Higher VO2max Research Articles

Training and bioenergetic characteristics in elite male and female Kenyan runners.

This study compares the training characteristics and the physical profiles of top-class male and female Kenyan long-distance runners. The subjects were 20 elite Kenyan runners: 13 men (10-km performance time: 10-km performance time of 28 min, 36 s +/- 18 s) and 7 women (32 min, 32 s +/- 65 s). The male runners were separated into high-speed training runners (HST: N = 6) and low-speed training runners (LST: N = 7) depending on whether they train at speeds equal or higher than those associated with the maximal oxygen uptake (vVO2max ). All but one woman were high-speed training runners (female HST: N = 6). Subjects performed an incremental test on a 400-m track to determine VO2max, vVO2max, and the velocity at the lactate threshold (vLT). Within each gender among the HST group, 10-km performance time was inversely correlated with vVO2max (rho = -0.86, P = 0.05, and rho = -0.95, P = 0.03, for men and women, respectively). HST male runners had a higher VO2max, a lower (but not significantly) fraction of vVO2max (FVO2max ) at the lactate threshold, and a higher energy cost of running (ECR). Among men, the weekly training distance at vVO2max explained 59% of the variance of vVO2max, and vVO2max explained 52% of the variance of 10-km performance time. Kenyan women had a high VO2max and FVO2max at vLT that was lower than their male HST counterparts. ECR was not significantly different between genders. The velocity at the VO2max is the main factor predicting the variance of the 10-km performance both in men and women, and high-intensity training contributes to this higher VO2max among men.

Relationship between body composition, blood volume and maximal oxygen uptake.

It has long been known that body mass and, more specifically, lean body mass are strongly correlated with maximal oxygen uptake (VO2max) in man and animals. However, there are no data to date describing this phenomenon in the horse. The purpose of this paper is to examine the relationship between body composition and VO2max in the horse. Twenty-three healthy and unfit Standardbred mares performed an incremental exercise test (GXT) to measure VO2max. Rump fat thickness (RTH), a measure of fat covering, was measured using B-mode ultrasound. Plasma volume, total blood volume and red cell volume were determined, using the Evan's Blue dye dilution technique and packed cell volume. VO2max was correlated with body mass (r = 0.541; P<0.01) and exercise haematocrit (exHCT; r = 0.407; P<0.05) but not RTH or the other haematological variables. To eliminate the influence of body mass on the individual variables, a regression analysis was performed on the mass-residuals of VO2max, RTH, plasma volume and exHCT. The residuals of VO2max were correlated negatively with the residuals of RTH (r = -0.687; P = 0.0003) and positively with the residuals of exHCT (r = 0.422; P = 0.045) but not plasma volume. VO2max could be predicted from a linear combination of the residuals of RTH and exHCT (r = 0.767; P<0.0001). These data indicate that VO2max in the horse is significantly related to fat-free mass (FFM), independent of body mass. Red blood cells from the splenic reserve constitute an important factor in the horse's ability to achieve a high VO2max. Therefore, lean body mass may be a more appropriate basis for assessing metabolic function in the athletic horse.

Maximal Physiological Responses to Deep-Water and Treadmill Running in Young and Older Women

The purpose of this study was to assess the difference in maximal physiological responses between an acute bout of deep-water running (DWR) and treadmill running (TMR) in young and older adults. Participants were 9 young and 9 older women who performed maximal DWR and TMR tests. Maximal measures included oxygen consumption (VO2max), heart rate (HRmax), ventilation (VE), respiratory-exchange ratio (RER), and blood lactate (BLac). The young women exhibited higher VO2max, HRmax, VE, and BLac than did the older women for both exercise conditions (p &lt; .05). Lower VO2max and HRmax values were observed with DWR for both age groups (p &lt; .05). No significant differences were found for VE, RER, and BLac in either group between exercise conditions, nor a significant interaction between exercise conditions or ages for any of the variables measured. The data suggest that although older adults exhibit lower maximal metabolic responses, differences between DWR and TMR responses occur irrespective of age.

