Physical work capacity and effect of endurance training in visually handicapped boys and young male adults

Summary The purpose of the present study was to evaluate the relationship between several physical fitness parameters and eyesight divided into 3 grades in visually handicapped boys and young male adults, and to investigate the effect of mild exercise training on physical and psychic symptoms as well as cardiorespiratory fitness. Four subjects were totally blind (TB), 6 were semi-blind (SB) and 27 had amblyopia (AM). Physical fitness tests consisted of maximal oxygen uptake (V _{O 2max}), maximal pedalling speed and power, maximal stepping rate, and isometric knee extention strength. Compared with AM and SB groups, the TB group was inferior in all physical fitness parameters. Especially,V _{O 2max} in TB (26 ml · kg^–1 · min^–1) was about 56% of that in agematched Japanese sighted subjects and was significantly low compared with the AM and SB groups. Both muscle strength and maximal pedalling power corresponded to about 50% that of the age-matched sighted group. Six SB and 4 TB students (¯x=17.7 years) were trained for 6 weeks on a bicycle ergometer at an intensity of 50%V _{O 2max}. Training was undertaken for 3 days per week and maintained for 60 min per session. After training, physical and psychic symptoms determined by the Cornell Medical Index improved significantly. These results indicate that low physical work capacity in visually handicapped boys and young male adults is due to the lack of physical activity, and that mild endurance training is effective in improving physical and psychic symptoms as well as cardiorespiratory fitness.     

Effect of continuous and interval exercise training on the PETCO2 response during a graded exercise test in patients with coronary artery disease

OBJECTIVE:

The purpose of this study was to evaluate the following: 1) the effects of continuous exercise training and interval exercise training on the end-tidal carbon dioxide pressure (PETCO₂) response during a graded exercise test in patients with coronary artery disease; and 2) the effects of exercise training modalities on the association between PETCO₂ at the ventilatory anaerobic threshold (VAT) and indicators of ventilatory efficiency and cardiorespiratory fitness in patients with coronary artery disease.

METHODS:

Thirty-seven patients (59.7±1.7 years) with coronary artery disease were randomly divided into two groups: continuous exercise training (n = 20) and interval exercise training (n = 17). All patients performed a graded exercise test with respiratory gas analysis before and after three months of the exercise training program to determine the VAT, respiratory compensation point (RCP) and peak oxygen consumption.

RESULTS:

After the interventions, both groups exhibited increased cardiorespiratory fitness. Indeed, the continuous exercise and interval exercise training groups demonstrated increases in both ventilatory efficiency and PETCO₂ values at VAT, RCP, and peak of exercise. Significant associations were observed in both groups: 1) continuous exercise training (PETCO₂VAT and cardiorespiratory fitness r = 0.49; PETCO₂VAT and ventilatory efficiency r = -0.80) and 2) interval exercise training (PETCO₂VAT and cardiorespiratory fitness r = 0.39; PETCO₂VAT and ventilatory efficiency r = -0.45).

CONCLUSIONS:

Both exercise training modalities showed similar increases in PETCO₂ levels during a graded exercise test in patients with coronary artery disease, which may be associated with an improvement in ventilatory efficiency and cardiorespiratory fitness.     

Effect of low-intensity continuous training on lung function and cardiorespiratory fitness in both cigarette and hookah smokers

Background

The decline in cardiorespiratory fitness and lung function was higher in smokers. Training method could mitigate some of the negative consequences of smoking among smokers unable or unwilling to quit.

Objective

To examine the effects of continuous training on lungs functional capability and cardiorespiratory fitness in smokers.

Methods

Fifteen cigarette smokers, 14 hookah smokers, and 14 nonsmokers were assigned to low-intensity continuous training (20–30 minutes of running at 40% of maximum oxygen uptake (O₂max)). Lung function and cardiorespiratory fitness parameters were determined using respectively spirometer and treadmill maximal exercise test.

