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Purpose: The long-term development of talent in endurance sports is a topic of interest. Among various factors, the importance of total hemoglobin mass (tHb_mass) and the potential benefits of being an altitude-native athlete remain unclear, particularly in young categories. This study aimed to investigate the impact of altitude and training content on hematological characteristics by comparing young male cyclists age 15–16 and 17–18 years who were born and trained at a moderate altitude (ie, greater than or equal to 2500 m; MA) and cyclists who were born and trained at low altitude (below 1000 m; LA). Methods: tHb_mass (in grams and grams per kilogram), measured by using the optimized carbon monoxide rebreathing method during an incremental test on a cycle ergometer; hematocrit percentage, hemoglobin concentration; and erythrocyte, blood, and plasma volume were measured in youth male cyclists age 15–16 years and junior cyclists age 17–18 years who were born and trained at MA versus LA. All variables were analyzed with a 2-way (age [youth cyclist vs junior cyclist] × altitude level [MA vs LA]) analysis of variance with subsequent Tuckey post hoc test. Results and Conclusion: Some altitude-induced benefits were reported in cyclists at age 15–16 years in the MA group with higher values in hematocrit percentage, hemoglobin concentration, and tHb_mass (grams per kilogram) (P < .05) than their LA counterparts. This was also observed at age 17–18 years (P < .001), except for tHb_mass, wherein no significant difference was found between MA and LA groups. In contrast, plasma volume was lower in MA than LA junior cyclists. New Findings : (1) The altitude of birth and residence could generate an advantage in tHb_mass in young male cyclists age 15–16 and 17–18 years who train at MA compared with cyclists who are born and train at LA. (2) Altitude-induced benefits in physiological variables (hematocrit percentage, hemoglobin concentration, tHb_mass in g·kg⁻¹) were reported in cyclists at age 15–16 years and partially at age 17–18 years. In contrast, plasma volume was lower in MA than in LA junior cyclists. This may impact the strategies for identifying and developing talent in cycling.

Purpose: We examined the reliability of force parameters derived from the isometric midthigh pull (IMTP) and their correlation with the functional capacities of young soccer players. Methods: Data were collected from 20 young professional soccer players within and between 2 sessions (after 1 wk) using a 1000-Hz force plate. Results: Performance outputs in all IMTP parameters were consistent and showed moderate to excellent reliability (intraclass correlation coefficient = .72–1.00) within and between sessions. However, all parameters reported a marginal ability to detect chronic changes in performance (smallest worthwhile change [SWC] < standard error of measurement [SEM]) except for peak vertical force (PF) parameters, which showed good usefulness (SWC > SEM). Absolute PF was correlated with the countermovement-jump (CMJ) total impulse (CMJ-TI; r = .54), whereas relative PF (to body mass) was correlated with CMJ height, CMJ peak power, and the last speed of the 30:15 Intermittent Fitness Test (V _IFT; r = .40 to .63). IMTP time-dependent forces were correlated with CMJ-TI (r = .52 to .62). The IMTP impulse parameters were positively correlated with CMJ-TI (r = .48 to .58) and negatively with V _IFT (r = −.44 to −.38). None of the IMTP parameters were correlated either with the CMJ mean propulsive force or with any linear acceleration times. Conclusions: All IMTP parameters can be adopted by practitioners involved with testing young soccer players based on their acceptable reliability criteria. However, caution should be taken when interpreting the time-dependent variables based on their marginal usefulness when assessing performance. Generally, a greater PF was associated with a greater vertical power based on its correlation to CMJ.

Purpose: Adequate physical fitness is a key requirement for elite footballers. Maximal fitness tests are the standard for evaluating fitness but are often fatiguing and time consuming. This study investigated the ability of various minimally invasive protocols to reflect changes in standard parameters of football players’ physical fitness. Methods: Twenty-one elite junior footballers performed 2 standard fitness tests (stepwise incremental treadmill test with blood-lactate and heart-rate [HR] measurements and Yo-Yo Intermittent Recovery 1 test) and various proxy fitness evaluations (submaximal runs with measurement of exercise HR and HR recovery and external-to-internal load ratios with data collected during match play) 3 times over the course of 19 weeks. Changes in the standard parameters were compared with changes in proxy parameters. Results: Changes in maximal endurance performance showed small to moderate associations with HR-based proxy parameters (r = −.1 to −.46; P = .004–.56), whereas changes in the running velocity at anaerobic threshold had trivial to moderate associations (r = −.07 to −.39; P = .01–.67). Alterations in HR recovery following 2 short, submaximal runs were very largely correlated with changes in the running velocity corresponding to an HR of 170 beats·min⁻¹ (r = −.74 and r = –.75; P < .001). Changes in external-to-internal load ratios derived from match play were not significantly correlated with changes in any of the standard parameters (r = −.03 to .31; P > .05). Conclusions: Parameters of maximal running performance and parameters describing physiological thresholds do not seem to be adequately captured by different minimally invasive protocols. In contrast, HR recovery following short, submaximal runs may be a valid tool to monitor changes in aerobic endurance adaptations.

