Increasing Exercise Intensity Research Articles

Changes in health promoting behavior during COVID-19 physical distancing: Utilizing wearable technology to examine trends in sleep, activity, and cardiovascular indicators of health.

The COVID-19 pandemic incited unprecedented restrictions on the behavior of society. The aims of this study were to quantify changes to sleep/wake behavior and exercise behavior, as well as changes in physiological markers of health during COVID-19 physical distancing. A retrospective analysis of 5,436 US-based subscribers to the WHOOP platform (mean age = 40.25 ± 11.33; 1,536 females, 3,900 males) was conducted covering the period from January 1st, 2020 through May 15th, 2020. This time period was separated into a 68-day baseline period and a 67-day physical distancing period. To provide context and allow for potential confounders (e.g., change of season), data were also extracted from the corresponding time periods in 2019. As compared to baseline, during physical distancing, all subjects fell asleep earlier (-0.15 hours), woke up later (0.29 hours), obtained more sleep (+0.21 hours) and reduced social jet lag (-0.13 hours). Contrasting sleep behavior was seen in 2019, with subjects falling asleep and waking up at a similar time (-0.01 hours; -0.03 hours), obtaining less sleep (-0.14 hours) and maintaining social jet lag (+0.06 hours) in corresponding periods. Individuals exercised more intensely during physical distancing by increasing the time spent in high heart rate zones. In 2020, resting heart rate decreased (-0.90 beats per minute) and heart rate variability increased (+0.98 milliseconds) during physical distancing when compared to baseline. However, similar changes were seen in 2019 for RHR (-0.51 beats per minute) and HRV (+2.97 milliseconds), suggesting the variation may not be related to the introduction of physical distancing mandates. The findings suggest that individuals improved health related behavior (i.e., increased exercise intensity and longer sleep duration) during physical distancing restrictions. While positive changes were seen to cardiovascular indicators of health, it is unclear whether these changes were a direct consequence of behavior change.

Partitioning The Work Of Breathing During Running And Cycling Using Optoelectronic Plethysmography

Work of breathing (B) derived from a single lung volume and pleural pressure is limited and does not fully characterize the mechanical work done by the respiratory musculature. It has long been known abdominal activation increases with increasing exercise intensity, yet the mechanical work done by these muscles is not reflected in B. Optoelectronic plethysmography (OEP) is a 3-dimentional motion analysis tool that measures the positions and displacements of reflective markers on the thorax and abdomen to calculate volume changes. Importantly, OEP permits an assessment of the ribcage and abdominal contribution to volume changes during breathing. PURPOSE: We sought to: (1) show the volumes measured using OEP (VCW) were comparable to volumes from flow integration (Vt) during cycling and running, and (2) to demonstrate that partitioned ribcage and abdominal volume from OEP could be utilized to quantify the mechanical work done by the ribcage (BRC) and abdomen (BAB) during exercise. METHODS: We fit 11 subjects (6 males/5 females; age, 26 ± 3 years; body mass, 73 ± 10 kg; height, 177 ± 6 cm; maximal oxygen uptake, 55.2 ± 9.8 ml/kg/min) with 89 reflective markers, and esophageal and gastric balloon catheters. Subjects completed an incremental cycling test to exhaustion and a series of submaximal treadmill running trials. RESULTS: We found good agreement between VCW vs. Vt during cycling (bias = 0.002) (p > 0.05) and running (bias = 0.016) (p > 0.05). From rest to maximal-exercise, BAB increased by 84% (range: 30-99%; BAB: 1 ± 1 J/min to 61 ± 52 J/min). The relative contribution of the abdomen increased from 17 ± 9% at rest to 26 ± 16% during maximal-exercise. CONCLUSION: Our study highlights and provides a quantitative measure of the role of the abdominal muscles during exercise. Incorporating the work done by the abdomen allows for a greater understanding of the mechanical tasks required by the respiratory muscles under physiologically relevant conditions such as exercise. Moreover, our approach could be used to gain insight into how the respiratory system functions under pathophysiological conditions and injury.

Exercise Induced Analgesia But Not Mood State Varies With Exercise Intensity.

