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Match Running Performance in Australian Football Is Related to Muscle Fiber Typology

Henry J. Hopwood, Phillip M. Bellinger, Heidi R. Compton, Matthew N. Bourne, Wim Derave, Eline Lievens, Ben Kennedy, and Clare L. Minahan

Purpose: To examine the association between muscle fiber typology and match running performance in professional Australian football (AF) athletes. Methods: An observational time–motion analysis was performed on 23 professional AF athletes during 224 games throughout the 2020 competitive season. Athletes were categorized by position as hybrid, small, or tall. Athlete running performance was measured using Global Navigation Satellite System devices. Mean total match running performance and maximal mean intensity values were calculated for moving mean durations between 1 and 10 minutes for speed (in meters per minute), high-speed-running distance (HSR, >4.17 m·s−1), and acceleration (in meters per second squared), while intercept and slopes were calculated using power law. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus and expressed as a carnosine aggregate z score (CAZ score) to estimate muscle fiber typology. Mixed linear models were used to determine the association between CAZ score and running performance. Results: The mean (range) CAZ score was −0.60 (−1.89 to 1.25), indicating that most athletes possessed a greater estimated proportion of type I muscle fibers. A greater estimated proportion of type I fibers (ie, lower CAZ score) was associated with a larger accumulation of HSR (>4.17 m·s−1) and an increased ability to maintain HSR as the peak period duration increased. Conclusion: AF athletes with a greater estimated proportion of type I muscle fibers were associated with a greater capacity to accumulate distance running at high speeds, as well as a greater capacity to maintain higher output of HSR running during peak periods as duration increases.

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Accuracy of Heart-Rate-Recovery Parameters Assessed From a Wrist-Worn Photoplethysmography Monitor (Polar Unite)

Quentin Bretonneau, Etienne Peruque-Gayou, Etienne Wolfs, and Laurent Bosquet

Purpose: The accuracy of heart rate (HR) measured with a wrist-worn photoplethysmography (PPG) monitor is altered during rest–exercise and exercise–rest transitions, which questions the validity of postexercise HR-recovery (HRR) parameters estimated from this device. Methods: Thirty participants (50% female) randomly performed two 13-minute sequences (3′ rest, 5′ submaximal-intensity exercise, and 5′ passive recovery) on treadmill and bicycle ergometers. HR was measured concomitantly with a 10-lead electrocardiogram (ECG) and a wrist-worn PPG monitor (Polar Unite). HRR was assessed by calculating Δ60 (the difference between HR during exercise and HR 60 s after exercise cessation) and by fitting HRR data into a monoexponential model. Results: By focusing on Δ60 and τ (the time constant of the monoexponential curve), levels of association (r) of the Unite versus the 10-lead ECG were high to very high (.73 < r < .93), and coefficients of variation were >20% (in absolute value), except for Δ60 in the bicycle ergometer condition (11.7%). In 97% of cases, the decrease in HR after exercise appeared later with the Unite. By adjusting the time window used for the analysis according to this time lag, coefficients of variation of Δ60 decreased below 10% in the bicycle ergometer condition. Conclusions: If a wrist-worn PPG monitor is used to assess HRR, we recommend performing the submaximal-intensity exercise on a bicycle ergometer and focusing on Δ60. Furthermore, to obtain a more accurate Δ60, the time lag between the end of the exercise and the effective decrease in HR should also be considered before the calculation.

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Remote Determination of Critical Speed and Critical Power in Recreational Runners

Ben Hunter, Adam Ledger, and Daniel Muniz-Pumares

Purpose: This study aimed to compare estimations of critical speed (CS) and work completed above CS (D′), and their analogies for running power (critical power [CP] and W′), derived from raw data obtained from habitual training (HAB) and intentional maximal efforts in the form of time trials (TTs) and 3-minute all-out tests (3MTs) in recreational runners. The test–retest reliability of the 3MT was further analyzed. Methods: Twenty-three recreational runners (4 female) used a foot pod to record speed, altitude, and power output for 8 consecutive weeks. CS and D′, and CP and W′, were calculated from the best 3-, 7-, and 12-minute segments recorded in the first 6 weeks of their HAB and in random order in weeks 7 and 8 from 3 TTs (3, 7, and 12 min) and three 3MTs (to assess test–retest reliability). Results: There was no difference between estimations of CS or CP derived from HAB, TT, and 3MT (3.44 [0.63], 3.42 [0.53], and 3.76 [0.57] m · s−1 and 281 [41], 290 [45], and 305 [54] W, respectively), and strong agreement between HAB and TT for CS (r = .669) and CP (r = .916). Limited agreement existed between estimates of D′/W′. Moderate reliability of D′/W′ was demonstrated between the first and second 3MTs, whereas excellent reliability was demonstrated for CS/CP. Conclusion: These data suggest that estimations of CS/CP can be derived remotely, from either HAB, TT, or 3MT, although the lower agreement between D′/W′ warrants caution when using these measures interchangeably.

