Purpose: The study had 3 purposes: (1) to develop an index using machine-learning techniques to predict the fitness status of soccer players, (2) to explore the index’s validity and its relationship with a submaximal run test (SMFT), and (3) to analyze the impact of weekly training load on the index and SMFT outcomes. Methods: The study involved 50 players from an Italian professional soccer club. External and internal loads were collected during training sessions. Various machine-learning algorithms were assessed for their ability to predict heart-rate responses during the training drills based on external load data. The fitness index, calculated as the difference between actual and predicted heart rates, was correlated with SMFT outcomes. Results: Random forest regression (mean absolute error = 3.8 [0.05]) outperformed the other machine-learning algorithms (extreme gradient boosting and linear regression). Average speed, minutes from the start of the training session, and the work:rest ratio were identified as the most important features. The fitness index displayed a very large correlation (r = .70) with SMFT outcomes, with the highest result observed during possession games and physical conditioning exercises. The study revealed that heart-rate responses from SMFT and the fitness index could diverge throughout the season, suggesting different aspects of fitness. Conclusions: This study introduces an “invisible monitoring” approach to assess soccer player fitness in the training environment. The developed fitness index, in conjunction with traditional fitness tests, provides a comprehensive understanding of player readiness. This research paves the way for practical applications in soccer, enabling personalized training adjustments and injury prevention.
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Predicting Soccer Players’ Fitness Status Through a Machine-Learning Approach
Mauro Mandorino, Jo Clubb, and Mathieu Lacome
Mixed-Method Precooling Enhances Self-Paced 20-km Cycling Time-Trial Performance When Apparent Temperature Is >46 °C but May Not Be a Priority in <46 °C
Julian Andro P. Ramos, Kagan J. Ducker, Hugh Riddell, Olivier Girard, Grant J. Landers, and Carly J. Brade
Purpose: Precooling (PreC) may only benefit performance when thermal strain experienced by an individual is sufficiently high. We explored the effect of mixed-method PreC on 20-km cycling time-trial (CTT) performance under 3 different apparent temperatures (AT). Methods: On separate days, 12 trained or highly trained male cyclists/triathletes completed six 20-km CTTs in 3 different ATs: hot-dry (35 °C AT), moderately hot-humid (40 °C AT), and hot-humid (46 °C AT). All trials were preceded by 30 minutes of mixed-method PreC or no PreC (control [CON]). Results: Faster 2.5-km-split completion times occurred in PreC compared with CON in 46 °C AT (P = .02), but not in 40 °C AT (P = .62) or 35 °C AT (P = .57). PreC did not affect rectal and body temperature during the 20-km CTT. Skin temperature was lower throughout the CTT in PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = 1.00) and 35 °C AT (P = 1.00). Heart rate had a greater rate of increase during the CTT for PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = .57) and 35 °C AT (P = 1.00). Ratings of perceived exertion (P < .001) and thermal comfort (P = .04) were lower for PreC compared with CON in 46 °C AT only, while thermal sensation was not different between PreC and CON. Conclusion: Mixed-method PreC should be applied prior to 20-km CTTs conducted in hot-humid conditions (≥46 °C AT). Alternatively, mixed-method PreC may be a priority in moderately hot-humid (∼40 °C AT) conditions but should not be in hot-dry (∼35 °C AT) conditions for 20-km CTT.
The Day-by-Day Periodization Strategies of a Giro d’Italia Podium Finisher
Gabriele Gallo, Manuel Mateo-March, Andrea Fuk, Emanuela Faelli, Piero Ruggeri, Roberto Codella, and Luca Filipas
Purpose: The aim of this study was to describe the day-by-day training and racing characteristics in preparation for the Giro d’Italia of 1 world-class road cyclist who achieved a place on the podium in the final general classification of the Giro d’Italia. Methods: Day-by-day power meter training and racing data of 1 study subject (road cyclist; age 25 y; relative maximum oxygen consumption 81 mL·min−1·kg−1; relative 20-min record power output 6.6 W·kg−1) covering the 152 days leading up to the podium in the Giro d’Italia final general classification were retrospectively analyzed. Daily load, daily volume, and intensity distribution were considered. Results: During training a pattern alternating “hard days” versus “easy days” was observed, as significant amounts of medium or high intensity, or load, were not performed for more than 2 consecutive days This pattern was achieved combining high volume (>4 h) with a significant amount of medium and high intensity within the same training sessions. During training, when training load and intensity increased, the density of “easy days” augmented. In 1-week stage races and the Giro d’Italia, 3 to 8 consecutive days with significant amounts of medium and high intensity were performed. A high number of training sessions with small amounts of medium- and high-intensity volume was observed: 38 days accumulating 3 to 10 minutes at medium intensity and 29 days spending 1 to 9 minutes at high intensity. Conclusion: These data provide novel insights about the day-by-day periodization strategies leading to a top 3 in the Giro d’Italia general classification.
Effect of Acute Sodium Bicarbonate and Caffeine Coingestion on Repeated-Sprint Performance in Recreationally Trained Individuals: A Randomized Controlled Trial
Carmen Ferragut, Paola Gonzalo-Encabo, Álvaro López-Samanes, David Valadés, and Alberto Pérez-López
Introduction: The acute and isolated ingestion of sodium bicarbonate (NaHCO3) and caffeine (CAF) improves performance and delays fatigue in high-intensity tasks. However, it remains to be elucidated if the coingestion of both dietary supplements stimulates a summative ergogenic effect. This study aimed to examine the effect of the acute coingestion of NaHCO3 and CAF on repeated-sprint performance. Methods: Twenty-five trained participants (age: 23.3 [4.0] y; sex [female/male]: 12/13; body mass: 69.6 [12.5] kg) participated in a randomized, double-blind, placebo (PLA) -controlled, crossover study. Participants were assigned to 4 conditions: (1) NaHCO3 + CAF, (2) NaHCO3, (3) CAF, or (4) PLA. Thus, they ingested 0.3 g/kg of NaHCO3, 3 mg/kg of CAF, or PLA. Then, participants performed 4 Wingate tests (Wt), consisting of a 30-second all-out sprint against an individualized resisted load, interspersed by a 1.5-minute rest period between sprints. Results: Peak (Wpeak) and mean (Wmean) power output revealed a supplement and sprint interaction effect (P = .009 and P = .049, respectively). Compared with PLA, NaHCO3 + CAF and NaHCO3 increased Wpeak performance in Wt 3 (3%, P = .021) and Wt 4 (4.5%, P = .047), while NaHCO3 supplementation increased mean power performance in Wt 3 (4.2%, P = .001). In Wt 1, CAF increased Wpeak (3.2%, P = .054) and reduced time to Wpeak (−8.5%; P = .008). Plasma lactate showed a supplement plus sprint interaction (P < .001) when NaHCO3 was compared with CAF (13%, P = .031) and PLA (23%, P = .021). Conclusion: To summarize, although the isolated ingestion of CAF and NaHCO3 improved repeated-sprint performance, the coingestion of both supplements did not stimulate a synergic ergogenic effect.
Volume 19 (2024): Issue 2 (Feb 2024)
Monitoring Readiness to Train and Perform in Female Football: Current Evidence and Recommendations for Practitioners
Marco Beato, Esben Elholm Madsen, Jo Clubb, Stacey Emmonds, and Peter Krustrup
Purpose: Monitoring player readiness to train and perform is an important practical concept in football. Despite an abundance of research in this area in the male game, to date, research is limited in female football. The aims of this study were, first, to summarize the current literature on the monitoring of readiness in female football; second, to summarize the current evidence regarding the monitoring of the menstrual cycle and its potential impact on physical preparation and performance in female footballers; and third, to offer practical recommendations based on the current evidence for practitioners working with female football players. Conclusions: Practitioners should include both objective (eg, heart rate and countermovement jump) and subjective measures (eg, athlete-reported outcome measures) in their monitoring practices. This would allow them to have a better picture of female players’ readiness. Practitioners should assess the reliability of their monitoring (objective and subjective) tools before adopting them with their players. The use of athlete-reported outcome measures could play a key role in contexts where technology is not available (eg, in semiprofessional and amateur clubs); however, practitioners need to be aware that many single-item athlete-reported outcome measures instruments have not been properly validated. Finally, tracking the menstrual cycle can identify menstrual dysfunction (eg, infrequent or irregular menstruation) that can indicate a state of low energy availability or an underlying gynecological issue, both of which warrant further investigation by medical practitioners.
Validity and Reliability of Finger-Strength Testing in 6 Common Grip Techniques for the Assessment of Bouldering Ability in Men
Karl Söderqvist, Fredrik Identeg, Jonas Zimmerman, Eric Hamrin Senorski, Mikael Sansone, and Henrik Hedelin
Objective: To determine the criterion validity and test–retest reliability of isometric finger-strength testing in 6 differentiated grip techniques for the assessment of bouldering ability among male climbers. Methods: We recruited participants at climbing gyms in Sweden and through online advertisements. We included climbers over 15 years of age with a minimum bouldering performance level of 17 International Rock Climbing and Research Association (IRCRA) for men and 15 IRCRA for women. We tested unilateral, maximal isometric peak finger strength in the front 3 drag, half crimp, closed crimp, 35 sloper, 45 × 90-mm, and 90 × 90-mm pinch through maximal force deloaded of a force plate. We analyzed criterion validity, test–retest reliability, and capacity to determine bouldering performance ability using a stepwise multivariable regression model. Results: Women were excluded from the analysis due to insufficient sample size (n = 16). Thirty-two male participants were included in the primary analysis. The median (interquartile range) age in the advanced and elite group was 27 (25; 35) and 23 (22; 32) years, respectively. The half crimp for the participants’ weak and strong hand displayed the highest ability to determine bouldering grade performance, explaining 48% to 58% of the variance. In the stepwise regression, maximal strength in the half crimp and the front 3 drag collectively explained 66% of the variance for performance. Conclusion: Strength in the half crimp proved the most important performance indicator. The results of this study provide a reliable and valid framework for maximal isometric peak finger-strength testing in advanced and elite male boulderers.