The analgesic and psychoactive effects of exercise (EX) are well established. Despite this, the EX intensity needed to elicit an optimal effect on these phenomena is unknown. PURPOSE: To compare the effect of EX intensity on post EX analgesia and subjective psychoactive mood state. METHODS: Six subjects (1 male; 5 females; age = 20.6 ± 0.8 yrs) were tested for maximal aerobic exercise capacity (VO2max) using a graded cycling test. Following the VO2max, each subject was studied once a week using control conditions or 45%, 65% and 75%-85% of their VO2max in randomized order. Each EX bout lasted 30 mins and consisted of a 5-min warm-up, 20-mins at the assigned EX workload and a 5-min cooldown. The control session consisted of 30-mins of sitting on a cycle with no EX. EX analgesia was assessed by finding minimal pain threshold (MPT) before and following EX using a pain algometer on the extensor carpi radialis and was measured in Newtons (N). The Psychoactive Effects Questionnaire (PEQ), comprised of 36 questions that assess the subjective dopaminergic effects associated with the effects psychoactive drugs, was administered before and after EX. Blood lactate (BL) was also assessed at the same timepoints as MPT and PEQ. Breath by breath oxygen consumption was measured during EX using indirect calorimetry. Change in (Δ) MPT and PEQ (PreEX vs PostEX) was quantified using a two-tailed Student’s T-Test. The effect of EX intensity on MPT and PEQ was assessed by a one-way repeated measures ANOVA. Data are shown as mean ± SEM. RESULTS: BL increased in a linear fashion in response to increased EX intensity (R = 0.50; p < 0.001). Control MPT was 29.8 ± 2.1 N. There was a change in MPT, following each EX session (Control vs. 45% = 37.6 ± 1.4; 65% = 39.5 ± 0.5; 85% = 42.9 ± 1.1; p < 0.05). EX at 75%-85% had a greater impact on MPT relative to the 45% (85% = 13.02 ± 1.0 ∆N vs. 45% = 7.8 ± 1.5 ∆N; p < 0.05) session but not the 65% session (9.5 ± 1.5 ∆N; p > 0.05). There was no difference between the 45% and 65% EX session (p > 0.05). PEQ was significantly increased following EX by 118 ± 12.1% (p < 0.05). Unlike MPT, PEQ did not change dependent upon the intensity of the EX session (p < 0.05). CONCLUSION: Higher intensity EX (85% VO2max) appears to elicit a greater analgesic effect relative to lower intensity (45% VO2max). While EX increases PEQ it does not appear to be sensitive to EX intensity.

Alterations in Surface Electromyography of the Upper Leg Muscles at Specified Respiratory Exchange Ratio Thresholds Ranges During a Maximal Exercise Test

Introduction: Assessing muscle electromyography (EMG) in conjunction with physiological alterations to exercise may be valuable to determine a more holistic approach to exercise-induced fatigue. Methods: Thirteen, recreationally trained individuals (n = 7 female, n = 6 males) underwent a maximal exercise test. Throughout the test, physiological variables were measured in addition to surface electromyography (sEMG) of the upper legs. Physiological and sEMG data was then grouped in to four category thresholds based on respiratory exchange ratios (RER) greater than 0.95. Results: There was a main effect of group (p &lt; 0.001) as an increase in exercise intensity assessed by RER threshold ranges resulted in a subsequent reductions in sEMG frequencies with the exception of the sEMG frequencies recorded at VO2peak (p &lt; 0.055). Conclusions: Upper leg sEMG frequencies decrease with increases in high intensity exercise, with the exception of near maximal loads.

Repeatability of Thoracoabdominal Wall Compartmental Contributions to Tidal Volume during Low‐, Moderate‐ and Heavy‐Intensity Exercise