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Rethinking Sport Science to Improve Coach–Researcher Interactions

Irineu Loturco

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Volume 18 (2023): Issue 10 (Oct 2023)

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An Updated Panorama of Blood-Flow-Restriction Methods

Brendan R. Scott, Olivier Girard, Nicholas Rolnick, James R. McKee, and Paul S.R. Goods

Background: Exercise with blood-flow restriction (BFR) is being increasingly used by practitioners working with athletic and clinical populations alike. Most early research combined BFR with low-load resistance training and consistently reported increased muscle size and strength without requiring the heavier loads that are traditionally used for unrestricted resistance training. However, this field has evolved with several different active and passive BFR methods emerging in recent research. Purpose: This commentary aims to synthesize the evolving BFR methods for cohorts ranging from healthy athletes to clinical or load-compromised populations. In addition, real-world considerations for practitioners are highlighted, along with areas requiring further research. Conclusions: The BFR literature now incorporates several active and passive methods, reflecting a growing implementation of BFR in sport and allied health fields. In addition to low-load resistance training, BFR is being combined with high-load resistance exercise, aerobic and anaerobic energy systems training of varying intensities, and sport-specific activities. BFR is also being applied passively in the absence of physical activity during periods of muscle disuse or rehabilitation or prior to exercise as a preconditioning or performance-enhancement technique. These various methods have been reported to improve muscular development; cardiorespiratory fitness; functional capacities; tendon, bone, and vascular adaptations; and physical and sport-specific performance and to reduce pain sensations. However, in emerging BFR fields, many unanswered questions remain to refine best practice.

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The V ˙ O 2 max Legacy of Hill and Lupton (1923)—100 Years On

Grégoire P. Millet, Johannes Burtscher, Nicolas Bourdillon, Giorgio Manferdelli, Martin Burtscher, and Øyvind Sandbakk

Purpose: One hundred years ago, Hill and Lupton introduced the concept of maximal oxygen uptake ( V ˙ O 2 max ), which is regarded as “the principal progenitor of sports physiology.” We provide a succinct overview of the evolvement of research on V ˙ O 2 max , from Hill and Lupton‘s initial findings to current debates on limiting factors for V ˙ O 2 max and the associated role of convective and diffusive components. Furthermore, we update the current use of V ˙ O 2 max in elite endurance sport and clinical settings. Practical Applications and Conclusions: V ˙ O 2 max is a healthy and active centenarian that remains a very important measure in elite endurance sports and additionally contributes as an important vital sign of cardiovascular function and fitness in clinical settings. Over the past 100 years, guidelines for the test protocols and exhaustion criteria, as well as the understanding of limiting factors for V ˙ O 2 max , have improved dramatically. Presently, possibilities of accurate and noninvasive determination of the convective versus diffusive components of V ˙ O 2 max by wearable sensors represent an important future application. V ˙ O 2 max is not only an indicator of cardiorespiratory function, fitness, and endurance performance but also represents an important biomarker of cardiovascular function and health to be included in routine assessment in clinical practice.

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Highly Trained Biathletes With a Fast-Start Pacing Pattern Improve Time-Trial Skiing Performance by Pacing More Evenly

Thomas Losnegard, Magne Lund-Hansen, Erland Vedeler Stubbe, Even Dahlen Granrud, Harri Luchsinger, Øyvind Sandbakk, and Jan Kocbach

