Significant Increase In VO2max Research Articles

Training response of adolescent Kenyan town and village boys to endurance running

To investigate the response to endurance training on physiological characteristics, 10 Nandi town boys and 14 Nandi village boys 16.5 and 16.6 years of age, respectively, from western Kenya performed 12 weeks of running training. The study was performed at altitude (approximately 2000 m.a.s.l. approximately 595 mm Hg). Training heart rate and speed were registered during every training session throughout the entire training period. While town and village boys trained at similar heart rates (172.1 vs. 172.5 beats min(-1)), the training speed of the town boys was 9% lower compared with the village boys (12.4 vs. 13.6 km h(-1), P<0.001). Significant increases in VO2max were observed in the town boys (from 50.3 to 55.6 mL kg(-1) min(-1), P<0.001) and in village boys (from 56.0 to 59.1 mL kg(-1) min(-1), P<0.002). Significant decreases in submaximal heart rate (from 172.4 to 160.3 beats min(-1) (P<0.005)), blood lactate (from 2.7 to 1.4 mmol L(-1) (P<0.005)) and ammonia concentration (from 102.0 to 71.4 micromol L(-1) (P<0.01)) at 9.9 km h(-1) were observed in the town boys, while similar decreases in heart rate (from 170.2 to 159.2 beats min(-1) (P<0.001)), blood lactate (from 2.4 to 1.4 mmol L(-1) (P<0.001)) and ammonia concentration (from 102.5 to 72.7 micromol L(-1) (P<0.001)) at 10.9 km h(-1) were observed in the village boys. The oxygen cost of running was decreased from 221.5 to 211.5 mL kg(-1) km(-1) (P<0.03) in the town boys and from 220.1 to 207.2 mL kg(-1) km(-1) (P<0.01) in the village boys. The 5000 m performance time of the town boys was significantly greater than that of the village boys (20.25 vs. 18.42 min (P = 0.01)). It is concluded that no difference was observed in trainability with respect to VO2max, running economy, submaximal heart rate, and submaximal blood lactate and ammonia concentration between Kenyan Nandi town and village boys. The higher performance level of the village boys was likely due to a higher VO2max of these boys.

Heart rate versus %VO2max: age, sex, race, initial fitness, and training response--HERITAGE.

In the HERITAGE Family Study, heart rate (HR) associated with various percentages of maximal oxygen intake (VO2max) was used to prescribe exercise intensity. When fitness improved, HR at the same power output (PO) decreased, and PO was increased to produce the prescribed HR. Although we assumed that subjects were again working at the same %VO2max, there were no studies with a large heterogeneous population to determine whether this was correct. Therefore, 653 subjects with complete data were classified by age, sex, race, initial VO2max, and VO2max response after 20 wk of training. All groups had a significant increase in VO2max and a significant decrease in HR at the same absolute PO after training but no difference in HR at the same relative intensity. Training does not affect HR at a given %VO2max in a heterogeneous population of men and women, blacks and whites aged 17-65 yr with different initial VO2max values and different responses to training.

EFFECTS OF HIGH INTENSITY INTERVAL TRAINING IN HYPEROXIA COMPARED TO NORMOXIA

PURPOSE This study was designed to determine if the increased intensity required to maintain training heart rate(HR) during interval workloads for hyperoxic breathing (H), as compared to normoxia (N), would result in increased training response. METHODS Seven athletes (19–28 yrs, mean VO2max 52 ml/kg) completed a training program consisting of 6 weeks of bike ergo work 3 days/week, 1hr/day, at 80–85% max HR, 4min work interval and 2 min rest. During training the HR intensity range was maintained by increasing the load. Using a single blind design, subjects were randomly assigned to H or N breathing conditions for the work intervals. For H condition 100% O2 was humidified and delivered through a mixing system with room air producing 57–60% O2, while for N the identical system was used without the O2 mix. After a 12 week training break, included to allow return to baseline values, a second identical 6 week training protocol was completed with the other breathing condition. Pre and post each training program measurements of VO2max, performance time at 90% VO2max and cardiorespiratory response to a steady state workload at 80% VO2max were completed. RESULTS There were no significant differences in any of these parameters between the pre-test results for each training period. Both H and N training programs showed significant increases in VO2max and performance time and although the increases were greater for H they were not significantly different. HR was reduced 10% more for the H program than N at the 80% VO2max load. The load increase throughout the 6 weeks of training needed to maintain the required HR was 15% greater for H. CONCLUSION Overall, these responses for a relatively modest training volume, suggest that the increased training intensity required to maintain target HR for H resulted in improved cardiorespiratory response to work. Whether performance variables would be significantly elevated by H training with an increased training volume requires further study.