AEROBIC FITNESS OF 9-YEAR OLD CHILDREN IN SPECIAL TURKU CORONARY RISK FACTOR INTERVENTION STUDY

PURPOSE: To examine aerobic fitness (VO2max) and the association of physical activity and body weight with fitness in a randomized prospective Special Turku Coronary Risk Factor Intervention Project for Children. The study includes 654 9-year old children. The intervention families receive nutritional counselling twice a year aiming at CHD prevention. Control children received “normal” guidance at the well-baby clinics and school health care. METHODS: The VO2max of 205 children (89 girls, 116 boys; 111 intervention children, 94 controls) was estimated using 20-meter shuttle run test (Leger & Lambert 1982). The test began at a slow running speed (8 km/h) and ended when the child could no longer sustain the pace. Physical activity was assessed by a questionnaire in 114 children. The children were divided into two groups: physically active (n = 78) or sedentary (n = 36) according to physical activity index (> 16 active, < 16 sedentary). The index is based on frequency, duration and intensity of daily physical activity (Raitakari et al. 1994). The body weight was measured. RESULTS: Body weight was similar in boys and girls and also in active and sedentary children. The mean (± SD) VO2max of all children was 48.0 ± 16.6 ml/kg/min (36 ± 12 shuttles). Boys ran more shuttles than girls (39 ± 13 vs 33 ± 11) and had higher VO2max (50.3 ± 16.4 ml/kg/min and 48.0 ± 16.7 ml/kg/min. The physically active children had higher VO2max than sedentary: 50.3 ± 18.1 ml/kg/min vs. 48.0 ± 14.9, × ml/kg/min, p = 0.004 (37 ± 14 vs 31 ± 10 shuttles). Nutritional counselling did not influence VO2max. CONCLUSION: Physically active children have better maximal oxygen uptake than sedentary. Nine-year-old boys have higher VO2max than girls. Nutritional counselling did not affect children's physical activity habits or fitness.

EFFECT OF HIGH INTENSITY SUBMAXIMAL WORK, WITH OR WITHOUT A REST PERIOD, ON SUBSEQUENT VO2MAX

A common protocol to evaulate endurance athletes is a two-step lactate profile-VO2max test. A typical procedure provides 20–30 min rest between profile and max. The effect of the profile and/or the rest period on the subsequent VO2max value is not known. PURPOSE: To examine effects of preceding high intensity submaximal exercise, with or without rest, on a subsequent rapid ramp VO2max test. METHODS: Ten endurance-trained males completed three separate exercise trails: an incremental run to fatigue (MAX), a continuous lactate profile-VO2max test (C), and a discontinuous lactate profile-VO2max test (DC). Protocol for C and DC were identical except for a 20-minute rest period between the lactate profile and VO2max test during DC. All trials were separated by 24 hours. MAX was always completed first; C and DC were randomized between the second and third day. RESULTS: No differences in VO2max between trials were evident (MAX = 62.67 ml/kg/min, C = 61.20 ml/kg/min, DC = 58.29 ml/kg/min; p = .059). Subjects with a ± 7.5% fall in VO2max from MAX (Responders) were compared to those with < 7.5% fall (Non-Responders). DC Responders (n = 5) had higher VO2max during MAX than DC Non-Responders (n = 5) (Responders = 67.64 ml/kg/min, Non-Responders = 57.70 ml/kg/min; p = .008). C Responders (n = 2) achieved a VO2max of 71.05 ml/kg/min during MAX; C Non-Responders (n = 8) achieved a VO2max of 60.58 ml/kg/min during MAX. CONCLUSIONS: The trend for lower DC VO2max values, coupled with the DC Responder results, suggests a reduction in VO2max in some athletes if maximal exercise is preceded by high intensity submaximal exercise and a rest period. The effects of preceding high intensity exercise without rest on the achievement of VO2max are still unclear. Supported by the United States Olympic Committee.

OLDER OARSMEN HAVE A HIGHER CARDIO-RESPIRATORY FUNCTION THAN SEDENTARY YOUNG MEN

It has been reported that the older individuals who continue to have a high level of physical activity maintain a high level of aerobic capacity regardless of inevitable decrease of maximal heart rate (HRmax). PURPOSE: We examined the influence of rowing training on the cardio-respiratory function of elderly individuals. METHODS: Fifteen older men (age, 62 ± 3 yr; height, 172 ± 3cm; body mass, 71 ± 5kg; body fat, 17 ± 4%), who have kept rowing training for 40 yrs, were compared to young untrained men matched for body size and composition (age, 24 ± 1 yr, height, 174 ± 5cm; body mass, 70 ± 8kg; body fat, 17 ± 5%). Older oarsmen wereü@alsoü@compared to young oarsmen matched for body size (age, 21 ± 2 yr, height, 174 ± 3cm; body mass, 71 ± 4kg; body fat, 11 ± 3%). All subjects underwent a progressive running test to determine maximal oxygen uptake (VO2max), and HRmax, maximal expiratory ventilation (VEmax), and the oxygen (O2) pulse at VO2max. RESULTS: Older oarsmen possessed a lower HRmax than that young untrained men, and young oarsmen (172 vs. 199, 195 beatüEmin−1). Older oarsmen had a higher VO2max than young untrained men (3.3 vs. 3.0 lüEmin−1; 46.0 vs. 43.1 mlüEkg−1üEmin−1), but had a lower VO2max than young oarsmen (3.3 vs. 4.6 lüEmin−1; 46.0 vs. 64.3 mlüEkg−1üEmin−1). Older oarsmen possessed a lower O2 pulse at VO2max than young oarsmen (19 vs. 24 mlüEbeat−1), but had a higher O2 pulse than young untrained men (19 vs. 15 mlüEbeat−1). CONCLUSION: This study suggests that rowing exercise renders older individuals maintain a high aerobic capacity exceeding that young untrained men, and that rowing is one of desirable exercises to produce health benefits for the older people. Supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology (PI: M. Higuchi) and a Foundation for Comprehensive Research on Aging and Health from the Ministry of Health, Labour, and Welfare (PI: Y. Sato, M. Higuchi).

VALIDATION OF 5-MIN RUNNING TEST IN PREDICTING AEROBIC CAPACITY

The velocity (vVO2max) associated with VO2max has been proved to be correlated with performance. The purpose of the study was to validate the field test of vVO2max, 5-min running test proposed by Bethon(1997), in predicting individual aerobic capacity. Twenty male running athletes and sedentary people (23.65 ± 5.86 yrs) were recruited in this study. The subjects participated in four tests including Bruce test for VO2max, 5mile/h steady speed test for running economy,5min running test and 1 mile walk/run test. The athletes' performance of 1500m, 3000m, 5000m, 10000m were also recorded. Pearson's moment product correlation and stepwise regression analysis revealed that the vVO2max was highly correlated with VO2max (r = 0.93, p < .05) as well as 1 mile walk/run test (r = 0.91, p < .05) and different distance performances. The VO2max in 5mile/h running test in treadmill was also correlated with VO2max (r = 0.48, p < .05). The regression equation was developed as following: VO2max (ml/kg/min) = 14.96 VO2max · 4.68, SEE = 4.65ml/kg/min, R2 = 0.87. These results suggest that: 1) In subjects of different fitness levels, people with higher VO2max could run more economically; 2) vVO2max not only well-evaluate individual aerobic capacity but also effectively predict the performance of different distances.

Waist circumference and VO2max are associated with metabolic and hemostatic risk in premenopausal nurses.