The patterns of breathing and the thoracoabdominal wall compartmental contributions to tidal volume at different exercise intensities are typically assessed during a single laboratory visit, where individuals complete progressively higher intensity stages of exercise. The relative contributions of the thoracic and abdominal compartments have been reported to be invariant across exercise intensities; however, inter-individual differences have been observed. Therefore, the purpose of this study was to assess the repeatability of the compartmental contributions to tidal volume during low-, moderate-, and heavy-intensity exercise. It was hypothesized that the inter-individual differences in the compartmental contributions would be repeatable day-to-day for each intensity. Seven healthy adults (2 female, age: 28±7 yr, peak oxygen uptake: 45±5 ml·min-1·kg-1) completed two step exercise tests on separate days, consisting of low-, moderate-, and heavy-intensity stages for each individual based on their ramp exercise responses. Tidal volume and breathing rate were assessed using a bi-directional turbine, and thoracic and abdominal contributions to tidal volume were measured by respiratory inductance plethysmography. Day-to-day repeatability was evaluated using the intra-class correlation coefficient (ICC). With increasing exercise intensity, the tidal volume (p<0.001) and breathing rate (p<0.001) increased, but no differences in tidal volume (p=0.97; low: 1.14±0.21 L vs. 1.22±0.48 L, moderate: 2.02±0.49 L vs. 1.92±0.54 L, heavy: 2.51±0.60 L vs. 2.54±0.59 L) or breathing rate (p=0.94; low: 18±4 breaths·min-1 vs. 17±6 breaths·min-1, moderate: 22±8 breaths·min-1 vs. 23±7 breaths·min-1, heavy: 37±9 breaths·min-1 vs. 37±10 breaths·min-1) were observed between testing days. The relative contribution of the thoracic (low: 64±12% vs. 63±15%, moderate: 66±12% vs. 64±14%, heavy: 67±11% vs. 67±12%) and abdominal (low: 36±12% vs. 37±15%, moderate: 34±12% vs. 36±14%, heavy: 33±11% vs. 33±12%) compartments did not differ significantly between test days (p=0.59), or exercise intensities (p=0.38). However, there were inter-individual differences in how the compartmental contribution to tidal volume changed with exercise intensity, as the relative contribution of the thoracic compared to abdominal compartment increased with higher intensity exercise for 3 subjects, decreased for 1 subject, and remained relatively constant for 3 subjects. These inter-individual differences to increasing exercise intensity do not appear random, as the test-retest repeatability of the compartmental contribution to tidal volume was good to excellent for low (ICC=0.87, p=0.003), moderate (ICC=0.89, p=0.002) and heavy (ICC=0.93, p=0.001) exercise. Future work should seek to identify factors contributing to the observed inter-individual differences in compartmental contribution to tidal volume with increasing exercise intensity and whether these impart functional consequences.

Effects of Weekly Interval Training at High Intensity interval training on Dynamic Cardiorespiratory Responses to Exercise

Purpose Previously we reported that high-intensity interval training (HIIT) at 80% maximal work-rate (WRmax), even when performed at a low frequency of once a week, markedly improves maximal cardiorespiratory function and maximal performance time (Med Sci Sports Exerc. 2015). However, it has not been determined whether more intense interval exercise training will have the similar effect on maximal oxygen uptake (VO2max) or alter the dynamics of the cardiorespiratory response during maximal exercise. The purpose of this study was to examine whether or not the same effect can be obtained, even with HIIT at 95%WRmax for 8 weeks which further increased exercise intensity than the previous study. Methods Seventeen healthy male college students were randomly assigned to one of the two following groups; high-intensity interval training group (HIT; n = 9) and control group (n = 8). HIT group performed the training on a cycle ergometer once a week for 8 weeks. The training was consisted of three bouts until volitional fatigue at 95%WRmax. Cardiorespiratory function during maximal ramp and step (high-intensity) exercise test was investigated before and after the intervention period. Results The training resulted in increased VO2max (+9%, p = 0.037), maximal heart rate (+4%, p = 0.023) and maximal minute ventilation (+19%, p = 0.007) during maximal ramp test, respectively. Significant changes in the dynamic response of heart rate and blood pressure at the onset of high-intensity exercise were observed after the training program compared with baseline, and improvement in exhaustion time was also observed (+ 93%, P < 0.001). In addition, increased left ventricular posterior wall thickness at rest was also observed after training (+12%, p = 0.004). Conclusion The present results indicate that more intense HIIT performed at a low frequency once a week not only increased maximal cardiorespiratory function and exercise performance, but also induced cardiovascular adaptation in the enhancement of heart rate and blood pressure response during step exercise, as well as induces cardiac morphological adaptations involving left ventricular hypertrophy, as we have already found in previous studies.

