The ultraendurance triathlete: a physiological profile

To better characterize the athletes who participate in ultraendurance triathlons, 14 triathletes in training for the Hawaii IRONMAN triathlon were studied. A physical and physiological profile was developed from anthropometric measurements and oxygen uptake during maximal exercise on a treadmill, cycle ergometer, and arm ergometer. A comparison of the maximal values among exercise modes and between males and females was made. A comparison of height, weight, and percent body fat of these triathletes with elite athletes from the sports of swimming, cycling, and running showed the physique of triathletes to be most similar to that of cyclists. Oxygen uptake at maximal exercise was, for males and females, respectively: 68.8 ml X kg-1 X min-1, 65.9 ml X kg-1 X min-1 on the treadmill; 66.7 ml X kg-1 X min-1, 61.6 ml X kg-1 X min-1 on the cycle ergometer; and 49.1 ml X kg-1 X min-1, 39.7 ml X kg-1 X min-1 on the arm ergometer. When comparing the highest oxygen uptake attained at maximal exercise in any one of the three exercise modes, the male triathletes are comparable to swimmers, but have a lower aerobic capacity than cyclists or distance runners. The female triathletes studied were able to attain oxygen uptake values greater than those previously reported for female athletes.     

The effect of body position on the energy cost of cycling

Energy expenditure during bicycling on flat terrain depends predominantly on air resistance, which is a function of total frontal area (bicycle and rider), coefficient of drag, and air speed. Body position on the bicycle may affect energy expenditure by altering either frontal area or coefficient of drag. In this study, oxygen uptake (VO2) was measured for each of four body positions in 10 cyclists (8 males, 2 females, 24 +/- 2 yr, 67.7 +/- 3.3 kg, VO2max = 65.8 +/- 1.5 ml.kg-1.min-1) while each bicycled up a 4% incline on a motor-driven treadmill (19.3 km.h-1), thereby eliminating air resistance. Positions studied included: 1) seated, hands on brake hoods, cadence 80 rev.min-1; 2) seated, hands on dropped bar (drops), 80 rev.min-1; 3) standing, hands on brake hoods, 60 rev.min-1; and 4) seated, hands on brake hoods, 60 rev.min-1. Subjects rode their own bicycles, which were equipped with a common set of racing wheels. Energy expenditure, expressed as VO2 per unit combined weight, was not significantly different between drops and hoods positioning (30.2 +/- 0.6 vs 29.9 +/- 0.9 ml.kg-1.min-1) but was significantly greater for standing compared with seated cycling (31.7 +/- 0.4 vs 28.3 +/- 0.7 ml.kg-1.min.-1, P less than 0.01). These results indicate that body posture can affect energy expenditure during uphill bicycling through factors unrelated to air resistance.     

Exercise mode affects the time to achieve VO2max without influencing maximal exercise time at the intensity associated with VO2max in triathletes

The objective of this study was to analyze, in triathletes, the possible influence of the exercise mode (running x cycling) on time to exhaustion (TTE) and oxygen uptake (VO2) response during exercise performed at the intensity associated with the achievement of maximal oxygen uptake (IVO2max). Eleven male triathletes (21.8 +/- 3.8 yr) performed the following tests on different days on a motorized treadmill and on a cycle ergometer: 1) incremental tests in order to determine VO2max and IVO2max and, 2) constant work rate tests to exhaustion at IVO2max to determine TTE and to describe VO2 response (time to achieve VO2max - TAVO2max, and time maintained at VO2max-TMVO2max). No differences were found in VO2max, TTE and TMVO2max obtained on the treadmill tests (63.7 +/- 4.7 ml . kg (-1) . min (-1); 324.6 +/- 109.1 s; 178.9 +/- 93.6 s) and cycle ergometer tests (61.4 +/- 4.5 ml . kg (- 1) . min (-1); 390.4 +/- 114.4 s; 213.5 +/- 102.4 s). However, TAVO2max was influenced by exercise mode (145.7 +/- 25.3 vs. 176.8 +/- 20.1 s; in treadmill and cycle ergometer, respectively; p = 0.006). It is concluded that exercise modality affects the TAVO2max, without influencing TTE and TMVO2max during exercise at IVO2max in triathletes.     

