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Eva Piatrikova, Nicholas J. Willsmer, Marco Altini, Mladen Jovanović, Lachlan J.G. Mitchell, Javier T. Gonzalez, Ana C. Sousa, and Sean Williams

Purpose: First, to examine whether heart rate variability (HRV) responses can be modeled effectively via the Banister impulse-response model when the session rating of perceived exertion (sRPE) alone, and in combination with subjective well-being measures, are utilized. Second, to describe seasonal HRV responses and their associations with changes in critical speed (CS) in competitive swimmers. Methods: A total of 10 highly trained swimmers collected daily 1-minute HRV recordings, sRPE training load, and subjective well-being scores via a novel smartphone application for 15 weeks. The impulse-response model was used to describe chronic root mean square of the successive differences (rMSSD) responses to training, with sRPE and subjective well-being measures used as systems inputs. Changes in CS were obtained from a 3-minute all-out test completed in weeks 1 and 14. Results: The level of agreement between predicted and actual HRV data was R 2 = .66 (.25) when sRPE alone was used. Model fits improved in the range of 4% to 21% when different subjective well-being measures were combined with sRPE, representing trivial-to-moderate improvements. There were no significant differences in weekly group averages of log-transformed (Ln) rMSSD (P = .34) or HRV coefficient of variation of Ln rMSSD (P = .12); however, small-to-large changes (d = 0.21–1.46) were observed in these parameters throughout the season. Large correlations were observed between seasonal changes in HRV measures and CS (changes in averages of Ln rMSSD: r = .51, P = .13; changes in coefficient of variation of Ln rMSSD: r = −.68, P = .03). Conclusion: The impulse-response model and data collected via a novel smartphone application can be used to model HRV responses to swimming training and nontraining-related stressors. Large relationships between seasonal changes in measured HRV parameters and CS provide further evidence for incorporating a HRV-guided training approach.

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Adam Mallett, Phillip Bellinger, Wim Derave, Eline Lievens, Ben Kennedy, Hal Rice, and Clare Minahan

Purpose: To determine the association between estimated muscle fiber typology and the start and turn phases of elite swimmers during competition. Methods: International and national competition racing performance was analyzed from 21 female (FINA points = 894 ± 39: 104.5 ± 1.8% world record ratio [WRR]) and 25 male (FINA points = 885 ± 54: 104.8 ± 2.1% WRR) elite swimmers. The start, turn, and turn out times were determined from each of the swimmers’ career best performance times (FINA points = 889 ± 48: 104.7 ± 2.0% WRR). Muscle carnosine concentration was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus and was expressed as a carnosine aggregate z score relative to an age- and gender-matched nonathlete control group to estimate muscle fiber typology. Linear mixed models were employed to determine the association between muscle fiber typology and the start and turn times. Results: While there was no significant influence of carnosine aggregate z score on the start and turn times when all strokes and distance events were entered into the model, the swimmers with a higher carnosine aggregate z score (ie, faster muscle typology) had a significantly faster start time in 100-m events compared with the swimmers with a lower carnosine aggregate z score (P = .02, F = 5.825). The start and turn times were significantly faster in the male compared with the female swimmers in the 100-m events compared with other distances, and between the 4 different swimming strokes (P < .001). Conclusion: This study suggests that start times in sprint events are partly determined (and limited) by muscle fiber typology, which is highly relevant when ∼12% of the overall performance time is determined from the start time.

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Enrico Perri, Carlo Simonelli, Alessio Rossi, Athos Trecroci, Giampietro Alberti, and F. Marcello Iaia

