Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 314)

This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1988

Balancing stress and recovery in sports

To reach elite level in sports, athletes have to start their intensive and time-consuming training at an early stage. The road to the top is a stressful one, not only due to the physiological stress of training, but also caused by psychological and social stress. In order to improve performance athletes continuously challenge their personal boundaries. This may lead to a local or general overload of the human body that results into injuries, illnesses and overtraining. Overtraining is characterized by an unexplained decrement in sport-specific performance and is often coupled with symptoms such as increased fatigue, poor concentration, disturbed mood, and altered eating and sleeping patterns. Full recovery may take months to years. Monitoring stress and recovery may help to optimize performance and prevent a local or general overload. Clinical measurements showed that mood state and hormonal responses to a double maximal exercise protocol provided valuable information to confirm the diagnosis of overtraining.

Heart Rate Variability, Neuromuscular and Perceptual Recovery Following Resistance Training

We quantified associations between changes in heart rate variability (HRV), neuromuscular and perceptual recovery following intense resistance training (RT). Adult males (n = 10) with \u3e1 year RT experience performed six sets to failure with 90% of 10 repetition maximum in the squat, bench press, and pull-down. Changes (∆) from pre- to immediately (IP), 24 and 48 h post-RT were calculated for neuromuscular performance markers (counter-movement jump peak power and mean concentric bench press and squat velocity with load corresponding to 1.0 m∙s−1) and perceived recovery and soreness scales. Post-waking natural logarithm of the root-mean square of successive differences (LnRMSSD) in supine and standing positions were recorded pre-RT (5 day baseline), IP and two mornings post-RT. All parameters worsened at IP (p \u3c 0.05). LnRMSSD measures were not different from baseline by 24 h. Neuromuscular markers were not different from pre-RT by 48 h. Perceptual measures remained suppressed at 48 h. No significant associations among ∆ variables were observed (p = 0.052–0.978). These data show varying timeframes of recovery for HRV, neuromuscular and perceptual markers at the group and individual level. Thus, post-RT recovery testing should be specific and the status of one metric should not be used to infer that of another

Blood glucose response during cardiopulmonary exercise testing in individuals with type 1 diabetes

To characterise blood glucose responses in cardiopulmonary exercise testing (CPET) in individuals with type 1 diabetes and to assess the impact of hyperglycaemia vs euglycemia on physiological and metabolic responses during CPET in T1DM. This study was a retrospective, secondary analysis of pooled CPET data from three randomised controlled trials using identical 1-minute incremental test stages. Participants followed standardised glycaemic management criteria prior to exercise. During CPX testing, cardiopulmonary variables were measured continuously whilst blood glucose (BG) and lactate values were obtained minutely via capillary earlobe sampling. Anaerobic threshold (AT) was determined using the modified V-slope index by the ventilatory equivalents for CO2 and O2 (VE/VCO2, VE/VCO2), expressed as a function of VO2. Data were reported as mean±SD and analysed by a students paired t-test with p≤0.05. Data from 36 individuals with T1DM HbA1c 7.3±1.1%, age 32±13 years, diabetes duration 17±10 years, maximum heart rate 180±13 bpm and V̇ O2max of 3.2±0.9 L.min-1 were included. BG values remained equivalent to sitting concentrations (8.91±2.47 mmol.L-1) at each stage of the CPET protocol. The change in BG above the anaerobic threshold was differently significantly from the change in BG below the AT (Sit–AT; +0.2±0.7 vs. AT-Peak; -0.5±0.8 mmol.L-1, [i.e. Δ 0.7], p<0.001). The rate of change (ROC) between values showed that the change in the ROC from Sit-AT to AT-Peak was significantly different between groups (Sit-AT; Δ0.004±0.06 vs. AT-Peak; Δ-0.049±0.10 mmol.L-1 , p=0.01). Between Hyperglycaemia (Hyper) vs. Euglycemia (Eu), BG remained comparable within each respective starting BG levels. The magnitude of change in BG from Sit-AT was significantly differentbetween groups (Hyper Δ-0.09±0.35 vs. Eu Δ+0.32±0.76 p=0.030). Hyper from Sit-AT had a significantly different magnitude in the ROC to AT-Peak (-0.04±-0.06 mmol.L-1/min, p=0.032) but not in the Eu group. We found that under correct CPET protocol, glycaemia is minimally disturbed and does not result in hypoglycaemia or changes in performance outcomes. However, starting exercise with high blood glucose levels (hyperglycaemia) impacts some cardio-metabolic outcomes during maximal and recovery phases around CPET

The effect of high Intensity interval training (HIIT) upon resting and ambulatory blood pressure in physically inactive males and females

Purpose: Physical inactivity is associated with and increased risk of hypertension and cardiovascular disease. High intensity interval training (HIIT) has been shown to reduce resting blood pressure. However, the response of HIIT upon ambulatory blood pressure has been limited, despite evidence highlighting that the use of ambulatory blood pressure monitoring can be of clinical significance. Therefore, the aim of the present study was to investigate the effects of HIIT upon resting and ambulatory blood pressure. Methods: In a randomised controlled trial 41 physically inactive males and females (aged 23 ± 2.7 years) completed 4 weeks of HIIT. The HIIT protocol consisted of 3 x 30s maximal cycle ergometer sprints with a resistance of 7.5% body weight, with 2 minutes active recovery in between intervals. In total, 12 sessions were performed. Ambulatory blood pressure was measured using a Welch Allyn 6100 ambulatory blood pressure monitor. Results: Following the 4-week HIIT intervention, it was reported that there were statistically significant reductions in resting systolic blood pressure (-6.86 ± 8.76 mmHg, P < 0.041) when compared against the control group. It was also reported that there was a statistically significant reduction in 24-hour systolic blood pressure (-4.06 ± 8.08 mmHg, P < 0.008), 24-hour diastolic blood pressure (-3.43 ± 8.18 mmHg, P < 0.012) and 24-hour mean blood pressure (-2.17 ± 4.04 mmHg, P < 0.002) when compared against the control group. Conclusion: A 4-week HIIT programme was associated with a significant decrease in resting systolic blood pressure in addition to significant reductions in 24 hour systolic, diastolic and mean ambulatory blood pressure

Investigating the Effects of Endurance Training on Heart Rate Variability in Female Swimmer Athletes

It is important for elite endurance athletes to have practical and reliable means of measuring fatigue throughout their training. Variations in Autonomic Nervous System activity (ANS) may provide an effective marker of fatigue and of recovery. ANS control of heart rate is well known to be affected by exercise training, and those adaptations can be determined using measures of heart rate variability (HRV). Previous research has examined the effect of training on HRV and ANS control of heart rate in males, there is a lack of any comprehensive studies that address adaptations in female athletes. Therefore, the purpose of this study was to investigate the changes in HRV and ANS fluctuations in female swimmer athletes throughout an entire collegiate swim season. 9 Division I female swimmers (Age: 20.6±1.01) were used to determine HRV at three different points in their competitive training: pre-season, mid-season, and post-season. During each testing session, HRV was measured both at rest and during a maximal 400 yd freestyle swim. Heart rate values were determined using Polar™ heart rate monitors, and the HRV analyses was conducted using Kubios 2.0 HRV analysis software. Global ANS balance was shown to significantly shift towards Sympathetic (SNS) predominance during the mid-season testing and significantly shift towards parasympathetic (PNS) predominance during post-season testing. HRV analysis appears to be an appropriate tool to monitor the effects of physical training loads on performance and fitness in female athletes, and it can be used to help identify and prevent overtraining states

Furthering the understanding of interstitial glucose on ECG metrics in people with type 1 diabetes

Cardiovascular autonomic neuropathy is a common complication of type 1 diabetes and can be considered the leading cause of mortality. It is increasingly important to detect early ECG alterations in healthy individuals with type 1 diabetes to help prevent the future onset of cardiovascular autonomic neuropathy and reduce mortality. This thesis aims to further understand the effect interstitial glucose has on ECG parameters during an eight-hour resting period, a novel low-intensity twenty-watt exercise test and a six-hour nocturnal period in individuals with type 1 diabetes. This thesis is a secondary analysis study including sixteen individuals absent of disease with generally well-controlled type 1 diabetes. Results revealed a reduction in QT (ms), QTc (ms) and HF (ms2) during the low-intensity exercise test during hyperglycaemia compared to euglycaemia. The increased rate of decline in interstitial glucose reduced heart rate (bpm), rMSSD (ms) and pNN50 (%) during the 6-hour nocturnal period. This thesis concludes that interstitial glucose results in some ECG alterations during parasympathetic withdrawal and the nocturnal period in a healthy disease-free cohort of individuals with type 1 diabetes. There was no effect of relatively similar interstitial glucose levels on ECG parameters during the 8-hour resting period