Medicine and Science in Sports and Exercise最新文献

Purpose: This study assessed the individual and combined effects of sports bras and breast volume on pulmonary system and respiratory symptom responses to exercise in recreationally active females.

Methods: Twenty-three healthy females (18-27 yr; bra sizes 32B-36DDD) were divided into small and large breast volume groups (SBV and LBV, respectively) around median volume (324 mL; mean ± SD SBV: 284 ± 38 mL vs LBV: 560 ± 97 mL; P < 0.001, g = 3.84). Participants completed three 5-min bouts of constant-load cycle exercise at 30%, 60%, and 90% of their peak power output while wearing a high-support sports bra, low-support sports bralette, or their personal (self-selected) sports bra in randomized order. Measurements included ventilation, breathing pattern, respiratory pressures, diaphragm electromyogram (EMGdi), and ratings of perceived exertion (RPE), breathlessness (intensity and unpleasantness), and chest tightness due to bra.

Results: Compared with low-support and personal sports bras, the high-support sports bra evoked stronger sensations of restricted breathing and chest tightness ("slight" to "moderate" restriction in n = 7 (30%) vs n = 1 (4%) in low-support and personal bras; P = 0.014). There was, however, no evidence of greater concomitant inspiratory constraints, EMGdi, or inspiratory muscle pressure generation in either bra (all P > 0.05). Notably, LBV compared with SBV, participants reported greater RPE ( P = 0.037, ηp2 = 0.20), breathlessness intensity ( P = 0.039, ηp2 = 0.20), and unpleasantness ( P = 0.041; ηp2 = 0.19), which, in the setting of comparable pulmonary system responses to exercise, was likely driven by stronger perceived chest tightness and/or bra awareness in LBV participants.

Conclusions: Despite evoking mild-to-moderately severe chest tightness due to bra during exercise, correctly fitted sports bras, whether low- or high-support, do not impose a physiological burden to the respiratory system and its response to mild-to-heavy intensity exercise in otherwise healthy females.

Purpose: The purpose of this study is 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 to 15 and 30 to 36 wk of 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 min of sleep, sedentary behavior, or LPA to MVPA was associated with 20% (relative risk [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 min 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 percentage.

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.

Purpose: This study compared the effects of off- and on-bike resistance training (RT) on endurance cycling performance as well as muscle strength, power, and structure.

Methods: Well-trained male cyclists were randomly assigned to incorporate two sessions/week of off-bike (full squats, n = 12) or on-bike (all-out efforts performed against very high resistances and thus at very low cadences, n = 12) RT during 10 wk, with all RT-related variables (number of sessions, sets, and repetitions, duration of recovery periods, and relative loads [70% of one-repetition maximum]) matched between the two groups. A third, control group ( n = 13), did not receive any RT stimulus, but all groups completed a cycling training regime of the same volume and intensity. Outcomes included maximum oxygen uptake (V̇O 2max ), off-bike muscle strength (full squat) and on-bike ("pedaling") muscle strength, and peak power capacity (Wingate test), dual-energy X-ray absorptiometry-determined body composition (muscle/fat mass), and muscle structure (cross-sectional area, pennation angle).

Results: No significant within/between-group effect was found for V̇O 2max . Both the off-bike (mean Δ = 2.6%-5.8%) and on-bike (4.5%-7.3%) RT groups increased squat and pedaling-specific strength parameters after the intervention compared with the control group (-5.8% to -3.9%) ( P < 0.05) with no significant differences between them. The two RT groups also increased Wingate performance (4.1% and 4.3%, respectively, vs -4.9% in the control group, P ≤ 0.018), with similar results for muscle cross-sectional area (2.5% and 2.2%, vs -2.3% in the control group, P ≤ 0.008). No significant within/between-group effect was found for body composition.

Conclusions: The new proposed on-bike RT could be an effective alternative to conventional off-bike RT training for improving overall and pedaling-specific muscle strength, power, and muscle mass.

Introduction: Patients with heritable thoracic aortic disease (HTAD) are often restricted from sports and certain types of exercise. This study was designed to investigate the effect of lifetime exercise exposure and competitive sports participation on quality of life (QOL) in patients 15-35 yr old with syndromic (Marfan syndrome, Loeys-Dietz syndrome, and vascular Ehlers-Danlos syndrome) and nonsyndromic HTAD (nsHTAD).

Methods: This cross-sectional study used questionnaires to assess lifetime exercise exposure and utilized the PedsQL QOL Inventory. We developed an exercise exposure score (EES) to quantify lifetime exercise exposure. Questionnaires were completed via telephone with complimentary medical record review.

Results: Forty patients were enrolled. Mean age was 26 yr. The diagnosis was Marfan syndrome in 83%. Despite 88% of patients being restricted by their provider, 65% reported competitive sports participation and 93% reported recreational exercise. Participants with an EES greater than the median had significantly better total QOL scores compared with those below the median (78 vs 65, P = 0.03). There were significant positive correlations between current frequency of exercise and psychosocial QOL (slope = 3.9, 95% CI = 1.2-6.6, P = 0.005), physical QOL (slope = 8.1, 95% CI = 4.1-12, P < 0.001), and total QOL score (slope = 6.0, 95% CI = 3.1-9.0, P < 0.001). We found no difference in aortic size or need for surgical intervention between those above and below the median EES, or between those who did and did not participate in competitive sports.

Conclusions: Despite exercise restrictions, young HTAD patients are physically active. Increased lifetime exercise and current physical activity levels were associated with improved QOL in HTAD patients.

Objective: Existing literature indicates that females generally demonstrate higher fatigue resistance than males during isometric contractions. However, when it comes to single-limb dynamic exercises, the intricate interplay between performance fatigability (PF), cardiovascular responses, and muscle metabolism in relation to sex differences remains underexplored.

Purpose: This study investigates how sex affects the relationship between muscle oxidative characteristics and the development of PF during dynamic single-leg exercise.

Methods: Twenty-four young healthy participants (12 males vs 12 females) performed a constant-load single-leg knee extension task (85% peak power output; 60 rpm) to exhaustion (TTE). Neuromuscular assessments via transcranial magnetic and peripheral stimulations were conducted before and after exercise to evaluate central and peripheral factors of PF. Vastus lateralis muscle biopsies were obtained for mitochondrial respiration and immunohistochemistry analyses.

Results: Participants performed similar total work (28 ± 7 vs 27 ± 14 kJ, P = 0.81) and TTE (371 ± 139 vs 377 ± 158 s, P = 0.98); after the TTE, females' maximal isometric voluntary contraction (MVIC: -36% ± 13% vs -24% ± 9%, P = 0.006) and resting twitch (RT; -65% ± 9% vs -40% ± 24%, P = 0.004) force declined less. No differences were observed in supraspinal neuromuscular factors ( P > 0.05). During exercise, the cardiovascular responses differed between sexes. Although fiber type composition was similar (type I: 47% ± 13% vs 56% ± 14%, P = 0.11), males had lower mitochondrial net oxidative capacity (61 ± 30 vs 89 ± 37, P = 0.049) and higher Complex II contribution to maximal respiration (CII; 59% ± 8% vs 48% ± 6%, P < 0.001), which correlated with the decline in MVIC ( r = -0.74, P < 0.001) and RT ( r = -0.60, P = 0.002).

Conclusions: Females display greater resistance to PF during dynamic contractions, likely due to their superior mitochondrial efficiency and lower dependence on mitochondrial CII activity.

Purpose: Burn injuries that require grafting impair thermoregulation, which may dissuade individuals with such injuries from being physically active. We tested the hypothesis that cooling modalities attenuate core temperature elevations and perceptions of heat stress during physical activity in the heat among adults with well-healed burn injuries.

Methods: Adults with no burn injuries (non-burned), 20%-40% body surface area burn injuries (moderate burn), and >40% body surface area burn injuries (large burn) performed 1 h of moderate-intensity exercise (2.5 ± 0.2 mph and 2% grade) on four different occasions in two environmental conditions (30°C and 39°C, 40% relative humidity). Within each environmental condition, we applied one of the following cooling modalities, random assigned, for each visit: no cooling (control), fan at 4 m·s -1 (fan), water spray every 5 min (water spray; scaled to burn area size), or a combination of water spray + fan.

Results: In 30°C, perceptual strain index (PeSI) was reduced in the non-burned and moderate burn groups with water spray + fan, whereas PeSI was reduced with all cooling modalities in the large burn group. The cooling modalities did not affect core temperature responses. In the 39°C environment, water spray and water spray + fan attenuated the elevation in core temperature ( P ≤ 0.007) only in the large burn group. In the moderate burn group, PeSI was decreased with water spray + fan ( P = 0.017). In the large burn group, both water spray alone and water spray + fan ( P ≤ 0.041) lowered PeSI.

Conclusions: For both environments across burn groups, the applied cooling modalities were generally more effective at reducing indices of perceptual strain relative to indices of thermal strain (e.g., core temperature).

Background: Blood flow restriction training (BFRT) is a popular rehabilitation intervention after anterior cruciate ligament reconstruction (ACLR). However, there are a lack of clinical trials establishing the efficacy of using BFRT during rehabilitation to improve quadriceps muscle function.

Purpose: The purpose of this study is to evaluate the efficacy of blood flow restriction training to improve quadriceps muscle strength, morphology, and physiology, and knee biomechanics in individuals after ACLR in a double-blind, randomized, placebo-controlled clinical trial (NCT03364647).

Methods: Forty-eight athletes (20 females/28 males) were randomly assigned to low-load strength training with active BFRT or standard of care strength training with a sham unit. Treatment occurred for 1-month pre-surgery and 4 to 5 months post-surgery with both groups following the same standard rehabilitation protocol. Outcome variables were measured at baseline and 4 to 5 months post-surgery. Quadriceps muscle strength (isometric and isokinetic peak torque and rate of torque development) was measured on an isokinetic dynamometer. Quadriceps muscle morphology (physiological cross-sectional area, fibrosis) was determined using magnetic resonance imaging. Quadriceps muscle physiology (fiber type, fiber cross-sectional area, satellite cell abundance, collagen content, fibrogenic/adipogenic progenitor cells) was evaluated with muscle biopsies of the vastus lateralis. Knee extensor moment and knee flexion angle were measured via three-dimensional gait analysis. Change scores were calculated as: post-intervention - baseline. Two-sample t -tests were then used to assess between-group differences for each outcome variable.

Results: No significant between-group differences were found for any outcome variable.

Conclusions: The addition of BFRT to a rehabilitation program for athletes pre- and post-ACLR was no more effective than standard rehabilitation for improving quadriceps muscle function. Clinicians should consider the value of BFRT relative to the cost, time, and discomfort for patients in light of these results.

Purpose: The objective of this study is to investigate the effects of acute diet and exercise manipulation on resting metabolic rate (RMR) measurement variability and dual-energy x-ray absorptiometry (DXA) body composition estimates.

Methods: Ten male and 10 female endurance athletes (12 cyclists, 5 triathletes, 4 runners) of tier 2 ( n = 18) to tier 3 ( n = 2) caliber underwent five conditions using a Latin square counterbalance design. For 24 h, athletes consumed a diet providing excessive energy availability (EA) (75 kcal⋅kg fat-free mass (FFM) -1 ) without exercise (GEA rest ), high-EA (45 kcal⋅kg FFM -1 ) without (HEA rest ) or with exercise (HEA ex ), or low-EA (15 kcal⋅kg FFM -1 ) without (LEA rest ) or with exercise (LEA ex ). Exercise involved two bouts of cycling (morning bout: 149 ± 34 min at 55% of maximal aerobic capacity (V̇O 2max ); afternoon bout: 60 min at 65% of V̇O 2max ) that resulted in a cumulative exercise energy expenditure of 30 kcal⋅kg FFM -1 . The following day, RMR and DXA measurements occurred after a 10-h fast and 12-h postexercise.

Results: There were neither sex differences in relative RMR ( P = 0.158) nor effects of any of the five conditions on RMR ( P = 0.358). For both male and female athletes, FFM estimates were decreased following the LEA rest (-0.84 ± 0.66 kg; P = 0.001) and LEA ex (-0.65 ± 0.86 kg; P = 0.016) conditions compared with the GEA rest condition and following the LEA rest (-0.73 ± 0.51 kg; P = 0.001) and LEA ex (-0.54 ± 0.79 kg; P = 0.024) conditions compared with the HEA ex condition. There was no effect of condition on fat mass estimates ( P = 0.819).

Conclusions: Acute periods of diet and exercise manipulation did not create artifacts in next-day RMR measurements. However, as changes in estimates of FFM were seen, diet and exercise should be controlled in the 24-h before DXA scans.

Purpose: The objective of this study is to investigate the effect of exercise intensity on standing shooting performance and related technical variables in elite biathletes performing roller skiing and live shooting outdoors.

Methods: Nineteen male biathletes performed two 5-shot series in the following order of exercise intensity: rest, low (percentage of maximum heart rate, 73 ± 4; blood lactate, 1.5 ± 0.3 mmol·L -1 ), moderate (84 ± 3; 2.4 ± 0.6), "race-pace" (90 ± 2; 4.5 ± 0.8), and "final-lap" (i.e., near-maximal effort: 93 ± 3; 8.7 ± 1.4). Except for rest, each shooting series was preceded by 1-km roller ski skating on a competition track. Rifle movements and triggering were determined from marker-based motion capture and accelerometer data. The primary variables were shooting outcome (hit/miss) and distance from center (dC), determined from an electronic target, and barrel velocity. Mediation analyses for shooting outcome and dC were conducted with barrel velocity (mean over last 0.25 s before triggering) as mediator and intensity as predictor.

Results: Exercise intensity increased the likelihood of miss at "race" (odds ratio (OR), 2.2; 95% CI, 1.0-4.7) and "final-lap" (OR, 2.8; 95% CI, 1.4-5.8) intensities compared with rest, with no meaningful differences between rest, low, and moderate intensities. Furthermore, intensity affected dC (~32 ± 15 mm at rest, low, and moderate, 36 ± 20 mm at "race," and 40 ± 23 mm at "final-lap"; P < 0.001). Barrel velocity was a partial mediator of both shooting outcome and dC, explaining some, but not all, of the effect of intensity.

Conclusions: Exercise intensity seems to have a clear negative effect on standing shooting performance in biathlon, which is partially explained by an increase in barrel velocity. Deteriorating effects were mainly seen at the two highest (race-like) intensities. Accordingly, for specificity reasons, more shooting practice should perhaps be performed at higher, competition-like exercise intensities than what is currently the norm.

Purpose: This study aimed to provide evidence for the interpretation of the projected frontal area (PFA) during front crawl. To achieve this goal, we developed a method for calculating the PFA of each body segment using digital human technology and compared the pressure drag under two calculation conditions: a combination of the PFA with and without accounting for the horizontal velocity of each body segment.

Methods: Twelve competitive male swimmers performed a 15-m front crawl at 1.20 m·s -1 . The three-dimensional positions of the reflective markers attached to the swimmer's body were recorded using an underwater motion-capture system. Based on the body shape of each swimmer obtained from the photogenic body scanner, individual digital human body models were created with the color of the model's vertices divided into eight body segments. The time series of the volumetric swimming motion was reconstructed using inverse kinematics. The PFA of each body segment was then calculated by the automatic processing of a series of parallel frontal images. The pressure drag index, defined as the value excluding the drag coefficient while simultaneously considering the PFA and the horizontal velocity, was calculated under two conditions: the static condition (accounting for only the PFA of each body segment) and the dynamic condition (accounting for the PFA and horizontal velocity of each body segment).

Results: Notably, the pressure drag index was higher under the static condition than under the dynamic condition for the humerus, ulna, and hand segments ( P < 0.001).

Conclusions: The results obtained using our methodology indicate that the PFA of the upper limb segments overestimates their contribution to pressure drag during front crawl under the static condition.