Objective: Limited research has directly compared the effectiveness of aqua- and land-based exercises for postexercise recovery. This study aimed to fill this gap by comparing the effects of these 2 types of exercises on postexercise recovery. Methods: Sixteen male college athletes participated in an 8-day experimental study. The initial 2 days were dedicated to determining the intensity levels for the muscle-damaging exercise and recovery jogging. In a crossover design, participants underwent 2 sets of experimental trials. They were randomly assigned to either an aqua or land recovery intervention for days 3 to 5, and after a 1-week washout period they switched to the opposite intervention for days 6 to 8. Muscle soreness, creatine kinase, anaerobic performance, countermovement-jump height, and flexibility were assessed at different time points: baseline, immediately after downhill running, within 1 hour after jogging, and 24 hours and 48 hours after aqua or land jogging. Results: Significant group × time interaction effects were detected in the perceived soreness of the hamstring and quadriceps. However, the post hoc analysis showed no significant difference between aqua and land jogging groups. No significant group × time interaction effect was observed in creatine kinase, anaerobic performance, countermovement-jump height, or flexibility. Conclusion: Aqua and land jogging have similar recovery effects on muscle soreness and performance-based parameters.

Purpose: Different studies indicate that female players in team sports such as soccer tend to have a lower change-of-direction (COD) deficit (CODD) than their male counterparts and that players who performed better in linear and curved sprints tended to have a worse CODD, suggesting that maximum speed does not equate to a faster COD. This study assessed how performance variables related to speed and jumping influence the variability of %CODD among adult highly trained female soccer players. Methods: Fifty-two highly trained female soccer players (age 23.1 [3.25] y; height 163.6 [5.49] cm; weight 59.7 [5.71] kg) participated in this study and performed 180COD, 40-m sprint, countermovement jump, and standing broad jump tests. Results: Significant correlations were found between 180CODL, %CODDR, %CODDL, and between-limbs standing broad jump asymmetry (r = .28–.74). A very large correlation existed between %CODDR and %CODDL (r = .91). Regression analyses indicated a strong inverse relationship between the 10-m sprint time and %CODDR and %CODDL. No predictive models were found for 180COD in either limb. Differences in performance variables such as 180CODR, 180CODL, and asymmetry %CODD were significant between the high- and low-%CODD groups, with moderate to large effect sizes. Conclusion: The present study suggests that specific physical-performance variables, particularly acceleration and unilateral horizontal jumping, are vital to improving COD in highly trained female soccer players, highlighting the need for specific training interventions.

Objective: Passive stiffness, a biomechanical parameter, has a potential influence on running economy, thus playing a pivotal role in performance. This study aimed to quantify passive stiffness of the Achilles tendon and gastrocnemius muscle using myotonometry throughout an incremental running protocol. Methods: Twenty-one male participants underwent a multistage incremental test (Bordeaux test) on a treadmill until exhaustion. Passive stiffness of the gastrocnemius muscle and Achilles tendon was measured using a MyotonPRO device. Measurements were taken before, during, and after the incremental test. Results: Our findings indicated that passive stiffness of the medial gastrocnemius decreased at rest between prerun and postrun assessments (−20.12 N·m⁻¹, P = .012). Furthermore, during the test, stiffness increased at low intensity (at 50% of maximal aerobic speed: +104.8 N·m⁻¹, P = .042), returning to baseline values as intensity increased. Conclusions: Throughout an incremental running protocol, both Achilles tendon and gastrocnemius muscle stiffness initially increased and then decreased with escalating percentages of maximal aerobic speed. A deeper understanding of stiffness in running can inform more effective recommendations for runners’ strengthening and training.

Purpose: This study aimed to assess the effect of playing different pick-and-roll (PnR) defensive tactical options during small-sided games (SSGs) on external and internal loads in female basketball players. Methods: Twelve female basketball players (age 28 [2] y; stature 175 [6] cm; body mass 65 [7] kg; playing experience 18 [4] y) belonging to a team competing in the Lithuanian second division were recruited for this study. Across 3 experimental sessions and in a randomized order, players performed 3 SSGs sharing the same features but using 3 defensive strategies on the middle PnR action: Switch, Trap, and Drop. External load was measured using PlayerLoad (PL); the number of accelerations, decelerations, and changes of direction, classified based on their intensities as low (<2.5 m·s⁻²), medium (2.5–3.5 m·s⁻²), and high (>3.5 m·s⁻²); and jumps categorized as low (<40 cm) and high (≥40 cm). Internal load was measured via rating of perceived exertion (RPE). Results: Higher PL values in SSGs including Trap defense were found compared with Drop (P < .001, ES = 0.69, moderate) and Switch (P = .001, ES = 0.60, moderate). Additionally, a higher number of accelerations was registered in Trap defense compared with Drop defense (P = .027, ES = 0.99, moderate). Trap defense also led to higher RPE compared with Switch (P = .003, ES = 1.49, large) and Drop (P = .004, ES = 1.42, large) defense. Conclusions: Different defensive strategies on the middle PnR can influence the external and internal loads during SSGs, and female basketball coaches should consider the high demand of the Trap defense when designing SSGs.

Purpose: The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE) during intermittent exercise in hot conditions. Methods: Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and a natural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Results: Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P < .001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P < .001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P = .02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P = .03) and sweat rate (1.5 [0.4] L·h⁻¹ vs 1.2 [0.3] L·h⁻¹; P = .02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]), there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Conclusions: Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected.