International journal of sports physiology and performance最新文献

Purpose: Identifying the determinants of performance is fundamental to talent identification and individualizing training prescription. Consequently, the aim of this study was to determine whether estimated muscle typology is associated with the key mechanical characteristics of track sprint cycling.

Methods: Sixteen world-class and elite track cyclists (n = 7 female) completed a laboratory session wherein torque-cadence and power-cadence profiles were constructed to determine maximal power output (Pmax), optimal cadence (Fopt), and maximal cadence (Fmax), and fatigue rate per pedal stroke was determined during a 15-second maximal sprint at Fopt. Muscle typology was estimated by measuring carnosine content via proton magnetic resonance spectroscopy in the gastrocnemius and soleus.

Results: Using partial correlation analysis to account for sex, greater muscle carnosine content (ie, greater estimated proportion of type II fibers) was associated with a greater Pmax (r = .68, P = .007), Fmax (r = .77, P = .0014), Fopt (r = .61, P = .0196), and absolute fatigue rate (W·stroke-1; r = -.55, P = .0418) but not relative fatigue rate (%peak power·stroke-1; r = -.33, P = .246).

Conclusions: The findings from this study substantiate the mechanical differences in muscle-fiber types derived from single muscle-fiber studies and highlight the importance of estimated muscle typology for sprint cycling performance.

Normal science is about assessing what is already known about a topic, about what needs to be known, and careful methods to collect the data required to answer the scientific question. It is the mainstay of scientific progress. But sometimes, luck or chance (eg, serendipity) plays a significant role in scientific process. We trace career experiences in our lives to show how serendipity, the gift that Mother Nature gives to science, has a nontrivial role in scientific progress and professional careers. This gift often encourages us to change the focus of experiments or to look for the answers to our questions in ways that were not immediately obvious.

Purpose: This study examined whether physical demands during soccer matches differ between sea level and altitude, considering variations by playing position.

Methods: Thirty-seven professional players were monitored during 22 matches (11 at sea level and 11 at altitudes of 2200-4090 m) with global navigation satellite systems. Independent mean differences were used to compare in-match physical demands (ie, total distance, distance covered at specific speed intervals, accelerations [ACCs] and decelerations [DECs], and maximal speed) between locations for 5 playing positions (central defenders, fullbacks, central midfielders, wide midfielders, and forwards).

Results: At altitude, players covered shorter total distances (P < .001) and less distance in the 14.4- to 19.8-km/h (P < .001), 19.8- to 25.2-km/h (P < .001), and >25.2-km/h (P < .001) speed ranges. They also performed fewer ACCs (2.0-3.5 m/s2, P < .001; 3.5-6.0 m/s2, P < .001) and DECs (-3.5 to -2 m/s2, P < .001; -6.0 to -3.5 m/s2, P < .001) and achieved lower maximal speeds (P < .001). The impact of altitude varied by position: Central midfielders showed reduced performance in all variables, while central defenders (distance > 25.2 km/h, ACCs [2.0 and 3.5 m/s2], DECs [-3.5 and -2.0 m/s2], and maximal speed), fullbacks (distance > 25.2 km/h, ACCs, and DECs [-3.5 and -2.0 m/s2]), and forwards (distances [total, 19.8-25.2 km/h, and >25.2 km/h] and ACCs [-3.5 and -6.0 m/s2]) presented unclear differences (P > .05) between locations.

Conclusion: Our study highlights the importance of considering playing positions when assessing the in-match activity profiles of sea-level resident soccer players competing at moderate to high altitudes.

Purpose: This study explored endurance athletes' and coaches' views on recovery strategies, focusing on their use across competition levels, perceived importance and effectiveness, and common barriers.

Methods: Endurance athletes (26.6% international, 35.7% national, 28.7% regional, and 9.1% other levels; mean experience 10.04 [7.84] y, n = 143) and coaches (mean experience 17.45 [12.44] y, n = 20) completed an online survey on frequency of usage, perceived importance, effectiveness, and common barriers of 25 recovery strategies. Data were coded and analyzed thematically. A Fisher exact test (P < .05) was conducted on 5-point Likert-scale responses.

Results: Predominant strategies among athletes were hydration, hot showers, and carbohydrate (mean scores 4.62 [0.60], 4.32 [0.82], and 4.17 [0.87]). Only antioxidants showed significant variation in use across levels (P = .033). Coaches favored warm-down/cooling (4.56 [0.62]), hydration (4.41 [0.80]), and extra protein (4.12 [0.70]). Both groups ranked hydration as most important and effective. Athletes ranked extra protein and warm-down/cooling second and third, while coaches considered extra sleep/naps, warm-down/cooling, and extra protein equally important. Barriers of both populations included insufficient time (14.41%), limited knowledge (13.72%), lack of resources (12.63%), and skepticism regarding benefits and effectiveness (12.63%).

Conclusions: Athletes show no significant differences in recovery choices based on competitive level, except for antioxidants. Coaches and athletes have partially different views on effective recovery. Furthermore, a lack of time, as well as a lack of (shared) knowledge and education, hinders the effective implementation of recovery strategies for athletes.

Purpose: The purpose of this study was to investigate, in distance runners, the acute effects of moderate durations (60 s per leg) of static (SS) and dynamic stretching (DS) on running economy (RE) and performance.

Methods: Twelve recreational runners completed a randomized crossover design. Initially, the second ventilatory threshold (VT2) and the speed associated with the maximal oxygen uptake (VO2max) (vVO2max) were determined through an incremental test. Then, participants completed submaximal continuous-running (75%VT2 and 85%VT2) and running-until-exhaustion (vVO2max) tests preceded by 3 warm-ups: running plus SS or DS (SS or DS conditions) and running without stretching (NS condition). The SS and DS conditions consisted of 5 minutes of running plus 10 minutes of SS or DS, respectively, and the NS condition consisted of 15 minutes of running without stretching. RE at 75%VT2 and 85%VT2, time to exhaustion, and total running distance were evaluated. Rating of perceived exertion was also assessed.