In 21 nurses (34.4+/-3.9 yr), VO2max physical activity, body composition and lifestyle parameters were measured to determine which of these characteristics are related to metabolic and hemostatic risk for cardiovascular disease. Physical activity was assessed with the 7-day recall interview. VO2max was measured in a progressive and continuous treadmill test to volitional fatigue. Fasting insulin, total cholesterol, HDL-C, triglycerides, fibrinogen, tPA-act, tPA-ag, and PAI-1-ag were determined from fasting blood samples. Contrary to our expectation, there was no association of physical activity with any of these risk indicators. High VO2max was associated with lower levels of insulin and fibrinogen. Regression analyses indicated that metabolic and hemostatic risk indicators, as measured in healthy premenopausal nurses, were mainly predicted by waist circumference and oral contraceptive use.

Energy cost and energy sources of ball routine in rhythmic gymnasts.

The energy cost and the different energy sources of competitive rhythmic ball-routines were assessed in nine young elite rhythmic gymnasts (13-16 years of age). The overall energy requirement of ball exercise (VO2eq) was obtained by adding the amount of VO2 during exercise above resting (VO2ex) to the VO2 up to the fast component of recovery (VO2al) and to the energy equivalent of peak blood lactate accumulation (VO2la-) of recovery. The lactate (La) curve up to 25 minutes of recovery always showed La peaks at 3 min after exercise (4.0 +/- 0.4 mmol/l) and values still above rest at 25 min (2.3 +/- 0.5 mmol/l). Although ball routines were short in duration (90 s), the metabolic power requirement was 1.1 times higher than the subject's VO2max. The energy cost (VO2eq) amounted to 81 +/- 5 ml x kg(-1). Higher fractions of VO2eq were VO2ex 49% and VO2al 42%, while the remaining 9% was due to VO2la-. The aerobic source resulted in the most utilized system due to the subjects' high VO2max (52.7 ml x kg(-1) x min(-1)) and anaerobic threshold (LT = 84.4%). The HR and the peak lactate values of ball routine were similar to the values recorded at LT step during treadmill test. Although the HR and VO2 values were significantly correlated (during pre-exercise, exercise, and fast recovery), the exercise intensity derived from HR Kanvonen method during ball routine did not correspond to the % of VO2max.

NATURAL SELECTION ON THERMOGENIC CAPACITY OF HIGH-ALTITUDE DEER MICE.

Adaptive explanations that rely on physiological arguments are common, but tests of hypotheses about the significance of whole-animal physiological performance (e.g., aerobic capacities) are rare. We studied phenotypic selection on the thermogenic capacity (i.e., maximal rate of oxygen consumption [VO2 max] elicited via cold exposure) of high-altitude (~3800 m) deer mice (Peromyscus maniculatus). A high VO2 max equates to a high capacity for heat production and should favor survival in the cold environments prevalent at high altitude. Strong directional selection favored high VO2 max, at least in one year. The selection for increased VO2 max is consistent with predictions derived from incorporating our physiological data into a biophysical model. During another year, we found weak evidence of selection for decreased body mass. Nonlinear selection was not significant for any of the selection episodes we studied. The strong directional selection for VO2 max that we observed suggests that-given ample genetic variation-aerobic metabolism and perhaps endothermy may have evolved rapidly on the geological time scale.

EFFECTS OF VARYING CRANK LENGTHS ON EXERCISE VO2 RESPONSE AND LOWER LIMB KINEMATICS

1814 The energetic response to exercise is dependent, in part, upon the fiber type composition of the exercising muscle and its recruitment pattern. Altered crank lengths produce a change in the magnitude of force application and, theoretically, movement patterns associated with the cycling movement. We hypothesized that altered crank lengths would produce a change in the pedaling kinematics and recruitment pattern of fiber within the exercised muscles and thereby alter the VO2 response (kinetics and maximum). Seven male cyclists performed incremental and constant load cycle ergometry for measurement of VO2 max and VO2 kinetics, respectively. Each cyclist used his own bicycle which was then attached to a Schwinn Velodyne. The three crank lengths used were 165, 170, and 175 mm. The cadence was individualized. Analysis of videotapes taken during the first and last minute of each exercise bout provided two-dimensional kinematic data on the lower extremities. Results indicated that: (1) there was a higher VO2 max at fatigue for the 170 mm crank arms for 5 of the 7 cyclists (p≤.02); (2) the rapid VO2 kinetics, defined as VO2 at 3 minutes, was significantly higher while cycling with the 170 mm crank arms; (3) crank length did not affect the slow component response (p≥.10); (4) hip joint range of motion was the only kinematic parameter affected by fatigue, increasing with the onset of fatigue; and (5) the range of motion about the knee and hip joints was greater for increasing crank lengths. We conclude that varying the crank length within the range normally used by competitive cyclists affects exercise VO2, lower limb kinematics, and possibly fiber type recruitment patterns.

