International journal of sports physiology and performance最新文献

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.

Aims: We described and compared performances and pacing strategy (PS) across sculling age groups and boat classes.

Methods: Over 10 years of Rowing World Championships data for the men's A and B finals of under-19, under-23, and senior in single (1×), double (2×), and quadruple (4×) sculls were analyzed.

Results: Velocity and stroke frequency (SF) were lower for younger athletes for all boat classes. Age group (t1057 = 10.8, P < .001, effect size [ES] = 0.10-small) and boat class (t1057 = 30.7, P < .001, ES = 0.47-moderate) were associated with boat velocity, whereas only boat class (t1057 = 14.0, P < .001, ES = 0.16-small) was associated with SF. Statistical parametric mapping showed that PS for velocity was different between boat classes between the start line and the 500-m mark (P < .001), whereas PS for SF was different between age groups from the start line to the 150-m mark (P = .004), while boat classes differed at 250, 750, 1250, 1750, and 1950 m (P < .05). Principal-component analysis showed the variance explained in the PS came from the age groups for all 3 boat classes from 0 to 150 m and ∼1900 m.

Conclusion: Velocity and SF increased with athlete age and boat size. PS for velocity differed between boat classes, while PS for SF varied across age groups and boat types as shown by statistical parametric mapping. Principal-component analysis showed that most variance was associated with age and early-race splits, reflecting tactical pacing strategies. These findings offer practical insights for athletes, coaches, and sport scientists aiming to optimize training and performance.

Purpose: During very short (≤15 s) high-intensity (∼100% maximum rate of oxygen uptake [VO2]) intervals, defined here as microintervals, VO2 and lactate concentrations can remain near the first lactate threshold (LT1). However, no research has yet identified microinterval combinations that maintain acute responses entirely within the low-intensity zone below LT1, accounting for oscillations caused by pulsating power output.

Methods: Thirteen endurance athletes cycled for four 45-minute exercises: continuous low-intensity exercise (CON; power: 88% LT1) and 3 microinterval exercises alternating 111% power associated to maximum rate of VO2 and ∼60 W, with cycles of 4-6, 7-23, and 10-20 s.

Results: Compared with CON, heart rate and VO2 did not exceed LT1 more during microintervals (P ≥ .26, effect size ≤ 0.44), and rating of perceived exertion was greater only during 10-20 s (3.1 [0.8] vs 2.4 [0.7], P = .01). Blood lactate and mean respiratory exchange ratio did not differ between exercises (analysis of variance P ≥ .36). All mean responses of 4-26 and 7-23 were equivalent to CON (P ≤ .02). Oscillation of the examined variables during microintervals was largely greater than CON only for heart rate (>100% greater; P ≤ .001, effect size ≥ 1.7), while oscillation of VO2 was at most 25% greater (P ≥ .02, effect size ≤ 0.70).

Conclusions: Microintervals could be classified as oscillating low-intensity exercises as they fulfill the traditional low-intensity criteria-responses of almost all internal variables did not exceed those of CON, not even fat oxidation. Microinterval exercises form a unique exercise class in which high-intensity muscular work blends with mild metabolic perturbation.

Purpose: This study assessed the validity and agreement of the low-cost Coospo H808S chest-strap heart-rate (HR) monitor compared with the Polar H10 during varied conditions.

Methods: Fifteen recreational runners (25 [5] y) participated in the study. Each participant wore both the Polar H10 and Coospo H808S simultaneously, with strap placement randomized. HR and HR variability (HRV) were recorded for 5 minutes in 3 conditions: supine, seated, and low-intensity running (rating of perceived exertion 2-3/10). The last 4 minutes of each recording were analyzed using Kubios HRV software, with both raw and medium-filtered data. Agreement between devices was evaluated using intraclass correlation coefficients (ICCs) and Bland-Altman plots.