EFFECT OF EXERCISE ON SERUM REMNANT LIPOPROTEINS IS DIFFERENT ACCORDING TO INITIAL SERUM REMNANT LEVELS

There is a growing body of evidence that indicates triglyceride (TG)-rich lipoprotein remnants are a critical risk factor for coronary artery diseases. There have been limited studies, however, that examine how modifications in lifestyle can affect these atherogenic remnants. PURPOSE To assess the hypothesis that a physically active lifestyle can reduce atherogenic remnants, particularly in subjects with high serum remnant levels. METHODS This study included 46 middle-aged sedentary subjects (mean±SD, 50.6±5.7y, 25 males and 21 females) who were instructed to perform 30–60 min of aerobic exercise, such as brisk walking, at least 3 times a week for 3 months. We assigned the subjects to three groups according to their serum remnant-like lipoprotein particles cholesterol (RLP-C) levels, which was used as an index of serum remnant levels, at baseline (high group: 7.6–31.9 mg/dl, n=16, middle group: 5.5–7.5 mg/dl, n=15, low group: 2.1–5.2 mg/dl, n=15). RESULTS During the exercise period, weekly exercise frequency and duration remained the same among these three groups, and a significant increase in VO2max was detected in all groups after the 3-month exercise period. Although there was no significant change in RLP-C in the low group (baseline, one month after and 3 months after: 4.0±0.9, 5.1±2.4, 4.1±1.5 mg/dl), in the middle group there was a significant reduction in RLP-C after the 3-month exercise period (6.5±0.8, 7.2±4.3, 4.7±1.3 mg/dl; P < 0.01). Furthermore, a significant decrease in RLP-C was observed in the high group after one month and 3 months of exercise (15.2±7.9, 9.7±4.0, 8.4±4.1 mg/dl; P < 0.01). The reduction in RLP-C was remarkable in comparison with that of serum TG levels in the middle (119±27, 123±60, 95±26 mg/dl) and high groups (186±81, 133±60, 158±71 mg/dl). CONCLUSION Regular aerobic exercise contributes to the reduction of serum remnant lipoproteins, especially in subjects with a higher remnant level.

Evaluation of a Healthy-Lifestyle Approach to Weight Management

Background.Obesity and overweight have reached near-epidemic proportions in the United States. There is a need to further investigate intervention strategies designed to help individuals manage their weight by improving diet and exercise behaviors. We designed a multidisciplinary weight management program that included healthy eating, regular exercise, and behavioral changes based on the Transtheoretical Model. The program focused on a healthy lifestyle rather than weight loss. Methods. Overweight and obese adults ( n = 144; BMI = 32.5 ± 3.8) participated in a 6-month clinic-based weight management program. The first 3 months of the program were intense (twice weekly for 2 h) followed by 3 months of reduced clinical contact. Assessments completed at baseline, 3 months, and 6 months included weight, body composition, BMI, total cholesterol, HDL-C, LDL-C, and 24-h diet recalls. VO 2max was assessed at baseline and at 3 months. Results. Subjects experienced significant decreases in weight, percentage body fat, BMI, total cholesterol, LDL-C, total caloric intake, and the percentage of energy intake from dietary fat as well as a significant increase in VO 2max ( P < 0.05) at 3 months. Changes were maintained at 6 months, with weight, total cholesterol, and LDL-C demonstrating further improvement. Conclusions. A clinic-based weight management program that focuses on lifestyle is successful at promoting changes in exercise and dietary behaviors. These changes appear to promote good health, as evidenced by moderate weight loss, increased cardiorespiratory fitness, and improved lipid profiles.