Results

Continuous training improved forced expiratory volume in one second (FEV₁) and forced expiratory flow at 50% of FVC (FEF50 %) in all participants, smokers and nonsmokers (p < 0.05). In contrast, forced vital capacity (FVC) improvement was significant only among cigarette smokers (CS) (+1.7±2.21%, p < 0.01) and hookah smokers (HS) (+1.3±1.7 %, p < 0.05). Likewise, an improvement in cardiorespiratory fitness in both smokers groups without significant changes in diastolic blood pressure (DBP) for CS group and in velocity at maximum oxygen uptake (vO₂max) for HS group.

Conclusion

The low-intensity continuous training improves cardiorespiratory fitness and reduces lung function decline in both cigarette and hookah smokers. It seems to be beneficial in the prevention programs of hypertension. It could have important implications in prevention and treatment programs in smokers unable or unwilling to quit.     

High cardiorespiratory fitness is more beneficial in pre-diabetic men than women

OBJECTIVES:

To investigate gender-specific relationships between cardiorespiratory fitness and factors that predict the development of diabetes and to identify the risk factors that predict fasting plasma glucose and 2-hour plasma glucose levels.

INTRODUCTION:

Different risk factors (e.g., low cardiorespiratory fitness) may cause elevated plasma glucose levels in men compared to women. Therefore, gender-specific analyses are needed.

METHODS:

Cardiorespiratory fitness (maximal power output achieved during a standard cycle ergometry test), resting blood pressure, total serum cholesterol, high-density lipoprotein cholesterol and triglyceride levels were measured in 32 pre-diabetic men (mean age: 57.2±6.8 years; mean body mass index (BMI): 28.5±3.0 kg/m²) and 40 pre-diabetic women (mean age: 55.0±7.3 years, mean BMI: 30.4±5.7 kg/m²). A stepwise regression with backward variable selection was performed to construct models that predict 2-hour and fasting plasma glucose levels.

RESULTS:

Maximal power output was inversely related to the 2-hour plasma glucose level in the entire group (r = −0.237, p<0.05), but this relationship was significant only for males (r = −0.404, p<0.05). No significant correlation was found between female gender and cardiorespiratory fitness. Age and cardiorespiratory fitness were significant predictors of 2-hour plasma glucose levels in men. High-density lipoprotein cholesterol was predictive of 2-hour plasma glucose levels in women. Triglycerides in women and BMI in men were the only predictors of fasting plasma glucose levels.

CONCLUSIONS:

These findings may have consequences for the development of gender-specific diabetes prevention programs. Whereas increasing cardiorespiratory fitness should be a key goal for men, improving the lipid profile seems to be more beneficial for women. However, the present results do not negate the positive effects of increasing cardiorespiratory fitness in women.     

Exercise-induced improvements in cardiorespiratory fitness and heart rate response to exercise are impaired in overweight/obese postmenopausal women

OBJECTIVE:

The purpose of this study was to compare the heart rate response to exercise and the exercise-induced improvements in muscle strength, cardiorespiratory fitness and heart rate response between normal-weight and overweight/obese postmenopausal women.

METHODS:

Sedentary women (n = 155) were divided into normal-weight (n = 79; BMI <25 kg/m²; 58.3±8.6 years) and overweight/obese (n = 76; BMI ≥25 kg/m²; 58.3±8.6 years) groups, and have their 1-repetition maximum strength (adjusted for body mass), cardiorespiratory fitness and heart rate response to a graded exercise test compared before and after 12 months of a three times-per-week exercise-training program.

RESULTS:

Overweight/obese women displayed decreased upper and lower extremity muscle strengths, decreased cardiorespiratory fitness, and lower peak and reserve heart rates compared to normal-weight women. After follow-up, both groups improved their upper (32.9% and 41.5% in normal-weight and overweight/obese women, respectively) and lower extremity(49.5% and 47.8% in normal-weight and overweight/obese women, respectively) muscle strength. However, only normal-weight women improved their cardiorespiratory fitness (6.6%) and recovery heart rate (5 bpm). Resting, reserve and peak heart rates did not change in either group.

