Medicine and Science in Sports and Exercise最新文献

Purpose: There is controversy whether there are meaningful physiological differences between hypobaric (HH) and normobaric hypoxia (NH). This study aimed to compare the cardiorespiratory responses to acute HH and NH under strictly controlled conditions. We hypothesized no differences at rest and during submaximal exercise, whereas during maximal exercise, a higher maximal ventilation (V̇Emax), peripheral oxygen saturation (SpO2) and maximal oxygen consumption (V̇O2max) in HH than in NH.

Methods: In a randomized, single-blind, crossover design, eight young healthy subjects (three females) were studied in an environmental chamber in which either the barometric pressure (HH) or the inspired oxygen fraction (NH) was reduced to the equivalent of ~4000 m altitude. Measurements were taken at rest, during submaximal (moderate and high intensity) and maximal cycling exercise.

Results: All resting parameters were similar between HH and NH, except for a lower root mean square of the successive R-R interval differences in HH (p < 0.05). SpO2 was 2% higher in HH at all exercise intensities (p < 0.05). During submaximal exercise, minute ventilation was similar between HH and NH. However, HH yielded a 7% lower tidal volume during moderate-intensity exercise (p < 0.05) and a lower respiratory exchange ratio during high-intensity exercise (p < 0.01). V̇Emax and V̇O2max were 11% and 6% higher in HH, respectively (p < 0.01 for both). SpO2 at maximal exercise was positively correlated with V̇Emax, V̇Emax/V̇O2max and V̇O2max.

Conclusions: The higher V̇O2max found in HH than in NH can be attributed to the higher V̇Emax counteracting desaturation at maximal exercise. Conversely, submaximal SpO2 improved in HH through mechanisms other than increased ventilation. These findings are likely due to respiratory muscle unloading in HH, which operated through different mechanisms depending on exercise intensity.

Purpose: We determined the effects of shorter affected side (AS) crank arm lengths and cycling with two different prostheses on joint and crank power, asymmetry, and net efficiency.

Methods: Twelve participants with a TTA rode at 1.5 W·kg -1 with equal (175 mm) and shorter AS crank arms (160, 165, 170 mm) using a daily-use prosthesis and CSP. We used statistical parametric mapping to determine differences in instantaneous joint and crank power between prostheses and linear mixed-effects models to compare average joint and crank power, asymmetry, and net efficiency.

Results: Shorter AS crank arm lengths reduced the magnitude of peak positive ( P ≤ 0.001) and negative ( P < 0.001) crank power on the AS. Use of a CSP increased the magnitude of peak positive knee power ( P < 0.001) and decreased the magnitude of peak negative crank power ( P < 0.001) on the AS compared with a daily-use prosthesis. Shorter AS crank arm lengths while using a CSP reduced average hip joint ( P = 0.014) and hip transfer ( P = 0.025) power asymmetry from 35% to 20% and 118% to 62%, respectively. However, we found no significant differences in AS average joint or crank power, knee joint or crank power asymmetry, or net efficiency.

Conclusions: Cycling at 1.5 W·kg -1 with unequal crank arm lengths and CSP improves hip joint power and hip transfer power asymmetry but does not alter crank asymmetry or net efficiency for recreational cyclists with a TTA.

Purpose: Ventilatory constraints are common during exercise in children, but the effects of obesity and sex are unclear. The purpose of this study was to investigate the effects of obesity and sex on ventilatory constraints (i.e., expiratory flow limitation (EFL) and dynamic hyperinflation) during a maximal exercise test in children.

Methods: Thirty-four 8- to 12-yr-old children without obesity (18 females) and 54 with obesity (23 females) completed pulmonary function testing and maximal cardiopulmonary exercise tests. EFL was calculated as the overlap between tidal flow-volume loops during exercise and maximal expiratory flow-volume loops. Dynamic hyperinflation was calculated as the change in inspiratory capacity from rest to exercise.