Purpose: To investigate the relationship between the training load (TL = rate of perceived exertion × training time) and wellness index (WI) in soccer. Methods: The WI and TL data were recorded from 28 subelite players (age = 20.9 [2.4] y; height = 181.0 [5.8] cm; body mass = 72.0 [4.4] kg) throughout the 2017/2018 season. Predictive models were constructed using a supervised machine learning method that predicts the WI according to the planned TL. The validity of our predictive model was assessed by comparing the classification’s accuracy with the one computed from a baseline that randomly assigns a class to an example by respecting the distribution of classes (B1). Results: A higher TL was reported after the games and during match day (MD)-5 and MD-4, while a higher WI was recorded on the following days (MD-6, MD-4, and MD-3, respectively). A significant correlation was reported between daily TL (TLMDi) and WI measured the day after (WIMDi+1) (r = .72, P < .001). Additionally, a similar weekly pattern seems to be repeating itself throughout the season in both TL and WI. Nevertheless, the higher accuracy of ordinal regression (39% [2%]) compared with the results obtained by baseline B1 (21% [1%]) demonstrated that the machine learning approach used in this study can predict the WI according to the TL performed the day before (MD<i). Conclusion: The machine learning technique can be used to predict the WI based on a targeted weekly TL. Such an approach may contribute to enhancing the training-induced adaptations, maximizing the players’ readiness and reducing the potential drops in performance associated with poor wellness scores.

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Teun van Erp, Marcel Kittel, and Robert P. Lamberts

Purpose: To describe the performance and tactical sprint characteristics of a world-class sprinter competing in the Tour de France. In addition, differences in the sprint tactics of 2 teams and won versus lost sprints are highlighted. Method: Power output (PO) and video footage of 21 sprints were analyzed. Position in the peloton and number of teammates supporting the sprinter at different times before the finish line together with PO for different time intervals were determined. Sprints were classified as team Shimano (2013–2014) and team Quick-step (2016–2017), as well as won or lost. Results: The sprinter was highly successful, winning 14 out of the 21 sprints. At time intervals 10 to 5, 3 to 2, and 1.5 to 1 minute, POs were significantly lower in team Quick-step compared with team Shimano, but the sprinter was positioned further away from the front at 10, 2, 1.5, 1, and 0.5 minutes at team Quick-step compared with team Shimano. The PO was higher at time interval 0.5 to 0.25 minutes before the finish line with team Quick-step when compared with team Shimano. The position of the sprinter in the peloton in lost sprints was further away from the front at 0.5 minutes before the finish compared with won sprints, while no differences were noted for PO and the number of teammates between won and lost sprints. Conclusions: Differences in sprint tactics (Shimano vs Quick-step) influence the PO and position in the peloton during the sprint preparation. In addition, the position at 0.5 minutes before the finish line influences the outcome (won or lost) of the sprint.

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Luke Hogarth, Mark McKean, Max McKenzie, and Tyler Collings

Purpose: This study established the relationship between isometric midthigh pull (IMTP) peak force and court-based jumping, sprinting, and change of direction (COD) performance in professional netball players. The change in IMTP peak force in response to sport-specific training was also examined. Methods: IMTP peak force and court-based jumping, sprinting, and COD were collected in 18 female athletes contracted to a Suncorp Super Netball team. Linear regression models established the relationship between absolute and normalized strength values and court-based performance measures in the participant cohort. Changes in IMTP peak force and court-based performance measures were examined following 2 consecutive preseason training blocks in a subset of participants. Results: The IMTP peak force values normalized to body mass were found to be determinants of court-based jumping, sprinting, and COD performance in the participant cohort (R 2 = .34–.65, P ≤ .016). The participants showed increases in absolute (mean ± SE = 398 ± 68.5 N, P < .001, Hedge g = 0.70 [−0.05 to 1.35]) and normalized IMTP peak force (mean ± SE = 4.6 ± 0.78 N·kg−1, P < .001, Hedge g = 0.47 [−0.04 to 0.97]) over 2 consecutive training blocks that coincided with improvements in jumping, sprinting, and COD performances. Conclusion: IMTP peak force is a determinant of court-based jumping, sprinting, and COD performance and is sensitive to training in professional netball players. These results support the utility of the IMTP test to monitor the development and maintenance of maximal lower body muscular strength in these athletes.