CONCLUSIONS:

Overweight/obese women displayed impaired heart rate response to exercise. Both groups improved muscle strength, but only normal-weight women improved cardiorespiratory fitness and heart rate response to exercise. These results suggest that exercise-induced improvements in cardiorespiratory fitness and heart rate response to exercise may be impaired in overweight/obese postmenopausal women.     

Tracking of BMI,fatness and cardiorespiratory fitness from adolescence to middle adulthood: the Zagreb Growth and Development Longitudinal Study

Background: Effective intervention strategies aiming to improve cardiorespiratory fitness and to decrease body fatness are needed. However, long-term stability of these traits is not well understood.

Aim: To assess long-term tracking of cardiorespiratory fitness and body fatness from late adolescence to middle adulthood.

Subjects and methods: The sample consisted of 50 participants (31 boys) from the Zagreb Growth and Development Longitudinal Study who were followed up in adulthood (median age?=?43). Fatness was evaluated through BMI and skin-folds, while cardiorespiratory fitness was assessed using a cardiopulmonary exercise test. Inter-age partial correlation coefficients were calculated to evaluate tracking.

Results: Body mass index and skin-folds showed moderate tracking from age 15 years to middle adulthood (partial r?=?0.55, p?r?=?0.52, p?r?=?0.38, p?r?=?0.30, p?=?0.03), while ventilatory aerobic and anaerobic thresholds did not show significant tracking.

Conclusions: The results of this study indicate that preventive efforts aiming to increase cardiorespiratory fitness should include all adolescents, irrespective of their cardiorespiratory fitness status. Conversely, strategies aiming at obesity prevention should focus on high-risk groups of adolescents.     

Higher cardiorespiratory fitness attenuates the risk of atherosclerosis associated with ADRB3 Trp64Arg polymorphism

Purpose

β3-Adrenergic receptor (ADRB3) Trp64Arg polymorphism is associated with atherogenic risk factors that include weight gain, insulin resistance, and diabetes. Habitual exercise brings higher cardiorespiratory fitness and results in the amelioration of atherosclerotic risk factors. However, the effects of cardiorespiratory fitness level and ADRB3 Trp64Arg polymorphism on the risk of cardiovascular disease remain unclear. A cross-sectional investigation of 877 Japanese men and women (18–75 years old) was performed to clarify the effects of cardiorespiratory fitness on the relationship between ADRB3 Trp64Arg polymorphism and risk of cardiovascular disease.

Method

Common carotid intima-media thickness (ccIMT) and blood lipid profiles were assessed as surrogate markers of atherosclerosis. We measured peak oxygen uptake ( \(\dot V\) O_2peak) during incremental cycle ergometer exercise testing. Subjects were divided into groups with high (High-Fit) and low (Low-Fit) levels of cardiorespiratory fitness based on the median value of \(\dot V\) O_2peak for sex and decade.

Results

Levels of body fat, triglycerides, and plasma glucose were lower and high-density lipoprotein cholesterol levels and \(\dot V\) O_2peak were higher in High-Fit subjects than Low-Fit subjects. ADRB3 Trp64Arg polymorphism did not significantly affect ccIMT or blood lipid profiles. In Low-Fit subjects, ccIMT was higher in individuals with the Arg/Arg genotype compared to the Trp/Trp and Trp/Arg genotypes (each P < 0.0001); however, ADRB3 polymorphism had no effect in High-Fit subjects.

Conclusion

Higher levels of cardiorespiratory fitness may attenuate the risk of atherosclerosis associated with ADRB3 Trp64Arg polymorphism.     