Results: Maximal minute ventilation was not different between children with and without obesity. Average end-inspiratory lung volumes (EILV) and end-expiratory lung volumes (EELV) were significantly lower during exercise in children with obesity (EILV: 68.8% ± 0.7% TLC; EELV: 41.2% ± 0.5% TLC) compared with children without obesity (EILV: 73.7% ± 0.8% TLC; EELV: 44.8% ± 0.6% TLC; P < 0.001). Throughout exercise, children with obesity experienced more EFL and dynamic hyperinflation compared with those without obesity ( P < 0.001). Also, males experienced more EFL and dynamic hyperinflation throughout exercise compared with females ( P < 0.001). At maximal exercise, the prevalence of EFL was similar in males with and without obesity; however, the prevalence of EFL in females was significantly different, with 57% of females with obesity experiencing EFL compared with 17% of females without obesity ( P < 0.05). At maximal exercise, 44% of children with obesity experienced dynamic hyperinflation compared with 12% of children without obesity ( P = 0.002).

Conclusions: Obesity in children increases the risk of developing mechanical ventilatory constraints such as dynamic hyperinflation and EFL. Sex differences were apparent with males experiencing more ventilatory constraints compared with females.

Introduction: Twenty-four-hour movement behaviors: moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), sedentary behavior (SB), and sleep are crucial factors affecting older adults' health. Using a compositional data analysis approach, this study examined the associations of time spent in these four movement behaviors with cardiometabolic health, physical fitness, and mental health among older adults. Furthermore, this study identified the estimated changes in aforementioned health outcomes by reallocating SB time to other movement behaviors.

Methods: A population-based cross-sectional study of 4562 participants (67.68 ± 5.03 yr; 55.8% female) were implemented in Hubei China between July 25 and November 19, 2020. Measures included demographics, movement behaviors, cardiometabolic indicators (body mass index, waist circumference, waist-hip ratio, percentage body fat, systolic and diastolic blood pressure), physical fitness, and mental health outcomes (depressive symptoms and loneliness). Compositional data analyses were implemented in R.

Results: MVPA and sleep time were associated with greater health outcomes (all P < 0.001), except blood pressure ( P = 0.13-0.83). LPA time was associated with waist circumference ( B = 0.313, P = 0.009), waist-hip ratio ( B = 0.003, P = 0.003), physical fitness ( B = 0.36, P < 0.001), and mental health indicators (both P < 0.001). Reallocating 30-min SB to MVPA and sleep was associated with predicated improvements in all health outcomes, except blood pressure, whereas reallocating 30-min SB to LPA resulted in predicted improvements in physical fitness (0.187 units), depressive symptoms (-0.264 units), and loneliness (-0.395 units). For dose-effect relationships, reallocating 5-60 min of SB to MVPA showed greatest benefits for all health outcomes.

Conclusions: This study provides timely empirical evidence for future interventions and policymaking on promoting healthy aging during the post-COVID-19 era. The findings underline the importance of including 24-h movement behaviors in future health promotion among older adults.

Purpose: Step count is an intuitive measure of physical activity frequently quantified in health-related studies; however, accurate step counting is difficult in the free-living environment, with error routinely above 20% in wrist-worn devices against camera-annotated ground truth. This study aimed to describe the development and validation of step count derived from a wrist-worn accelerometer and assess its association with cardiovascular and all-cause mortality in a large prospective cohort.

Methods: We developed and externally validated a self-supervised machine learning step detection model, trained on an open-source and step-annotated free-living dataset. Thirty-nine individuals will free-living ground-truth annotated step counts were used for model development. An open-source dataset with 30 individuals was used for external validation. Epidemiological analysis was performed using 75,263 UK Biobank participants without prevalent cardiovascular disease (CVD) or cancer. Cox regression was used to test the association of daily step count with fatal CVD and all-cause mortality after adjustment for potential confounders.

Results: The algorithm substantially outperformed reference models (free-living mean absolute percent error of 12.5% vs 65%-231%). Our data indicate an inverse dose-response association, where taking 6430-8277 daily steps was associated with 37% (25%-48%) and 28% (20%-35%) lower risk of fatal CVD and all-cause mortality up to 7 yr later, compared with those taking fewer steps each day.

Conclusions: We have developed an open and transparent method that markedly improves the measurement of steps in large-scale wrist-worn accelerometer datasets. The application of this method demonstrated expected associations with CVD and all-cause mortality, indicating excellent face validity. This reinforces public health messaging for increasing physical activity and can help lay the groundwork for the inclusion of target step counts in future public health guidelines.

