Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme最新文献

Intense exercise training with insufficient recovery time is associated with reductions in neuromuscular performance. However, it is unclear how single muscle fibre mechanical function and myofibrillar Ca2+ sensitivity contribute to these impairments. We investigated the effects of overload training on joint-level neuromuscular performance and cellular-level mechanical function. Fourteenathletes (4 female, 10 male) underwent a 3-week intensified training protocol consisting of up to 150% of their regular training hours with three additional high-intensity training sessions per week. Neuromuscular performance of the knee extensors was assessed via maximum voluntary contraction (MVC) force, electrically evoked twitch contractions, and a force-frequency relationship. Muscle biopsies were taken from the vastus lateralis to assess single fibre mechanical function. Neither MVC force nor twitch parameters were altered following training (all p>0.05), but a rightward shift in the force-frequency curve was observed with average reduction in force of 6-27% across frequencies 5-20Hz (all p<0.05). In single fibres, maximal force output was not reduced following training, but there was a rightward shift in the force-pCa curve driven by a 6% reduction in Ca2+ sensitivity (p<0.05). These data indicate intensified training leads to impaired Ca2+ sensitivity at the single fibre level, which in part explains impaired neuromuscular function at the joint level during lower frequencies of activation. This is an important consideration for athletes, as performance is often assessed at maximal levels of activation, and these underlying impairments in force generation may be less obvious.

Disabling atrial fibrillation (AF)-related symptoms and different testing settings may influence day-to-day cardiopulmonary exercise testing (CPET) measurements, which can affect exercise prescription for high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (M-VICT) and their outcomes. This study examined the reliability of CPET in patients with AF and assessed the proportion of participants achieving minimal detectable changes (MDC) in peak oxygen consumption (V̇O2peak) following HIIT and M-VICT. Participants were randomized into HIIT or M-VICT after completing two baseline CPETs: one with cardiac stress technologists (CPETdiag) and the other with a research team of exercise specialists (CPETresearch). Additional CPET was completed following 12 weeks of twice-weekly training. Reliability of CPETdiag and CPETresearch was assessed by intraclass correlation coefficient (ICC) and dependent t-tests. The MDC score was calculated for V̇O2peak using a reliable change index. The proportion of participants achieving MDC was compared between HIIT and M-VICT using chi-square analysis. Eighteen participants (69±7 years, 33% females) completed two baseline CPETs. ICC was significant for all measured variables. However, peak power output (POpeak: 124±40 vs. 148±40 watts, p<0.001) and HR (HRpeak: 136±22 vs. 148±30 bpm, p=0.023) were significantly greater in CPETresearch than CPETdiag. Few participants achieved MDC in V̇O2peak (5.6 mL/kg/min) with no difference between HIIT (0%) and M-VICT (10.0%, p=0.244). POpeak and HRpeak differed significantly in patients with AF when CPETs were repeated under different settings. Caution must be practiced when prescribing exercise intensity based on these measures as under-prescription may increase the number of exercise non-responders.

A competitive sport season represents a multidimensional stressor where physical and psychological stress may render an athlete susceptible to energy deficiency (ED). Downstream effects of ED can include a reduction in measured-to-predicted resting metabolic rate (RMR_ratio), indicating metabolic compensation. A pathway linking stress, eating attitudes, and metabolic compensation has not been explored. To test if sport-specific stress is associated with eating attitudes and metabolism in endurance athletes (18-22 years) at different phases of a competitive season, we assessed two groups of athletes: 26 swimmers (15 female and 11 male) during peak season (PEAK), and 26 runners (female) across pre- (PRE) and off-season (OFF). Stress (RESTQ-52), eating attitudes (cognitive restraint (CR), drive for muscularity (DM), and body dissatisfaction), and metabolism (RMR_ratio) were assessed. In PRE, sport-specific stress and CR were negatively correlated with RMR_ratio (R = -0.58; p < 0.05, and R = -0.57; p < 0.05, respectively). In PEAK, sport-specific stress and DM were negatively correlated with RMR_ratio (R = -0.64; p < 0.05; R = -0.40; p < 0.05, respectively). DM was positively related to sport-specific stress (R = 0.55; p < 0.05). During OFF, there was no relation between RMR_ratio and sport-specific stress. In runners, there was a change in stress from PRE-to-OFF with highest reported stress during PRE (p < 0.05) versus OFF. Regression analyses revealed that sport-specific stress and CR were significant predictors of RMR_ratio during PRE and PEAK (p < 0.05), but not OFF (p > 0.05). Associations between stress, eating attitudes, and metabolic compensation in endurance athletes during PRE and PEAK season suggest that during heavier training, metabolic compensation may be linked to upstream eating attitudes associated with sport-stressors.