Association of maturation,sex, and body fat in cardiorespiratory fitness

The aims of this cross‐sectional study were 1) to estimate changes in body composition and cardiorespiratory fitness across stages of pubertal maturation, and 2) to describe the relationship between maturity status and body fatness, regional fat distribution, and cardiorespiratory fitness. The sample consisted of 494 children (254 males, 240 females), 8–16 years of age. Height and weight were measured with standard anthropometric methods. Percentage of fat (%F) was estimated from two skinfold thicknesses and regional fat distribution was estimated by the ratio of the subscapular to the triceps skinfold (S/T ratio). Biological maturity was based on self‐assessment of breast stages in females and pubic hair stages in males. A maximal multistage 20‐m shuttle run was used to predict maximal aerobic capacity from maximal aerobic speed. Both VO₂max and 20SRT‐time were used as indicators of cardiorespiratory fitness. ANCOVA with age as the covariate was used. There were significant differences among girls across pubertal stages. Among boys, only weight and height differed significantly by stage of maturity. When adjusted for maturity status, cardiorespiratory fitness expressed either as VO₂/kg body mass or 20SRT‐time was inversely associated with %F in both sexes. This suggests that sexual maturity status alone accounts for a small portion of the variance in aerobic fitness. Height, %F and the S/T ratio were also significantly associated with VO₂/kg body mass and 20SRT‐time. Am. J. Hum. Biol. 14:707–712, 2002. © 2002 Wiley‐Liss, Inc.     

Differential Association of Adiposity Measures with Heart Rate Variability Measures in Koreans

Purpose

Although obesity has been associated with imbalances in cardiac autonomic nervous system, it is unclear whether there are differential relationships between adiposity measures and heart rate variability (HRV) measures. We aimed to examine differences in the relationship between adiposity measures and HRV indices in a healthy Korean population.

Materials and Methods

In all, 1409 non-smokers (811 males, 598 females) without known histories of cardiovascular (CV), endocrine, or neurological diseases underwent adiposity measurements [(body mass index (BMI), percentage of body fat mass (PBF), and waist-to-hip ratio (WHR)], the HRV assessment (SDNN, RMSSD, LF, HF, LF/HF, and pNN50), and examination for CV risk factors (fasting glucose, LDL-cholesterol, HDL-cholesterol, triglycerides, hs-CRP, and blood pressure).

Results

Compared with BMI and PBF, WHR was more strongly correlated with each HRV index and more likely to predict decreased HRV (<15 percentile vs. ≥15 percentile of each HRV index) in ROC curves analysis. In linear regression analysis, all adiposity measures were inversely associated with each HRV measure before adjusting for age, gender, and CV risk factors (p<0.05). After adjusting for the covariates, WHR was inversely related to RMSSD, LF, and pNN50; PBF with RMSSD, HF, and pNN50; BMI with RMSSD (p<0.05). The inversed association between HRV indices and the gender-specific WHR tertile was significant for subjects with BMI ≥25 kg/m², but not for those with BMI <25 kg/m².

Conclusion

WHR and PBF appear to be better indicators for low HRV than BMI, and the association between abdominal adiposity and HRV may be stronger in overweight subjects.     

Heart rate response at the onset of exercise in an apparently healthy cohort

Background

The exercise test is a powerful non-invasive tool for risk stratifying patients with or suspected of having cardiovascular disease (CVD). Heart rate (HR) response during and following exercise has been extensively studied. However, the clinical utility of HR response at the onset of exercise is less understood. Furthermore, conflicting reports exist regarding whether a faster vs. slower HR acceleration represents a CVD risk marker. The primary study purpose was to describe HR acceleration early in exercise in apparently healthy individuals.

Methods

Retrospective analyses were performed in a sample (N = 947) representing a range of age and fitness (11–78 years; VO_2peak 17–49 mL kg^?1 min^?1). HR response was defined over the initial 7 min of the protocol. Associations between HR acceleration and CVD risk factors were also assessed.

