International journal of sports physiology and performance最新文献

{"title":"Caffeine Shifts Substrate Utilization Toward Fat During Outdoor Running at Fatmax: A Randomized Field-Based Crossover Study.","authors":"Iván Villalba, Víctor Solano-Lizcano, Adrián Rodríguez-Castaño, Christel García-Ortiz, Luis E Ranieri, Arturo Casado, Juan Del Coso, Daniel Trujillo-Colmena","doi":"10.1123/ijspp.2026-0194","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0194","url":null,"abstract":"<p><strong>Purpose: </strong>Although caffeine-induced increases in fat oxidation are well established under laboratory conditions, evidence during field-based exercise is limited. Therefore, this study aimed to examine the acute effects of 3 mg·kg-1 of caffeine on fat oxidation during a 1-hour field-based outdoor run performed at the individual intensity eliciting maximal fat oxidation (Fatmax).</p><p><strong>Methods: </strong>Fourteen healthy, endurance-trained runners (11 men, 3 women; V˙O2max = 58.6 [6.3] mL·kg-1·min-1) participated in a randomized, double-blind, placebo-controlled, crossover experiment. Participants completed 1 preexperimental trial to determine V˙O2max and Fatmax, followed by 2 experimental trials. During the experimental trials, participants ingested either caffeine (3 mg·kg-1) or a placebo 60 minutes before a 1-hour run at their individual Fatmax intensity covered on a 1.97-km outdoor running course. Substrate oxidation rates and energy expenditure were measured via indirect calorimetry using a portable gas analyzer and calculated through stoichiometric equations while heart rate was continuously monitored and ratings of perceived exertion were recorded using the Borg scale.</p><p><strong>Results: </strong>Caffeine significantly increased total fat oxidation during the 1-hour run (33.62 [9.23] vs 40.46 [11.32] g; P = .018; d = 0.76) and decreased carbohydrate oxidation (93.16 [37.84] vs 77.32 [30.35] g; P = .036; d = 0.66) compared with placebo, with no effect on total energy expenditure (P = .936). Caffeine also reduced the rating of perceived exertion (9 [2] vs 8 [2]; P = .024; d = 0.75) with no effect on heart rate (P = .140).</p><p><strong>Conclusion: </strong>Acute ingestion of 3 mg·kg-1 of caffeine enhances fat oxidation during 1 hour of running at Fatmax under field-based conditions, suggesting that caffeine may be an effective nutritional strategy to optimize fat utilization during real-world submaximal endurance exercise.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-10"},"PeriodicalIF":3.3,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148880014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hand and Forearm Cooling Alters Perceptual Comfort but Not Self-Paced Cycling Performance in the Heat.","authors":"Joshua Nowlan, Phillip J Wallace, Johnathan Ljubanovich, Toby Mündel, Christopher J Tyler, Stephen S Cheung","doi":"10.1123/ijspp.2026-0112","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0112","url":null,"abstract":"<p><strong>Purpose: </strong>We tested the effectiveness of hand and forearm per-cooling on self-paced cycling performance in the heat. We hypothesized that continuous, localized cooling would attenuate thermal strain and improve thermal perception, thereby enhancing performance.</p><p><strong>Methods: </strong>Ten trained cyclists (7 males and 3 females; 34 [12] y, 174.4 [8.2] cm, 75.5 [10.6] kg, 55.3 [10.7] mL·kg-1·min-1) completed 3 randomized 20-km cycling time trials in the heat (35 °C, 50% relative humidity) while immersing their forearms and hands in a circulating water bath at 10 °C, 20 °C, or 32 °C (control) throughout.</p><p><strong>Results: </strong>Whole-body thermal comfort was significantly reduced in the 10 °C and 20 °C trials compared with the 32 °C trial (both P ≤ .005). However, time to completion did not improve with either 10 °C (36.6 [2.1] min) or 20 °C (36.8 [2.2] min) compared with control (37.0 [1.9] min, P = .476), nor did power output (10 °C: 202 [39] W, 20 °C: 201 [42] W, 32 °C: 202 [37] W; P = .988) or pacing strategy. Physiological strain was also not different across conditions for both mean heart rate (P = .535) and rectal temperature change (10 °C: +1.3 [0.7] °C, 20 °C: +1.3 [0.5] °C, 32 °C: +1.5 [0.4] °C; P = .153).</p><p><strong>Conclusion: </strong>Despite perceptual benefits, passive water immersion of the extremities did not improve time-trial performance and appears insufficient to lower the physiological strain experienced during a self-paced 20-km time trial in the heat.