CHANGES IN AEROBIC CAPACITY, LACTATE THRESHOLD, AND RPE IN COMPETITIVE ADOLESCENT FEMALE DISTANCE RUNNERS

1607 Training adaptations in fit adult athletes across a season have been documented, however, little has been conducted concerning these changes in adolescent female competitors. The purpose of this study was to examine the changes in VO2max, lactate threshold (LT), and RPE in high school female distance runners. Seven high school female distance runners (mean ± SD; VO2max = 48.97 ± 5.30; age = 14.57 ± 0.79) completed a discontinuous progressive treadmill protocol to exhaustion (GXT) during weeks 1, 4, and 7 of a competitive track and field season. Blood lactate (Bla) accumulation was determined during each stage of the GXT from a finger tip blood sample and LT (VO2 at 4 mM) was calculated using a regression line between the two successive workloads that produced the BLa above and below 4 mM. The training regimen consisted of two distinct phases. Training protocol from week 1 to week 4 was 15.92 ± 8.12 km/week with two interval sessions. From week 5 to week 7 the training protocol was 20.14 ± 8.12 km/week with 2 or 3 interval sessions. Training in week 7 corresponded to the heaviest training period just prior to the end of season taper. Repeated measures ANOVAs revealed: 1) a significant increase in VO2max; 2) a significant decrease in percent fat; and 3) no significant change in body weight. VO2max at week 4 and week 7 was 54.09 ± 3.29 and 52.62 ± 4.87, respectively. Compared to week 1, the 6% increase in LT at week 4 and 2% increase at week 7 were not significant. Finally, exercise HR and RPE during the first three stages of the GXT were found to be significantly reduced at weeks 4 and 7. These results suggest that aerobic training in adolescent girls increases aerobic capacity and alters the perception of effort at low and moderate intensities.

Effect of 6 weeks of endurance training on the lactate minimum speed

The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s :age 23 +/- 4 years;body mass 69.7 +/- 9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23 +/- 4 years; body mass 72.7 +/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO 2max , running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol.l -1 ; and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO 2max , running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol.l -1 or the lactate minimum speed.In the training group, there was a significant increase in VO 2max (from 47.9 +/- 8.4 to 52.2 +/- 2.7 ml.kg -1 .min -1 ), running speed at the maximal lactate steady state (from 13.3 +/- 1.7 to 13.9 +/- 1.6 km.h -1 ), running speed at the lactate threshold (from 11.2 +/- 1.8 to 11.9 +/- 1.8 km.h -1 ) and running speed at a blood lactate concentration of 3 mmol.l -1 (from 12.5 +/- 2.2 to 13.2 +/- 2.1 km.h -1 ) (all P ≪ 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0 +/- 0.7 to 10.9 +/- 1.7 km.h -1 ). The results demonstrate that the lactate minimum speed,when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity.

THE EFFECTS OF ENDURANCE EXERCISE TRAINING ON RESTING METABOLIC RATE IN SEDENTARY, OVERWEIGHT PRE AND POSTMENOPAUSAL FEMALES.

782 Five premenopausal (32 ± 10 yrs, 80 ± 11 kg, 41 ± 7% fat) and six postmenopausal women (60 ± 11 yrs, 89 ± 13 kg, 37± 5% fat) performed treadmill walking for forty minutes, three times per week for twelve weeks at 60 - 65% of their heart rate reserve. Four sedentary women (50 ± 12 yrs, 79 ± 14 kg, 39 ± 6% fat) served as control subjects. There were no significant differences in physical characteristics between the groups. Each subject underwent pre-training and post-training measurements of body weight, resting metabolic rate (RMR), body composition, VO2 max, resting plasma thyroid hormones and catecholamines, and seven-day dietary recall. Analysis of variance with repeated measures revealed significant increases in VO2 max (22.3 vs. 25.1 ml/kg/min, n=11, p<0.05) and total body water (29 ± 5 vs. 30 ± 6 L, p<0.05) with no significant changes in body weight, lean body mass or body fat percentage following training. No significant increases were seen in RMR for the training group (n = 11) (1.81 vs. 1.96 ml/kg/min, NS; 137 vs. 143 ml/min, NS; 66 vs. 69 kcal/min, NS) however, there were trends for time by group interactions for RMR in terms of ml/kg/min (p =.069), ml/min (p =.071) and kcal/min (p =.067). No significant changes in plasma catecholamines, thyroid hormones or dietary intake were seen following the training period. These data suggest that exercise training of greater duration and/or intensity may be necessary for the detection of significant changes in RMR and its related hormonal mechanisms in overweight, sedentary women.