Cardiopulmonary and Metabolic Responses to Additional Weights on Ankle and Wrist during Walking in Healthy College Students

Carrying weights in the hands and ankles is an alternative method of increasing exercise intensity in walking for individuals who cannot jog or run at higher speeds and may increase energy expenditure. However, previous findings were inconsistent regarding cardiopulmonary and metabolic responses to additional weights on the ankles and wrists. PURPOSE The purpose of our study is to determine the effects of additional weights on the ankles and wrists in relation to cardiopulmonary and metabolic responses during walking exercise in young and healthy college students. It was hypothesized that there is no difference in oxygen consumption, substrate utilization, and total caloric expenditure among no weight, ankle weight, and wrist weight conditions during walking exercise on the treadmill. METHODS Sixteen relatively healthy and young college individuals (BMI ≥ 18 kg/m2 and ≤25 kg/m2 and 18-30 yrs.) were recruited. Each participant visited 5 times. The first visit consisted of a maximal aerobic fitness test (VO2peak). The second visit consisted of finding the participant's treadmill speed that correlates with 40% of the VO2peak. The third visit consisted of walking for thirty minutes at 40% of their VO2peak without any weights added. The fourth and fifth visits consisted of the same procedure as the third visit, only with the additional weight (1.5% of body weight) added to each limb on either the ankles or wrists. The order in which the ankle and wrist trials occur was randomly assigned. Cardiopulmonary and metabolic responses were measured via indirect calorimetry. One-way RM ANOVA was used to determine differences in oxygen consumption (VO2), heart rate (HR), fat and carbohydrate (CHO) utilization, and total energy expenditure between walking conditions. RESULTS VO2 was lowest for no weight followed by wrist and ankle weight conditions, respectively (16.89±0.47, 17.86±0.48, and 19.05±0.68 ml/kg/min). Also, VO2 was significantly higher in ankle weight than wrist weight condition. HRs were also lowest for no weight followed by wrist and ankle weight conditions, respectively (120.4±1.9, 125.9±2.7, and 130.2±2.4 bpm). HRs were significantly higher in ankle weight than wrist weight condition. The rate of total EE (kcal/min) during walking was significantly increased with additional weights on the ankle (5.88±0.34 kcal/min) and the wrist (5.38±0.33 kcal/min), compared to no weights added (5.18±0.28kcal/min) and the rate of total EE was significantly higher in ankle weight than wrist weight condition. However, the rate of fat utilization was not different among no weight, ankle weight, and wrist weight conditions during walking. CONCLUSION Our findings demonstrated that the cardiopulmonary and metabolic responses to additional weights on the ankles and wrists were significantly greater than no weight added during walking exercise. Moreover, the VO2, HRs and total EE during the moderate intensity of walking were higher when additional weights were added especially on the ankle, compared to the wrist location. Therefore, the findings of our study may provide that carrying weights in the hands and/or ankles is an alternative walking method of increasing exercise intensity, thereby elevating caloric expenditure and maintaining healthy body weights in young individuals.

Excessive Exercise Training Impairs Mitochondrial Function

As exercise intensity increases, mitochondrial function and glucose regulation improve. Yet, some athletes report anecdotally that there is a training

Can non-responders be ‘rescued’ by increasing exercise intensity? A quasi-experimental trial of individual responses among humans living with pre-diabetes or type 2 diabetes mellitus in Canada

IntroductionExercise is recommended to improve glycaemic control. Yet, individual changes in glycaemic control following exercise can vary greatly, meaning while some significantly improve others, coined ‘non-responders’, do not. Increasing the...

Modelling the relationships between arterial oxygen saturation, exercise intensity and the level of aerobic performance in acute hypoxia

The aim of this study was to establish a model to estimate the level of arterial oxygen saturation (SpO2) and help determine the appropriate hypoxic dose in humans exercising in acute hypoxia. SpO2 values were collected in seven untrained (UTS) and seven endurance-trained male subjects (ETS) who performed six cycle incremental and maximal tests at sea level and at simulated altitudes of 1000, 1500, 2500, 3500 and 4500m. Oxygen uptake was continuously measured and maximal oxygen uptake ([Formula: see text]) was determined in each subject and at each altitude. Intensity was expressed as percentage of [Formula: see text]. There were strong non-linear relationships between altitude and SpO2 at low, moderate and high intensity both in ETS and UTS (r = 0.97, p < 0.001). SpO2 was significantly correlated to exercise intensity at sea level and at all simulated altitudes in ETS but only from 2500m in UTS. There were inverse correlations between SpO2 and sea-level [Formula: see text] at all altitudes, which were stronger from 2500m and with the increase in exercise intensity. The three-variable model we established predicts (p < 0.001) the SpO2 level of individuals exercising in acute hypoxia based on their sea-level [Formula: see text], the intensity of exercise and the altitude level. The model demonstrates that the drop of SpO2 during exercise in acute hypoxia is larger with the increase in both sea-level [Formula: see text] and exercise intensity. The model also highlights that the pivotal altitude from which the fall in SpO2 is exacerbated is between 2000 and 2500m, depending on both sea-level [Formula: see text] and exercise intensity.