Results

Mean increases in HR were 18 ± 9 and 23 ± 11 beats at minute one, for men and women, respectively (p < 0.05). After adjusting for gender and pre-exercise HR, only modest associations were observed between the change in HR at minute one and body mass index, resting blood pressure, cigarette smoking, physical activity, HR reserve, and cardiorespiratory fitness.

Conclusion

There was wide variability in HR acceleration at the onset of exercise in this apparently healthy cohort. A lower increase in HR during the first minute of exercise was associated with a better CVD risk profile, including higher cardiorespiratory fitness, in apparently healthy individuals. These data suggest a greater parasympathetic influence at the onset of exercise may be protective in an asymptomatic population.     

Physical fitness,fatigue, and quality of life after liver transplantation

Fatigue is often experienced after liver transplantation. The aims of this cross-sectional study were to assess physical fitness (cardiorespiratory fitness, neuromuscular fitness, body composition) in liver transplant recipients and to explore whether physical fitness is related to severity of fatigue. In addition, we explored the relationship between physical fitness and health-related quality of life. Included were 18 patients 1–5 years after transplantation (aged 48.0 ± 11.8 years) with varying severity of fatigue. Peak oxygen uptake during cycle ergometry, 6-min walk distance, isokinetic muscle strength of the knee extensors, body mass index, waist circumference, skinfold thickness, severity of fatigue, and health-related quality of life were measured. Cardiorespiratory fitness in the liver transplant recipients was on average 16–34% lower than normative values (P ≤ 0.05). Furthermore, the prevalence of obesity seemed to be higher than in the general population (17 vs. 10%). We found no deficit in neuromuscular fitness. Cardiorespiratory fitness was the only fitness component that was related with severity of fatigue (r _s = −0.61 to r _s = -0.50, P ≤ 0.05). Particularly cardiorespiratory fitness was related with several aspects of health-related quality of life (r _s = 0.48 to r _s = 0.70, P ≤ 0.05). Results of our study imply that cardiorespiratory fitness and body composition are impaired in liver transplant recipients and that fitness is related with severity of fatigue (only cardiorespiratory fitness) and quality of life (particularly cardiorespiratory fitness) in this group. These findings have implications for the development of rehabilitation programs for liver transplant recipients.     

Augmented limb blood flow during neurovascular stress in physically fit women

The study examined whether cardiorespiratory fitness modifies cardiovascular responses by normotensive men and women during the Stroop color‐word interference test. Independent of age and an estimate of body fatness, fitness level was positively related (R² = .39 and .51) to increases in limb blood flow and vascular conductance, coherent with cardiac‐vagal withdrawal and a decrease in heart period, among women but not men. Fitness was unrelated to changes in systolic and diastolic blood pressures and muscle sympathetic nerve activity. The augmented hemodynamic responses among fitter women were not consistent with passive vasodilation via withdrawal of sympathetic neural tone. The results encourage further gender comparisons testing whether fitness augments limb blood flow during mental stress by neurohumoral and flow‐mediated vasodilatory mechanisms or by increased cardiac output.     

Cardiorespiratory fitness and its association with body composition and physical activity in Hong Kong Chinese women aged from 55 to 94 years

Background

Low levels of cardiorespiratory fitness have proven to be associated with a higher risk of premature death from all causes, specifically from cardiovascular disease. However, there has been no study conducted to describe the cardiorespiratory fitness normative values in Chinese midlife and elderly.

Objectives

To provide normative values of cardiorespiratory fitness expressed as maximal oxygen uptake (VO_2max) and its association with body composition and physical activity in Chinese midlife and elderly women in Hong Kong.

Methods

659 Chinese women aged from 55 to 94 years were recruited from two existing cohorts: the carotid atherosclerosis in women Hong Kong cohort study and the Osteoporotic Fractures in Women (MsOS) Hong Kong cohort study. Symptom-limited maximal exercise testing on an electrically braked bicycle ergometer was performed to assess VO_2max, where the subject was connected to a calibrated metabolic cart for gas analysis. Their body composition and physical activity data were also assessed.