The effect of training specificity on maximal and submaximal physiological responses to treadmill and cycle ergometry

The purpose of this study was to investigate the effect of training specificity during maximal and submaximal treadmill (TM) and bicycle ergometer (BE) exercise. A group of trained runners (RG, no. 7) and trained bikers (BG, no. 7) underwent graded exercise testing on both TM and BE, utilizing the same testing protocol within each exercise mode for both groups. Data for VO2 HR and BP were collected during each 3 min stage. Group by trial ANOVAs followed by Tukey's post hoc analysis, showed no group difference in VO2max, HRmax or BPmax during TM exercise. However, during each of the first four submaximal 3 min stages, VO2 and HR were significantly less (p less than .05) in RG vs BC, with no significant difference in BP. During BE exercise, VO2max was significantly less for both groups compared with TM (RG-59.6 vs 50.1 ml.kg-1.min-1 BS-59.4 vs 55.1 ml.kg-1.min-1) (p less than .05), with BG exhibiting the greater BEmax (p less than .05). RG also had a reduced HRmax during BE exercise (p less than .05). Both groups showed greater BPmax during BE vs TM exercise (p less than .05). Although submaximal VO2 was slightly less during BE for each stage in RG than BG, these differences were not significant as measured either by ml.kg-1.min-1 or l.min-1. Both submaximal HR and BP mirrored the VO2 response, with no significant differences between RG and BG. These data agree with previous studies, showing a greater effect of training specificity during maximal BE than during maximal TM exercise. However, during submaximal exercise, training specificity appear to have a greater effect during TM than BE exercise.     

Ventilatory threshold and maximal oxygen uptake during cycling and running in triathletes

VO2max and the ventilatory threshold (Tvent) were measured during cycle ergometry (CE) and treadmill running (TR) in a group of 10 highly trained male triathletes. Tvent was indicated as the VO2 at which the ventilatory equivalent for oxygen increased without a marked rise in the ventilatory equivalent for carbon dioxide. Triathletes achieved a significantly higher VO2max for TR (75.4 +/- 7.3 ml.kg-1.min-1) than for CE (70.3 +/- 6.0 ml.kg-1.min-1). Mean CE VO2max was 93.2% of the TR value. Average VO2max values for CE and TR compared favorably with values reported for elite single-sport athletes and were greater than those previously reported for other male triathletes. CE Tvent occurred at 3.37 +/- 0.32 l.min-1 or 66.8 +/- 3.7% of CE VO2max, while TR Tvent was detected at 3.87 +/- 0.33 l.min-1 or 71.9 +/- 6.6% of TR VO2max. The VO2 (l.min-1) at which Tvent occurred for TR was significantly higher than for CE (P less than 0.001). Although the VO2 values at TR Tvent expressed as a percentage of VO2max were consistently higher than for CE, the difference between the means did not reach statistical significance (P greater than 0.05). The average Tvent for CE (as %VO2max) was nearly identical to Tvent values reported in the literature for competitive male cyclists, whereas TR Tvent was lower than recently reported values for elite distance runners and marathoners. We speculate that triathlon training results in general (cross-training) adaptations which enhance maximal oxygen uptake values, whereas anaerobic threshold adaptations occur primarily in the specific muscle groups utilized in training.     