Time Spent Near V˙O2max During Different Cycling Self-Paced Interval Training Protocols.

Cyclists may increase exercise intensity by prolonging exercise duration and/or shortening the recovery period during self-paced interval training, which could impact the time spent near V˙O2max. Thus, the main objective of this study was to compare the time spent near V˙O2max during 4 different self-paced interval training sessions. After an incremental test, 11 cyclists (mean [SD]: age = 34.4 [6.2]y; V˙O2max=55.7 [7.4] mL·kg-1·min-1) performed in a randomized order 4 self-paced interval training sessions characterized by a work-recovery ratio of 4:1 or 2:1. Sessions comprised 4 repetitions of 4 minutes of cycling with 1 minute (4/1) or 2 minutes (4/2) of active recovery or 8 minutes of cycling with 2 minutes (8/2) or 4 minutes (8/4) of active recovery. Time spent at 90% to 94% (t90V˙O2max), ≥95% (t95V˙O2max), and 90% to 100% V˙O2max (tV˙O2max) was analyzed in absolute terms and relative to the total work duration. Power output, heart rate, blood lactate, and rating of perceived exertion were compared. The 8/4 session provided higher absolute tV˙O2max and t95V˙O2max than 8/2 (P = .015 and .029) and 4/1 (P = .002 and .047). The 4/2 protocol elicited higher relative tV˙O2max (47.7% [26.9%]) and t95V˙O2max (23.5% [22.7%]) than 4/1 (P = .015 and .028) and 8/2 (P < .01). Session 4/2 (275 [23] W) elicited greater mean power output (P < .01) than 4/1 (261 [27] W), 8/4 (250 [25] W), and 8/2 (234 [23] W). Self-paced interval training composed of 4-minute and 8-minute work periods efficiently elicit tV˙O2max, but protocols with a work-recovery ratio of 2:1 (ie,4/2 and 8/4) could be prioritized to maximize tV˙O2max.

The influence of exercise intensity and exercise mode on gastrointestinal damage.

Strenuous exercise increases gastrointestinal damage, but the dose-response relationship is yet to be elucidated. It is also commonly believed that running causes greater gastrointestinal damage than cycling. Two randomised, crossover studies aimed to 1) quantify gastrointestinal damage with increasing exercise intensity, and 2) determine if running was associated with greater gastrointestinal damage than cycling. Following a maximal oxygen uptake (V̇O2max) test, participants completed 3 cycling trials at different intensities (60min at 40%, 60% and 80% V̇O2max; n= 10 (5 female, 5 male)) (INTENSITY), or 1 running and 1 cycling trial (45 min at 70% V̇O2max; n= 11 (3 female, 8 male)) (MODE). Venous blood samples were collected pre- and post-exercise to measure gastrointestinal damage via intestinal fatty acid binding protein (I-FABP). In INTENSITY, I-FABP magnitude of change was greater at 80% V̇O2max than 40% V̇O2max (p< 0.01). In MODE, I-FABP magnitude of change was greater with cycling (mean (SD)) (84.7 (133.2)% d= 1.07) compared with running (19.3 (33.1)%, d= 0.65) with a moderate effect (d= 0.68, p= 0.024). Rating of perceived exertion (RPE) and heart rate (HR) were higher during cycling (RPE p< 0.0001; HR p< 0.0001) but rectal temperature was not different between modes (p= 0.94). While gastrointestinal damage increases with increasing exercise intensity, running was not associated with greater gastrointestinal damage than cycling. Novelty: A fraction of the anaerobic threshold, rather than a fraction of V̇O2max, may be more predictive of intensity that results in exercise induced gastrointestinal damage. The mode of exercise may not be as important as intensity for inducing gastrointestinal damage. Improving anaerobic threshold may reduce susceptibility to gastrointestinal damage when exercising at high intensities.