ASSESSMENT OF 1998 ACSM RECOMMENDED QUANTITY AND QUALITY OF EXERCISE FOR DEVELOPING AND MAINTAINING CARDIORESPIRATORY AND MUSCULAR FITNESS, AND FLEXIBILITY

1413 This study investigated physiological and behavioral changes occurring in supervised [S] (N=16); mean age ± SD=43.9 ± 8.9 yrs) and non-supervised [NS] (N=14); mean age ± SD=37.4 ± 8.0 yrs) groups of an 8-wk fitness and Wellness program following 1998 guidelines for the quantity and quality of cardiorespiratory and muscular fitness and flexibility in healthy adults (ACSM, 1998). Subjects (men=37%; women=63%) were recruited from the National Institute of Education, Singapore. Pre- and post-assessment consisted of a health screening, blood profile, body composition scan (DXA, Hologic QDR4500), cycle ergometer submaximal aerobic capacity, 1-RM bench and leg press, sit-&-reach, nutritional and activity log. Seminars conducted weekly provided a broad spectrum of topics related to health and Wellness. Exercise prescriptions and workout sessions individualized the program for the two groups; however, the NS group received no special attention. Results indicated no differences, except age (due to random assignment) between groups during pre-test. During post-test, higher VO2 max (S=11.6%; NS=9.2%), and lower body fat (S=−6.6%; NS=−4.7%) and low density lipoprotein (S=−12.8%; NS=−13.4%) were found (P<0.05). Higher adherence to the ACSM guidelines was evident for the S group (47.0±21.0%) compared to the NS group (35.0±18.0%). The NS group responded more positively to a questionnaire concerning behaviors related to participation and the S group documented more psycho-social barriers to exercise. Findings support that greater benefits to the 1998 ACSM guidelines occurred when subjects were supervised.

MAXIMAL OXYGEN CONSUMPTION AND BODY COMPOSITION PLAY A GREATER ROLE IN DETERMINING INSULIN SENSITIVITY THAN HORMONE REPLACEMENT IN POSTMENOPAUSAL WOMEN

1938 Little is known about the combined effects of physical activity and hormone replacement therapy (HRT) on insulin sensitivity in postmenopausal (PM) women. We sought to determine if there was an interaction effect of physical activity and HRT status on glucose and insulin metabolism in PM women. Twenty endurance-trained (age 65±4 yrs; VO2max 38.7±5.6 mL/kg/min), 16 active (age 63±6 yrs; VO2max 26.5±2.3 mL/kg/min), and 15 sedentary PM women (age 64±6 yrs; VO2max 23.7±3.6 mL/kg/min) underwent an insulin-assisted frequently-sampled intravenous glucose tolerance test according to the methods of Bergman. Twenty women were using combined estrogen + progesterone HRT and 31 women were not on HRT. Insulin, sensitivity index (SI) was determined using the MINMOD program and the acute insulin response to glucose (AIRG) was determined as the mean plasma insulin concentration during the first 10 min after the glucose injection minus the basal plasma insulin concentration. The athletes tended to have higher SI and lower AIRG compared to the physically active and sedentary groups. However, there was no significant interaction effect of physical activity and HRT status on SI or AIRG. (Table)TableStepwise linear regression analyses using the entire group (n=51) revealed that the only variables to account for a significant amount of the variability in SI and AIRG were VO2max (r=0.36, p=0.009) and fat-free mass (r=0.28, p=0.05), respectively. The athletic PM women had lower percent body fat, higher VO2max, and greater fat-free mass than the active and sedentary groups. These results suggest that VO2max and body composition have a greater influence on determining glucose and insulin metabolism than HRT status. Supported by PA Affiliate of the American Heart Association and AARP Andrus Foundation.

