component (LO: from 0.38 +/- 0.10 to 0.29 +/- 0.09 L x min(-1); HI: from 0.41 +/- 0.28 to 0.30 +/- 0.28 L x min(-1); both P < 0.05; CON: from 0.54 +/- 0.22 to 0.66 +/- 0.38 L.min; NSD). CONCLUSIONS: Six weeks of low-intensity continuous training and high-intensity interval training were similarly effective in enhancing VO2 on-kinetics following step transitions to moderate and severe exercise in previously untrained subjects.     

Voluntary training in mice and submandibular lymphocyte response to acute exercise

INTRODUCTION: Submandibular lymph nodes (SLN) are important for immune responses to antigens in the eye and oral mucosa. Athletes and exercise participants may be at increased risk of ocular, oral, and upper respiratory tract infections. PURPOSE: This study was conducted to examine the effects of voluntary training on the distribution, number, and apoptotic status of SLN lymphocytes in response to an acute bout of strenuous exercise. METHODS: Female C57BL/6 mice were assigned to voluntary wheel-running (WR) exercise (N=20) or were sedentary (N=10) for 16 wk. SLN lymphocytes were examined immediately (EX+Imm) or 24 h (EX+24 h) following strenuous treadmill exercise, or exposure to treadmill conditions without running (NonEX). Intracellular glutathione (GSH), mitochondrial membrane potential (MMP), cell viability (propidium iodide uptake, PI), surface phosphatidylserine (Annexin V), T-lymphocyte (CD3, CD4, CD8), and B-lymphocyte (CD19) phenotype distribution and number were assessed. RESULTS: The WR mice had a higher number and percent CD8 SLN lymphocytes, higher MMP, and lower Annexin V/PI SLN lymphocytes than controls. Regardless of training status, an acute bout of strenuous exercise decreased the total and phenotype specific (CD3, CD4, CD8) number of cells, MMP, and GSH levels immediately after exercise. CONCLUSION: WR in mice improved some aspects of cell viability in SLN lymphocytes compared with controls, but did not prevent the transient cell loss after acute treadmill exercise. Given the depletion in intracellular GSH levels, oxidative stress may account for the decline in SLN lymphocyte numbers following acute exercise. Loss of SLN lymphocytes may have consequences for ocular, oral, and upper respiratory tract health in some exercise participants and athletes during periods of overtraining.