IMPROVEMENT IN RENAL FUNCTION IN OLDER HYPERTENSIVES IS ASSOCIATED WITH INCREASE IN MAXIMAL AEROBIC CAPACITY.

906 A number of cross-sectional and longitudinal studies have reported declines in renal function and maximal aerobic capacity (VO2max) with age. The present study was undertaken to test whether aerobic exercise training would improve renal function in older, sedentary hypertensives. Renal plasma flow(RPF) and glomerular filtration rate (GFR) were determined by plasma and urinary clearances of 131I-hippuran and 99mTc-DTPA, respectively, before and after 6 months of aerobic exercise training @70% VO2max) in 16 older (62±2 yrs: mean±SEM) sedentary, hypertensive (165±3/81±2 mm Hg) individuals. Following 6 months of aerobic exercise training there was a significant increase in VO2max(18.0±1.0 vs. 20.4±1.1 ml/kg/min, P=0.0004). However, as a group there were no significant changes in RPF (227±14 vs. 229±15 ml/min/1.73m2, P=0.88), GFR (75±6 vs. 74±7 ml/min/1.73m2, P=0.87) or the calculated (GFR/RPF), glomerular filtration fraction (FF: 0.34±0.03 vs. 0.35±0.04, P=0.88). When the change in VO2max was related to the change in measures of renal function, there were inverse relationships between the change in VO2max and changes in GFR (r=-0.41, P=0.11) and FF (r=-0.56, P=0.02). In addition, there was a significant positive relationship between the change in VO2max and the change in RPF (r=0.58, P=0.02). These data, suggest that improvements in renal function with training in older individuals are dependent upon the improvement in VO2max. We hypothesize that the age-associated decline in renal function is attenuated by aerobic exercise training. FigureFigure

Intensity of training and physiologic adaptation in patients with chronic obstructive pulmonary disease.

The applicability of high-intensity training and the possibility of inducing physiologic adaptation to training are still uncertain in patients with severe chronic obstructive pulmonary disease (COPD). The purposes of this study were to evaluate the proportion of patients with moderate to severe COPD in whom high-intensity exercise training (30-min exercise session at 80% of baseline maximal power output [Wmax]) is feasible, and the response to training in these patients. We also sought to evaluate the possible influence of disease severity on the training intensity achieved and on the development of physiologic adaptation following endurance training. Forty-two patients with COPD (age = 66 +/- 7 yr, FEV1 = 38 +/- 13% predicted, [mean +/- SD]) were evaluated at baseline and after a 12-wk endurance training program. Each evaluation included a stepwise exercise test on an ergocycle up to the individual maximal capacity during which minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), and arterial lactic acid concentrations were measured. The training consisted of 25 to 30-min exercise sessions on a calibrated ergocycle three times a week, with a target training intensity at 80% of Wmax. The training intensity was adjusted with the objective of reaching the target intensity, but also to ensure that the cycling exercise could be maintained for the specified duration. The training intensity sustained for the duration of each exercise session averaged 24.5 +/- 12.6, 51.7 +/- 17.4, 63.8 +/- 22.4, and 60.4 +/- 22.7% of Wmax at Weeks 2, 4, 10, and 12, respectively. High-intensity training was achieved in zero, three, five, and five patients at Weeks 2, 4, 10, and 12, respectively. A significant increase in VO2max and Wmax occurred with training (p < 0.0002). This improvement in exercise capacity was accompanied by a 6% and 17% reduction in VE and in arterial lactic acid concentration for a given work rate, respectively (p < 0.0001), suggesting that physiologic adaptation to training occurred. The intensity of training achieved, in % Wmax, was not influenced by the initial VO2max, age, or FEV1. The effects of training were compared in patients with an FEV1 > or = 40% or < 40% predicted. Percent changes in VO2max, Wmax, and VE, were significant and of similar magnitude for both groups, whereas the decrease in arterial lactic acid for a given work rate reached statistical significance only in those patients with an FEV1 > or = 40% predicted. We conclude that although most patients were unable to achieve high-intensity training as defined in this study, significant improvement in their exercise capacity was obtained and physiologic adaptation to endurance training occurred. The training intensity expressed as a percent of the individual maximum exercise capacity, and the relative effectiveness of training, were not influenced by the severity of airflow obstruction.