Ventilatory threshold and maximal oxygen uptake during cycling and running in female triathletes

Maximal oxygen uptake (VO2max) and the ventilatory threshold (Tvent) were measured during cycle ergometry (CE) and treadmill running (TR) in a group of 10 highly trained female triathletes. Tvent was defined as the VO2 at which the ventilatory equivalent for oxygen increased without a marked rise in the ventilatory equivalent for carbon dioxide. Female triathletes achieved a significantly higher mean (+/- SE) relative VO2max for running (63.6 +/- 1.2 ml.kg-1.min-1) than for cycling (59.9 +/- 1.3 ml.kg-1.min-1). When oxygen uptake measured at the ventilatory threshold was expressed as a percent of VO2max, the mean value obtained for TR (74.0 +/- 2.0% of VO2max) was significantly greater than the value obtained for CE (62.7 +/- 2.1% of VO2max). This occurred even though the total training time and intensity were similar for the two modes of exercise. Female triathletes had average running and cycling VO2max values that compared favorably with maximal oxygen uptake values previously reported for elite female runners and cyclists, respectively. However, mean running and cycling Tvent values (VO2 Tvent as%VO2max) were lower than recently reported values for single-sport athletes. The physiological variability between the triathletes studied and single-sport athletes may be attributed in part to differences in training distance or intensity, and/or to variations in the number of years of intense training in a specific mode of exercise. It was concluded that these triathletes were well-trained in both running and cycling, but not to the same extent as female athletes who only train and compete in running or cycling.     

Aerobic fitness: II. Orthostasis and VO2peak following head-down tilt.

To determine whether endurance exercise trained (ET) subjects would experience greater reductions in peak oxygen delivery and orthostatic tolerance (OT) than untrained (UT) subjects, both peak oxygen uptake (VO2peak) during upright bicycle ergometry and tolerance time during 70 degrees head-up tilt (HUT) were compared within and between groups before and after 4 h of -6 degrees head-down tilt (HDT). Eight ET subjects with a mean VO2peak of 61.7 +/- 1.6 ml.kg-1.min-1 were matched for age, height, and weight with eight UT subjects (VO2peak = 38.4 +/- 1.7 ml.kg-1.min-1). Following HDT, decreases in plasma volume (PV) were larger for ET subjects (-3.7 +/- 0.5 ml.kg-1) than for UT subjects (-2.3 +/- 0.3 ml.kg-1), P less than 0.03. Reductions in VO2peak for ET subjects (-5.4 +/- 1.1 ml.kg-1.min-1) were also greater than for UT subjects (-2.4 +/- 0.8 ml.kg-1.min-1), P less than 0.05. The ET (N = 6) subjects also had a significant decrease in OT time (-13.0 +/- 4.2 min) during post-HDT HUT, which was not observed for the UT group (N = 6). A significant inverse correlation was found pre-HDT VO2peak and the change in OT time, r = -0.74, P less than 0.01. The decrease in OT was also significantly correlated to the PV decrease, r = 0.59, P less than 0.04. The UT subjects had significantly augmented pressor responses to HUT manifested by the increases in both HR and MAP following HDT.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Elite special forces: physiological description and ergogenic influence of blood reinfusion

We measured the physical exercise capabilities of U.S. Army Special Forces soldiers (male) and determined the subsequent ergogenic influence of autologous blood reinfusion. Twelve subjects (Ss) completed maximal exercise treadmill testing in a comfortable (Ta = 20 degrees C, Tdp = 9 degrees C) environment. Six Ss were later transfused with a 600 ml autologous red blood cell (50% Hct) NaCl glucose-phosphate solution and completed identical maximal exercise tests 3 and 10 d posttransfusion. Pretransfusion, the 12 Ss had a maximal oxygen uptake (VO2max) of 4.36 +/- 0.56 L . min-1 and 55 +/- 4 ml . kg-1 . min-1 with a heart rate of 188 +/- 10 b . min-1 and ventilatory equivalent for oxygen of 37 +/- 3. For the 6 reinfused Ss, hemoglobin and red cell volume (RCV) increased by 10% (p less than 0.05) and 11% (p less than 0.05), respectively, posttransfusion. Reinfusion increased (p less than 0.05) VO2max from 4.28 +/- 0.22 L . min-1 (54 +/- 5 ml . kg-1 . min-1) to 4.75 +/- 0.42 L . min-1 (60 +/- 6 ml . kg-1 . min-1) and 4.63 +/- 0.21 L . min-1 (59 +/- 6 ml . kg-1 . min-1) at 3 and 10 d posttransfusion, respectively. No significant relationship was found between the individual change in RCV and VO2max values pre- to posttransfusion. We conclude that Special Forces soldiers have high levels of aerobic fitness that can be further increased by blood reinfusion for at least 10 d.     