Cardiorespiratory Responses of Trained Boys to Treadmill and Arm Ergometry: Effect of Training Specificity

The purpose of this study was to examine the maximal cardiorespiratory responses of trained adolescent male swimmers (SWM, N = 18), soccer players (SOC, N = 18), and moderately active reference subjects (CON, N = 16) to treadmill running (TRD) and arm ergometry (ARM). Mean values (±SD)for skeletal age were similar among the three groups (12.5± 1.9, 12.7 ± 1.1, and 12.5 ± 1.6 years, for the SWM, SOC, and CON, respectively). Allometric scaling procedures, relating VO2max and body mass, were used and mass exponents of .80 and .74 were identified for TRD and ARM data, respectively. During TRD testing SOC attained significantly higher VO2max values when expressed in ml · kg−1 · min−1, or ml · kg−0.80 · min−1 than the other two groups. However, during ARM testing, the SWM achieved significantly higher VO2peak values (ml · kg−0.74 · min−1 and scaled to arm-CSA) than SOC. The ratio of ARM-VAT to TRD-VAT was significantly higher in SWM (50.1± 9%) compared to SOC (41.2±5%), or CON (41.9 ± 6%).

ATTITUDES TOWARD EXERCISE AND FITNESS/ACTIVITY VARIABLES IN ADOLESCENTS

682 The relationship between attitudes towards exercise (benefits/barriers) and physical activity (PA) or fitness (VO2max) has been studied in adults; however, little has been done with attitudes towards exercise in youth. Thus, this study assessed attitudes towards exercise (AtE) in middle school-age children and examined the relationship between those attitudes and the children's VO2max, self-reported PA, body mass index (BMI), and sum of triceps and subscapular skinfolds (ΣSF). The AtE scale, which included both benefits and barriers to exercise, was developed and pilot tested by the Cardiovascular Health in Children and Youth Study. Middle-school aged children(1510 6th/7th graders; 49.8% female, 27.2% nonwhite) from 29 middle schools completed questionnaires to measure PA in the past week and AtE. Height, weight, triceps and subscapular skinfolds and VO2max (submaximal cycle ergometer) were measured. The overall mean AtE score was 32 (possible range = 10-40). Boys had more positive AtE than girls (32.4 vs 31.9; p =0.02), but no racial differences were found. AtE was correlated with PA and VO2max(PA r =0.20; VO2max r =0.20; p =0.0001). AtE was also weakly but significantly inversely related to BMI (r = -0.14) and ΣSF (r =-0.17). Regardless of gender, subjects with high benefits scores, compared to those with high barriers scores had significantly (p =0.0001) higher mean PA scores(253.2 vs 193.1), higher VO2max (39.6 vs 35.7 ml/kg/min), lower mean BMI (20.3 vs 22.2 kg/m2) and lower ΣSF (26.8 vs 34.2 mm). These results suggest that, although youth tend to have positive attitudes towards exercise, their attitudes can differentiate between high active/fit and low active/fit youth of similar ages, regardless of gender.

RELATIONSHIP OF LEPTIN TO PHYSICAL ACTIVITY LEVELS AND AEROBIC POWER OF ADOLESCENTS

871 This study examined the relationship between the ob gene hormone leptin and physical activity (PA) or aerobic power (VO2max) in 125 youth, aged 12-15 yr. PA was obtained from a 32-activity questionnaire, VO2max was estimated from submaximal cycle ergometry, sum of skinfold(ΣSF) was obtained from triceps and subscapular sites, while fasting leptin was measured via RIA kit. The sample was 63 girls, 62 boys, 39 African American, 81 Caucasian, and 5 of other races. Compared to the girls, the boys had higher PA scores (284 ±150 vs 227±110; p=0.017), higher VO2max (37.8±10.5 vs 31.5±7.5 ml/kg/min, p=0.0002), and lower ΣSF (28.7±17.5 vs 34.6±15.6 mm; p= 0.05). Leptin levels were higher for girls than boys: 15.7±10.3 vs 9.7±9.6 ng/ml; p= 0.001. Significant (p=0.0001) gender-specific correlations between VO2max and leptin were found (boys: r= 0.597, girls: r=0.649). PA and leptin were not significantly correlated (boys: r= -0.057; girls: r=-0.010; p>0.65). Multiple regression analysis within genders for the association of PA, VO2max, ΣSF with leptin, were significant: boys r2=0.761; girls r2=0.744. ΣSF accounted for majority of the variance for boys (partial r2= 0.76) and girls (partial r2=0.705). The partial r2 for VO2max was 0.025 for girls(p=0.04), but did not contribute significantly for boys (p>0.15). PA was not a significant contributor for either gender. These data suggest that in early adolescents, aerobic power is only marginally associated with leptin levels, while PA levels appears unrelated to resting leptin concentrations.

GENDER DIFFERENCES IN MAXIMAL HEART RATE AMONG VARIOUS FITNESS CATEGORIES

1377 The effects of gender on maximal heart rate (MHR) is not well documented in the literature. To determine whether gender influences MHR, we evaluated data from 1003 healthy men and women (age range 39-46 years) undergoing symptom limited exercise treadmill testing. Baseline assessment included history and physical examination to exclude illness and medications, and maximal parameters including heart rate, blood pressure, and expired gas analysis. Fitness level was categorized into Low (VO2max < 26 ml/kg/min), Average(VO2max 27-38 ml/kg/min), and High (VO2max > 39 ml/kg/min). Peak RQ and RPE were similar at maximal O2 consumption. TableTableStatistical analysis was performed by ANOVA. MHR differed for the Low Fitness category ( p<0.001). No gender difference was observed in maximal heart rate for the Average and High Fitness groups. CONCLUSION: There appears to be a gender difference in maximal heart rate in Low Fit individuals and predicted maximal heart rate formula (220-age) may be excessive for Low Fit individuals.

Relevance of individual characteristics for human heat stress response is dependent on exercise intensity and climate type.

Multiple heterogeneous groups of subjects (both sexes and a wide range of maximal oxygen uptake VO2max, body mass, body surface area (AD),% body fat, and AD/mass coefficient) exercised on a cycle ergometer at a relative (%VO2max, REL) or an absolute (60 W) exercise intensity in a cool (CO 21 degrees C, 50% relative humidity), warm humid (WH 35 degrees C, 80%) and a hot dry (HD 45 degrees C, 20%) environment. Rectal temperature (Tre) responses were analysed for the influence of the individual's characteristics, environment and exercise intensity. Exposures consisted of 30-min rest, followed by 60-min exercise. The Tre was negatively correlated with mass in all conditions. Body mass acted as a passive heat sink in all the conditions tested. While negatively correlated with VO2max and VO2max per kilogram body mass in most climates, Tre was positively correlated with VO2max and VO2max per kilogram body mass in the WH/REL condition. Thus, when evaporative heat loss was limited as in WH, the higher heat production of the fitter subjects in the REL trials determined Tre and not the greater efficiency for heat loss associated with high VO2max. Body fatness significantly affected Tre only in the CO condition, where, with low skin blood flows (measured as increases in forearm blood flow), the insulative effect of fat was pronounced. In the warmer environments, high skin blood flows offset the resistance offered by peripheral adipose tissue. Contrary to other studies, Tre was positively correlated with AD/mass coefficient for all conditions tested. For both exercise types used, being big (a high heat loss area and heat capacity) was apparently more beneficial from a heat strain standpoint than having a favourable AD/mass coefficient (high in small subjects). The total amount of variance in Tre responses which could be attributed to individual characteristics was dependent on the climate and the type of exercise. Though substantial for absolute exercise intensities (52%-58%) the variance explained in Tre differed markedly for relative intensities: 72% for the WH climate with its limited evaporative capacity, and only 10%-26% for the HD and CO climates. The results showed that individual characteristics play a significant role in determining the responses of body core temperature in all conditions tested, but their contribution was low for relative exercise intensities when evaporative heat loss was not restricted. This study demonstrated that effects of individual characteristics on human responses to heat stress cannot be interpreted without taking into consideration both the heat transfer properties of the environment and the metabolic heat production resulting from the exercise type and intensity chosen. Their impact varies substantially among conditions.