This study investigated sex-specific differences in high-energy phosphate, glycolytic, and mitochondrial enzyme activities and also metabolite transporter protein levels in the skeletal muscles of adult (5 months old), middle-aged (12 months old), and advanced-aged (24 months old) mice. While gastrocnemius glycogen content increased with age regardless of sex, gastrocnemius triglyceride levels increased only in advanced-aged female mice. Aging decreased creatine kinase and adenylate kinase activities in the plantaris muscle of both sexes and in the soleus muscle of male mice but not in female mice. Irrespective of sex, phosphofructokinase and lactate dehydrogenase (LDH) activities decreased in the plantaris and soleus muscles. Additionally, hexokinase activity in the plantaris muscle and LDH activity in the soleus muscle decreased to a greater extent in aged male mice compared with those in aged female mice. Mitochondrial enzyme activities increased in the plantaris muscle of aged female mice but did not change in male mice. The protein content of the glucose transporter 4 in the aged plantaris muscle and fatty acid translocase/cluster of differentiation 36 increased in the aged plantaris and soleus muscles of both sexes, with a significantly higher content in female mice. These findings suggest that females possess a better ability to maintain metabolic enzyme activity and higher levels of metabolite transport proteins in skeletal muscle during aging, despite alterations in lipid metabolism. Our data provide a basis for studying muscle metabolism in the context of age-dependent metabolic perturbations and diseases that affect females and males differently.

Low creatine availability may be linked to an elevated risk of neuronal damage, yet this association remains inadequately explored at the population level. Utilizing 2013-2014 National Health and Nutrition Examination Survey data, the current study found a negative correlation between dietary creatine intake and serum levels of neurofilament light chain (NfL; a biomarker for neuronal damage) in a cohort of 1912 individuals (52.2% females) aged 20-75 years. This inverse association persisted even after adjusting for other nutritional variables known to influence neuronal viability. The observed pattern, where increased dietary creatine intake was associated with reduced circulating NfL levels, suggests potential protective effects of creatine against neuronal injury.

Cerebral hemodynamics have been quantified during exercise via transcranial Doppler ultrasound, as it has high-sensitivity to movement artifacts and displays temporal superiority. Currently, limited research exists regarding how different exercise modalities and postural changes impact the cerebrovasculature across the cardiac cycle. Ten participants (4 females and 6 males) ages 20-29 completed three exercise tests (treadmill, supine, and upright cycling) to volitional fatigue. Physiological data collected included middle cerebral artery velocity (MCAv), blood pressure (BP), heart rate, and respiratory parameters. Normalized data were analyzed for variance and effect sizes were calculated to examine differences between physiological measures across the three exercise modalities. Systolic MCAv was greater during treadmill compared to supine and upright cycling (p < 0.001, (large) effect size), and greater during upright versus supine cycling (p < 0.017, (large)). Diastolic MCAv was lower during treadmill versus cycling exercise only at 60% maximal effort (p < 0.005, (moderate)) and no differences were observed between upright and supine cycling. No main effect was found for mean and diastolic BP (p > 0.05, (negligible)). Systolic BP was lower during treadmill versus supine cycling at 40% and 60% intensity (p < 0.05, (moderate-large)) and greater during supine versus upright at only 60% intensity (p < 0.003, (moderate)). The above differences were not explained by partial pressure of end-tidal carbon dioxide levels (main effect: p = 0.432). The current study demonstrates the cerebrovascular and cardiovascular systems respond heterogeneously to different exercise modalities and aspects of the cardiac cycle. As physiological data were largely similar between tests, differences associated with posture and modality are likely contributors.

