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Mathieu Lacome, Simon Avrillon, Yannick Cholley, Ben M. Simpson, Gael Guilhem and Martin Buchheit

Aim: To compare the effect of low versus high volume of eccentric-biased hamstring training programs on knee-flexor strength and fascicle length changes in elite soccer players. Methods: A total of 19 elite youth soccer players took part in this study and were randomly assigned into 2 subgroups. For 6 weeks in-season, the groups performed either a low-volume (1 set per exercise; 10 repetitions in total) or a high-volume (4 sets; 40 repetitions) eccentric training of their knee flexors. After 6-weeks midtraining (MID), players performed the alternate training regimen. Each training set consisted of 4 repetitions of the Nordic hamstring exercise and 6 repetitions of the bilateral stiff-leg deadlift. Eccentric knee-flexor strength (NordBord) as well as biceps femoris long head and semimembranosus fascicle length (scanned with ultrasound scanner) were assessed during pretraining (PRE), MID, and posttraining (POST) tests. Results: Knee-flexor eccentric strength very likely increased from PRE to MID (low volume: +11.3% [7.8%] and high volume: 11.4% [5.3%]), with a possibly-to-likely increase in biceps femoris long head (+4.5% [5.0%] and 4.8% [2.5%]) and semimembranosus (+4.3% [4.7%] and 6.3% [6.3%]) fascicle length in both groups. There was no substantial changes between MID and POST. Overall, there was no clear between-group difference in the changes from PRE to MID and MID to POST for neither knee-flexor eccentric strength, biceps femoris long head, nor semimembranosus fascicle length. Conclusions: Low-volume knee-flexor eccentric training is as effective as a greater training dose to substantially improve knee-flexor strength and fascicle length in-season in young elite soccer players. Low volume is, however, likely more appropriate to be used in an elite team facing congested schedules.

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Adam Grainger, Paul Comfort and Shane Heffernan

Purpose: Partial body cryotherapy (PBC) has been shown to be beneficial for postexercise recovery; however, no study has demonstrated the effectiveness of PBC for recovery following elite rugby union training. Rugby union is a unique sport that involves high-velocity collisions and may induce greater performance decrements than other sports; thus, PBC could be beneficial. The application of PBC in “real world” has rarely been investigated during the competitive phase of a playing season and warranted investigation. Methods: In a counterbalanced sequential research design, professional rugby athletes (n = 18; age 25.4 [4.0] y; training age 7.2 [4.0] y; mass 99.8 [10.6] kg; height 188.3 [6.0] cm) were assigned to a 12-week PBC intervention, washout period (4 wk), and reassessed as their own controls. Self-reported well-being, muscle soreness, sleep quality, and countermovement jump height were assessed before and 40 hours after “real-world” training. Wilcoxon signed-rank tests and Cohen d were used for statistical analysis. Results: No differences were observed between PBC and control conditions (P > .05; d = 0.00–0.14) for well-being (−0.02% [0.08%] vs 0.01% [0.06%]), muscle soreness (−0.01% [0.11%] vs 0.01% [0.16%]), sleep quality (−0.03% [0.14%] vs 0.10% [0.29%]), or countermovement jump height (36.48–36.59 vs 38.13–37.52 cm; P = .54). Conclusions: These results suggest PBC is ineffective for the restoration of selected performance parameters during the performance maintenance phase of the competitive season. To ascertain the appropriation of its use, future investigations should seek to assess the use of cryotherapies at various phases of the elite rugby union competitive season.

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Erin Calaine Inglis, Danilo Iannetta, Daniel A. Keir and Juan M. Murias

Purpose: To evaluate whether the coherence in the oxygen uptake (V˙O2) associated with the respiratory compensation point (RCP), near-infrared spectroscopy-derived muscle deoxyhemoglobin ([HHb]) break point ([HHb]BP), and maximal lactate steady state (MLSS) would persist at the midpoint and endpoint of a 7-month training and racing season. Methods: Eight amateur male cyclists were tested in 3 separate phases over the course of a cycling season (PRE, MID, and POST). Testing at each phase included a ramp-incremental test to exhaustion to determine RCP and [HHb]BP. The PRE and POST phases also included constant power output rides to determine MLSS. Results: Compared with PRE, V˙O2 at both RCP and [HHb]BP was greater at MID (delta: RCP 0.23 [0.14] L·min−1, [HHb]BP 0.33 [0.17] L·min−1) and POST (delta: RCP 0.21 [0.12], [HHb]BP 0.30 [0.14] L·min−1) (P < .05). V˙O2 at MLSS also increased from PRE to POST (delta: 0.17 [12] L·min−1) (P < .05). V˙O2 was not different at RCP, [HHb]BP, and MLSS at PRE (3.74 [0.34], 3.64 [0.40], 3.78 [0.23] L·min−1) or POST (3.96 [0.25], 3.95 [0.32], 3.94 [0.18] L·min−1) respectively, and RCP (3.98 [0.33] L·min−1) and [HHb]BP (3.97 [0.34] L·min−1) were not different at MID (P > .05). PRE–MID and PRE–POST changes in V˙O2 associated with RCP, [HHb]BP, and MLSS were strongly correlated (range: r = .85–.90) and demonstrated low mean bias (range = −.09 to .12 L·min−1). Conclusions: At all measured time points, V˙O2 at RCP, [HHb]BP, and MLSS were not different. Irrespective of phase comparison, direction, or magnitude of V˙O2 changes, intraindividual changes between each index were strongly related, indicating that interindividual differences were reflected in the group mean response and that their interrelationships are beyond coincidental.

