Effects of isometric resistance training and detraining on ambulatory blood pressure and morning blood pressure surge in young normotensives.

Isometric resistance training (IRT) has been shown to reduce resting and ambulatory blood pressure (BP), as well as BP variability and morning BP surge (MBPS). However, there are no data available regarding how long after cessation of IRT these effects are maintained. Therefore, the purpose of this study was to determine the effects of 8 weeks of detraining on resting BP, ambulatory BP and MBPS following 8 weeks of IRT in a population of young normotensive individuals and to further substantiate previously reported reductions in MBPS following IRT. Twenty-five apparently healthy participants with resting BP within the normal range (16 men, age = 23 ± 6 years; 9 women, age = 22 ± 4 years, resting BP: 123 ± 5/69 ± 7 mmHg) were randomly assigned to a training-detraining (TRA-DT, n = 13) or control (CON, n = 12) group. Resting BP, ambulatory BP and MBPS were measured prior to, after 8 weeks of bilateral leg IRT using an isokinetic dynamometer (4 × 2-min contractions at 20% MVC with 2-min rest periods, 3 days/week) and following an 8-week detraining period. There were significant reductions in 24-h ambulatory systolic BP (SBP) and calculated SBP average real variability (ARV) following IRT that were maintained after detraining (pre-to-post detraining, -6 ± 4 mmHg, p = 0.008, -2 ± 1.5 mmHg, p = 0.001). Similarly, the training-induced decreases in daytime SBP and daytime SBP ARV (pre-to-post detraining, -5 ± 6 mmHg, p = 0.001; -2 ± 1.2 mmHg, p = 0.001, respectively), MBPS (pre-to-post detraining, -6 ± 9 mmHg, p = 0.046) and resting SBP (pre-to-post detraining, -4 ± 6 mmHg, p = 0.044) were preserved. There were no changes in night-time or night-time SBP ARV across all time points (pre-to-post detraining, -1 ± 8 mmHg, p = 1.00, -0.7 ± 2.9 mmHg, p = 1.00). These results confirm that IRT causes significant reductions in resting BP, ambulatory BP, ambulatory ARV and MBPS. Importantly, the changes remained significantly lower than baseline for 8 weeks after cessation of training, suggesting a sustained effect of IRT.

Reproducibility of limb power outputs and cardiopulmonary responses to exercise using a novel swimming training machine.

The purpose of this study was to determine the reproducibility of limb power outputs and cardiopulmonary responses, to incremental whole-body exercise using a novel swimming training machine. 8 swimmers with a mean age of 23.7 ± 4.6 (yrs), stature 1.77 ± 0.13 (m) and body mass of 74.7 ± 2.8 (kg) gave informed consent and participated in repeat exercise testing on the machine. All subjects performed 2 incremental exercise tests to exhaustion using front crawl movements. From these tests peak oxygen consumption (VO(2peak)), peak heart rate (HR(peak)), peak power output (W (peak)) and individual limb power outputs were determined. Results showed there were no significant differences between test 1 and 2 for any variable at exhaustion, and the CV% ranged from 2.8 to 3.4%. The pooled mean values were; VO(2peak) 3.7 ± 0.65 L.min⁻¹, HR (peak) 178.7 ± 6.6 b.min⁻¹ and W (peak) 349.7 ± 16.5 W. The mean contributions to the total power output from the legs and arms were (37.3 ± 4.1% and 62.7 ± 5.1% respectively). These results show that it is possible to measure individual limb power outputs and cardiopulmonary parameters reproducibly during whole-body exercise using this training machine, at a range of exercise intensities.

Biomarkers of cardiovascular disease risk in 40-65-year-old men performing recommended levels of physical activity, compared with sedentary men.

OBJECTIVE: Both the UK Department of Health and the US Centers for Disease Control and Prevention have recommended at least 30 minutes of moderate-intensity physical activity on most days for health. Specific mention is made of beneficial effects upon blood lipids. The purpose of this study was to compare biomarkers of cardiovascular disease risk in men who perform physical activity in accordance with these recommendations with those who do not. METHODS: 128 healthy men, aged 40-65 years, were recruited. 61 were classified as active (performing at least the minimum recommended physical activity of > or =4 metabolic equivalents (METs), for 6 months immediately before the study) and 67 as sedentary. Fasting blood was drawn for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides, and apolipoproteins (Apo) A-1 and B. Low-density lipoprotein cholesterol (LDL-C) was estimated using the Friedewald equation. RESULTS: The median (interquartile range) physical activity level was 7.0 (5.0-10.7) versus 1.0 (0-1.8) hour/week at > or =4 METs (active versus sedentary; p<0.001). Apo A-1 was higher in the active men (p = 0.032). No significant differences were found for TC, HDL-C, LDL-C, TC:HDL-C, triglycerides, Apo B, or the Apo B:A-1 ratio. CONCLUSIONS: These findings suggest that physical activity performed according to the recommendations used in this study favourably influenced Apo A-1. The finding that cholesterol and triglycerides were not different in men achieving the recommended physical activity levels compared with sedentary men contradicts some of the claims made within the published recommendations. However, intervention studies are needed to clarify these preliminary findings.

Arm and leg power output in swimmers during simulated swimming.

PURPOSE: Previously, it has not been possible to compare power output of the arms and legs during simulated swimming using dry-land ergometry. The purpose of this study was to determine arm-pulling and leg-kicking power using isokinetic dry-land ergometry. METHODS: Twenty-two highly trained male swimmers of mean (+/- SD) age, 23 +/- 3.6 yr; body mass, 78 +/- 5.9 kg; and stature, 1.79 +/- 0.04 m were recruited to the study. First, subjects performed 10 s of all-out exercise at each of five resistance settings, with 1 h rest in between, to determine the best maximal pull velocity (MPVopt). Second, they performed an all-out 30-s test at MPVopt, which was repeated the following day. These repeated 30-s tests were performed separately using simulated front-crawl arm-pulling and leg-kicking, on a computer-interfaced swim bench and purpose-built leg-kicking ergometer. Peak and mean power output (PPO; MPO) were determined from regression analysis of the power vs time relationship. RESULTS: The mean (+/- SEM) PPO for arms and legs were 304 +/- 22 W versus 435 +/- 36 W. For MPO, the means were 225 +/- 31 W vs 312 +/- 26 W, respectively. These values were attained at mean MPVopt of 2.5 +/- 0.2 m x s(-l) for arms and 2.3 +/- 0.4 m x s(-1) for legs. The variation in PPO from repeated testing was 7.3% for arms and 8.3% for legs. CONCLUSIONS: These results show that the legs can sustain greater power output than the arms during simulated swimming. Also, the intra-subject variation in measurement of power output is small using these dry-land ergometers. These methods of assessment might be useful in explaining swimming performance and in monitoring changes that take place during training.

Power output measurement during treadmill cycling.

The study aim was to consider the use of a motorised treadmill as a cycling ergometry system by assessing predicted and recorded power output values during treadmill cycling. Fourteen male cyclists completed repeated cycling trials on a motorised treadmill whilst riding their own bicycle fitted with a mobile ergometer. The speed, gradient and loading via an external pulley system were recorded during 20-s constant speed trials and used to estimate power output with an assumption about the contribution of rolling resistance. These values were then compared with mobile ergometer measurements. To assess the reliability of measured power output values, four repeated trials were conducted on each cyclist. During level cycling, the recorded power output was 257.2 +/- 99.3 W compared to the predicted power output of 258.2 +/- 99.9 W (p > 0.05). For graded cycling, there was no significant difference between measured and predicted power output, 268.8 +/- 109.8 W vs. 270.1 +/- 111.7 W, p > 0.05, SEE 1.2 %. The coefficient of variation for mobile ergometer power output measurements during repeated trials ranged from 1.5 % (95 % CI 1.2 - 2.0 %) to 1.8 % (95 % CI 1.5 - 2.4 %). These results indicate that treadmill cycling can be used as an ergometry system to assess power output in cyclists with acceptable accuracy.

Relationships between pulse wave velocity and heart rate variability in healthy men with a range of moderate-to-vigorous physical activity levels.

Pulse wave velocity (PWV) is associated with heart rate variability (HRV) in 24-39-year-old men. This study of 40-65-year-old men ranging in moderate-to-vigorous physical activity levels investigated whether (a) PWV is related to spectral HRV, (b) using normalised units for HRV influences that relationship, and (c) HRV predicts PWV when other factors, including age and blood pressure, are accounted for. Subjects were healthy men (N=115), mean (SD) age 50.8 (7.1) years. Carotid-femoral PWV was measured using Complior. HRV was derived from a 5 min ECG for total, high-frequency, and low-frequency power (TP, HF, and LF, respectively), the LF/HF ratio, and normalised units for HF (HFnu) and LF (LFnu). Non-parametric data were natural log-transformed. PWV was 8.5 (1.4) m s-1. TP, HF, LF, LF/HF, HFnu and LFnu were 1908 (2195) m s2, 577 (1034) m s2, 457 (514) m s2, 1.5 (1.3), 46.8 (17.9), and 49.4 (19.4), respectively. PWV was inversely associated with TP (R2=0.061, p=0.008), HF (R2=0.095, p=0.001), LF (R2=0.086, p=0.002) and HFnu (R2=0.040, p=0.031), but was not associated with LF/HF (R2=0.020, p=0.136) or LFnu (R2=0.028 p=0.076). Only age and systolic blood pressure (adjusted R2=0.306, p<0.001) predicted PWV in multivariate analysis. This study has shown that PWV was weakly associated with TP and HF. The use of normalised units only influenced the relationship between PWV and LF. Finally, relationships between PWV and HRV are mediated through age and systolic blood pressure in this population of men ranging in moderate-to-vigorous physical activity level.

Time course of changes in bilateral arm power of swimmers during recovery from injury using a swim bench.

OBJECTIVES: There has been little research on the time course of recovery from injury in athletes. This is especially the case for recovery in arm power in injured swimmers. The purpose of this study was to compare the power output of the injured and non-injured arms of swimmers during recovery from injury by use of a maximal exercise test on a computer interfaced isokinetic swim bench. METHODS: Thirteen swimmers (five men and eight women; age 18.8 (3.2) years; stature 1.76 (0.05) m; body mass 61.7 (5.9) kg; mean (SD)) gave written informed consent and were recruited to this study throughout a three year period. All subjects had experienced non-aquatic soft tissue injury to their dominant-side shoulder or upper arm in the three months before participation, but had been allowed to return to swimming training. All of the subjects had injured their dominant arm and the mean time for absence from training was 3.7 (1.1) weeks. At return to training and at four, eight, and twelve weeks thereafter, subjects performed two all-out 30 second tests on the swim bench by simulating the swimming arm action. From these tests, peak power output (PPO), mean power output (MPO), and power decay (PD) for each arm during the 30 seconds of exercise could be determined by averaging the two tests. The differences between return to training and the four, eight, and twelve week periods were analysed using repeated measures analysis of variance with Tukey b post hoc test. RESULTS: The repeated testing showed 95% confidence intervals of +/- 11.4 W for PPO, +/- 9.5 W for MPO and +/- 0.5 for PD. When the swimmers returned to training the results showed that PPO was 179 (21.9) v 111 (18.1) W (P = 0.02), MPO was 122 (9.8) v 101 (8.8) W (P = 0.01), and PD was 2.5 (0.6) v 5.2 (1.9) (P = 0.001) for non-injured and injured arms respectively (all values mean (SEM)). There were similar differences at four weeks which disappeared after eight weeks, except for that of PPO which was still evident (187.3 (21.9) v 156.8 (18.1) W; P = 0.01). At 12 weeks there were no differences between the non-injured and injured arm on any of the indices of arm power (P > 0.05). CONCLUSIONS: These results suggest that, using the swim bench power test, differences in bilateral arm power output after injury persist for at least eight weeks after return to swimming training. These findings support the need for prolonged rehabilitation after such injury. This would best include physiotherapy and a training programme within which special consideration is given to the recuperation process.

Cardiopulmonary responses to exercise in swimmer using a swim bench and a leg-kicking ergometer.

There are few studies on the relative cardiopulmonary demands of the arm-stroke and the leg-kicking action in swimmers, mainly because of the absence of a suitable dry-land ergometer. Therefore, the purpose of this study was to compare the cardiopulmonary responses to exercise using a swim bench and a leg-kicking ergometer. Twelve highly-trained male swimmers with mean age of 20.3 +/- 1.9 (yrs), stature 1.77 +/- 0.04 (m) and body mass of 73.7 +/- 3.3 (kg) gave written informed consent and performed two separate incremental exercise tests on subsequent days. These tests used either a swim bench for assessment of arm-stroke or a specially designed front crawl leg-kicking ergometer. Oxygen consumption (VO2), heart rate (HR) and exercise intensity were recorded throughout both exercise tests. Peak oxygen consumption (VO2peak), peak heart rate (HRpeak) and peak exercise intensity (EIpeak) were also recorded. Furthermore, the relationships between submaximal heart rate and exercise intensity (HR/EI) and between oxygen consumption and exercise intensity (VO2/EI) for arm or leg exercise were explored. Mean values for VO2peak, HRpeak and EIpeak for a arm-stroke and leg-kick respectively were; 3.22 +/- 0.31 vs 3.76 +/- 0.42 (1 x min(-1); P=0.02), 170 +/- 3 vs 176 +/- 3 (b x min(-1); P=0.07) and 124.2 +/- 9.4 vs 141.3 +/- 12.7 (watts; P=0.01). The mean VO2peak and EIpeak for arm-stroke represented 85% and 88% respectively of the same measures for leg-kick. The HR/EI and VO2/EI relationships were shown to be linear (at least r=0.94, P<0.05 and r=0.96; P<0.01 respectively) and the differences in the gradients and elevations of these relationships for arm-stroke vs leg-kick were significant (at least P<0.05; ANCOVA). These results show that highly-trained swimmers can achieve similar peak levels of oxygen consumption when using the arms or the legs. The ability to assess the cardiopulmonary responses to front-crawl arm-stroking and leg-kicking relative to exercise intensity might be useful in understanding the importance of the arm and leg components of whole body metabolism in swimmers, especially during training programmes.

Responses of bone turnover markers to repeated endurance running in humans under conditions of energy balance or energy restriction.

Distance running in humans has been associated with both positive and negative effects on the balance of bone remodelling. There is evidence to suggest that the negative effects may be linked to a failure to balance energy expenditure with an adequate energy intake. Energy restriction is known to reduce the synthesis and serum concentration of insulin-like growth factor 1 (IGF-1), which plays an important role in bone formation. The purpose of the present study was to compare the effects of repeated periods of prolonged treadmill running, under conditions of either energy balance or energy restriction, on markers of bone turnover and serum IGF-1 concentration in trained distance runners. Eight male distance runners [mean age 25.1 (SD 5.9) years, maximal oxygen uptake 61.8 (SD 4.9) ml x kg(-1) x min(-1)] undertook an exercise and diet regime on two separate occasions, 2 weeks apart. On each occasion they performed an intensive, 60 min treadmill run on 3 consecutive days. On one occasion their energy intake was restricted to approximately 50% of their estimated energy requirement (RES), whereas on the other occasion they remained in energy balance (BAL). The N-terminal pro-peptide of type 1 collagen (P1NP), osteocalcin and IGF-1 were measured in serum collected between 0800 and 0900 hours, when fasted and rested, on the day before and the day after each regime. The cross-linked N-telopeptides of type 1 collagen and deoxypyridinoline were measured from 24 h urine collections made on the day before and the final day of each regime and adjusted for creatinine excretion. The results showed that the serum concentration of both P1NP and IGF-1 declined by 15% (P = 0.008) and 17% (P = 0.007) respectively in response to RES, but did not change in response to BAL (P > 0.05). A strong relationship was observed between the magnitude of the reduction in the serum concentration of P1NP and IGF-1 after RES (r = 0.97; P < 0.001). There were no changes in the other bone markers in response to either regime. The results suggested that in trained distance runners, repeated periods of prolonged running do not affect the balance of bone turnover unless energy balance is simultaneously altered. These findings support the link between a negative energy balance, a reduced synthesis or serum level of IGF-1 and reduced collagen synthesis. They may also help to explain the bone remodelling imbalance that has been observed in some male and female distance runners.

Respiratory arrest in a male athlete after running through a wheat field.

