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

This study aimed to determine the energy requirements, physiological consequences, and recovery rate from the Australian Special Forces Selection Course. Ninety-three male soldiers (mean ± SD, 28.1 ± 3.6 years, 1.81 ± 0.1 m, 85.1 ± 8.1 kg) volunteered for this study. Body composition via dual-energy X-ray absorptiometry, hormones and resting metabolic rate were assessed before, immediately after, and at 1, 3, 5, and 8 weeks post-course. Energy expenditure, assessed via doubly-labelled water during the first 10 days of the course significantly exceeded energy intake (expenditure: 7680 ± 1095 kcal^.day^-1, intake: 3859 ± 704 kcal^.day ^-1). Body mass (Δ -6.8 ± 1.9 kg, p < 0.01), fat mass (Δ -4.2 ± 1.0 kg, p < 0.0001) and lean mass (Δ -3.0 ± 1.7 kg, p < 0.0001) were significantly reduced in response to the course and returned to baseline 1-3 weeks post-course. Total testosterone, free testosterone, free triiodothyronine, free thyroxine and insulin like growth factor-1 significantly (p < 0.001) declined following the course, while cortisol and sex hormone binding globulin increased (p < 0.001). All hormones, except insulin like growth factor-1, returned to baseline concentrations within 1-3 weeks post-course. Resting metabolic rate decreased (p < 0.01) in response to the course, and subsequently rebounded above baseline levels at 1 week post-course. The Special Forces Selection Course involved high energy output and a substantial caloric deficit, resulting in body mass loss and significant hormonal disruption that took weeks to recover. These results highlight the energy requirements, physiological consequences, and recovery processes from the Australian Special Forces Selection Course.

Explosive movements requiring high force and power outputs are integral to many sports, posing distinct challenges for the neuromuscular system. Traditional resistance training can improve muscle strength, power, endurance, and range of motion; however, evidence regarding its effects on athletic performance, such as sprint speed, agility, and jump height, remains conflicting. The specificity of resistance training movements, including velocity, contraction type, and joint angles affects performance outcomes, demonstrates advantages when matching training modalities with targeted sports activities. However, independent of movement speed, the intent to contract explosively (ballistic) has also demonstrated high velocity-specific training adaptations. The purpose of this narrative review was to assess the impact of explosive or ballistic contraction intent on velocity-specific training adaptations. Such movement intent may predominantly elicit motor efferent neural adaptations, including motor unit recruitment and rate coding enhancements. Plyometrics, which utilize rapid stretch-shortening cycle movements, may augment high-speed movement efficiency and muscle activation, possibly leading to improved motor control through adaptations like faster eccentric force absorption, reduced amortization periods, and quicker transitions to explosive concentric contractions. An optimal training paradigm for power and performance enhancement might involve a combination of maximal explosive intent training with heavier loads and plyometric exercises with lighter loads at high velocities. This narrative review synthesizes key literature to answer whether contraction intent or movement speed is more critical for athletic performance enhancement, ultimately advocating for an integrative approach to resistance training tailored for sports-specific explosive action.

We investigated whether pedal cadence (60 vs. 100 rpm) affects oxygen uptake (V̇O₂) and power output (PO) at two indexes of the heavy-to-severe-intensity domain boundary (i.e., critical power (CP) and respiratory compensation point (RCP)) and their correspondence. Fourteen adults (7 females, 23 ± 2 years) cycled at 60 and 100 rpm during: (i) a "step-ramp-step" protocol to identify V̇O₂ and PO at RCP; (ii) 4-5 exhaustive constant-PO bouts for CP identification; and (iii) a constant-power bout at CP to identify V̇O₂ at CP. Separate two-way repeated measures Analysis of variance assessed whether V̇O₂ and PO were affected by index (CP vs. RCP) and cadence (60 vs. 100 rpm). The V̇O₂ was not affected by index (mean difference (MD) = 73 ± 197 mL·min^-1; p = 0.136) but there was an index × cadence interaction (p = 0.014), such that V̇O₂ was higher at 100 versus 60 rpm for CP (MD = 142 ± 169 mL·min^-1; p = 0.008), but not RCP (p = 0526). The PO was affected by cadence (MD = 13 ± 9 W; p < 0.001) and index (MD = 8 ± 11 W; p = 0.016), with no cadence × index interaction (p = 0.168). The systematic bias in PO confirms cadence-specificity of CP and RCP. The relationship between these indexes and their change in unison in PO suggests a mechanistic link between these two heavy-to-severe domain boundary candidates.

Prolonged sitting reduces lower-limb resistance vessel function (RVF), whereas increasing aerobic fitness levels enhance lower-limb RVF. However, it is unknown whether having higher aerobic fitness offers protection against prolonged sitting-induced declines in RVF. This study investigated the relationships between aerobic fitness versus reductions in lower-limb RVF following a 3 h bout of uninterrupted sitting. In 30 healthy young adults (19♀, 24 ± 6 years), aerobic fitness was assessed during a graded, maximal cycling test. Relative peak oxygen consumption (V̇O₂peak) was determined via indirect calorimetry (37.5 ± 8.6 (24.7-60.7 mLO₂/kg/min). Popliteal blood flow (PBF) was recorded via duplex ultrasonography. Lower-limb RVF was assessed in the seated posture and quantified as the peak PBF and area under the curve (PBF_AUC, first minute of hyperemia) responses to 5 min of distal cuff-induced ischemia. The lower-limb RVF assessment was performed before and after a sitting. Peak PBF decreased following sitting (473 ± 254 to 387 ± 199 mL/min, P = 0.024), while PBF_AUC remained unchanged (6145 ± 3063 versus 6446 ± 3826 mL, P = 0.758). Relative V̇O₂peak was not associated with Pre-sitting peak PBF (R = 0.236, P = 0.210) or PBF_AUC (R = -0.026, P = 0.889). Furthermore, relative V̇O₂peak was also not associated with sitting-induced reductions in peak PBF (R = -0.145, P = 0.444). The reductions in peak PBF following sitting support previous work demonstrating that prolonged uninterrupted sitting negatively impacts lower-limb RVF. In contrast, prolonged sitting did not alter the PBF_AUC response, suggesting that peak PBF responses may provide a more sensitive index of sitting-induced declines in RVF. In young, healthy individuals, aerobic fitness did not impact baseline or sitting-induced reductions in lower-limb RVF.

The physiological mechanisms involved in augmented cholinergic agonist-induced sweating in exercise-trained individuals remain unclear. This study hypothesizes that nitric oxide synthase (NOS) contributes to augmented pilocarpine-induced sweating in habitually exercise-trained individuals. Endurance-trained and untrained men (n = 15 each) iontophoretically received 1% L-NAME, a NOS inhibitor, and saline (control) in the forearm and then administered 0.001% and 1% pilocarpine to evaluate sweat rate. L-NAME administration attenuated pilocarpine-induced sweating by 10% in the exercise-trained (P = 0.004) but not in untrained (P = 0.764) groups independent of pilocarpine concentrations. Results indicate that NOS partially contributes to increased cholinergic sweating in exercise-trained men.

The modulation of the Hoffmann (H) reflex amplitude during agonist and antagonist muscle contractions provides relevant information on the neural control of leg muscles but remains largely unknown in older adults. This study investigated the H-reflex gain in the soleus muscle at rest and during plantar flexor (PF) and dorsiflexor (DF) muscle contractions performed at 10%, 20%, and 30% of the maximal electromyographic (EMG) activity (EMG_MVC) in 12 young (23-35 years) and 12 old adults (61-76 years). The reflex gain was measured as the slope of the relation between H-reflex amplitude and background EMG activity. The stimulation intensity was set to evoke at rest an H reflex in the ascending phase of its recruitment curve preceded by an M wave (5%-10% of its maximal amplitude; M_max). During PF contractions, the H-reflex amplitude increased with the increase in contraction intensity in both groups with a greater reflex gain (p = 0.024) in young (1.2 (0.5)% M_max/% EMG_MVC) than older adults (0.7 (0.4)% M_max/% EMG_MVC). During DF contractions, the H-reflex amplitude decreased in both groups, with a more negative reflex gain (p = 0.009) in young (-6.8 (2.8)% M_max/% EMG_MVC) than older adults (-2.7 (4.0)% M_max/% EMG_MVC). The decrease in H-reflex amplitude was linearly associated with the increase in tibialis anterior EMG in both groups. The present study showed a smaller reflex gain in older adults in soleus during submaximal PF and DF contractions, suggesting a decreased ability to adjust the excitatory afferent inputs during PF contractions, and to modulate reciprocal inhibition during DF contractions.

Visiting an air-conditioned location during heat exposure reduces physiological strain; however, the effects on gastrointestinal barrier dysfunction and renal ischemia remain unexplored. We compared serum protein responses during a 9 h heat exposure (40.3 °C, 9.3% relative humidity) in 17 older adults without cooling (control) and 19 older adults with a cooling break (∼23 °C) during hours 5 and 6 (cooling). IFABP and sCD14 increased similarly across groups. NGAL was 3.2 pg/mL [1.9, 6.1] lower in the cooling group during heat exposure. A 2 h cooling centre exposure did not ameliorate gastrointestinal barrier dysfunction, but did a reduce a surrogate marker of renal ischemia. ClinicalTrials.gov identifier: NCT04353076.

We aimed to evaluate whether food marketing frequency in recreation and sport facilities (RSFs) in Canada differed by the presence of food sponsorship policies, food sponsorship agreements, and food service contracts. We conducted a cross-sectional study of 85 RSFs using an observational audit using the Food and Beverage Marketing Assessment Tool for Settings (FoodMATS) and a facility survey. All instances of food marketing in RSF were recorded in the FoodMATS and the presence of food sponsorship policies, food sponsorship agreements, and food service contracts from the last fiscal year were reported in the survey by facility managers/directors. Mann-Whitney U tests evaluated differences in food marketing frequency by presence of policies (yes/no), agreements (1+/0), and contracts (1+/0). Food marketing frequency did not differ between RSF with and without a food sponsorship policy (14.5 vs. 18.0, p = 0.37). Food marketing frequency was significantly greater in RSF with food sponsorship agreements (26.5 vs. 12.5, p < 0.001) and food service contracts (60.0 vs. 21.0, p < 0.001), compared to RSF without. Only 22.4% and 16.8% of food marketing instances were linked to current food sponsorship agreements and food service contracts, respectively. Sponsorship agreements and contracts may contribute to food marketing in RSF, but they do not explain all marketing instances. Future research should seek to clarify the origin of food marketing exposures, and the opportunities to use policy documents (e.g., facility policies, sponsorship agreements, and food service contracts) to improve healthy food environments, including food marketing in RSF.