Purpose: Chronic, high-altitude hypoxic exposure increases the risk of high-altitude pulmonary hypertension (PH). Emerging evidence shows maternal exercise may improve offspring resistance to disease throughout life. The purpose of this study is to determine if maternal exercise mitigates chronic hypoxic-induced changes in the offspring indicative of high-altitude PH development.

Methods: Female adult C57BL/6J mice were randomly allocated to nonexercise or exercise conditions. Exercise consisted of voluntary running wheel exercise for 4 wk during the perinatal period. Three days after birth, the pups remained at low altitude (normoxia) or were exposed to hypobaric hypoxia of 450 mm Hg to simulate ~4500 m of altitude exposure until 8 wk of age. The study consisted of four groups: hypoxia + nonexercise pregnancy, hypoxia + exercise, or the respective normoxia conditions (normoxia + nonexercise or normoxia + exercise). Offspring body size, motor function, right ventricular systolic pressure (RVSP), and cardiopulmonary morphology were assessed after 8 wk in normoxia or hypoxia.

Results: Both hypoxic groups had smaller body sizes, reduced motor function, increased hematocrit, RVSP, muscularization in medium-sized pulmonary arteries, as well as right ventricular hypertrophy and contractility compared with the normoxic groups ( P < 0.05).

Conclusions: Chronic hypoxia simulating 4500 m attenuated growth, lowered motor function, and elicited PH development. Voluntary maternal exercise did not significantly decrease RVSP in the offspring, which aligned with a lack of effect to attenuate abnormal body size and cardiopulmonary development due to chronic hypoxia. These findings are preliminary in nature, and more powered studies through larger group sizes are required to generalize the results to the population.

Introduction: The study aimed to investigate to what extent acute endurance exercise, especially eccentric exercise and cardiorespiratory fitness, affects the metabolic profile of CD4 + cells.

Methods: Fifteen male, healthy adults aged between 20 and 33 yr with a maximal oxygen uptake (V̇O 2max ) between 44 and 63 mL·kg -1 ·min -1 performed a downhill run (DR) and a level run (LR) for 45 min at 70% of their V̇O 2max on a treadmill in a crossover design. Blood samples were taken before (T0), directly after (T1), 3 h after (T3), and 24 h (T24) after each exercise for analyzing leukocyte numbers and cytokine levels. Isolated CD4 + cells were incubated for 4 h in autologous resting versus 3 h after exercise serum (T3 DR and T3 LR), and subsequently, cellular respiration, transcriptomic, and metabolomics profiles were measured.

Results: The systemic immune inflammation index increased significantly after DR and LR at T1 and T3 ( P < 0.001). In contrast, the transcriptomic and metabolic profile of CD4 + cells showed no significant alterations after incubation in T3 exercise serum. However, cardiorespiratory fitness positively correlated with the maximal mitochondrial respiration in CD4 + cells after incubation with T3 LR serum ( r = 0.617, P = 0.033) and with gene expression of oxidative phosphorylation and levels of different metabolites. Similarly, V̇O 2max was associated with an anti-inflammatory profile on RNA level. Lower lactate, methylmalonic acid, and d -gluconic acid levels were found in CD4 + cells of participants with a high V̇O 2max ( P < 0.001).

Conclusions: Acute exercise leads to a mild proinflammatory milieu with only small changes in the metabolic homeostasis of CD4 + cells. High cardiorespiratory fitness is associated with a metabolic shift to oxidative phosphorylation in CD4 + cells. Functional relevance of this metabolic shift needs to be further investigated.

Purpose: We investigated whether longitudinally assessed physical activity (PA) and adherence specifically to World Health Organization PA guidelines mitigate or moderate mortality risk regardless of genetic liability to cardiovascular disease (CVD). We also estimated the causality of the PA-mortality association.

Methods: The study used the older Finnish Twin Cohort with 4897 participants aged 33 to 60 yr (54.3% women). Genetic liability to coronary heart disease and systolic and diastolic blood pressure was estimated with polygenic risk scores (PRS) derived from the Pan-UK Biobank ( N ≈ 400,000; >1,000,000 genetic variants). Leisure-time PA was assessed with validated and structured questionnaires three times during 1975 to 1990. The main effects of adherence to PA guidelines and the PRS × PA interactions were evaluated with Cox proportional hazards models against all-cause and CVD mortality. A cotwin control design with 180 monozygotic twin pairs discordant for meeting the guidelines was used for causal inference.