A male athlete suffered complete respiratory arrest after collapsing at the entrance to an Accident and Emergency Department of a hospital. He was resuscitated and recovered fully after several hours. He had multiple wheals on both legs and had complained of severe breathlessness before collapsing. The athlete had run through a wheat field, upon finding his usual pathway overgrown, which had caused wheat pollen to be released. He had been a mild asthmatic for 30 years and had recalled some mild urticaria after exercise but had never experienced exercise-induced asthma, or hay fever. Subsequent allergy tests showed negative for wheat but positive for house dust mite and grass mix. It is possible that the symptoms were triggered either by the running itself, inhalation of allergens other than wheat pollen, skin abrasions caused by contact with wheat stalks, or a combination of these factors.

The reproducibility of cardiopulmonary responses to exercise using a swim bench.

The purpose of this study was to establish reproducible assessments of cardiopulmonary responses to exercise using a computer-interfaced isokinetic swim bench. Five male and four female highly trained swimmers with mean age of 19.2 +/- 1.2 (yrs), stature 1.75 +/- 0.02 (m) and body mass of 65.8 +/- 2.9 (kg) performed an incremental exercise test on two occasions within one week. Oxygen consumption (VO(2)), heart rate (HR) and exercise intensity were recorded throughout the exercise test. Measurements were made of the peak oxygen consumption (VO(2peak)), peak heart rate (HR(peak)) peak exercise intensity (EI(peak)) and the submaximal heart rate vs exercise intensity (HR/EI) and oxygen consumption vs exercise intensity (VO(2)/EI) relationships. The values for VO(2peak), HR(peak) and EI(peak) from all tests were 2.85 +/- 0.26 (I.min(-1)), 171 +/- 2.8 (b.min(-1)) and 86.2 +/- 6.8 (watts) respectively. The differences in these peak values from repeated tests were 0.06 I.min(-1), 1.8 b.min(-1) and 1.3 W, which were not significant (p > 0.05; paired t-test). These represented 2.1, 1.0 and 1.5% respectively. The HR/EI and VO(2)/EI relationships were shown to be linear (at least r = 0.99 and r = 0.98 respectively) and the differences in these relationships from repeated tests were not significant (p > 0.05, ANCOVA) showing adjusted mean differences of 0.02 I.min(-1) and 0.5 b.min(-1) for the group. These results suggest that this method, which uses a swim bench, provides reproducible measurement of the cardiopulmonary responses to exercise in swimmers.

Comparison of cardiopulmonary responses to two types of dry-land upper-body exercise testing modes in competitive swimmers.

In this study we compared cardiopulmonary responses to upper-body exercise in 12 swimmers, using simulation of the front-crawl arm-pulling action on a computer-interfaced isokinetic swim bench and arm cranking on a modified cycle ergometer. Subjects adopted a prone posture; exercise was initially set at 20 W and subsequently increased by 10 W. min(-1). The tests were performed in a randomised order at the same time of day, within 72 h. The highest (peak) oxygen consumption (VO(2peak)), heart rate (HR(peak)), blood lactate ([la(-)](peak)) and exercise intensity (EI(peak)) were recorded at exhaustion. Mean (SEM) peak responses to simulated swimming were higher than those to arm cranking for VO(2peak) [2.9 (0.2) vs 2.4 (0.1) l x min(-1); P = 0.01], HR(peak) [174 (2) vs 161 (2) beats x min(-1); P = 0.03], and EI(peak) [122 (6) vs 102 (5) W; P = 0.02]. However, there were no significant differences in [la(-)](peak) [9.6 (0.6) vs 8.2 (0.6) mmol x l(-1); P = 0.08]. Thus simulated swimming is the preferred form of dry-land ergometry for the assessment of swimmers.

Bone turnover in amenorrhoeic and eumenorrhoeic women distance runners.