Purpose: In sprint biathlon, a J-shaped pacing pattern is commonly used. We investigated whether biathletes with a fast-start pacing pattern increase time-trial skiing and shooting performance by pacing more evenly. Methods: Thirty-eight highly trained biathletes (∼21 y, 27 men) performed an individual 7.5 (3 × 2.5 km for women) or 10-km (3 × 3.3 km for men) time trial on roller skis with a self-selected pacing strategy (day 1). Prone (after lap 1) and standing shooting (after lap 2) stages were performed using paper targets. Based on their pacing strategy in the first time trial (ratio between the initial ∼800-m segment pace on lap 1 and average ∼800-m segment pace on laps 1–3), participants were divided into an intervention group with the fastest starting pace (INT, n = 20) or a control group with a more conservative starting pace (CON, n = 18). On day 2, INT was instructed to reduce their starting pace, while CON was instructed to maintain their day 1 strategy. Results: INT increased their overall time-trial performance more than CON from day 1 to day 2  (mean ± 95% CI; 1.5% ± 0.7% vs 0.0% ± 0.9%, P = .02). From day 1 to day 2, INT reduced their starting pace (5.0% ± 1.5%, P < .01), with reduced ratings of perceived exertion during lap 1 (P < .05). For CON, no change was found for starting pace (−0.8% ± 1.2%) or ratings of perceived exertion between days. No differences were found for shooting performance for either group. Conclusion: Highly trained biathletes with a pronounced fast-start pattern improve skiing performance without any change in shooting performance by pacing more evenly.

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Minimal Number of Events Required for Acceleration–Speed Profiling in Elite Women’s Soccer

Patrick Cormier, Ming-Chang Tsai, Cesar Meylan, Victor H.T. Soares, David C. Clarke, and Marc Klimstra

Purpose: To determine the minimum number of events (training or matches) for producing valid acceleration–speed (AS) profiles from global navigation satellite system (GNSS) data. Methods: Nine elite female soccer players participated in a 4-week training camp consisting of 19 events. AS profile metrics calculated from different combinations of athlete events were compared to force–velocity (FV) profile metrics from 2 × 40-m stand-alone sprint effort trials, using the same GNSS 10-Hz technology. Force–velocity profiles were calculated, from which AS profiles were obtained. AS profiles from training and matches were generated by plotting acceleration and speed points and performing a regression through the maximal points to obtain the AS metrics (theoretical maximal speed, x-intercept [in meters per second], theoretical maximal acceleration, y-intercept [in meters per second squared], and the slope per second). A linear mixed model was performed with the AS metrics as the outcome variables, the number of events as a fixed effect, and the participant identifier as a mixed effect. Dunnett post hoc multiple comparisons were used to compare the means of each number of event grouping (1–19 events) to those estimated from the dedicated sprint test. Results: Theoretical maximal speed and theoretical maximal acceleration means were no longer significantly different from the isolated sprint reference with 9 to 19 (small to trivial differences = −0.31 to −0.04 m·s−1, P = .12–.99) and 6 to 19 (small differences = −0.4 to −0.28 m·s−2, P = .06–.79) events, and the slopes were no longer different with 1 to 19 events (trivial differences = 0.06–0.03 s−1, P = .35–.99). Conclusions: AS profiles can be estimated from a minimum of 9 days of tracking data. Future research should investigate methodology resulting in AS profiles estimated from fewer events.

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The Relationship Between Isometric and Dynamic Strength Following Resistance Training: A Systematic Review, Meta-Analysis, and Level of Agreement

Lachlan P. James, Jonathon Weakley, Paul Comfort, and Minh Huynh

Background: Maximal lower-body strength can be assessed both dynamically and isometrically; however, the relationship between the changes in these 2 forms of strength following resistance training is not well understood. Purpose: To systematically review and analyze the effects of resistance training on changes in maximal dynamic (1-repetition-maximum back squat, deadlift, and power clean) and position-matched isometric strength (isometric midthigh pull and the isometric squat). In addition, individual-level data were used to quantify the agreement and relationship between changes in dynamic and isometric strength. Methods : Databases were systematically searched to identify eligible articles, and meta-analysis procedures were performed on the extracted data. The raw results from 4 studies were acquired, enabling bias and absolute reliability measures to be calculated using Bland–Altman test of agreement. Results: Eleven studies met the inclusion criteria, which resulted in 29 isometric–dynamic change comparisons. The overall pooled effect was 0.13 in favor of dynamic testing; however, the prediction interval ranged from g = −0.49 to 0.75. There was no evidence of bias (P = .825) between isometric and dynamic tests; however, the reliability coefficient was estimated to be 16%, and the coefficient of variation (%) was 109.27. Conclusions: As a range of future effects can be expected when comparing isometric to dynamic strength changes following resistance training, and limited proportionality exists between changes in these 2 strength qualities, there is strong evidence that isometric and dynamic strength represent separate neuromuscular domains. These findings can be used to inform strength-assessment models in athlete populations.