Effect of longitudinal physical training and water immersion on orthostatic tolerance in men

To test the hypothesis that moderately intense physical training has no effect on orthostasis, orthostatic and fluid-electrolyte-endocrine responses to 60 degrees head-up tilt were compared before and after 6 h of water immersion (34.5 +/- 0.1 degrees C) up to the neck following 6 months of exercise training. During the tilt test the five male subjects (27-42 years) each wore a lower-body positive-pressure suit (MAST-111A antishock trousers). The tilt procedure consisted of a 40-min supine control period (suit deflated), followed by a maximum 90-min tilt period (suit inflated to 50 +/- 5 mm Hg for 30 min, then deflated for 60 min or until presyncope). The mean +/- S.E. pretraining cycle ergometer peak VO2 was 3.20 +/- 0.14 L.min-1 (39 +/- 2 ml.min-1.kg-1), 3.36 +/- 0.27 L.min-1 (42 +/- 4 ml.min-1.kg-1) after 3 months (N.S.), and increased by 18% to 3.78 +/- 0.36 L.min-1 (48 +/- 5 ml.min-1.kg-1, +22%, p less than 0.05) posttraining. During pretraining, water immersion tilt tolerance decreased from 74 +/- 16 min before to 34 +/- 9 min (delta = 40 min, p less than 0.05) after immersion. During posttraining, water immersion tilt tolerance decreased similarly from 74 +/- 16 min preimmersion to 44 +/- 13 min (delta = 30 min, p less than 0.05) postimmersion (74 vs. 74 min, N.S.; 34 vs. 44 min, N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerobic requirements of overground versus treadmill running

There is general agreement that the oxygen demand of level running is similar for both the treadmill (TM) and overground situations at speeds under 260 m X min-1. However, controversy exists with regard to inclined running. The prevailing view, represented by the ACSM prediction formulas, is that overground hill running is theoretically more costly than inclined treadmill running. This study was designed to investigate the problem from an empirical standpoint. Seven male subjects performed overground and TM running at two grades (0 and 5.7%) over a range of speeds between 136-286 m X min-1. For the outdoor trials, subjects covered a distance of 950 m at a constant pace, and expired gas was collected over the last 150 m. Matching trials were then performed on the treadmill at the same speed and % grade. Regression lines were calculated for speed vs oxygen consumption (VO2). For TM and overground level running, these were: VO2 (ml.kg-1.min-1)= 0.222 X speed (m.min-1) - 1.33 and VO2 (ml.kg-1.min-1) = 0.202 X speed (m.min-1) + 3.21 respectively. The regression lines from TM and overground inclined running were: VO2 (ml.kg-1.min-1) = 0.237 X speed (m.min-1) + 7.53. and VO2 (ml.kg-1.min-1) = 0.233 X speed (m.min-1) + 7.78 respectively. A 2 X 3 X 2 ANOVA revealed that the differences between mean values for VO2 for level TM running vs level overground running and grade TM running vs grade overground running were not statistically significant (0.10 less than P less than 0.25).(ABSTRACT TRUNCATED AT 250 WORDS)     

Characteristic feature of oxygen cost at simulated laboratory triathlon test in trained triathletes.