Bone remodelling has not been assessed in women distance runners with chronic amenorrhoea. The purpose of this study was to compare indices of bone turnover and energy balance in runners with chronic amenorrhoea, runners with a history of regular menstrual cycles and sedentary controls. Subjects comprised 3 groups of 9 women, matched for age [mean+/-SEM: 27.2+/-1.8 yrs] and categorised as amenorrhoeic runners (AmR), eumenorrhoeic runners (EuR) and eumenorrhoeic sedentary controls (SC). Serum concentrations of bone formation markers [osteocalcin (OC), carboxy-terminal propeptide of type 1 collagen (P1CP), bone alkaline phosphatase (BAP)], E2, total T3 and IGF-1 were measured from a fasting morning blood sample. Urine levels of bone resorption markers [pyridinoline (Pyr) and deoxypyridinoline (Dpyr)] were measured and corrected for creatinine excretion. Mean daily energy balance (EB) was calculated by subtracting dietary energy intake (EI) from energy expenditure (EE) estimated from reported activity patterns over 7 days. The results showed that all bone turnover markers were lower in AmR than in EuR or SC (P<0.001: OC, BAP and P1CP; P<0.05: Pyr and Dpyr). Furthermore, when z-scores for each bone marker in runners were calculated against mean values for SC (by subtracting each measure of bone turnover from the mean value for SC and expressing the difference as a fraction of the SD of this mean value), bone resorption appeared to outweigh formation in AmR, but not in EuR. Serum concentrations of E2, T3 and IGF-1 were also lower in AmR than in EuR or SC (P<0.001: all hormones), as was EB (P<0.001). These findings suggested that in AmR there was some factor which was reducing bone turnover and in particular, bone formation. This factor might have been linked to an energy deficit and the effects of this deficit on body mass, body composition and metabolism.

Lactate and cardiopulmonary responses to simulated arm-pulling and leg-kicking in collegiate and recreational swimmers.

Investigations into the changes due to training in the metabolism of the arms or the legs in swimmers of different training status are limited. The purpose of this study was to compare the lactate and cardiopulmonary responses to simulated arm-pulling and leg-kicking in collegiate and recreational swimmers. Sixteen males (9 collegiate swimmers; SW, 7 recreational swimmers; RSW, mean+/-SD; age 22+/-3 years, body mass 81+/-9 kg, stature 1.84+/-0.06 m), gave written consent and performed continuous incremental exercise tests using either simulated front-crawl arm-pulling or leg-kicking. Lactate concentration (HLa) and oxygen consumption (VO2) were determined at 20 W intervals and at exhaustion (HLa(peak); VO2(peak)). The exercise intensity at a lactate concentration of 4 mM (EI4mM) and at exhaustion (EI(peak)) for arm-pulling and leg-kicking were also established. The arm:leg ratios for EI4mM, HLa(peak) and VO2(peak) were computed. The results showed that for arm-pulling, the SW had higher EI4mM (P=0.02), EI(peak) (P=0.006), but lower HLa(peak) (P=0.03) compared to the RSW. For leg-kicking, none of the responses differed significantly. These results suggest that it is rather the metabolism and local muscle endurance of the arms that are enhanced with competitive swimming endurance.

Relation between bone turnover, oestradiol, and energy balance in women distance runners.

OBJECTIVE: To explore relations between biochemical markers of bone turnover, indices of nutritional status, and serum oestradiol concentration in women distance runners. METHODS: Thirty three women distance runners of mean age (SD) 27.2 (1.8) years participated. Eighteen were defined as eumenorrhoeic, nine as amenorrhoeic, and six as oligomenorrhoeic. Mean (SD) running distance was 47.6 (22.4) km/week. Using bivariate correlation and regression analysis, serum levels of osteocalcin and bone alkaline phosphatase (BAP) and also urine deoxypyridinoline/creatinine (Dpyr/Cr) were correlated with mean daily energy balance, body mass index (BMI; kg/m2), and serum levels of total 3,5,3'-triiodothyronine and oestradiol within each group by menstrual status. RESULTS: All the amenorrhoeic women were in negative energy balance; they had a lower BMI, lower serum levels of oestradiol, triiodothyronine, osteocalcin and BAP and a lower urine Dpyr/Cr than any of the oligomenorrhoeic or eumenorrhoeic women. These variables were also lower in oligomenorrhoeic than in eumenorrhoeic women. Positive correlations were observed between serum levels of osteocalcin or BAP and both BMI and serum oestradiol concentration in amenorrhoeic, but not in oligomenorrhoeic or eumenorrhoeic women. Urine Dpyr/Cr did not correlate with any other variable within any group. Serum oestradiol concentration correlated positively with BMI in amenorrhoeic and oligomenorrhoeic, but not eumenorrhoeic women. CONCLUSIONS: Positive correlations between serum levels of bone formation markers, BMI and serum oestradiol concentration in our amenorrhoeic runners suggested that their reduced bone formation was linked to a low BMI and an oestrogen deficiency. Reduced bone turnover in amenorrhoeic distance runners has not previously been shown. These findings emphasise the importance of body mass and its possible link with a chronic energy deficit and hypothalamic dysfunction on bone remodelling balance in amenorrhoeic runners.