LEFT VENTRICULAR DIASTOLIC FUNCTION AND AEROBIC POWER AFTER EXERCISE TRAINING AND CALCIUM CHANNEL BLOCKADE 1023

Recent studies have shown that the calcium channel blocker verapamil improves left ventricular diastolic function (LVDF) in healthy elderly with diastolic dysfunction. Cross-sectional studies also suggest that physically fit elderly may have LVDF parameters similar to the young. The purpose of this study was to compare resting LVDF and the exercise performance of older men following:1. 12 weeks of daily oral 240mg verapamilSR (V) administration, and 2. short term high intensity exercise training (XT). Nine healthy sedentary older men (68 +/- 3y), with evidence of LVDF using Doppler echocardiography, participated in both the drug (1) and exercise (2) programs separated by 2 months. Before (pre) and after (post) both programs resting LVDF was assessed using Doppler echocardiography, and aerobic power (VO2max) assessed during cycle ergometry. Both XT and V produced significant increases in VO2max of 12% respectively (p<0.05) with no difference between the groups. Doppler studies showed a significant reduction in the isovolumic relaxation time (IVRT) following XT (pre=0.095s vs post=0.072s) and V(pre=0.095s and post=0.069), and a significant increase in the ratio of early to late flow velocity (E/A) after XT (pre=0.94 vs post=1.21) and V (pre=0.94 vs post=1.26). No differences were observed in Doppler studies between XT and V. The comparable results of XT and V on LVDF in healthy older men with pre-existing diastolic dysfunction suggest that repeated elevations of venous return and heart rate with high intensity XT may improve calcium handling and hence LV function.

Impact of aerobic training on fitness and quality of life in multiple sclerosis

Fifty-four multiple sclerosis (MS) patients were randomly assigned to exercise (EX) or nonexercise (NEX) groups. Before and after 15 weeks of aerobic training, aspects of fitness including maximal aerobic capacity (VO2max), isometric strength, body composition, and blood lipids were measured. Daily activities, mood, fatigue, and disease status were measured by the Profile of Mood States (POMS), Sickness Impact Profile (SIP), Fatigue Severity Scale (FSS), and neurological examination. Training consisted of 3 x 40-minute sessions per week of combined arm and leg ergometry. Expanded Disability Status Scale (EDSS) scores were unchanged, except for improved bowel and bladder function in the EX group. Compared with baseline, the EX group demonstrated significant increases in VO2max, upper and lower extremity strength, and significant decreases in skinfolds, triglyceride, and very-low-density lipoprotein (VLDL). For the EX group, POMS depression and anger scores were significantly reduced at weeks 5 and 10, and fatigue was reduced at week 10. The EX group improved significantly on all components of the physical dimension of the SIP and showed significant improvements for social interaction, emotional behavior, home management, total SIP score, and recreation and past times. No changes were observed for EX or NEX groups on the FSS. Exercise training resulted in improved fitness and had a positive impact on factors related to quality of life.

Exercise training in older men and women: Effects on cardiovascular and renal function

This study investigated the effects of endurance exercise training on cardiovascular and renal function in healthy, older adults. Twenty-three sedentary men and women, 68.2 ± 4.6 (mean ± SD) years of age completed medical screening, including ECG studies and serum chemistries, graded exercise testing, maximal oxygen uptake (VO2max) determinations, and renal function testing prior to being randomly assigned to an exercise group (EG, n = 13), or to a non-exercising control group (CG, n = 10). The EG completed 16 weeks (3-bouts · wk−1) of supervised exercise training on treadmills and stair-climbers, progressing in intensity from 50% to 85% of maximal heart rate reserve. Effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were measured by single-bolus I.V. radioisotope injections, VO2max was measured during maximum exercise testing. The EG showed a significant increase in VO2max (from 21.8 ml · kg−1 min−1 to 26.0 ml · kg−1 · min−1; p = 0.0009), while the CG showed no change (p = 0.05). There were no significant changes in ERPF or GFR in either group after the 16-wk training or control periods (p > 0.05). These data suggest that although endurance exercise training improves cardiorespiratory function in older adults, renal function is neither improved nor adversely affected.