Effects of Load and Focus of Attention on Mechanical Parameters During Bench-Press Throw in Resistance-Trained Men
Olaf Prieske, Vidar Andersen, Tom A. Moberg Johansen, and Atle H. Saeterbakken
Purpose: Power output is dependent on the load used during exercise such as bench-press throw (BPT). Attentional focus (external [EXT] vs internal [INT]) during exercise significantly modulates power performance. The purpose of the present study was to examine the effects of load and attentional focus on mechanical parameters during BPT. Methods: In a crossover study, 31 resistance-trained men (mean age 23.5 [3.0] y) performed BPT at 30% (light), 50% (moderate), and 70% (heavy) of 1-repetition maximum (1-RM) using an INT or EXT focus of attention in randomized order. A linear encoder was used to identify barbell vertical displacement, throw time, peak/average velocity, force, and power during the concentric lifting phase. Results: Statistical analysis revealed significant load × focus interaction effects for velocity and vertical displacement (P ≤ .045; 0.66 ≤ d ≤ 0.89). Post hoc analyses indicated significantly larger velocities and displacements at 30% and 70% of 1-RM in favor of EXT (P ≤ .038; 0.79 ≤ d ≤ 1.13) but similar values at 50% of 1-RM (P > .05). Furthermore, significant main effects of load were found for throw time, force, and power (P < .001; 4.20 ≤ d ≤ 14.0). While time and force gradually increased with higher loads (P < .001; 1.45 ≤ d ≤ 14.0), power output was larger at 50% compared with 30% and 70% 1-RM (P < .001; 3.09 ≤ d ≤ 7.07), irrespective of attentional focus. Conclusions: The present findings indicated that practitioners may use EXT over INT attentional focus to enhance velocity and vertical displacement during BPT at light and heavy loads (ie, 30% and 70% 1-RM). At moderate loads (ie, 50% 1-RM), mechanical bench-press parameters appear to be less affected by attentional focus.
Relationship Between Objective and Subjective Markers of Muscle Recovery in Professional Handball Players
Alexander-Stephan Henze, Lynn Matits, Jochen Huth, and Frieder Mauch
Purpose:
To evaluate the relationship between items of the Short Recovery and Stress Scale (SRSS) related to physical stress and recovery and the biomarker creatine kinase (CK) in professional handball.
Methods:
CK and SRSS items (physical performance capability, overall recovery, muscular stress, and overall stress) were assessed in an observational study of 16 adult male professional handball players from a team in the highest German league during the 2019–20 preseason. Their preseason training schedule included several microcycles, each consisting of 3 consecutive days of intense training followed by a rest day. On 5 of these rest days, when players were classified as nonrested, and the 5 immediately following days, when players were classified as rested, players completed the SRSS between 8:00 and 9:00 AM, followed by blood sampling. Correlations between SRSS items were performed using Kendall τ. The relationship between each SRSS item and CK levels over time was examined using a mixed-effects model with a random intercept.
Results:
CK levels and SRSS stress items were significantly higher and SRSS recovery items were significantly lower in nonrested players. SRSS items were significantly positively or negatively correlated (all items: P < .001) and showed a significant effect indicating lower CK levels in rested players (all items: P ≤ .001;
Sleep Quality in Team USA Olympic and Paralympic Athletes
Travis Anderson, Natalia Galan-Lopez, Lee Taylor, Eric G. Post, Jonathan T. Finnoff, and William M. Adams
Adequate sleep is crucial for elite athletes’ recovery, performance readiness, and immune response. Establishing reference ranges for elite athletes enables appropriate contextualization for designing and targeting sleep interventions. Purpose: To establish sleep-quality reference ranges for Olympic and Paralympic cohorts using the Pittsburgh Sleep Quality Index (PSQI) and explore differences based on sex and sport types. Methods: Team USA athletes (men = 805, women = 798) completed the PSQI as part of a health-history questionnaire. Descriptive statistics were used to create reference ranges and linear models, and χ 2 test of independence determined differences in PSQI global and component scores between sex, games, season, and participation. Results: Six hundred thirty-two (39.43%) athletes reported poor sleep (PSQIGlobal ≥ 5). Men displayed later bedtimes (P = .006), better global PSQI scores, shorter sleep latency, less sleep disturbance, and less use of sleep medication than women (all P < .001). Winter Games participants had later bedtime (P = .036) and sleep offset time (P = .028) compared with Summer Games athletes. Team-sport athletes woke earlier than individual-sport athletes (P < .001). Individual-sport athletes were more likely to have low (P = .005) and mild (P = .045) risk for reduced sleep duration than team-sport athletes. Conclusion: These data provide PSQI-specific reference ranges to identify groups at greatest risk for poor sleep, who may benefit most from targeted sleep interventions.