Results: Running economy at 75%VT2 resulted significantly better in the DS than in the NS (P < .001) and in the SS (P < .05). Time to exhaustion and total running distance were significantly improved in DS compared with NS (P < .001) and SS (P < .01). No differences in rating of perceived exertion among conditions were found.

Conclusions: Our results showed that, in recreational distance runners, a preexercise moderate-duration bout of DS improved RE and enhanced total running distance and time to exhaustion, whereas 60 seconds of SS did not induce significant improvements. Overall, our study demonstrates the effectiveness of moderate DS durations in optimizing RE and performance parameters, showing that such effects depend on the stretching modality used.

Purpose: This study investigated associations between environmental temperatures and match running performance in 4 professional football leagues.

Methods: Running performance indicators including total, high-speed, and sprint distances were collated from 1610 matches from the German Bundesliga 1 and 2, Japanese J-League, and Turkish SüperLig. Environmental data for each of these matches were obtained for dry-bulb and wet-bulb globe temperatures (WBGT) retrospectively from public sources. Linear regressions were used to determine relationships between running performance indicators and both temperature and WBGT for individual leagues. Furthermore, linear mixed models were used to determine associations across all 4 leagues, accounting for differences between them as random effects. Bonferroni corrections were applied to account for multiple tests.

Results: Overall, combined-league data showed that total distance (95% CI, -0.50 to 0.37; β: -0.36), number of high-speed runs (95% CI, -4.57 to 2.93; β: -0.29), high-speed distances (95% CI, -0.07 to 0.05; β: -0.28), number of sprints (95% CI, -2.72 to 2.07; β: -0.39), and sprint distances (95% CI, -0.05 to 0.03; β: -0.22) were all lower when WBGT was higher (P < .001), whereas the peak speed recorded per match (95% CI, 0.01 to 0.03; β: 0.18) was higher when WBGT was higher (P < .001). Models with temperature instead of WBGT derived similar results.

Conclusion: Warmer environmental conditions were associated with lower total, high-speed, and sprint distances covered. These responses may result from an increased thermoregulatory load or indirectly from an adapted individual or team-tactical pacing strategy in warmer conditions. Teams should consider strategies to counter such effects to avoid lower distances covered at high intensities that are related to success in football.

Purpose: This study examined the relationship of prematch travel and in-camp training on ensuing physical and technical match performance of footballers (soccer) competing for a national team.

Methods: Match running and technical performance data were obtained from 68 national-team footballers competing in international matches (N = 108). Match performance data were aligned with the confirmed travel durations, time-zone change, travel direction, and time between arrival and kickoff for the travel to the match. In addition, in-camp training load from the 3 days prior to national-team matches was also collated. Linear mixed models assessed relationships between travel and training measures with physical and technical match performance outcomes.

Results: Travel variables explained little variance in outcomes (R2 = .02-.16). Traveling eastward was associated with an increase in total (P = .042) and very high-speed distance (P = .030) in matches and a 5% decrease in pass accuracy (P = .012). Greater time-zone difference was associated with increased match decelerations (P = .027), while arriving later for matches was associated with increased total (P = .041) tackles. Increases in training high-speed distance were associated with increases in match high-speed distance (P = .004) and number of decelerations (P < .001). An increase in training total distance was associated with a decrease in match decelerations (P = .002).

Conclusions: Prematch travel appeared to have minimal effects on physical and technical performance in this national team. Training loads prior to matches may have some relationship with match running performance, and, thus, readiness to train should be a priority for athletes arriving in national-team camps.

Purpose: To investigate metabolism and exercise economy during prolonged race simulation (>4 h) in a world-class, full-distance triathlete to help guide/adjust strategies for training, nutrition, hydration, and thermoregulation.

Methods: Two experimental race-simulation days, designed to mimic the demands of a full-distance triathlon, were executed by a world-class male triathlete (MD; 25 y, body weight 82 kg, V˙O2max 6.2 L·min-1, blood lactate threshold ∼410 W, and 18 km · h-1 in cycling and running) who at the time ranked second in the world. Race simulation was performed 23 and 10 days prior to competing in Challenge Roth 2023, where MD won in a new world record/best time (7:24:40 h:min:s). Both test days lasted ∼4 to 5 hours with physiologic testing every ∼45 to 60 minutes in a "stationary" setting during cycling on a direct-mount trainer (∼320 W) and treadmill running (16 km · h-1), enabling gas exchange measurements (V˙O2 and respiratory exchange ratio) and other physiologic measurements of interest (ie, core temperature and heart rate). This was combined with "real activity" as repeated loops in an open-air field setting at expected race pace in swimming, biking, and running.

Results: V˙O2 was maintained at ∼4.2 L·min-1, with carbohydrates being the dominant fuel for oxidation as respiratory exchange ratio values dropped from ∼1 at the start of cycling to ∼0.85 during running. Cycling economy was stable, whereas a slight impairment in running economy occurred over time.

Conclusion: High aerobic energy turnover and stable exercise economy can be maintained in a world-class record-breaking triathlete for prolonged period of time (+4 h), showcasing the importance of both for success in competition.

Purpose: The long-term development of talent in endurance sports is a topic of interest. Among various factors, the importance of total hemoglobin mass (tHbmass) 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: tHbmass (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 tHbmass (grams per kilogram) (P < .05) than their LA counterparts. This was also observed at age 17-18 years (P < .001), except for tHbmass, 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 tHbmass 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, tHbmass 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.