A comparison between laddermill and treadmill maximal oxygen consumption

Maximal O2 consumption (VO2max) is an index of the capacity for work over an 8 h workshift. Running on a treadmill is the most common method of eliciting it, because it is an easy, natural exercise, and also, by engaging large muscle masses, larger values are obtained than by other exercises. It has been claimed, however, that climbing a laddermill elicits a still higher VO2max, probably because more muscle mass is apparently engaged (legs + arms) than on the treadmill (legs only). However, no data in support of this claim have been presented. To see if differences exist, we conducted progressive tests to exhaustion on 44 active coal miners, on a laddermill (slant angle 75 degrees, vertical separation of rungs 25 cm) and on a treadmill set at a 5% gradient. The subjects' mean (range) age was 37.4 (31-47) years, height 174.3 (164-187) cm, body mass 82.2 (64-103) kg. Mean (range) VO2max on the laddermill was 2.83 (2.31-3.64) l x min(-1) and 2.98 (2.03-4.22) l x min(-1) on the treadmill (P < 0.01, Student's paired t-test). Mean (range) of maximal heart rate f(cmax) (beats x min(-1)) on the laddermill and on the treadmill were 181.0 (161-194) and 181.3 (162-195), respectively (NS). Laddermill:treadmill VO2max was negatively related to both treadmill VO2max x kg body mass(-1) (r = -0.410, P < 0.01) and body mass (r = -0.409, P < 0.01). Laddermill:treadmill f(cmax) was negatively related to treadmill VO2max x kg body mass(-1) (r = -0.367, P < 0.02) but not to body mass (r = -0.166, P = 0.28). Our data would suggest that for fitter subjects (VO2max > 2.6 l x min or VO2max kg body mass(-1) > 30 ml x min(-1) x kg(-1)) and/or higher body masses (> 70 kg), exercise on the laddermill is not dynamic enough to elicit a VO2max as high as on the treadmill. For such subjects, treadmill VO2max would overestimate exercise capacity for jobs requiring a fair amount of climbing ladders or ladder-like structures.

Metabolic correlates of selection for swim stress-induced analgesia in laboratory mice.

The upper limits of metabolic rates and the links between maximal and resting metabolic rates in vertebrates have recently received a lot of attention, mainly due to their possible relationship to the evolution of endothermy. We measured peak metabolic rates during 3 min swimming in 20 degrees C water (Vo2swim), maximal metabolic rate (Vo2max) in -2.5 degrees C Helox, and basal metabolic rate (BMR) in two lines of mice selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA). We found that exercise combined with heat loss used for producing SSIA also acted as a selection agent, resulting in a 15% HA/LA line difference in Vo2swim. Core body temperature of HA mice (characterized by lower Vo2swim) was also on average 3.2 degrees C lower than that of LA mice. Furthermore, Vo2max of HA mice was lower than that of LA mice by 8% and accompanied by larger hypothermia. Thus mice with exceptionally high (or low) Vo2max tended to have exceptionally high (or low) Vo2swim, resulting in a positive correlation between Vo2swim and Vo2max. All these suggest that selection for SSIA produced genetically correlated responses in both Vo2swim and Vo2max. However, we did not observe HA/LA differences in BMR. Hence, changes in resting and maximum metabolic rates are not necessarily correlated. We hypothesize that the lack of such a correlation was partially due to the modulation of metabolic responses by SSIA.