Dancers are susceptible to relative energy deficiency in sport (RED-S), specifically low bone mineral density (BMD). Little is known about how dancers' BMD compares to other athletic populations. The objective of this study was to examine the association between participant characteristics and total body areal BMD (aBMD) among female pre-professional dancers compared to other female athletes. Two hundred sixty-nine females (132 pre-professional dancers (17.6 (3.2) years) and 137 sport participants (22.8 (2.6) years) were included in this study. aBMD (g/cm²) was estimated using dual X-ray absorptiometry. Multivariable linear regression was used to examine the association between height-adjusted z-scores of total body aBMD (aBMD-Z) and age (years), body mass index (BMI) (z-score), supplement intake, history of stress fracture, irregular menses, MRI/bone scan, 1-year injury history, oral contraceptives, and activity (dance/sport). Total body aBMD and aBMD-Z were lower in dancers than athletes (dancers: aBMD = 1.03 g/cm² (95% CI: 1.01, 1.05); aBMD-Z = -0.28 (-0.43, -0.12) (p < 0.001); athletes: aBMD = 1.14 g/cm² (95% CI: 1.12, 1.16); aBMD-Z = 0.41 (0.25, 0.57) (p < 0.001)). aBMD-Z increased with age (β = 0.054, 95% CI: 0.017, 0.092; p = 0.004) and BMI (β = 0.221, 95% CI: 0.006, 0.415; p = 0.043). Activity type modified the relationship between BMI and aBMD-Z (β = 0.323, 95% CI: 0.025, 0.621; p < 0.033) with a stronger positive association in dancers, compared to other female athletes. Dancers had lower total body aBMD and aBMD-Z than other female athletes. aBMD-Z increases with age in female pre-professional dancers and other female athletes. A stronger association exists between aBMD-Z and BMI in dancers than athletes. Future studies should consider changes in aBMD-Z during adolescence and associations with increased risk of bone injury.

The present investigation aimed to study the cardiovascular responses and the cerebral oxygenation (Cox) during exercise in acute hypoxia and with contemporary mental stress. Fifteen physically active, healthy males (age 29.0 ± 5.9 years) completed a cardiopulmonary test on a cycle ergometer to determine the workload at their gas exchange threshold (GET). On a separate day, participants performed two randomly assigned exercise tests pedaling for 6 min at a workload corresponding to 80% of the GET: (1) during normoxia (NORMO), and (2) during acute, normobaric hypoxia at 13.5% inspired oxygen (HYPO). During the last 3 min of the exercise, they also performed a mental task (MT). Hemodynamics were assessed with impedance cardiography, and peripheral arterial oxygen saturation and Cox were continuously measured by near-infrared spectroscopy. The main results were that both in NORMO and HYPO conditions, the MT caused a significant increase in the heart rate and ventricular filling rate. Moreover, MT significantly reduced (74.8 ± 5.5 vs. 62.0 ± 5.2 A.U.) Cox, while the reaction time (RT) increased (813.3 ± 110.2 vs. 868.2 ± 118.1 ms) during the HYPO test without affecting the correctness of the answers. We conclude that in young, healthy males, adding an MT during mild intensity exercise in both normoxia and acute moderate (normobaric) hypoxia induces a similar hemodynamic response. However, MT and exercise in HYPO cause a decrease in Cox and an impairment in RT.

There is a prominent sex-based difference in athletic performance such that males outperform females by 7%-14% in races from 100 m to marathon. In ultramarathons, the difference is often much smaller, leading to speculation that females are "built" for the sport. However, data are confounded by the low number of female participants; just 10%-30% in any given race. This study compared data from two ultramarathons where males and females competed in comparable numbers. There were 116 and 146 starters in the 50 mile and 100 mile races, respectively (52% female). Finish times were compared using t tests or Mann-Whitney U tests, a Chi-squared test of independence examined the relationship between sex and ranking, and multivariable linear regressions examined relationships between sex, age, and finish time. There were 96 finishers in the 50 mile race (46% female) and 91 finishers in the 100 mile race (45% female). The median finish time for 50 miles was 12.64 ± 2.11 h with no difference between sexes (1.2%, p = 0.441). However, the top-10 males finished the race ∼85 min faster than the top-10 females (13.8%, p = 0.045). The mean finish time for 100 miles was 31.58 ± 3.36 h with no difference between sexes (3.2%, p = 0.132) and no difference between the top-10 males and top-10 females (4.4%, p = 0.150). Linear and multivariable regression models using sex and age were unable to predict overall finish time in either race. In conclusion, the sex-based performance discrepancy shrinks to 1%-3% in ultramarathons when males and females compete in comparable numbers. Top-performing males still retain a considerable advantage over shorter distances.

High-intensity interval training (HIIT) prescriptions manipulate intensity, duration, and recovery variables in multiple combinations. Researchers often compare different HIIT variable combinations and treat HIIT prescription as a "maximization problem", seeking to identify the prescription(s) that induce the largest acute VO₂/HR/RPE response. However, studies connecting the magnitude of specific acute HIIT response variables like work time >90% of VO₂max and resulting cellular signalling and/or translation to protein upregulation and performance enhancement are lacking. This is also not how successful endurance athletes train. First, HIIT training cannot be seen in isolation. Successful endurance athletes perform most of their training volume below the first lactate turn point (