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-7"},"PeriodicalIF":3.3,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148880032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Effect of Nike ZoomX Vaporfly Next% 2 on Running Economy in Trained Distance Runners During a 20-km Run.","authors":"Camilla Prisak, Lea Kromann Etzerodt, Lasse Gliemann, Kurt Jensen","doi":"10.1123/ijspp.2025-0641","DOIUrl":"https://doi.org/10.1123/ijspp.2025-0641","url":null,"abstract":"<p><strong>Purpose: </strong>This study aimed to examine the effect of Nike ZoomX Vaporfly Next% 2 (VF) on running economy (RE) in trained to highly trained long-distance runners during a prolonged treadmill run (20 km), and whether VF could maintain the RE benefits over time compared with a conventional training shoe (TS).</p><p><strong>Methods: </strong>Fourteen trained to highly trained runners participated in 2 test sessions, completing a 20-km treadmill run in VF on one day and TS on another. Oxygen uptake, respiratory exchange ratio, and heart rate were measured throughout the run, and RE was calculated from the final 2 minutes of each stage (0, 5, 10, 15, and 20 km). Shoe order was randomized.</p><p><strong>Results: </strong>Ten participants completed both test days. RE was consistently lower in VF compared with TS throughout the running protocol, accompanied by lower oxygen consumption. No significant shoe × distance interaction was observed, indicating that the difference between shoe conditions remained stable over the 20-km run. Both shoes showed a nonsignificant tendency toward deteriorating RE over time.</p><p><strong>Conclusions: </strong>VF demonstrated lower metabolic cost and superior RE compared with TS during prolonged treadmill running. However, the progression of RE over time did not differ between shoe conditions, suggesting that VF provided a stable metabolic advantage rather than reducing the rate of RE deterioration.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-7"},"PeriodicalIF":3.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148864906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Re-Examining Pacing Profiles in Elite Cross-Country Olympic Mountain Biking: The Influence of the Start Loop and Performance Level.","authors":"Gabriel Protzen, Youssef El Moussaoui El Azhari, Juan García-López, Daniel Boullosa","doi":"10.1123/ijspp.2026-0139","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0139","url":null,"abstract":"<p><strong>Purpose: </strong>Current literature characterizes cross-country Olympic mountain bike pacing as a \"positive strategy\" (fast start followed by decline or stabilization). However, this interpretation may be confounded when a start loop (SL), a structurally distinct initial lap included to facilitate positioning, is analyzed with subsequent laps. This study aimed to (1) quantify the influence of the SL on interlap pacing variability and (2) characterize pacing across performance quartiles.</p><p><strong>Methods: </strong>Lap-by-lap timing data were analyzed for 934 elite finishers (543 men, 391 women) across 10 major 2024 events (World Cups, World Championships, and Olympic Games). Seven events included an SL, while 3 did not. Lap speeds were normalized to each athlete's mean race speed and analyzed using generalized estimating equations to assess lap effects and lap × performance quartile (first vs fourth) interactions. Interlap variability was quantified using coefficient of variation (CV).</p><p><strong>Results: </strong>When only structurally comparable laps were considered, interlap variability was consistently low. Races without an SL showed low variability (median CV < 1.0%), and similar values were observed when the SL was excluded (median CV 1.1% in men and 1.2% in women). Including the SL increased variability approximately 7-fold (median CV 8.5% men and 10.9% women; P < .05). Lap × performance quartile interactions were event-dependent and small. Lower-performing finishers tended to start relatively faster and finish relatively slower than top performers.</p><p><strong>Conclusions: </strong>Excluding the SL reveals relatively stable interlap pacing in elite cross-country Olympic mountain biking with limited between-lap variations, whereas its inclusion substantially inflates variability and accentuates apparent fast-start behavior.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-7"},"PeriodicalIF":3.