The effects of exercise training on hypothalamic-pituitary-adrenal axis reactivity and autonomic response to acute stress-a randomized controlled study.

BACKGROUND: Exercise training is suggested to have a stress-buffering effect on physiological reactions to acute stress. The so-called cross-stressor adaptation hypothesis is one of many theories behind the plausible effects, proposing that the attenuated physiological reaction seen in trained individuals in response to acute exercise is also seen when the individual is exposed to acute psychosocial stress. However, few randomized controlled trials (RCT) are available in this field. Therefore, the aim of the present trial was to study the effects of a 6-month aerobic exercise intervention on the physiological response to acute laboratory stress. METHODS: A two-armed RCT including untrained but healthy individuals aged 20-50 years was conducted. Assessments included a peak oxygen uptake test and a psychosocial stress test (the Trier Social Stress Test). A total of 88 participants went through both baseline and follow-up measures (48 in the intervention group and 40 in the control group) with a similar proportion of women and men (20 women and 28 men in the intervention group and 18 women and 22 men in the control group). Outcome measures were adrenocorticotrophic hormone, cortisol, systolic and diastolic blood pressure, and heart rate responses to acute psychosocial stress. RESULTS: Oxygen uptake and time-to-exhaustion increased significantly following the intervention, while a decrease was seen in the control group. The analyses showed attenuated responses to acute psychosocial stress for all variables in both groups at follow-up, with no differences between the groups. No correlation was seen between amount of exercise training and reactivity to the stress test. Despite the increased oxygen uptake in the intervention group, no differences were seen between the groups for any of the outcome variables at follow-up. CONCLUSIONS: In this study, the cross-stressor adaptation hypothesis could not be confirmed. Both groups showed decreased reactions indicating a habituation to the stress test. TRIAL REGISTRATION: ClinicalTrials.gov NCT02051127 . Registered on 31 January 2014-retrospectively registered.

A randomized controlled pilot study of the effects of 6-week high intensity hatha yoga protocol on health-related outcomes among students.

OBJECTIVE: Modern hatha yoga exercises (YE) provide an alternative form of physical activity which may reduce stress, facilitate recovery and improve health. This study investigated the short-term effects of high intensity hatha yoga exercises (HIY) on health-related outcomes. METHODS: A 6-week randomized controlled study was performed to compare HIY with a control group not changing their exercise behavior. Healthy students (N = 44; median age: 25 years, range 20-39 years; HIY: n = 21, including 3 men; control group: n = 23, including 3 men) novice to yoga participated in the intervention which included one weekly class and recommended home training. Participants provided self-reports in questionnaires before and after the intervention. Self-reports included anxiety and depression (Hospital Anxiety and Depression Scale), stress (Perceived Stress Scale), sleep quality (Pittsburgh Sleep Quality Index), insomnia (Insomnia Severity Index), subjective health complaints (Common Symptoms in General Practice Index) and self-rated health (single-item). RESULTS: After the 6-week intervention, there were no between-group differences in anxiety, depression, stress, sleep or self-rated health. However, when investigating associations within the HIY-group, a higher HIY-dose was related to less depression (r = 0.47; p = 0.03), improved sleep quality (r = 0.55; p = 0.01), and less insomnia (r = 0.49; p = 0.02). CONCLUSIONS: There were no short-term between-group effects of HIY on mental distress, sleep or self-rated health. However, within the HIY-group, a higher dose was associated with improved mental health in terms of depression and with improved sleep. Although future studies with larger samples are needed, these preliminary findings suggest short-term positive effects of HIY on health-related outcomes among students. TRIAL REGISTRATION NUMBER: NCT01305096.

Exercise training and physiological responses to acute stress: study protocol and methodological considerations of a randomised controlled trial.