Results

The body mass index was 23.4 kg/m² and the mean fat mass and lean body mass were 16.6 kg and 37.3 kg, respectively. The mean VO_2max was 20.3 ± 4.1 ml/kg/min (range, 7.9–35.7 ml/kg/min). VO_2max decreased with age, with the rate of decline 0.25 ml/kg/min/yr (7.1% per decade). In a subgroup of 475 women from the MsOS study, the decline in VO_2max was found to depend on ageing (β = 0.31, P < 0.001), body mass index (β = −0.30, P < 0.001) and levels of physical activity (β = 0.02, P < 0.001). Fat mass was also independently associated with VO_2max (β = −0.20, P < 0.001).

Conclusions

This study describes the normative values of VO_2max in a sample of Chinese midlife and elderly women which provides a valuable reference to assess health and fitness in Chinese elderly. Results from this study also suggested that body composition and levels of physical activity were important determinants of the age-related decline in VO_2max.     

Health-related morphological characteristics and physiological fitness in connection with nutritional,socio-economic status,occupational workload of tea garden workers

Background

Reports on the cardiorespiratory fitness and body composition of male workers engaged in processing of tea leaves in factories within the tea-estates of West Bengal, under the influence of physiological workload, are quite scanty.

Objectives

This cross-sectional study was conducted to evaluate morphometric characteristics based on physiological status and physical fitness of tea factory laborers who are continuously exposed to tea dust in their work environment for more than two years.

Methods

Subjects were divided into control and tea garden workers groups. Height and weight were measured and the body mass index (BMI) was computed. Physiological parameters such as resting heart rate, blood pressure, fitness variables like physical fitness index (PFI), energy expenditure (EE), handgrip strength and anthropometric parameters like mid-upper arm (MUAC), thigh circumference (TC), head circumference (HC) and waist-to-hip ratio (WHR) were measured.

Results

Body surface area (BSA), BMI, body fat percentage and fitness variables (PFI, EE) showed significant difference (p<0.05) between the two groups. Anthropometric measures (MUAC, TC, HC, WHR) reflected poor status among laborers.

Conclusions

The present study shows that the majority of workers had ectomorph stature, good physical fitness, but had poor nutritional status (BMI and WHR)     

A comparison of methods for quantifying training load: relationships between modelled and actual training responses

Purpose

To assess the validity of methods for quantifying training load, fitness and fatigue in endurance athletes using a mathematical model.

Methods

Seven trained runners ( $\dot{V}$ O₂max: 51.7 ± 4.5 mL kg^?1 min^?1, age: 38.6 ± 9.4 years, mean ± SD) completed 15 weeks of endurance running training. Training sessions were assessed using a heart rate (HR), running pace and rating of perceived exertion (RPE). Training dose was calculated using the session-RPE method, Banisters TRIMP and the running training stress score (rTSS). Weekly running performance (1,500-m time trial), fitness (submaximal HR, resting HR) and fatigue [profile of mood states, heart rate variability (HRV)] were measured. A mathematical model was applied to the training data from each runner to provide individual estimates of performance, fitness and fatigue. Correlations assessed the relationships between the modelled and actual weekly performance, fitness and fatigue measures within each runner.

Results

Training resulted in 5.4 ± 2.6 % improvement in 1,500-m performance. Modelled performance was correlated with actual performance in each subject, with relationships being r = 0.70 ± 0.11, 0.60 ± 0.10 and 0.65 ± 0.13 for the rTSS, session-RPE and TRIMP input methods, respectively. There were moderate correlations between modelled and actual fitness (submaximal HR) for the session-RPE (?0.43 ± 0.37) and TRIMP (?0.48 ± 0.39) methods and moderate-to-large correlations between modelled and actual fatigue measured through HRV indices for both session-RPE (?0.48 ± 0.39) and TRIMP (?0.59 ± 0.31) methods.