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148864914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strength and Conditioning Practices in Tennis: A Narrative Review of Contemporary Evidence.","authors":"Jaime Fernandez-Fernandez, Joshua Colomar, Ernest Baiget","doi":"10.1123/ijspp.2026-0148","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0148","url":null,"abstract":"<p><strong>Purpose: </strong>To provide a pragmatic synthesis of contemporary strength and conditioning evidence in tennis, integrating match demands, neuromuscular performance and injury-risk management, and practical testing/monitoring to support applied decision making from academy to professional settings.</p><p><strong>Methods: </strong>This narrative synthesis includes peer-reviewed primary studies and systematic reviews addressing tennis match demands, neuromuscular training and injury prevention, and monitoring/testing, with priority given to contemporary evidence available up to February 2026.</p><p><strong>Results: </strong>Tennis exhibits an intermittent high-intensity profile in which mechanical load is dominated by frequent accelerations, decelerations, and multidirectional changes of direction, while mean internal load is moderate but highly variable with repeated peaks during rallies. Evidence supports the relevance of lower- and upper-limb strength-power, stretch-shortening cycle function, and trunk control for performance and robustness, with practical implications for on-court intermittent conditioning, strength-power/robustness strategies, and low-burden monitoring.</p><p><strong>Conclusions: </strong>We propose a 3-domain applied framework: (1) on-court conditioning guided by rally structure and movement demands; (2) year-round strength-power and robustness training targeting the lower limb, trunk, and shoulder, with dose adjusted to tournament density and athlete history; and (3) concise monitoring combining a compact performance battery with low-burden internal/external load indices to support readiness and availability.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-8"},"PeriodicalIF":3.3,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148840292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of Training Load on Recovery, Wellness, and Performance in Elite Soccer Athletes.","authors":"Sam R Moore, Elena I Cantú, Abbie E Smith-Ryan","doi":"10.1123/ijspp.2026-0076","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0076","url":null,"abstract":"<p><strong>Purpose: </strong>Athlete monitoring has emerged as a common method to track athlete status and adjust training for optimal performance. Despite the influx of monitoring-related resources at the collegiate level, actual training load modifications are largely anecdotal. This prospective cohort study investigated relationships between previous day training load, objective nightly recovery, and next-day subjective wellness and max speed (MS) in elite soccer athletes across a collegiate season.</p><p><strong>Methods: </strong>Twenty-six collegiate female soccer athletes were tracked across the duration of their season (2024-2025) for training load (wearable global positioning systems monitors), objective nightly recovery (wearable recovery rings), next-day subjective wellness (morning wellness survey), and MS performance.</p><p><strong>Results: </strong>Previous day training load measures of distance and high-speed running were significant predictors of variables related to nightly objective sleep recovery, next day subjective readiness, and next day speed performance. High-speed running models consistently performed better than total distance for predicting changes in recovery, wellness, and MS.</p><p><strong>Conclusions: </strong>Numerous associations between previous day training load and objective and subjective measures increase accessibility of female athlete monitoring methods for applied practitioners. Although the magnitudes of coefficients vary, the consistency of significant findings across monitoring methods provides utility for continuous and comprehensive athlete monitoring, demonstrating the importance of subjective readiness measures beyond traditional performance metrics, while also addressing the paucity of literature in elite female athletes.