Interindividual variation in cardiometabolic health outcomes following 6months of endurance training in youth at risk of type 2 diabetes mellitus.

This study determined the interindividual variation in the cardiometabolic response to 6months of moderate or vigorous intensity exercise training (ET) among youth at risk for type 2 diabetes mellitus. Youth were randomized to moderate intensity ET (45-55% heart rate reserve; n = 31), vigorous intensity ET (70-85% heart rate reserve; n = 37), or control (n = 36). Only those attending ≥70% of ET sessions were included. Cardiometabolic measures included insulin sensitivity, hepatic triglyceride content, visceral adipose area, and cardiorespiratory fitness. The contribution of ET to interindividual variation was determined using the standard deviation of individual responses (SDIR) and considered meaningful if the SDIR surpassed the smallest worthwhile difference (SWD), calculated as 0.2× the standard deviation of the control group baseline values. ET meaningfully contributed to the interindividual variation among changes in peak oxygen uptake following moderate (SDIR: 2.04) and vigorous (SDIR: 3.43) ET (SWD: 1.17 mL·kgfat free mass-1·min-1), body fat percentage and hepatic triglyceride content following moderate-intensity ET (SDIR: 1.64, SWD: 1.05%; SDIR: 10.08, SWD: 1.06%, respectively), and visceral fat mass following vigorous ET (SDIR: 11.06, SWD: 7.13 cm2). Variation in the changes in insulin sensitivity were not influenced by ET. The contribution of ET to interindividual variation appears to be influenced by the desired outcome and prescribed intensity. Trial registration at ClinicalTrials.gov (identifier no.: NCT00755547). Novelty: The contribution of exercise to interindividual variation following training depends on the outcome and exercise intensity. Increasing exercise intensity does not systematically reduce non-response among youth at risk for type 2 diabetes.

A New Detection Method Defining the Aerobic Threshold for Endurance Exercise and Training Prescription Based on Fractal Correlation Properties of Heart Rate Variability.

The short-term scaling exponent alpha1 of detrended fluctuation analysis (DFA a1), a nonlinear index of heart rate variability (HRV) based on fractal correlation properties, has been shown to steadily change with increasing exercise intensity. To date, no study has specifically examined using the behavior of this index as a method for defining a low intensity exercise zone. The aim of this report is to compare both oxygen intake (VO2) and heart rate (HR) reached at the first ventilatory threshold (VT1), a well-established delimiter of low intensity exercise, to those derived from a predefined DFA a1 transitional value. Gas exchange and HRV data were obtained from 15 participants during an incremental treadmill run. Comparison of both VO2 and HR reached at VT1 defined by gas exchange (VT1 GAS) was made to those parameters derived from analysis of DFA a1 reaching a value of 0.75 (HRVT). Based on Bland Altman analysis, linear regression, intraclass correlation (ICC) and t testing, there was strong agreement between VT1 GAS and HRVT as measured by both HR and VO2. Mean VT1 GAS was reached at 39.8 ml/kg/min with a HR of 152 bpm compared to mean HRVT which was reached at 40.1 ml/kg/min with a HR of 154 bpm. Strong linear relationships were seen between test modalities, with Pearson’s r values of 0.99 (p < 0.001) and.97 (p < 0.001) for VO2 and HR comparisons, respectively. Intraclass correlation between VT1 GAS and HRVT was 0.99 for VO2 and 0.96 for HR. In addition, comparison of VT1 GAS and HRVT showed no differences by t testing, also supporting the method validity. In conclusion, it appears that reaching a DFA a1 value of 0.75 on an incremental treadmill test is closely associated with crossing the first ventilatory threshold. As training intensity below the first ventilatory threshold is felt to have great importance for endurance sport, utilization of DFA a1 activity may provide guidance for a valid low training zone.

Wearing a face mask during controlled-intensity exercise is not a risk factor for exertional heatstroke: A pilot study.