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Markus N.C. Williams, Vincent J. Dalbo, Jordan L. Fox, Cody J. O’Grady, and Aaron T. Scanlan

Purpose: To compare weekly training and game demands according to playing position in basketball players. Methods: A longitudinal, observational study was adopted. Semiprofessional, male basketball players categorized as backcourt (guards; n = 4) and frontcourt players (forwards/centers; n = 4) had their weekly workloads monitored across an entire season. External workload was determined using microsensors and included PlayerLoad (PL) and inertial movement analysis variables. Internal workload was determined using heart rate to calculate absolute and relative summated-heart-rate-zones workload and rating of perceived exertion (RPE) to calculate session-RPE workload. Comparisons between weekly training and game demands were made using linear mixed models and effect sizes in each positional group. Results: In backcourt players, higher relative PL (P = .04, very large) and relative summated-heart-rate-zones workload (P = .007, very large) were evident during training, while greater session-RPE workload (P = .001, very large) was apparent during games. In frontcourt players, greater PL (P < .001, very large), relative PL (P = .019, very large), peak PL intensities (P < .001, moderate), high-intensity inertial movement analysis events (P = .002, very large), total inertial movement analysis events (P < .001, very large), summated-heart-rate-zones workload (P < .001, very large), RPE (P < .001, very large), and session-RPE workload (P < .001, very large) were evident during games. Conclusions: Backcourt players experienced similar demands between training and games across several variables, with higher average workload intensities during training. Frontcourt players experienced greater demands across all variables during games than training. These findings emphasize the need for position-specific preparation strategies leading into games in basketball teams.

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Teun van Erp, Marcel Kittel, and Robert P. Lamberts

Purpose: To describe the intensity, load, and performance characteristics of a world-class sprinter competing in the Tour de France (TdF). Method: Power output (PO) data were collected from 4 editions of the TdF (2013, 2014, 2016, and 2017) and analyzed. Load, intensity distribution in 5 PO zones, and the maximal mean PO for multiple durations were quantified. Stages were divided in accordance with the 4 different editions of the TdF, as well as the 4 different stage types, that is, flat (FLAT), semimountainous (SMT), mountain (MT), and (team) time trials. In addition, based on their location within the stage, mountain passes were further classified as BEGINNING, MIDDLE, or END of the stage. Results: No differences in load, intensity, and performance characteristics were found when the 4 editions of the TdF were compared. Time trials were associated with higher intensities but a lower load compared to the other stage types. MT showed higher load and intensity values compared to FLAT and SMT stages. FLAT stages were higher in short maximal mean PO (≤1 min), whereas MT stages showed higher longer endurance maximal mean PO values (≥20 min). In addition, mountain passes situated at the BEGINNING of the stage were completed with a higher PO, cadence, and speed compared with mountain passes situated at the END. Conclusions: A world-class sprinter sustains a higher load and spends more time in the high-intensity zones when competing in the TdF than previously reported values suggested. To finish the MT stages as efficiently as possible, sprinters adopt a reverse pacing strategy.

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Zong-Yan Cai, Wen-Yi Wang, Yi-Ming Huang, and Chih-Min Wu

Purpose: The authors investigated the effect of foot cooling (FC) between sets in a leg press pyramid workout with resistance-trained participants. Methods: A total of 12 resistance-trained men (age = 21.8 [0.6] y; training experience = 1.7 [1] y) performed a pyramid workout, including 4 sets of 85% to 90% 1-repetition maximum leg press exercise to exhaustion with interset FC or noncooling in a repeated-measures crossover design separated by 5 days. The authors immersed the participants’ feet in 10°C water for 2.5 minutes between sets. Results: Two-way repeated-measures analysis of variance revealed that FC elicited significantly higher repetitions and electromyography (EMG) values of the vastus lateralis (simple main effect of condition) than did noncooling (P < .05) in the second (repetitions: 11 [3.5] vs 7.75 [3.2]; EMG: 63.4% [19.4%] vs 54.5% [18.4%]), third (repetitions: 8.9 [3.2] vs 6.4 [2.1]; EMG: 71.5% [17.4%] vs 60.6% [19.4%]), and fourth (repetitions: 7.5 [2.7] vs 5.1 [2.2]; EMG: 75.2% [19.6%] vs 59.3% [23.5%]) sets. The authors also detected a simple main effect of set in the FC and noncooling conditions on repetitions (P < .05) and in the FC condition on the vastus lateralis EMG values. Although the authors observed no time × trial interactions for the rating of perceived exertion, the authors observed main effects on the sets (7.7–9.6 vs 7.9–9.3, P < .05). Conclusions: Interset FC provides an ergogenic effect on a leg press pyramid workout and may offset fatigue, as indicated by higher repetitions and EMG response, without increasing perceived exertion.