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-8"},"PeriodicalIF":3.3,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148840319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of Ramadan on Body Composition in Elite Youth Soccer Players: A Case Study.","authors":"Ibrahim Akubat, Capucine Bartrand, Ben Simpson, Juan Jose Morillas Pedreno, Karim Chamari","doi":"10.1123/ijspp.2026-0034","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0034","url":null,"abstract":"<p><strong>Purpose: </strong>This case study examined the impact of Ramadan intermittent fasting on body composition in elite youth soccer players competing in Europe. Ramadan fasting poses unique physiological challenges for athletes, yet research in elite youth populations remains limited.</p><p><strong>Methods: </strong>Three male elite youth soccer players (aged 17-18 y) were monitored during Ramadan 2025. Body composition was assessed using dual-energy X-ray absorptiometry at the start and end of Ramadan. Variables included body mass (BM), lean BM, fat mass, fat-free mass, percentage body fat, and bone mineral density. Players maintained their usual training schedule and received tailored nutritional support, including periodized carbohydrate intake (5-10 g·kg BM-1) and protein targets (1.8-2.2 g·kg BM-1).</p><p><strong>Results: </strong>Body composition was largely maintained across the fasting period. Players A and C showed negligible changes. Player B demonstrated a notable reduction in BM (-2.21 kg), primarily due to decreased lean BM (-2.12 kg), despite stable fat mass. Bone mineral density remained unchanged for all players.</p><p><strong>Conclusions: </strong>Informed support strategies can help maintain body composition during Ramadan in elite youth soccer players but players may experience negative consequences and reductions in lean BM, indicating a need for individualized monitoring and intervention. Further research should explore dietary compliance and training load interactions to optimize performance and health during Ramadan intermittent fasting.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-3"},"PeriodicalIF":3.3,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148818381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Feet in or out: Exploring the Swim to Bike Transition in Junior Elite Triathletes.","authors":"Grant J Landers, Janay E Hendriks, Karen E Wallman","doi":"10.1123/ijspp.2025-0674","DOIUrl":"https://doi.org/10.1123/ijspp.2025-0674","url":null,"abstract":"<p><strong>Purpose: </strong>This study examined the effect of prior maximal intensity swimming on subsequent cycling performance and compared cycling with feet in shoes (IN) versus feet out of shoes (OUT) during the swim to bike transition in junior elite triathletes.</p><p><strong>Methods: </strong>Ten (3 females, 7 males) junior elite triathletes (mean [SD]; 19 [2] y; 172 [7] cm; 65 [6] kg) completed 3 trials separated by 7 days: a control cycling trial (CONT; no swim) and 2 experimental trials consisting of 750-m maximal intensity swim, followed by a 100-kJ maximal cycle effort (∼4 km equivalent) performed on a stationary cycle ergometer under IN and OUT conditions. Swimming was conducted in an outdoor pool with cycling performed in an adjacent laboratory 5 m from the pool. Transition time was defined as the time from swim completion to cycling commencement. Performance was determined by the time taken to complete transition and fixed cycle work.</p><p><strong>Results: </strong>Transition time was slower for IN (55.7 [6.1] s) than OUT (44.7 [5.7] s; P = .0001, d = 1.56). Cycle time was faster in CONT (289.2 [59.8] s) than IN (347.8 [78.6] s; d = 0.84) and OUT (376.9 [104.9] s; P = .0001, d = 1.03), with IN faster than OUT (P = .041). Combined transition and cycle times did not differ between conditions (P = .173, d = 0.23).</p><p><strong>Conclusion: </strong>Prior maximal intensity swimming impaired subsequent cycling performance. Although cycling with feet out of the shoes reduced transition time, it compromised cycling performance, resulting in no overall advantage in combined transition and cycle time. However, faster transitions may provide a tactical benefit in draft-legal events where early bike positioning is important.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-5"},"PeriodicalIF":3.3,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148818403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Position-Specific Differences in Physical and Technical-Tactical Match Demands Across FIFA U17, U20, and Men's World Cups.","authors":"Wonwoo Ju, Woohyuk Chang, Tae-Seok Jeong, Jordi Ferrandis, Ryland Morgans, Allistair McRobert","doi":"10.1123/ijspp.2026-0043","DOIUrl":"https://doi.org/10.1123/ijspp.2026-0043","url":null,"abstract":"<p><strong>Purpose: </strong>This study aimed to compare physical and technical-tactical match performance across 13 specialized positions in 3 competitive levels of international football: the FIFA U17 World Cup Indonesia 2023 (U17WC), FIFA U20 World Cup Argentina 2023 (U20WC), and FIFA Men's World Cup Qatar 2022 (MWC).