AimThis study aimed to measure the influence of wearing face masks on individuals’ physical status in a hot and humid environment.MethodsEach participant experienced different physical situations: (i) not wearing a mask (control), (ii) wearing a surgical mask, (iii) wearing a sport mask. An ingestible capsule thermometer was used to measure internal core body temperature during different exercises (standing, walking, and running, each for 20 min) in an artificial weather room with the internal wet‐bulb globe temperature set at 28°C. The change in the participants’ physical status and urinary liver fatty acid‐binding protein (L‐FABP) were measured.ResultsSix healthy male volunteers were enrolled in the study. In each participant, significant changes were observed in the heart rate and internal core temperatures after increased exercise intensity; however, no significant differences were observed between these parameters and urinary L‐FABP among the three intervention groups.ConclusionMask wearing is not a risk factor for heatstroke during increased exercise intensity.

Physical Activity of Preschool Children in COVID-19 Pandemic: Focusing on Activity Content and Exercise Intensity during Childcare

The present study examined the relationship between children’s activities at a nursery school and the amount of physical activity in the COVID-19 pandemic and obtained primary data to promote future childcare activities. Healthy preschool children aged 3 - 5 (N = 21) participated in the survey. Children wore an activity tracker (Polar, A360) on the wrist of the non-dominant hand for three hours in the morning on five days, just after the state of emergency was lifted. The measurements included “activity time”, “moderate-to-vigorous physical activity (MVPA) time”, and “average heart rate (HR)”. The activity time was defined as physical activity time with an intensity of over 60% HRmax (maximum heart rate). MVPA time was defined as time doing physical activity with an intensity higher than 70% HRmax. From the results of this study, in childcare under COVID-19 pandemic, the activity time of each day was 37.8 ± 25.0 min to 87.0 ± 34.7 min, and the MVPA time was 4.7 ± 6.3 min to 33.7 ± 26.1 min, and the average heart rate was 111.3 ± 7.3 bpm at the lowest and 126.8 ± 9.9 bpm at the highest. In particular, the time of MVPA, which is expected to improve physical strength, was approximately 15min on a five-day average, which was significantly shorter than previous studies. Children’s health and development of athletic ability are hindered by insufficient opportunities for physical activities and exercise because of the current COVID-19 pandemic. Securing exercise time and increasing exercise intensity should be considered in childcare to increase children’s physical activity in childcare.

Reduced Scattering Coefficient During Incremental Exercise Is Constant Without Being Affected by Changes in Muscle Oxygenation or Hemodynamics.

Previous studies have reported that the reduced scattering coefficient (μs') in the vastus lateralis changes during ramp-incremental exercise due to blood volume changes or accumulation of metabolic by-products. We aimed to clarify the influences of deoxygenation and blood volume changes during exercise on μs' dynamics in subjects with various aerobic capacities. Twenty-three healthy young men participated in this study. All subjects performed a ramp-incremental cycling exercise until exhaustion and were divided into two groups: lower (Low: n=12; peak pulmonary oxygen uptake per kg of fat-free mass (VO2peak), 54.2±5.3mL/kg/min) and higher aerobic capacity group (High: n=11; VO2peak, 69.7±5.2mL/kg/min) by median of VO2peak. Deoxygenated hemoglobin and myoglobin concentrations (deoxy[Hb+Mb]) and total [Hb+Mb] (total[Hb+Mb]) in the vastus lateralis were monitored during the exercise by three-wavelength (760, 800, and 830nm) time-resolved NIRS. Similarly, μs' at each wavelength was continuously monitored. With increasing exercise intensity, deoxy[Hb+Mb] and total[Hb+Mb] significantly increased in both groups, and the average values of the peak amplitudes of deoxy[Hb+Mb] and total[Hb+Mb] during exercise showed a 106.4% increase and a 17.9% increase from the start of the exercise, respectively. Furthermore, the peak amplitude of total[Hb+Mb] was significantly greater in High. Conversely, there were no changes in μs' at any wavelength during exercise and no differences between two groups, suggesting that the great deoxygenation and blood volume changes during incremental exercise have little effect on μs' dynamics.