BACKGROUND: This paper describes the protocol and methodological prerequisites for a randomised controlled exercise intervention. Selected baseline data from the study are also presented, demonstrating some methodological challenges related to exercise intervention trials. The aim of the trial was to study the effects of exercise training on physiological responses to acute psychosocial stress in untrained individuals. METHODS: Individuals with a low level of physical activity were invited to participate in an exercise intervention lasting for 6 months. A total of 119 participants were included and went through a peak oxygen uptake test and a psychosocial stress test at baseline. Adrenocorticotropic hormone (ACTH) and cortisol were measured in connection to the stress test to identify the physiological response. RESULTS: Almost 90% of the participants reported themselves as untrained, but results from the objectively measured oxygen uptake did not seem to correspond to the reported sedentary lifestyle. The primary outcome measures at baseline varied between individuals. The mean change from pre-test to peak value was 214% for ACTH and 94% for cortisol. Of these, 13 individuals did not respond in ACTH and/or and cortisol. DISCUSSION: Supposedly untrained individuals seeking participation in an exercise intervention might not be as untrained as they report, a methodological consideration of importance when evaluating the effects of training. Another important consideration is related to the primary outcome measure, which should be measurable and possible to affect. Absence of reaction at baseline means that changes can only be detected as an increased reaction.

Effects of High-Intensity Hatha Yoga on Cardiovascular Fitness, Adipocytokines, and Apolipoproteins in Healthy Students: A Randomized Controlled Study.

BACKGROUND: Yoga exercises are often used as a form of body and mind exercise to increase performance. However, knowledge about the physiologic effects of performing high-intensity Hatha yoga exercises over a longer time period remains limited. OBJECTIVE: To investigate the effects of high-intensity yoga (HIY) on cardiovascular fitness (maximal oxygen consumption, estimated from the Cooper running test), ratings of perceived exertion (RPE), heart rate (HR), heart rate recovery (HRR), blood pressure (BP), adipocytokines, apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and glycosylated hemoglobin (HbA1c) in healthy students. METHODS: The 44 participants (38 women and 6 men; median age, 25 years [range, 20-39 years]) were randomly assigned to an HIY or a control group. The HIY program was held for 6 weeks (60 minutes once a week). Cardiovascular fitness, RPE, HR, HRR, BP, adipocytokines, HbA1c, ApoA1, and ApoB were measured at baseline and after 6 weeks in both groups. RESULTS: HIY had no significant effects on cardiovascular fitness (mean dose: 390 minutes [range, 210-800 minutes]), HR, HRR, BP, or any of the blood parameters. However, secondary findings showed that [corrected] ApoA1 (1.47 ± 0.17 to 1.55 ± 0.16 g/L; p = 0.03) and adiponectin (8.32 ± 3.32 to 9.68 ± 3.83 mg/L; p = 0.003) levels increased significantly in the HIY group after 6 weeks. CONCLUSIONS: Six weeks of HIY did not significantly improve cardiovascular fitness. However, secondary findings showed that [corrected] ApoA1 and adiponectin levels increased significantly in the HIY group. This finding suggests that HIY may have positive effects on blood lipids and an anti-inflammatory effect.

Acute effects of reducing vertical displacement and step frequency on running economy.

This work studies the immediate effects of altering the vertical displacement of the center of mass (VD) and step frequency (SF) on the metabolic cost of level treadmill running at 16 km · h(-1) on 16 male runners. Alterations of VD, SF, and the product VD × SF was induced using a novel feedback system, which presents target and current values to the runner by visual or auditory display. Target values were set to 5 and 10% reductions from individual baseline values. The results were expressed as relative changes from baseline values. Alterations led to an increase in metabolic cost in most cases, measured as V(O2) uptake per minute and kilogram of body mass. Correlations were weak. Still, linear multiple regression revealed a positive coefficient (0.28) for the relationship between VD × SF and V(O2). Separate rank correlation tests showed negative correlation (τ = -0.19) between SF and V(O2) and positive correlation (τ = 0.16) between VD and V(O2). There is a coupling between VD and SF caused by the mechanics of running; hence, isolated reduction of either factor was hard to achieve. The linear model also showed a negative coefficient for the relationship between the height of the center of mass above the ground (CoMh) and V(O2). The effect size was small (multiple R(2) 0.07 and 0.12). Still the results indicate that reducing VD × SF by reducing the vertical displacement can have a positive effect on running economy, but a concurrent reduction in CoMh may diminish the positive effect. Midterm and long-term effects of altering the technique should also be studied.

Immediate effect of visual and auditory feedback to control the running mechanics of well-trained athletes.