</p><p><strong>Methods: </strong>Physical and technical-tactical data from 168 matches were analyzed, with 1535 full-match player observations retained across competitions and positions. Linear and generalized linear mixed models were used to examine competition, position, and their interaction effects on match demands.</p><p><strong>Results: </strong>U17WC players covered 2% to 4% lower total distance and 18% to 19% lower high-intensity running distance than U20WC and MWC players (P ≤ .0367; effect size: 0.2-0.5). MWC players recorded 11% to 31% greater sprinting distances and higher top speeds (P ≤ .0297; effect size: 0.1-0.5). Technical-tactical metrics generally increased with competition level, with MWC players performing more passes (+9% to 22%), offers to receive (+46% to 79%), ball receptions (+51% to 89%), and defensive pressures (+14% to 34%), alongside higher pass completion rates (+4%). In contrast, defensive actions such as tackles, blocks, clearances, and interceptions peaked at the U20WC. Across competitions, positional roles displayed systematic, position-dependent differences, with midfield and wide players demonstrating contrasts across a greater number of performance metrics, central defenders showing differences primarily in ball distribution, and forwards exhibiting increased technical-tactical involvement rather than greater running demands.</p><p><strong>Conclusions: </strong>These findings indicate that match performance differences were position-dependent across competitions, supporting the use of age-by-position benchmarks rather than generic age-group profiles.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-8"},"PeriodicalIF":3.3,"publicationDate":"2026-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148792836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multidimensional Comparison of Specific Strength Qualities Between Professional and Academy Rugby Union Players.","authors":"Leslie K D Payne, Matthew C Varley, David L Carey, Matthew W Driller, Lachlan P James","doi":"10.1123/ijspp.2025-0658","DOIUrl":"https://doi.org/10.1123/ijspp.2025-0658","url":null,"abstract":"<p><strong>Purpose: </strong>This study had 2 aims. First, to test whether a concise set of strength metrics representing established strength domains can classify rugby union players as professional or academy. Second, to identify which individual metrics most clearly distinguish tiers using discriminant analysis.</p><p><strong>Methods: </strong>Forty-three male rugby union players (professionals n = 20; academy n = 23) completed a full body strength battery including the isometric midthigh pull (IMTP), isometric bench press, isometric bench pull, dynamic back squat, dynamic bench press, dynamic bench pull, countermovement jump, and drop jump. Players were grouped by position (forwards and backs). Univariate tests and linear discriminant analyses compared playing level and identified the metrics which most strongly discriminated level.</p><p><strong>Results: </strong>IMTP net force at 100 ms was the strongest discriminator, with professionals exceeding academy players in both backs (+406.7 N, d = 1.97, P = .004) and forwards (+302.1 N, d = 1.19, P = .006), reflected by greater percentage contribution to the discriminant function (backs 36.6%; forwards 57.2%). The linear discriminant model correctly classified 100% of backs and 81.5% of forwards into professional or academy level. Professional forwards demonstrated greater countermovement jump momentum (+39.3 kg·m/s, d = 2.02), greater IMTP net peak force (+819 N, d = 2.61), and higher reactive strength index (+0.76 m/s, d = 1.68).</p><p><strong>Conclusion: </strong>Tier differences were evident for a subset of strength qualities. IMTP net force at 100 ms is a robust indicator of competitive level in rugby union and is complemented by upper body isometric pulling strength among backs.</p>","PeriodicalId":14295,"journal":{"name":"International journal of sports physiology and performance","volume":" ","pages":"1-9"},"PeriodicalIF":3.3,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148792878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}