Results: The raw data of the Coospo H808S demonstrated excellent agreement with the Polar H10 for HR and HRV in the supine condition (ICC > .96, P < .001). In the seated position, agreement remained excellent (ICC > .99, P < .001). During running, the HR agreement slightly decreased (ICC = .94, mean bias = -2.35), and root mean square of successive difference showed a marked reduction to poor agreement (ICC = -.24, mean bias = +17.6 milliseconds). After applying the filtering to the running HRV data, the agreement remained poor (ICC = .13, mean bias = -5.1 milliseconds).

Conclusions: The Coospo H808S is a low-cost valid alternative to the Polar H10 for HR and HRV assessments in resting conditions and HR during running, but it presents divergences during low-intensity running for time-domain vagally related HRV indices. Researchers and practitioners should be cautious when using HRV data from low-cost monitors in dynamic conditions.

Purpose: This study prospectively monitored changes in repeated-sprint swimming performance, blood lactate ([La]) concentration, and countermovement-jump (CMJ) performance during a 6-month training period with traditionally periodized endurance training in competitive swimmers.

Methods: Twenty well-trained sprint and middle-distance swimmers (mean [SD]; age = 18 [2] y, body mass = 69.6 [8.0] kg, height = 179 [6.1] cm) underwent body-composition assessment and completed a 7 × 50-m repeated-sprint test, with measurements of [La] and CMJ, before (October, preparation period) and after (April, early-competition period) a 6-month training period using traditional periodization.

Results: There were no significant improvements in swimming velocity, CMJ height, or changes in [La] from October to April, with considerable individual variation. However, there was a small but significant increase in fat-free mass (mean difference ± SD: 0.9 ± 2.2 kg), albeit with a small effect size, and no changes in body fat or body mass. Significant and expected decreases in performance (swimming and CMJ) across the repetitions of the 7 × 50-m repeated-sprint tests were observed, accompanied by increases in [La], all with large effect sizes, but there was no evidence that training affected these results (no significant interactions).

Conclusion: A 6-month training period with traditionally periodized endurance training failed to significantly improve repeated-sprint swimming performance, [La] response, or CMJ height in trained swimmers across the 2 training phases.

Purpose: This study investigated lower-limb asymmetry in speed climbers and its relationship with climbing time while exploring the underlying mechanisms through muscle-thickness and activation.

Methods: Nineteen speed climbers completed muscle-thickness measurements, single-leg countermovement-jump tests, and speed-climbing tests. Muscle thickness was assessed using ultrasound, single-leg countermovement-jump tests were performed on a force platform, and climbing tests were conducted on a standardized climbing wall. Data were used to calculate muscle thickness, peak force (Fpeak), rate of force development, and integrated electromyography [EMG] percentage (iEMG %). Correlation analysis assessed the relationship between lower-limb asymmetry and climbing time, while paired t tests and asymmetry indices were used to analyze differences and asymmetry levels.

Results: Results showed significant positive correlations between climbing time and asymmetry indices of Fpeak (r = .57, P = .028) and rate of force development (r = .52, P = .045). No significant differences were observed in Fpeak, rate of force development, muscle thickness, iEMG (%) during jumping, or iEMG (%) of the biceps brachii and medial gastrocnemius during climbing (P > .05). However, significant differences were found in rectus femoris iEMG (%) during climbing (P = .028, d = 0.89). Most asymmetry indices, except for Fpeak, muscle thickness, and iEMG (%) of the biceps brachii and medial gastrocnemius, exceeded 15%, indicating high asymmetry levels.

Conclusions: This study highlights significant lower-limb asymmetry in speed climbers, potentially affecting performance. Findings suggest neural-activation differences, rather than muscle thickness, as the primary contributors. Regular monitoring and targeted interventions are recommended to reduce asymmetry and its impact on performance.

Purpose: Acceleration-speed (AS) profiling provides a novel way to quantify soccer players' maximum running ability without requiring dedicated sprint tests. This study explored how normalizing player effort with AS profiles could reveal unique patterns of changes in effort compared with nonnormalized absolute values during distinct goal differential conditions throughout matches and across positions.