The relationship between serum oestradiol concentration and energy balance in young women distance runners.

Reproductive dysfunction in women distance runners has been linked to an imbalance between energy intake (EI) and energy expenditure (EE) which leads to an energy deficit. To determine whether ovarian suppression is associated with an energy deficit, the relationships between serum oestradiol (E2) concentration and indices of energy balance (EB) were explored in a group of women runners with a variety of menstrual patterns and a range of activity levels. Subjects comprised 33 women distance runners of mean (SD) age 27.2 (1.8) years. Sixteen of these women were defined as eumenorrhoeic (11-13 menstrual bleeds per year during the past 2 years), 8 as oligomenorrhoeic (< or = 3 menstrual bleeds per year for 2 years) and 9 as amenorrhoeic (absence of menses for > 1 year). Their volume of running training ranged from 36 to 97 km x wk(-1) [mean (SD): 68.6 (21.4) km x wk(-1). The body mass index (BMI) and percent body fat (BF) of each subject was measured. Their mean daily energy balance (EB) was calculated by subtracting their dietary EI from their estimated EE recorded over 7 days. Serum concentrations of E2, total T3 and IGF-1 were measured from a fasting blood sample (taken in early follicular phase for Eu women). Relationships between serum E2, T3 and IGF-1, EB, BMI and BF were explored using bivariate correlation and regression analysis. The results showed that the most powerful predictors of serum E2 concentration were estimated EB (r = 0.88, P<0.001), serum T3 (r=0.94, P<0.001) and IGF-1 (r=0.84; P<0.001). Weaker correlations were observed between serum E2 and BMI (r=0.42; P=0.008) and serum E2 and BF (r=0.48; P=0.004). These relationships add support to the hypothesis that reproductive dysfunction in women distance runners is associated with an energy deficit.

Loss of exercise training-induced bradycardia with continued improvement in fitness.

In sedentary individuals, the decrease in heart rate (HR) at a respiratory exchange ratio (R) of unity (HR/R = 1) is lost after 8 weeks of moderate-intensity exercise training. The purpose of this investigation was to examine the effect of training on HR/R = 1, using the exercise intensity (EI) at R = 1 (EI/R = 1) and the HR at a set EI (HR/EIS). In nine healthy volunteers, these indices showed small measurement variability and detected changes associated with 16 weeks of training in that EI/R = 1 and VO2/R = 1 increased, whereas HR/EIS, HR/R = 1 and HR/VO2 decreased. All of these changes were reversed when training ended. In a second trial in a further nine volunteers, the training programme was extended to 20 weeks, and again showed that the decrease in HR/R = 1 failed to progress after 8 weeks despite continued changes in other indices (increases in VO2/R = 1 and decreases in HR/VO2 elevation). The loss of HR/R = 1 decrease was attributed to equal and opposite effects on HR/EIS and EI/R = 1. However, the decreases in HR/EIS showed the same trend as HR/R = 1, with a lack of progression beyond 8-16 weeks. These findings suggest that different indices of cardiorespiratory fitness have different patterns of change and limitations during training. Those which rely on decreases in submaximal HR fail to detect adaptation during continued training. Using submaximal exercise test indices, detection of such changes is better achieved by the measurement of decreases in HR/VO2 elevation and increases in VO2/R = 1 values.

Indices for detection of changes in cardiorespiratory fitness during exercise training in man.