Effects of aerobic endurance training on gas exchange kinetics of older men

The kinetics of gas exchange at the on-transient of exercise are appreciably slowed in older individuals. Eight older men (72 yr) completed 6 months of aerobic cycle training. Ventilation and gas exchange kinetics were determined at the onset of a below threshold (ventilatory threshold, V(E)T) square wave exercise function and compared with control values (N = 4, age 70 yr). Gas exchange data were measured breath-by-breath and signal averaged data were fit with a monoexponential function to determine the time constants (tau). The training group showed significant increases in VO2max (20%) and VO2 at V(E)T (21%). The tau for oxygen uptake kinetics decreased significantly (62.2 +/- 15.5 to 31.9 +/- 7.0 s). The tau VCO2 (70.9 +/- 10.9 to 43.8 +/- 11.4 s) and tau VE (89.2 +/- 18.0 to 50.4 +/- 11.3) also were significantly faster posttraining; however, tau HR (38.1 +/- 20.5 to 28.6 +/- 7.2) was not significantly altered. Thus, with a vigorous training program, the kinetics of gas exchange of older individuals were faster, and approached values reported in fit young subjects.

The development of aerobic power in young athletes.

Previous studies investigating the effects of training in children have been hampered in their interpretation by the confounding effects of growth and development. We followed the development of maximal aerobic power (VO2max) in 453 athletes drawn from soccer, swimming, gymnastics, and tennis. Study design was of a mixed longitudinal type with five age cohorts (8, 10, 12, 14 and 16 yr) followed for 3 consecutive years. A multilevel regression modeling procedure was used to identify the independent effects of predictor variables while accounting for the effects of growth, such as changes in body size. When age, height, and weight were controlled for, VO2max in males significantly increased with pubertal status, indicated by the coefficient value of 0.15 l/min being greater than its associated SE of 0.07 l/min. Females showed a similar pattern, with a coefficient value of 0.13 +/- 0.07 l/min, although the significant increase in VO2max (P < 0.05) found in males in the latter stages of puberty was not shown in females. Swimmers had the highest VO2max values (P < 0.001) at all ages.

Increases in human skeletal muscle Na(+)-K(+)-ATPase concentration with short-term training.

To investigate the effect of short-term training on Na(+)-K(+)-adenosine triphosphatase (ATPase) concentration in skeletal muscle and on plasma K+ homeostasis during exercise, 9 subjects performed cycle exercise for 2 h per day for 6 consecutive days at 65% of maximal aerobic power (VO2 max). Na(+)-K(+)-ATPase concentration determined from biopsies obtained from the vastus lateralis muscle using the [3H]ouabain-binding technique increased 13.6% (P < 0.05) as a result of the training (339 +/- 16 vs. 385 +/- 19 pmol/g wet wt, means +/- SE). Increases in Na(+)-K(+)-ATPase concentration were accompanied by a small but significant increase in VO2 max (3.36 +/- 0.16 vs. 3.58 +/- 0.13 l/min). The increase in arterialized plasma K+ concentration and plasma K+ content determined during continuous exercise at three different intensities (60, 79, and 94% VO2 max) was depressed (P < 0.05) following training. These results indicate that not only is training capable of inducing an upregulation in sarcolemmal Na(+)-K(+)-ATPase concentration in humans, but provided that the exercise is of sufficient intensity and duration, the upregulation can occur within the first week of training. Moreover, our findings are consistent with the notion that the increase in Na(+)-K(+)-ATPase pump concentration attenuates the loss of K+ from the working muscle.

Development of maximal oxygen uptake in young elite male cross-country skiers: a longitudinal study.

The aim of this study was to investigate the effects of extensive endurance training (15-25 h per week) on the development of maximal oxygen uptake (VO2 max) in boys from puberty. Maximal oxygen uptake was measured a number of times each year from the age of puberty and for the next 6-9 years in seven young male elite cross-country skiers. Mean VO2 max was measured as 76.3 and 80.1 ml kg-1 min-1 at the ages of 14 and 15 years respectively. Despite the fast rate of growth during puberty, maximal aerobic power showed seasonal variations from the age of 14, reaching a plateau at the age of 15, whereas VO2 max (ml kg-2/3 min-1) increased continuously. It is concluded that, during puberty, boys probably attain significant increases in VO2 max when appropriate amounts of endurance training are undertaken.