Methods: AS profiles were developed from global navigation satellite system sensor data from 3 years of match play from a women's national soccer team. Acceleration and power data were then grouped into low, moderate, high, and very high speed domains using either nonnormalized maximum values or normalized values based on individualized AS profiles. Separate linear mixed model analyses were carried out for normalized and nonnormalized data.

Results: The analysis revealed that when examining changes in acceleration effort based on goal differential, both normalized and nonnormalized values showed a general increase in effort when either in a draw, or winning in the first half, and a general trend in sustained effort when losing in the first half or losing/drawn throughout the match. Furthermore, differences were mostly displayed at high to very high running-speed domains for normalized and moderate- to low-speed zones for nonnormalized metrics.

Conclusions: These findings highlight the value of using individual AS and power profiles to normalize effort to facilitate investigation of player- and position-specific differences and reveal important positional behaviors displayed when in draw, losing, or winning states from first to second halves.

Aim: To retrospectively describe the annual training characteristics of elite biathletes across different age groups over 2 decades.

Methods: Self-documented training-diary data from 18 elite biathletes (tier 4/5, 7 ♀, 11 ♂) between 1994 and 2014 were included in the study and classified by age group (junior: 16-18 y, U23: 19-23 y, senior: >23 y). Linear mixed models were used to analyze the effect of age group on training characteristics (intensity, distance, time, and modality shooting training) for each sex.

Results: Male biathletes increased their total training volume (TV) by 34% across age groups, while female biathletes did not show increasing TV with age. Endurance TV increased from junior to senior level by 35% and 23% in both men and women. The proportional distribution of low-intensity training, moderate-intensity training,, and high-intensity training was significantly different for both sexes between age groups. Senior male biathletes shot 4% and 15% more annual shots than Under-23s and juniors due to greater number of technical and in-competition shots, while females only increased in-competition shots at senior level.

Conclusion: This study provides further insights into the biathlon training puzzle, suggesting sex-specific differences in training strategies from junior to senior level. Our data may emphasize the importance of increasing endurance TV from junior to senior level by increasing the proportion of low-intensity training, with a reduction in moderate-intensity training and maintenance of high-intensity training when transitioning between age groups. Increasing the number of technical shots, as well as in-competition shots, while maintaining precision-shooting volumes may also be important for biathletes' long-term development.

Purpose: To evaluate the reliability and seasonal sensitivity of a fitness-testing battery in elite youth soccer players using 2 data-treatment methods: (1) the best score of multiple trials and (2) the mean of multiple trials.

Methods: Countermovement jump (CMJ), single-leg CMJ, isometric midthigh pull, Nordic hamstring strength, 10-m sprint, 505 change of direction, and the Bronco endurance test were assessed in 24 elite academy soccer players (age 17.6 [1.0] y, height 183.5 [8.5] cm, body mass 78.2 [8.5] kg) at preseason, midseason, and end of season.

Results: The CMJ, Nordic hamstring strength, 10-m sprint, 505 change of direction, and Bronco tests demonstrated high sensitivity to change (signal-to-noise ratio [SNR]: 1.14-3.08), with over 60% of athletes displaying an individual SNR >1.0. In contrast, single-leg CMJ and isometric midthigh pull relative peak force exhibited the lowest reliability and sensitivity (SNR: 0.93-1.19), with less than 60% of athletes demonstrating an individual SNR >1.0, suggesting limited utility for evaluating performance changes. While the mean of multiple trials generally yielded marginally better reliability and sensitivity, both data-treatment methods were similar.

Conclusions: The majority of the studied fitness tests were reliable and sensitive enough to detect meaningful changes over a season in elite youth soccer players. Practitioners can select either the best trial or mean of trials for data analysis, depending on their context. Overall, these findings illustrate the reliability and seasonal sensitivity of common fitness tests, enabling practitioners to prioritize tests that accurately monitor player performance changes.