A decrease in the elevation of the linear relation of heart rate on oxygen consumption (HR/VO2) throughout submaximal exercise testing has previously been used in individuals as an index of improvement in cardiorespiratory fitness after a moderate intensity training programme. In the present investigation, changes in HR/VO2 elevation and its variability were quantified and compared with those of other similar indices. These comprised changes in the level of oxygen consumption or heart rate attained at respiratory exchange ratio (R) of unity (VO2/R=1 or HR/R=1. In a first trial in six healthy volunteers, the decrease in HR/VO2 elevation caused by 16 weeks of training significantly exceeded measurement variability, and was associated with increases and decreases respectively in VO2/R=1 and HR/R=1. In a second trial in eight healthy volunteers, the three indices were obtained at four stages during the course of the 16 weeks of training, to grade the improvement in fitness. There were progressive changes in the three indices, the magnitude of which was greatest in the case of the HR/VO2 index. The findings make it possible quantitatively to obtain a graded measure of improvement in fitness during exercise training as indicated by the magnitude of decreases in HR/VO2 elevation.

The relationship between blood lactate and heart rate responses to swim bench exercise and women's competitive water polo.

The aim of this study was to explore the relationship between physiological responses to dry-land testing and to water polo playing. Eight female water polo players (mean+/-s: age 26.7+/-5.7 years, height 169+/-6 cm, body mass 65.3+/-7.0 kg) participated in two assessments. The first involved a discontinuous incremental arm test to exhaustion on an isokinetic swim bench. Blood lactate was determined from finger-prick blood samples and heart rate was recorded at increasing exercise intensities. The highest (peak) values for blood lactate (5.1+/-0.2 mmol l(-1)), exercise intensity (79+/-5.2 W) and heart rate (146+/-6 beats min(-1)) were recorded at exhaustion. Also, the exercise intensity and heart rate at a blood lactate concentration of 4 mmol l(-1) were established. The second assessment involved determination of blood lactate and heart rate immediately after each quarter of a different water polo game for each subject. The mean (+/-s(x)) blood lactate and heart rate for each quarter of the game were as follows: 3.5+/-0.4, 4.3+/-0.5, 4.3+/-0.7 and 4.6+/-0.5 mmol l(-1); 138+/-10, 149+/-12, 151+/-9 and 154+/-8 beats min(-1), respectively. None of the peak values on the swim bench correlated with blood lactate or heart rate responses to game-playing. However, the mean exercise intensity at 4 mmol l(-1) lactate (64+/-5 W) correlated with the fourth quarter values of both blood lactate concentration (r=-0.82, P=0.01) and heart rate (r=-0.93, P< 0.001). These results show that submaximal metabolic responses to exercise on a swim bench are closely correlated with metabolic responses to water polo game-playing.

The reproducibility of tolerance to lower-body negative pressure and its quantification.

The reproducibility of tolerance to lower-body negative pressure (LBNP) has not been assessed sufficiently. Furthermore, there has been confusion concerning the most appropriate index by which LBNP tolerance can be quantified. The purpose of this study was to assess the degree of reproducibility in presyncopal-symptom-limited LBNP (LBNPtol), using an LBNP chamber. Twenty physically active subjects [median age (range) 21 (18-27) years] underwent three successive LBNPtol tests with 72-120 h between each test. LBNPtol was quantified using the LBNP tolerance index (LTI; delta mmHg.min), cumulative stress index (CSI; mmHg.min), duration of negative pressure (DNP) and maximum magnitude of negative pressure (MNP). Heart rate (fc), systolic (SBP) and diastolic (DBP) blood pressures from the three repeated tests were compared during a control period. The changes from control to maximum response (fc, SBP, DBP) during LBNP were also compared, and percentage changes in estimated blood volume were measured. There were no statistical differences between any of these comparisons (P > 0.05). LTI and CSI were greater in the third test when compared to the first two tests (P < 0.05). The values for DNP and MNP were not statistically different between tests (P > 0.05). Measures of LTI and CSI showed an acceptable level of reproducibility for the first two repeated tests. However, there was an increase in LBNPtol on the third successive exposure to LBNP. These findings have shown that it is possible to achieve reproducible measures of tolerance to LBNP when using a custom-built chamber. This only applies to a test-retest procedure. Furthermore, these data also suggest that DNP and MNP do not adequately reflect the differences shown in LBNP tolerance when using LTI and CSI as measures.