International journal of sports physiology and performance最新文献

Purpose: Despite the increasing body of literature on badminton, no data exist concerning the energy cost of badminton movement, known as "footwork." This study introduces a novel experimental approach to assessing the energy cost of footwork by applying established metabolic measurement techniques to badminton-specific movement patterns for the first time. In addition, it aims to verify whether differences exist between 2 different movement combinations.

Methods: Seven male and 7 female badminton athletes (age 19 [4] y; body mass 64.9 [8.4] kg; height 1.72 [0.08] m; V˙O2peak 55.5 [10.3] mL·kg-1·min-1) completed 2 sets of 12 repetitions of 4 all-out preplanned footwork exercises with 30 seconds of passive recovery, using 2 types of steps (side step and running step). During exercises, respiratory data, blood lactate concentration, and net energy cost (CnetFW, J·kg-1·m-1) were determined, along with total exercise duration and average speed.

Results: CnetFW was 19.59 (4.46) for side step and 20.38 (4.52) J·kg-1·m-1 for running step. No significant differences in metabolic data, total exercise duration, or average speed were observed (P < .05). CnetFW data showed a positive linear correlation between energy cost and footwork speed (r = .62; r2 = .39; P = .0009).

Conclusions: CnetFW increases with speed, but there is no significant difference between the 2 types of footwork. Players and coaches can choose the most appropriate step combinations based on individual characteristics and specific game requirements.

Purpose: Topical menthol application improves thermal perception and enhances performance but reduces sweat production in hot environments. In the aquatic environment, where sweat evaporation is of limited thermoregulatory benefit (ie, minimal evaporation) and leads to dehydration and cardiovascular strain, downregulating thermoregulatory sweating may have little consequence. However, it may preserve hydration status and improve subsequent performance, especially in air (ie, after first transition in triathlon); we tested this hypothesis.

Method: Eight trained triathletes (age 36 [5] y; height 1.77 [0.1] m; mass 73.9 [8.0] kg) completed 2 experimental conditions with prior whole-body application of menthol GEL (40 g, 3.5% menthol) contrasted to NO-GEL. The protocol comprised 30 minutes of swimming (at 85% of 400-m personal best) in tropical water (29 °C) followed by a 20-km self-paced cycling time trial. Measures were deep body temperature (gastrointestinal pill), skin temperature, sweat production, rating of perceived exertion, thermal sensation, and thermal comfort. Paired t test and analysis of variance compared the data (.05 alpha level).

Results: Wet-bulb globe temperature equated to "red flag" conditions-heat-injury potential for all participants. Terminal gastrointestinal temperature was 38.8 °C (0.3 °C) and 38.8 °C (0.7 °C) and time-trial performance was 39:36 (04:31) and 40:53 (05:53) minutes in the GEL and NO-GEL conditions, respectively (P = .340; 95% CI, -222 to 88 s; d = -0.22). Sweat production increased in the GEL condition (1140 [257] mL) compared to the NO-GEL condition (961 [202] mL) (t = 2.482, P = .042; 95% CI, 08 to 349 mL; d = 0.77).

Conclusion: Menthol improved perception but increased thermoregulatory sweating and did not enhance performance (partial hypothesis support).

Purpose: Preseason in football is crucial for optimizing physical fitness, team cohesion, and tactical readiness. This study investigated the effects of 2 distinct preseason training environments-mild altitude with cooler conditions and sea level with higher heat and humidity-on cardiovascular fitness, readiness, and match intensity in professional football players.

Methods: Fifteen elite male players were monitored during 2 consecutive preseasons (2023-24 and 2024-25), with external- and internal-load parameters assessed via global positioning systems and heart-rate (HR) tracking systems. Cardiovascular fitness was evaluated using HR responses during submaximal running tests (HRex) and machine-learning models (Δ HR), and readiness was assessed through vertical stiffness (Kvert) and locomotor efficiency (Δ PL), also using machine-learning approaches.

Results: Multilevel regression analysis indicated that general fitness, represented by HRex, improved independently of environmental conditions and was primarily influenced by cumulative training load (γ = -0.045, P = .004). However, specific fitness (Δ HR) improved more significantly under higher temperatures (γ = 8.188, P = .009). Increased heat exposure reduced readiness levels, as reflected by declines in Kvert and Δ PL by the end of the sea-level preseason. Match intensity showed no significant differences between environments.