The (in)dependency of blood and sweat sodium, chloride, potassium, ammonia, lactate and glucose concentrations during submaximal exercise

PurposeTo reduce the need for invasive and expensive measures of human biomarkers, sweat is becoming increasingly popular in use as an alternative to blood. Therefore, the (in)dependency of blood and sweat composition has to be explored.MethodsIn an environmental chamber (33 °C, 65% relative humidity; RH), 12 participants completed three subsequent 20-min cycling stages to elicit three different local sweat rates (LSR) while aiming to limit changes in blood composition: at 60% of their maximum heart rate (HRmax), 70% HRmax and 80% HRmax, with 5 min of seated-rest in between. Sweat was collected from the arm and back during each stage and post-exercise. Blood was drawn from a superficial antecubital vein in the middle of each stage. Concentrations of sodium, chloride, potassium, ammonia, lactate and glucose were determined in blood plasma and sweat.ResultsWith increasing exercise intensity, LSR, sweat sodium, chloride and glucose concentrations increased (P ≤ 0.026), while simultaneously limited changes in blood composition were elicited for these components (P ≥ 0.093). Sweat potassium, lactate and ammonia concentrations decreased (P ≤ 0.006), while blood potassium decreased (P = 0.003), and blood ammonia and lactate concentrations increased with higher exercise intensities (P = 0.005; P = 0.007, respectively). The vast majority of correlations between blood and sweat parameters were non-significant (P > 0.05), with few exceptions.ConclusionThe data suggest that sweat composition is at least partly independent of blood composition. This has important consequences when targeting sweat as non-invasive alternative for blood measurements.

Plasma BCAA concentrations during exercise of varied intensities in young healthy men-the impact of endurance training.

BackgroundBranched-chain amino acids (BCAA) i.e., leucine (Leu), isoleucine (Ile) and valine (Val) are important amino acids, which metabolism play a role in maintaining system energy homeostasis at rest and during exercise. As recently shown lowering of circulating BCAA level improves insulin sensitivity and cardiac metabolic health. However, little is known concerning the impact of a single bout of incremental exercise and physical training on the changes in blood BCAA. The present study aimed to determine the impact of a gradually increasing exercise intensity—up to maximal oxygen uptake (VO2max) on the changes of the plasma BCAA [∑BCAA]pl, before and after 5-weeks of moderate-intensity endurance training (ET).MethodsTen healthy young, untrained men performed an incremental cycling exercise test up to exhaustion to reach VO2max, before and after ET.ResultsWe have found that exercise of low-to-moderate intensity (up to ∼50% of VO2max lasting about 12 min) had no significant effect on the [∑BCAA]pl, however the exercise of higher intensity (above 70% of VO2max lasting about 10 min) resulted in a pronounced decrease (p < 0.05) in [∑BCAA]pl. The lowering of plasma BCAA when performing exercise of higher intensity was preceded by a significant increase in plasma lactate concentration, showing that a significant attenuation of BCAA during incremental exercise coincides with exercise-induced acceleration of glycogen utilization. In addition, endurance training, which significantly increased power generating capabilities at VO2max (p = 0.004) had no significant impact on the changes of [∑BCAA]pl during this incremental exercise.ConclusionWe have concluded that an exercise of moderate intensity of relatively short duration generally has no effect on the [∑BCAA]pl in young, healthy men, whereas significant decrease in [∑BCAA]pl occurs when performing exercise in heavy-intensity domain. The impact of exercise intensity on the plasma BCAA concentration seems to be especially important for patients with cardiometabolic risk undertaken cardiac rehabilitation or recreational activity.

Stroke in young adults – a challenge for etiology, treatment and rehabilitation

Strokes occur rarely in individuals under the age of 45 and are even more uncommon under the age of 30, the etiology of this pathology in young adults being generally related to unknown or unusual causes. We present the cases of three young adults that suffered strokes with three different unusual etiologies. The three men were 30, 36 and 43 years old, with no pathological antecedents, with neurological symptoms characteristic for stroke. Because the differential diagnostics are sometimes tricky, in all three cases imagery was very helpful. It is necessary to emphasize that in these cases one of the most important things to know is the etiology. It is very important to treat the effect too; this is the reason why we never miss an opportunity to use alteplase when all conditions are met. Common rehabilitation regimes for young adults, who have suffered a stroke, include a combination of physiotherapy, occupational therapy, speech-language therapy, and pharmacological therapy. Strategies to improve motor recovery in young patients include constraint-induced movement therapy, robot-aided rehabilitation, virtual reality training, functional electrical stimulation, increased exercise intensity, and acupuncture. Keywords: stroke, young patients, etiology, thrombophilia, drugs abuse, artery dissection, rehabilitation,