BACKGROUND: The present study was carried out in order to investigate the respiratory and circulatory features during a simulated laboratory triathlon test in trained triathletes. METHODS: Experimental design: Sixteen male triathletes were divided into superior (n = 8) and slower triathletes (n = 8) according to their race time. These subjects performed both maximal exercise tests and a simulated laboratory triathlon test (ST). The latter test consisted of flume-pool swimming for 30 min, ergometer cycling for 75 min and treadmill running for 45 min as a continuous task. The exercise intensity was 60% of VO2 max during swimming, cycling and running, respectively. RESULTS: In slower triathletes, VO2, minute ventilation (VE), heart rate (HR) and temperature of external auditory canal were increased from an earlier stage compared with those in superior athletes. The percent increase (delta) of VO2, VE and HR between the 10th and last min of cycling and running stages in superior triathletes were significantly smaller than those in slower athletes. The oxygen cost (oxygen uptake/running velocity) of running stage was significantly lower in superior triathletes (0.220 +/- 0.020 ml.kg-1.m-1) compared with slower athletes (0.264 +/- 0.014 ml.kg-1.m-1). CONCLUSIONS: These results suggest that superior triathletes performed ST more economically than slower athletes and had excellent thermoregulatory adaptation.     

Influence of supplemental oxygen on the physiological response to the PO2 aerobic exerciser

Acute physiological responses to the "PO2-Aerobic Exerciser" (AE), a partial rebreathing device designed to stimulate training at altitudes, were studied in seven healthy men [mean VO2max = 56.1 +@- 10.1 (SD) ml X kg-1 X min-1] who performed cycle ergometer exercise to exhaustion in three experimental situations: a control test (C) breathing normal atmosphere: a test with the device (AE); and a test with the AE air supplemented with oxygen (AEO2'). Arterial oxygen saturation at rest for C, AE, and AEO2' studies was 97 +/- 1, 95 +/- 2, and 97 +/- 1%, respectively (P less than 0.05 for C vs AE and AE vs AEO2'), while at exhaustion it was 95 +/- 1, 87 +/- 2, and 95 +/- 1%, respectively (P less than 0.05 for C vs AE and AE vs AEO2'). Maximum work rate decreased from a control value of 1738 +/- 184 kg X min-1 to 1371 +/- 147 kg X min-1 during AE and remained below control levels during AEO2'; 1554 +/- 110 kg X min-1 (P less than 0.05). Beyond 60% of maximum work rate during AE, inspired CO2 increased to 0.026 +/- 0.005. Mouth pressure swings of up to -19.2 +/- 10.2 and 12.7 +/- 5.7 cm H2O were recorded during AE. While the PO2 aerobic exerciser induced a hypoxic stress, the pertubation imposed was not explained fully by arterial oxygen desaturation. Other factors such as hypercapnia and a flow resistive increase in the work of breathing appear to have influenced work capacity during the use of the device.     

Comparison of energy expenditure in men and women at rest and during exercise recovery.

The purpose of this study was to compare the energy expenditure (EE) of men and women at rest and during a 1 h recovery from 30 min of exercise at 40% of VO2max. Subjects were five physically active lean men (mean age, % fat, and VO2max = 34.8 +/- 8.1 years, 8.1 +/- 3.2% and 63.8 +/- 8 ml.kg-1.min-1, respectively) and five physically active lean women (mean age, % fat, and VO2max = 26.2 +/- 5.1 years, 17.6 +/- 4.5%, and 50.2 +/- 13.6 ml.kg-1.min-1, respectively). Energy expenditure (EE) was measured continuously by standard open circuit spirometry for 20 min at rest and for 1 h immediately after 30 min of exercise at 40% of VO2max. Independent t tests and ANCOVA were used to compare EE of men and women at rest and during exercise recovery. EE at rest in the men was significantly greater using a t test (p less than .05) than in the women but it was not when the data were adjusted with ANCOVA using body weight, VO2max in ml.kg-1.min-1, and percent body fat as covariates. The EE during 1 h of recovery was also significantly higher in the men using a t test (p less than .05) and after the data were adjusted for differences in VO2max (p less than .02). With body weight and percent fat as covariates. The EE during 1 h of recovery was also significantly higher in the men using a t test (p less than .05) and after the data were adjusted for differences in VO2max (p less than .02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Dissociation of the ventilatory and lactate thresholds following caffeine ingestion