The VO2max of recreational athletes before and after pregnancy

This study was designed to test the hypothesis that pregnancy has an added training effect (increases "absolute" VO2max) in well-conditioned, recreational athletes. VO2max was measured serially in 20 nonpregnant recreational athletes who maintained their exercise within +/- 10% of initial levels over a 15-month period and 20 similar women who conceived and continued exercise at a reduced level during pregnancy with a return to within 20% of initial levels by 12 wk postpartum. Initially the two groups were similar in terms of age (30 +/- 1 vs 30 +/- 2 yr), weight 57.6 +/- 7.2 vs 59.7 +/- 7.5 kg), max pulse rate (189 +/- 8 vs 187 +/- 10 bpm), and absolute (3083 +/- 469 vs 3138 +/- 464 ml.min-1) VO2max. In the nonpregnant group the values obtained 15 months later were unchanged (weight = 57.8 +/- 6.6 kg, max pulse = 191 +/- 7 bpm, VO2max = 2977 +/- 397 ml.min-1) while those who conceived had a significant increase in absolute VO2max that was evident 12-20 wk postpartum and was maintained at the time of final testing 36-44 wk postpartum (3368 +/- 435 ml.min-1). Both weight (60.1 +/- 8.1 kg) and maximum pulse rate (185 +/- 12 bpm) were unchanged. These data indicate that pregnancy is followed by a small but significant increase in VO2max in recreational athletes who maintain a moderate to high level of exercise performance during and after pregnancy.

Step ergometry: is it task-specific training?

Maximal exercise responses were measured before and after 10 weeks of training in two groups of men, one trained on a treadmill (n = 12) and the other on a step ergometer (n = 9); the groups were pre- and post-tested on both machines to examine the specificity of the training modes. Training for both groups consisted of 3 days week-1, 30 min day-1, progressing to 50 min day-1, at an intensity of 75%-80% heart rate maximum reserve. Pre-training maximal oxygen uptake (VO2max) was significantly higher on the treadmill for both groups (X = 8.5%). VO2max increased 6.9% on the treadmill (P less than 0.05) and 6.9% (P greater than 0.05) on the step ergometer after treadmill training. The small increases may be attributed to the specificity of the testing protocols used to elicit VO2max. Significant (P less than 0.01) increases in VO2max were found for both modalities after step-ergometry training (treadmill = 11.8%; step ergometer = 23.2%). These increases resulted in equal post-test VO2max values (4.05 l min-1; 51 ml kg-1 min-1) on the step ergometer and treadmill. The significant increases in VO2max found for both modalities after step-ergometry training shows that (1) step ergometry is an effective training modality, and (2) its effects can be measured on the treadmill and therefore it is not task-specific training.

Loss of abdominal fat and metabolic response to exercise training in obese women

Numerous studies have shown that a high accumulation of abdominal fat is associated with metabolic complications and with an increased risk of coronary heart disease. The present study examined the effects of changes in body fatness and in the level of abdominal fat on metabolic variables in a sample of 13 obese premenopausal women, aged 38.8 +/- 5.3 (SD) yr. Women exercised for 90 min at approximately 55% of maximal aerobic power (VO2 max) four to five times a week for a period of 14 mo. The training program induced a significant increase in VO2 max and a mean reduction in body fat mass of 4.6 kg (P less than 0.01), with no change in fat-free mass. Measurement of adipose tissue areas by computed tomography indicated a greater loss of abdominal fat compared with midthigh adipose tissue (P less than 0.05). The training program also produced significant reductions in the insulinogenic index measured during an oral glucose tolerance test and in plasma cholesterol (Chol), low-density lipoprotein (LDL)-Chol, and apolipoprotein (apo) B levels (P less than 0.05). Training also significantly increased plasma high-density lipoprotein (HDL)-apo A-I and HDL2-Chol levels and decreased plasma HDL3-Chol concentration (P less than 0.05). Whereas no change in postheparin plasma lipoprotein lipase activity was noted, a significant decrease in postheparin plasma hepatic triglyceride lipase activity was observed after training (P less than 0.005). Metabolic responses were not correlated with changes in VO2 max but were significantly correlated with the reduction in body fat mass and/or with the loss of deep abdominal fat.(ABSTRACT TRUNCATED AT 250 WORDS)