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Pablo Nájera-Ferrer, Carlos Pérez-Caballero, Juan José González-Badillo, and Fernando Pareja-Blanco

Purpose: This study aimed to analyze the response to 4 concurrent training interventions differing in the training sequence and in the velocity loss (VL) threshold during strength training (20% vs 40%) on following endurance and strength performance. Methods: A randomized crossover research design was used. Sixteen trained men performed 4 training interventions consisting of endurance training (ET) followed by resistance training (RT), with 20% and 40% VL, respectively (ET + RT20 and ET + RT40), and RT with 20% and 40% VL, respectively, followed by ET (RT20 + ET and RT40 + ET). The ET consisted of running for 10 minutes at 90% of maximal aerobic velocity. The RT consisted of 3 squat sets with 60% of 1-repetition maximum. A 5-minute rest was given between exercises. The oxygen uptake throughout the ET and repetition velocity during RT were recorded. The blood lactate concentration, vertical jump, and squat velocity were measured at preexercise and after the endurance and strength exercises. Results: The RT40 + ET protocol showed an impaired running time along with higher ventilatory equivalents compared with those protocols that performed the ET without previous fatigue. No significant differences were observed in the repetitions per set performed for a given VL threshold, regardless of the exercise sequence. The protocols consisting of 40%VL induced greater reductions in jump height and squat velocity, along with elevated blood lactate concentration. Conclusions: A high VL magnitude (40%VL) induced higher metabolic and mechanical stress, as well as greater residual fatigue, on the following ET performance.

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Steffen Held, Anne Hecksteden, Tim Meyer, and Lars Donath

Purpose: The present intervention study examined the effects of intensity-matched velocity-based strength training with a 10% velocity loss (VL10) versus traditional 1-repetition maximum (1RM) based resistance training to failure (TRF) on 1RM and maximal oxygen uptake (V˙O2max) in a concurrent training setting. Methods: Using the minimization method, 21 highly trained rowers (4 females and 17 males; 19.6 [2.1] y, 1.83 [0.07] m, 74.6 [8.8] kg, V˙O2max:64.9[8.5]mL·kg1·min1) were either assigned to VL10 or TRF. In addition to rowing endurance training (about 75 min·d1), both groups performed strength training (5 exercises, 80% 1RM, 4 sets, 2–3 min interset recovery, 2 times/week) over 8 weeks. Squat, deadlift, bench row, and bench press 1RM and V˙O2max rowing-ergometer ramp tests were completed. Overall recovery and overall stress were monitored every evening using the Short Recovery and Stress Scale. Results: Large and significant group × time interactions (P < .03, ηp2>.23, standard mean differences [SMD] > 0.65) in favor of VL10 (averaged +18.0% [11.3%]) were observed for squat, bench row, and bench press 1RM compared with TRF (averaged +8.0% [2.9%]). V˙O2max revealed no interaction effects (P = .55, ηp2=.01, standard mean difference < .23) but large time effects (P < .05, ηp2>.27). Significant group × time interactions (P = .001, ηp2>.54, SMD > |0.525|) in favor of VL10 were also observed for overall recovery and overall stress 24 and 48 hours after strength training. Conclusions: VL10 serves as a promising means to improve strength capacity at lower repetitions and stress levels in highly trained athletes. Future research should investigate the interference effects of VL10 in strength endurance sports and its effects when increasing weekly VL10 sessions within one macrocycle.