Caffeine ingestion prior to the start of exercise has been shown to have an effect on ventilatory parameters and substrate utilization. Changes in either substrate utilization or ventilatory parameters may influence the determination of the lactate threshold (LT) and/or the ventilatory threshold (VT). Therefore, it was the purpose of this investigation to determine whether the VT and LT occur at similar metabolic rates and what effect caffeine ingestion will have on these two measures. Ten male subjects completed two maximal exercise bouts on the treadmill using a single blind procedure. One trial was performed 45 min after the ingestion of caffeine citrate (CC) in an amount equal to 7.0 mg of anhydrous caffeine.kg-1 body weight. The second trial was performed 45 min after the ingestion of a gelatin powdered placebo (P). Ventilatory parameters were monitored on a breath-by-breath basis, and blood for lactate determination was obtained from an antecubital vein every minute. Maximal oxygen consumption did not differ significantly between the CC (60.3 +/- 5.2 ml.kg-1.min-1) and P (59.7 +/- 5.6 ml.kg-1.min-1) trials. Oxygen consumption (VO2) values during the P trial at the VT (40.2 +/- 6.1 ml.kg-1.min-1) and the LT (38.6 +/- 3.3 ml.kg-1.min-1) were not significantly different (P less than 0.05). During the CC trial, VO2 values at the VT (44.4 +/- 6.6 ml.kg-1.min-1) and the LT (39.7 +/- 5.8 ml.kg-1.min-1) were significantly different. When comparing the VO2 at the LTs between the CC and P trials, there was no significant difference. There was, however, a significant difference in VO2 at the VTs when comparing the two trials. These data demonstrate a dissociation between the VT and LT following caffeine ingestion and suggest that the use of the VT as an indicator of the LT may be inappropriate following ingestion of moderate dosages of caffeine.     

Oxygen uptake and heart rate responses during hypoxic exercise in children and adults

Control of ventilation and heart rate during exercise appears to undergo maturation, while aerobic metabolism (VO2) may not. Since we had previously found that hypoxia during exercise produced different ventilatory responses in children (C) compared to adults (A), we hypothesized that VO2 and heart rate kinetics during exercise would show similar maturational responses to hypoxia. To test this hypothesis, we examined the responses during progressive (ramp) and constant work rate tests in children and adults breathing either room air or hypoxic gas (FiO2 = 0.15). When corrected for body weight, children and adults had similar values for lactic acidosis threshold (LAT) (C: 29.1 +/- 5.0 ml.min-1.kg-1; A: 27.9 +/- 4.3) and VO2max (C: 40.7 +/- 8.6 ml.min-1.kg-1; A: 45.2 +/- 6.7) during normoxia. Hypoxia significantly lowered LAT (C: 27.5 +/- 5.4 ml.min-1.kg-1; A: 23.2 +/- 3.8; both P less than 0.05) and VO2max (C: 37.7 +/- 8.3 ml.min-1.kg-1; A: 40.1 +/- 5.3; both P less than 0.05) in both children and adults. Metabolic efficiency (delta VO2/delta work rate) and the VO2-heart rate relationship (delta VO2/delta HR/kg) were similar in the two groups and unaffected by hypoxia. During the constant work rate exercise, VO2 kinetics (time constant during phase 2 of the response (pi 1) and the O2 deficit) were similar between children and adults and were significantly slowed by hypoxia, consistent with current understanding of the control of oxidative metabolism. Finally, heart rate was increased at rest and during exercise with hypoxia, while the time to reach 75% of the end-exercise response was delayed significantly, in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heat acclimatization during summer running in the northeastern United States