Conclusions

These findings showed that each of the training load methods investigated are appropriate for quantifying endurance training dose and that submaximal HR and HRV may be useful for monitoring fitness and fatigue, respectively.     

Cardiorespiratory fitness protects against stress-related symptoms of burnout and depression

Objective

To examine how cardiorespiratory fitness and self-perceived stress are associated with burnout and depression. To determine if any relationship between stress and burnout/depression is mitigated among participants with high fitness levels.

Methods

197 participants (51% men, mean age = 39.2 years) took part in the study. The Åstrand bicycle test was used to assess cardorespiratory fitness. Burnout was measured with the Shirom–Melamed Burnout Questionnaire (SMBQ), depressive symptoms with the Hospital Anxiety and Depression Scale (HAD-D). A gender-matched stratified sample was used to ensure that participants with varying stress levels were equally represented.

Results

Participants with moderate and high fitness reported fewer symptoms of burnout and depression than participants with low fitness. Individuals with high stress who also had moderate or high fitness levels reported lower scores on the SMBQ Tension subscale and the HAD-D than individuals with high stress, but low fitness levels.

Conclusion

Better cardiovascular fitness seems to be associated with decreased symptoms of burnout and a better capacity to cope with stress.

Practical implications

Promoting and measuring cardiorespiratory fitness can motivate employees to adopt a more physically active lifestyle and thus strengthen their ability to cope with stress exposure and stress-related disorders.     

Monitoring changes in physical performance with heart rate measures in young soccer players

The aim of the present study was to verify the validity of using exercise heart rate (HRex), HR recovery (HRR) and post-exercise HR variability (HRV) during and after a submaximal running test to predict changes in physical performance over an entire competitive season in highly trained young soccer players. Sixty-five complete data sets were analyzed comparing two consecutive testing sessions (3–4 months apart) collected on 46 players (age 15.1 ± 1.5 years). Physical performance tests included a 5-min run at 9 km h⁻¹ followed by a seated 5-min recovery period to measure HRex, HRR and HRV, a counter movement jump, acceleration and maximal sprinting speed obtained during a 40-m sprint with 10-m splits, repeated-sprint performance and an incremental running test to estimate maximal cardiorespiratory function (end test velocity V _Vam-Eval). Possible changes in physical performance were examined for the players presenting a substantial change in HR measures over two consecutive testing sessions (greater than 3, 13 and 10% for HRex, HRR and HRV, respectively). A decrease in HRex or increase in HRV was associated with likely improvements in V _Vam-Eval; opposite changes led to unclear changes in V _Vam-Eval. Moderate relationships were also found between individual changes in HRR and sprint [r = 0.39, 90% CL (0.07;0.64)] and repeated-sprint performance [r = −0.38 (−0.05;−0.64)]. To conclude, while monitoring HRex and HRV was effective in tracking improvements in V _Vam-Eval, changes in HRR were moderately associated with changes in (repeated-)sprint performance. The present data also question the use of HRex and HRV as systematic markers of physical performance decrements in youth soccer players.     

Subjective sleep quality in relation to inhibition and heart rate variability in patients with panic disorder

Background

Patients with panic disorder (PD) are known to report impaired sleep quality and symptoms of insomnia. PD is an anxiety disorder characterised by deficient physiological regulation as measured by heart rate variability (HRV), and reduced HRV, PD and insomnia have all been related to impaired inhibitory ability. The present study aimed to investigate the interrelationships between subjectively reported sleep impairment, cognitive inhibition and vagally mediated HRV in a sample characterised by variability on measures of all these constructs.

Methods

Thirty-six patients with PD with or without agoraphobia were included. Cognitive inhibition was assessed with the Color–Word Interference Test from the Delis–Kaplan Executive Function System (D-KEFS), HRV was measured using high frequency (HF) power (ms²), and subjectively reported sleep quality was measured with the Pittsburgh Sleep Quality Index (PSQI).