Conclusions: Sea-level preseason training environments appear to promote faster specific fitness gains, likely due to cardiovascular adaptations. We hypothesize that these adaptations could be related to the effects of heat exposure, such as plasma volume expansion. However, it also results in lower readiness levels, affecting vertical stiffness and locomotor efficiency. These findings provide valuable insights for designing preseason programs to balance cardiovascular fitness gains and fatigue mitigation.

Purpose: To study the possible sex differences in muscle activity after a maximal intermittent fatiguing protocol (IFPmax) performed with a flywheel device.

Methods: Fifteen males and 17 females completed 10 sets of 10 half-squat repetitions with 3 minutes of passive recovery between sets as the IFPmax. Before and after the IFPmax, maximal isometric half-squat and countermovement jump were performed. Surface electromyography was used to analyze muscle activity in the gluteus maximus, vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and semitendinosus.

Results: Both sexes exhibited a similar decline in maximal isometric half-squat force and countermovement-jump flight time after the IFPmax. Although males demonstrated higher baseline power performance (F ≥ 4.99, P ≤ .013, ηp2≥.14), these differences were no longer significant at the end of the fatiguing protocol. A more pronounced decrease in electromyography activity of the agonist musculature was observed in males (F ≥ 4.84, P ≤ .036, ηp2≥.14), whereas delta analysis revealed a greater increase in antagonist muscle activity in females (P < .05). Hip-to-knee cocontraction ratio increased similarly in both sexes (F ≥ 10.14, P ≤ .004, ηp2≥.27). However, males and females adopted distinct muscle-activation patterns as fatigue developed.

Conclusions: Sex-related differences in muscle activity following an IFPmax performed with a flywheel device suggest the potential for higher training volumes and/or shorter recovery intervals for females. These findings provide valuable insights for the individualization and optimization of training protocols based on sex differences.

Purpose: This study investigated the periodization, testing, and monitoring practices of strength and conditioning practitioners across different levels of coaching experience and sports.

Methods: An online survey was completed by 58 practitioners (25 sports/events) from 9 Southeast and East Asian countries. The survey focused on periodization models, programming frameworks, unloading strategies, fitness assessments, and pretraining readiness monitoring. Frequency analysis and chi-square tests were used to assess data distribution and differences.

Results: Hybrid (multiple) periodization was favored over a single model for different training objectives (39%-45%), including very short-term training (≤4 wk). Emerging approaches including flexible programming were similarly adopted (43%). Program adjustment was primarily driven by athlete feedback (90%), self-observation (78%), and technical execution (74%). Major programming challenges identified were managing fatigue (72%), optimizing training stimuli (53%), specificity (50%), and adherence (47%). Deloading practices (95%) and tapering applications (91%) were common. Physical performance changes were primarily identified from testing (90%) but also from athlete/coach feedback (76%), monitoring (71%), training data (67%), and performance data/statistics (62%). Strength assessments were conducted 2 to 4 times yearly (67%) using 1 to 4 exercises (76%). Pretraining readiness was monitored via conversations (71%), wellness tools (46%), and performance devices (31%). Practitioners also utilized monitoring technology, force plates (21%), and velocity-tracking devices (23%). Training load was commonly quantified using volume load (81%) and session rating of perceived exertion (72%). None of the comparisons differed across experience levels and sport types (P > .05).

Conclusion: Practitioners employed a range of periodization models, often integrating flexible approaches. Unloading strategies were commonly implemented alongside various assessment methods. Technologies were used for monitoring, but conversational/subjective methods remained more widespread.

Background: Recent research findings suggest that a daily diet containing low carbohydrate (LCHO) consumption coupled with low energy availability (LEA, specifically what is termed problematic LEA [P-LEA]) exacerbates the risk of developing relative energy deficiency in sport (REDs). Regrettably, research evidence also indicates that dietary carbohydrates are likely underconsumed by many athletes in their daily diets. How these factors, P-LEA and LCHO intake, interact to precipitate the amplification of REDs risk is currently not entirely clear and is the source of much speculation.

Purpose: As such, we present herein a hypothetical model of how LCHO dietary intake and P-LEA exposure can interact to create an amplification of the endocrine disruptions associated with REDs, specifically via the development of a low triiodothyronine (T3) state, clinically referred to as low T3 syndrome. The hypothesis presented postulates that P-LEA + LCHO interact to promote reductions in T3 levels in part by inducing a greater cortisol response (at rest or exercise), which in turn inhibits the endocrine function involving the production of T3, as well as the conversion of thyroxine to T3. The resultant low T3 state in turn amplifies the negative hormonal consequences associated with REDs (eg, reduced reproductive, anabolic, and metabolic hormone levels).