Five highly trained distance runners (DR) were observed during controlled 90-min thermoregulation trials in spring (T1) and late summer (T2) to document the nature of heat acclimatization in the northeastern United States. These trials simulated environmental (30.3 +/- 0.1 degrees C dry bulb, 34.9 +/- 0.5% relative humidity, 4.47 m X s-1 wind speed) and exercise (treadmill running at 80, 120, 160, and 200 m X min-1) stresses encountered by DR during summer training in the northeastern United States. Between T1 and T2, DR trained outdoors for 14.5 +/- 0.4 wk, but consequently exhibited few physiological adaptations classically associated with heat acclimatization. Statistical comparison of T1 and T2 indicated no significant differences in mean heart rate, rectal temperature, sweat Na+ and K+, plasma Na+ and K+, or change in plasma volume during exercise. Mean weighted skin temperature was unchanged except at 50 min of exercise, and sweat rate was also unchanged except during the initial 30 min segment: 73 +/- 6 vs 93 +/- 8 ml X m-2 X h-1. Significant decreases (P less than 0.05) in submaximal VO2 were observed: T1 vs T2 values were 13.97 +/- 0.27 vs 10.19 +/- 1.19, 31.38 +/- 1.15 vs 27.91 +/- 1.45, and 44.97 +/- 0.85 vs 41.24 +/- 0.97 ml X kg-1 X min-1, at treadmill speeds of 80, 120, and 200 m X min-1, respectively. We conclude that DR did not require 14.5 wk of summer training to maintain safe rectal temperatures (less than or equal to 38.4 degrees C) during T1, which simulated the hottest days of summer in the northeastern United States.     

Effects of training specificity on the lactate threshold and VO2 peak

We examined the effects of training specificity on the lactate threshold (LT) and VO2peak. Sixteen male subjects completed VO2peak/LT protocols on the cycle ergometer (CE) and treadmill (TM) before and after a training program. The subjects were assigned to run training (N = 5), cycle training (N = 6), and control groups (N = 5). Subjects trained 4 day/week for 10 weeks at approximately 89% of pre-training VO2peak. Results indicated that run training increased VO2 at LT (VO2LT) within both the CE and TM protocols (17.9 to 22.5 ml/kg.min-1 for CE, 22.7 to 36.0 ml/kg.min-1 for TM, p less than 0.05) with the 58.5% increase in VO2LT for TM being greater than the 30.3% increase for CE (p less than 0.05). Cycle training resulted in a 38.7% increase in CE VO2LT (19.7 to 27.4 ml/kg.min-1, p less than 0.05) with no significant improvement in TM VO2LT (23.6 to 24.0 ml/kg.min-1). Similar increases in VO2peak were observed for CE and TM protocols for both cycle and run training groups (VO2peak increased by 11.9 to 20.7% in both CE and TM regardless of training mode). No changes were observed in the control group for any variable. The present data suggest that increases in LT resulting from training may be specific to the mode of exercise.     

Failure of target heart rate to accurately monitor intensity during aerobic dance

Fourteen untrained females (age 19 +/- 1, range 18-21) were studied to examine the heart rate-VO2 relationship during a single aerobic dance training session. These findings were used to help explain the changes in VO2max resulting from an aerobic dance training program. VO2max and body composition were determined before and after an 8 wk training period. In addition, the heart rate-VO2 responses to an aerobic dance training session were monitored and compared to the heart rate responses of treadmill jogging performed at the same VO2. The aerobic dance session elicited a significantly lower oxygen pulse than did treadmill exercise (7.2 +/- 0.3 vs 8.1 +/- 0.8 ml.beat-1; P less than 0.01). There were no significant changes in percent body fat, whereas VO2max increased by 11% (34.4 +/- 0.9 vs 38.1 +/- 0.8 ml.kg-1.min-1; P less than 0.05). No significant changes in any of the parameters tested were observed in 10 untrained controls. These findings indicate that the heart rate elicited from aerobic dance represents a lower relative exercise intensity (VO2) than that of running. Therefore, the assumption that aerobic dance training produces the same cardiovascular adaptations as running training when performed at the same target rate may be unwarranted.