Results

Cognitive inhibition was related to both Sleep latency and Sleep disturbances, whereas HRV was only related to Sleep disturbances. These relationships were significant also after controlling for depression.

Limitations

Correlational design.

Conclusion

Cognitive inhibition is related to key insomnia symptoms: sleep initiation and sleep maintenance. The data supports the psychobiological inhibition model of insomnia, and extends previous findings. Possible clinical implications of these findings are discussed.     

Heart rate variability during exertional heat stress: effects of heat production and treatment

Purpose

We assessed the efficacy of different treatments (i.e., treatment with ice water immersion vs. natural recovery) and the effect of exercise intensities (i.e., low vs. high) for restoring heart rate variability (HRV) indices during recovery from exertional heat stress (EHS).

Methods

Nine healthy adults (26 ± 3 years, 174.2 ± 3.8 cm, 74.6 ± 4.3 kg, 17.9 ± 2.8 % body fat, 57 ± 2 mL·kg·^?1 min^?1 peak oxygen uptake) completed four EHS sessions incorporating either walking (4.0–4.5 km·h^?1, 2 % incline) or jogging (~7.0 km·h^?1, 2 % incline) on a treadmill in a hot-dry environment (40 °C, 20–30 % relative humidity) while wearing a non-permeable rain poncho for a slow or fast rate of rectal temperature (T _re) increase, respectively. Upon reaching a T _re of 39.5 °C, participants recovered until T _re returned to 38 °C either passively or with whole-body immersion in 2 °C water. A comprehensive panel of 93 HRV measures were computed from the time, frequency, time–frequency, scale-invariant, entropy and non-linear domains.

Results

Exertional heat stress significantly affected 60/93 HRV measures analysed. Analyses during recovery demonstrated that there were no significant differences between HRV measures that had been influenced by EHS at the end of passive recovery vs. whole-body cooling treatment (p > 0.05). Nevertheless, the cooling treatment required statistically significantly less time to reduce T _re (p < 0.001).

Conclusions

While EHS has a marked effect on autonomic nervous system modulation and whole-body immersion in 2 °C water results in faster cooling, there were no observed differences in restoration of autonomic heart rate modulation as measured by HRV indices with whole-body cold-water immersion compared to passive recovery in thermoneutral conditions.     

Adolescent physical performance and adult physical activity in Flemish males

Limited information is available about the associations between adolescent fitness levels and adult physical activity. In the present study, these associations are investigated using different indicators of physical activity. It is hypothesized that both health‐ and performance‐related fitness characteristics, observed during the adolescent period, contribute equally to the explained variance in adult physical activity levels. Subjects were 109 Flemish males followed over a period of 27 years from 13 to 40 years of age in the Leuven Longitudinal Study on Lifestyle Fitness and Health. Performance and health‐related fitness characteristics were observed during the growth period and at 40 years of age. The Work Index, Leisure Time Index, and Sport Index of the Baecke questionnaire were used as indicators of physical activity together with triaxial accelerometry. Multiple regression and discriminant analyses contrasting extreme quintiles of activity groupings were used to analyse the associations. Only the Baecke Sport Index showed consistent significant associations (R² = 0.03 to R² = 0.23) with adolescent fitness levels observed at 13, 15, and 18 years. When upper and lower quintiles were contrasted, fitness characteristics observed at the three age levels during adolescence were significantly different for each of the three indices of the Baecke questionnaire at 40 years of age. Lowest associations (R² = 0.09 to R² = 0.17) were found for the Work Index, followed by the Leisure Time Index (R² = 0.12 to R² = 0.28) and Sport Index (R² = 0.25 to R² = 0.43). Highest associations were evident for the 18‐ to 40‐year interval. Performance‐ and health‐related fitness characteristics explain equally well the variance in physical activity indicators. Am. J. Hum. Biol. 13:173–179, 2001. © 2001 Wiley‐Liss, Inc.