The correlation between mechanical factors of running and running economy as measured by metabolic cost is a subject of much interest in the study of locomotion. However, no change in running technique has been shown to result in an immediate improvement in running economy on an intra-individual basis. To evaluate the effect of a modified running technique, it is probably necessary that the individual trains with the new technique for a longer period using a feedback system to control the new kinematics. In this study, we examine the feasibility of using visual and auditory feedback to adapt running technique according to a simplistic model of the mechanical cost of running. The model considers only the mechanical work against gravity, which is the product of the magnitude of the vertical displacement of the runner's centre of mass and the step-frequency. In the experiments reported here, 18 trained runners, running at 16 km · h(-1) on a treadmill, were given feedback on these parameters together with indicated target levels. In almost all cases, the runners were able to adjust their technique accordingly.

Evaluation of the Oxycon Mobile metabolic system against the Douglas bag method.

The aim of this study was to evaluate two versions of the Oxycon Mobile portable metabolic system (OMPS1 and OMPS2) in a wide range of oxygen uptake, using the Douglas bag method (DBM) as criterion method. The metabolic variables VO2, VCO2 respiratory exchange ratio and VE were measured during submaximal and maximal cycle ergometer exercise with sedentary, moderately trained individuals and athletes as participants. Test-retest reliability was investigated using the OMPS1. The coefficients of variation varied between 2 and 7% for the metabolic parameters measured at different work rates and resembled those obtained with the DBM. With the OMPS1, systematic errors were found in the determination of VO2 and VCO2 At submaximal work rates VO2 was 6-14% and VCO2 5-9% higher than with the DBM. At VO2(max) both VO2 and VCO2 were slightly lower as compared to DBM (-4.1 and -2.8% respectively). With OMPS2, VO2 was determined accurately within a wide measurement range (about 1-5.5 L min(-1)), while VCO2 was overestimated (3-7%). VE was accurate at submaximal work rates with both OMPS1 and OMPS2, whereas underestimations (4-8%) were noted at VO2(max). The present study is the first to demonstrate that a wide range of VO2 can be measured accurately with the Oxycon Mobile portable metabolic system (second generation). Future investigations are suggested to clarify reasons for the small errors noted for VE and VCO2 versus the Douglas bag measurements, and also to gain knowledge of the performance of the device under applied and non-laboratory conditions.

Minimal marker set for center of mass estimation in running.

The purpose was to study the validity of a recently proposed method [Forsell C, Halvorsen K. A method for determining minimal sets of markers for the estimation of center of mass, linear and angular momentum. Journal of Biomechanics 2009;42(3):361-5] for estimating the trajectory of the whole-body center of mass (CoM) in the case of running at velocities ranging from 10 to 22 km h(-1). The method gives an approximation to the CoM using the position of fewer markers on the body than the standard method of tracking each segment of the body. Fourteen male athletes participated. A standard method for determining the CoM from a model of 13 segments and using the position of 36 markers was used as reference method. Leave-one-out cross-validation revealed errors that decreased with increasing number of markers used in the approximative method. Starting from four markers, the error in absolute position of the CoM decreased from 15 mm to 3 mm in each direction. For the velocity of the CoM the estimation bias was neglectable, and the random error decreased from 0.15 to 0.05 m s(-1). The inter-subject and intra-subject variability in the estimated model parameters increased with increasing number of markers. The method worked well also when applied to running at velocities outside the range of velocities in the data used to determine the model parameters. The results indicate that a model using 10 markers represents a good trade-off between simplicity and accuracy, but users must take into account requirements of their specific applications.

Measurements of vertical displacement in running, a methodological comparison.

The aim was (1) to evaluate measurements of vertical displacements (V(disp)) of a single point on sacrum as an estimate of the whole body centre of mass (CoM) V(disp) during treadmill running and (2) to compare three methods for measuring this single point. These methods were based on a position transducer (PT), accelerometers (AMs) and an optoelectronic motion capture system. Criterion method was V(disp) of the whole body CoM measured with the motion capture system. Thirteen subjects ran at 10, 12, 14, 16, 18, 20 and 22 kmh(-1) with synchronous recordings with the three methods. Four measurements of the (V(disp)) were derived: (1) V(disp) of CoM calculated from a segment model consisting of 13 segments tracked with 36 reflective markers, (2) V(disp) of the sacrum recorded with the PT, (3) V(disp) of the sacrum calculated from the AM, and (4) V(disp) of the sacrum calculated as the mid point of two reflective markers (sacrum marker, SM) attached at the level of the sacral bone. The systematic discrepancy between the measurements of sacrum V(disp) and CoM V(disp) varied between 0 and 1.5mm and decreased with increasing running velocity and decreasing step duration. PT and SM measurements showed strong correlation, whereas the AM showed a variability increasing with velocity. The random discrepancy within each subject was 7 mm for all three methods. In conclusion single-point recordings of the sacrum V(disp) may be used to monitor changes in V(disp) of CoM during treadmill running.