Conclusions: Practically speaking, athletes and their coaches must recognize the importance of carbohydrates in the diet, specifically the amounts and the timing of their consumption; strive to avoid P-LEA exposure; and monitor for REDs indicators (eg, T3). Researchers are encouraged to pursue investigations to challenge and evaluate our proposed hypothesis concerning how low T3 is the critical factor in the negative hormonal consequences of REDs and the role cortisol plays in these outcomes.

Purpose: Core temperature (Tcore) monitoring is used in the prevention of heat illnesses and for heat-acclimation purposes. We examined the accuracy and precision of 2 commercially available devices (BandV2 and CORE) that estimate Tcore versus rectal temperature.

Method: Eight eumenorrheic females (V˙O2max: ∼41 mL·kg-1·min-1) completed 60 minutes of cycling in the follicular phase and the luteal phase over 2 separate cycles, wearing a minimally permeable clothing ensemble to amplify thermal load.

Results: Both devices proved to be precise at rest and during exercise. Between duplicate follicular and luteal tests, the CORE device bias was 0.1400 (0.33) °C and 0.0331 (0.42) °C, and the BandV2 device bias was 0.0418 (0.18) °C and -0.0171 (0.21) °C. Compared with rectal temperature, accuracy was below our preestablished criterion of ±0.27 °C. At rest, the devices underestimated Tcore: BandV2, -0.2735 (0.25) °C, and CORE, -0.2746 (0.28) °C, and at the 55-minute time point, both devices overestimated Tcore: BandV2, +0.5117 (0.37) °C, and CORE, +0.3319 (0.43) °C. The delta increase in Tcore did not differ between menstrual-cycle phases.

Conclusions: The BandV2 and CORE indirect sensors currently offer precise but not accurate estimates of Tcore.

Purpose: To examine the effects of sprint and change-of-direction (CoD) training, with and without the racket, on performance-related qualities of young tennis players.

Methods: Thirty-one young male players age 16.5 (0.3) years (body height 180.6 [4.6] cm; mass 71.5 [6.3] kg) were randomly allocated to a specific sprint and CoD training program using a tennis racket versus the same training without using the racket during an 8-week in-season training phase. Pretraining and posttraining included linear sprint (10 m with 5-m split times), CoD speed (5-0-5 CoD test, pro-agility test), and muscle power (bilateral and unilateral countermovement jumps, and the 10/5 repeated-jump test).

Results: Results showed a significant main effect of time for linear sprint speed (10-m: P < .001), CoD (P < .001), CoD deficit (P = .003), pro-agility (P = .044), and all analyzed jump measures (P values ranging from <.001 to .006). Selected significant group-by-time interactions were found, with 5-m (P = .008) and 10-m sprints (P = .021), CoD speed (P < .001), and pro-agility test (P = .018), as well as countermovement jumps (P < .001) and repeated-jump-test jump height (P = .003), favoring the no-racket group.

Conclusion: Although both training strategies have been shown to be effective in improving the physical fitness components analyzed, the use of specific sprint training without additional equipment (ie, racket) seems to be the most beneficial method to improve baseline capacities in young tennis players.

Purpose: The mucosal immune system serves as the first line of defense against pathogens; meanwhile, poor-quality sleep may potentially have detrimental effects on physical recovery and immunity in athletes. The present study aimed to examine the effect of sleep quality and oral immunity on postcompetition infection risk in young swimmers participating in a national swimming event.

Methods: Nineteen voluntary adolescent swimmers from a high school were enrolled. Hooper questionnaire, saliva samples, and sleep quality collected on the fifth day before the competition were recorded as baseline data, and saliva and sleep data on the day of the competition, collected before its start, were used as study data. The levels of salivary total protein (TP), α-amylase, salivary immunoglobulin A, lactoferrin, interleukin-6, and cortisol were measured, and athletes' sleep quality was also monitored.

Results: Compared with baseline, the Hooper Index indicated a significant decrease in sleep quality and an increase in stress level before the competition. Levels of α-amylase/TP, salivary immunoglobulin A/TP, and lactoferrin/TP significantly decreased on the morning of the competition, whereas interleukin-6 and cortisol levels showed a significant increase. Analysis of sleep variables in relation to postcompetition infections revealed a significant negative correlation between sleep efficiency, total sleep time, and the number of postcompetition medical visits.

Conclusions: Our findings suggest that the overall physiological factors contributing to the decline in athletes' salivary levels of α-amylase/TP, salivary immunoglobulin A/TP, and lactoferrin/TP and increased susceptibility to infections after competition may be related to sleep quality on the night before the competition.