Results: During the 17.4-yr (mean) follow-up (85,136 person-years), 1195 participants died, with 389 CVD deaths. PRS (per 1 SD increase) were associated with a 17% to 24% higher CVD mortality risk but not with all-cause mortality except for the PRS for diastolic blood pressure. Adherence to PA guidelines did not show significant independent main effects or interactions with all-cause or CVD mortality. Twins whose activity levels adhered to PA guidelines over a 15-yr period did not have statistically significantly reduced mortality risk compared with their less active identical twin sibling. The findings were similar among high, intermediate, and low genetic risk levels for CVD.

Conclusions: The genetically informed Finnish Twin Cohort data could not confirm that adherence to PA guidelines either mitigates or moderates genetic CVD risk or causally reduces mortality risk.

Introduction: The effects of breaking up sitting on gut hormone responses and free-living energy compensatory behaviors are still unclear in people of Asian ethnicity.

Methods: Twenty-six Asians including 13 lean individuals (Lean) and 13 individuals with centrally overweight/obesity (OW), aged between 20 and 45 yr, completed a randomized crossover study with either 5.5-h uninterrupted sitting (SIT) or 5.5-h sitting with 2-min walking at 6.4 km·h -1 every 20 min (ACTIVE) in the laboratory. Blood samples were collected at regular time points to examine postprandial glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and glucose-dependent insulinotropic polypeptide (GIP) concentrations. Free-living physical activity and energy intake were recorded using wearable devices and weighed food diaries outside the laboratory until midnight. Paired t -tests were conducted to compare responses between trials.

Results: Postprandial GLP-1 and PYY incremental area under the curve values were higher in the ACTIVE trial versus SIT in both Lean and OW groups (all, P < 0.05), but there was no difference in GIP in either group (both, P > 0.05). There were no differences in free-living physical activity (volume and intensity) or energy intake (total and macronutrients) between trials in either group (all, P > 0.05), resulting in greater total physical activity over the 24-h monitoring period in ACTIVE trial versus SIT trial (both, P < 0.05).

Conclusions: Breaking up sitting increases postprandial GLP-1 and PYY concentrations in Asians, but does not induce subsequent behavioral compensation, resulting in greater 24-h physical activity levels and lower relative energy intake, in inactive individuals irrespective of bodyweight status.

Purpose: To assess associations of theoretically reallocating time from sleep, sedentary behavior, or light intensity physical activity (LPA) to moderate/vigorous intensity physical activity (MVPA) during pregnancy with infant growth outcomes.

Methods: We used data from a cohort of pregnant individuals with overweight or obesity (n = 116). At 9-15 and 30-36 weeks gestation, waking movement was measured using wrist-worn accelerometers and sleep duration was self-reported. Outcomes were obtained from delivery electronic health records (birth) and study visits (12 months). We used compositional isotemporal substitution models.

Results: In early pregnancy, reallocating 10 minutes of sleep, sedentary behavior, or LPA to MVPA was associated with 20% (RR = 0.80; 95%CI: 0.75,0.85), 21% (RR = 0.79; 95%CI: 0.75,0.84), and 25% (RR = 0.75; 95%CI: 0.70,0.81) lower risk of large-for-gestational age (LGA) birthweight, respectively, and 17% (RR = 0.83; 95%CI: 0.75,0.91), 18% (RR = 0.82; 95%CI: 0.75,0.91), and 22% (RR = 0.78; 95%CI: 0.70,0.88) lower risk of rapid infant growth (birth to 12 months), respectively. In late pregnancy, reallocating 10 minutes to MVPA was associated with 18% to 22% lower risk of LGA birthweight, but was not associated with rapid infant growth. Reallocating time to MVPA in early or late pregnancy was not associated with high newborn body fat percent.

Conclusions: Our findings suggest beneficial associations of theoretically reallocating time from sleep, sedentary behavior, or LPA to MVPA, especially during early pregnancy, for reducing LGA birthweight and rapid infant growth.