Effects of glossopharyngeal pistoning for lung insufflation in elite swimmers.

PURPOSE: To investigate whether sessions of glossopharyngeal pistoning (GP) to lung volumes exceeding maximum inspiratory capacity in a group of extremely well-trained elite swimmers would affect maximum lung volumes and buoyancies. METHODS: Ten female and 16 male swimmers performed GP four times a week for 5 wk in addition to their regular swimming training program. Pulmonary function, chest expansion, hydrostatic weights (maximally inhaled and exhaled), and body composition (relative amounts of fat, bone, muscle, and fat-free tissue) were measured. RESULTS: Training compliance was 79% for the males and 82% for the females. Chest expansion increased significantly during the training period, by 1.0 cm and by 0.8 cm at the level of the xiphiod and the fourth costae for the males, and by 0.6 cm and 0.8 cm for the females. The buoyancy lifting force increased significantly by 0.17 and 0.37 kg for the males and the females, respectively. The females also increased their vital capacity significantly by 2%. No significant changes in body composition took place in either group. CONCLUSION: The lung volumes and buoyancies of swimmers can be increased by sessions of GP.

Older women's cardiovascular responses to deep-water running.

The aim of the study was to examine submaximal and maximal physiological responses and perceived exertion during deep-water running with a vest compared with the responses during treadmill running in healthy elderly women. Eleven healthy women 70 +/- 2 years old participated. On two different occasions they performed a graded maximal exercise test on a treadmill on land and a graded maximal exercise test in water wearing a vest. At maximal work the oxygen uptake was 29% lower (p < .05), the heart rate was 8% lower (p < .05), and the ventilation was 16% lower (p < .05) during deep-water running than during treadmill running. During submaximal absolute work the heart rate was higher during deep-water running than during treadmill running for the elderly women. The participants had lower maximal oxygen uptake, heart rate, ventilation, respiratory-exchange ratio, and rate of perceived exertion during maximal deep-water running with a vest than during maximal treadmill running. These responses were, however, higher during submaximal deep-water running than during treadmill running.

Work-time profile, blood lactate concentration and rating of perceived exertion in the 1998 Greco-Roman Wrestling World Championship.

The aim of this study was to examine work-time profiles, blood lactate concentrations and perceived exertion among Greco-Roman wrestlers in the 1998 World Championship. Forty-two senior wrestlers from nine nations were studied in 94 matches. Each match was recorded with a video camera (Panasonic AG 455, film rate: 25 Hz) and analysed for duration of work (wrestling) and rest (interrupt) periods. Blood lactate concentration was determined with an electrochemical device (Analox P-LM5) and a rating of perceived exertion scale (Borg) was used to estimate general exertion and exertion in the extremity and trunk muscles. The mean duration of the matches was 427 s (range 324-535 s), with mean durations of work and rest of 317 and 110 s, respectively. The mean periods of work and rest were 37.2 and 13.8 s, respectively. Mean blood lactate concentration was 14.8 mmol x 1(-1) (range 6.9-20.6). The difference in mean blood lactate concentration between the first- and final-round matches was not significant (P > 0.05). Blood lactate concentration was significantly higher (P < 0.04) in matches of long duration than in those of short duration. The mean general rating of perceived exertion for all matches was 13.8 according to the scale used. Most of the wrestlers (53.3%) perceived exertion to be highest in the flexors of the forearm, followed by the deltoids (17.4%) and the biceps brachii muscles (12.0%). In addition to a relatively high rating of perceived exertion in the arm muscles, this indicates a high specific load on the flexor muscles of the forearm.