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Andrea Nicolò, Marco Montini, Michele Girardi, Francesco Felici, Ilenia Bazzucchi and Massimo Sacchetti

Purpose: Variables currently used in soccer training monitoring fail to represent the physiological demand of the player during movements like accelerations, decelerations, and directional changes performed at high intensity. We tested the hypothesis that respiratory frequency (f R) is a marker of physical effort during soccer-related high-intensity exercise. Methods: A total of 12 male soccer players performed a preliminary intermittent incremental test and 2 shuttle-run high-intensity interval training (HIIT) protocols, in separate visits. The 2 HIIT protocols consisted of 12 repetitions over 9 minutes and differed in the work-to-recovery ratio (15:30 vs 30:15 s). Work rate was self-paced by participants to achieve the longest possible total distance in each HIIT protocol. Results: Work-phase average metabolic power was higher (P < .001) in the 15:30-second protocol (31.7 [3.0] W·kg−1) compared with the 30:15-second protocol (22.8 [2.0] W·kg−1). Unlike heart rate and oxygen uptake, f R showed a fast response to the work–recovery alternation during both HIIT protocols, resembling changes in metabolic power even at supramaximal intensities. Large correlations (P < .001) were observed between f R and rating of perceived exertion during both 15:30-second (r = .87) and 30:15-second protocols (r = .85). Conclusions: Our findings suggest that f R is a good marker of physical effort during shuttle-run HIIT in soccer players. These findings have implications for monitoring training in soccer and other team sports.

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Daniel Boullosa

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Seiichiro Takei, Kuniaki Hirayama and Junichi Okada

Purpose: The optimal load for maximal power output during hang power cleans (HPCs) from a mechanical perspective is the 1-repetition-maximum (1RM) load; however, previous research has reported otherwise. The present study thus aimed to investigate the underlying factors that determine optimal load during HPCs. Methods: Eight competitive Olympic weight lifters performed HPCs at 40%, 60%, 70%, 80%, 90%, 95%, and 100% of their 1RM while the ground-reaction force and bar/body kinematics were simultaneously recorded. The success criterion during HPC was set above parallel squat at the receiving position. Results: Both peak power and relative peak power were maximized at 80% 1RM (3975.7 [439.1] W, 50.4 [6.6] W/kg, respectively). Peak force, force at peak power, and relative values tended to increase with heavier loads (P < .001), while peak system velocity and system velocity at peak power decreased significantly above 80% 1RM (P = .005 and .011, respectively). There were also significant decreases in peak bar velocity (P < .001) and bar displacement (P < .001) toward heavier loads. There was a strong positive correlation between peak bar velocity and bar displacement in 7 of 8 subjects (r > .90, P < .01). The knee joint angle at the receiving position fell below the quarter-squat position above 70% 1RM. Conclusions: Submaximal loads were indeed optimal for maximal power output for HPC when the success criterion was set above the parallel-squat position. However, when the success criterion was defined as the quarter-squat position, the optimal load became the 1RM load.

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Andrea R. Taliaferro and Sean M. Bulger

The purpose of this study was to determine expert consensus regarding the essential characteristics of adapted physical education practicum experiences for preservice physical educators. Researchers used a 3-round Delphi procedure involving the repeated circulation of an online questionnaire to a panel of content experts (N = 24). During Round 1, panelists generated 70 items in response to an open-ended prompt. Then, panelists rated these recommendations on importance and feasibility in the following rounds. After the third round, 23 items were eliminated for failing to reach consensus. Of the remaining 47 items, 24 were both very important and feasible (both means >6), 21 were very important (mean ≥ 6) and probably feasible (mean ≥ 5), and 2 were feasible (mean ≥ 6) and moderately important (mean ≥ 5). Four major themes were identified through a post hoc qualitative cluster analysis: program context, teaching and learning activities, outcomes/soft skills, and evaluation of instructor performance.

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Nathan Philip Hilton, Nicholas Keith Leach, Melissa May Craig, S. Andy Sparks and Lars Robert McNaughton

Enteric-formulated capsules can mitigate gastrointestinal (GI) side effects following sodium bicarbonate (NaHCO3) ingestion; however, it remains unclear how encapsulation alters postingestion symptoms and acid–base balance. The current study aimed to identify the optimal ingestion form to mitigate GI distress following NaHCO3 ingestion. Trained males (n = 14) ingested 300 mg/kg body mass of NaHCO3 in gelatin (GEL), delayed-release (DEL), and enteric-coated (ENT) capsules or a placebo in a randomized cross-over design. Blood bicarbonate anion concentration, potential hydrogen, and GI symptoms were measured pre- and postingestion for 3 hr. Fewer GI symptoms were reported with ENT NaHCO3 than with GEL (p = .012), but not with DEL (p = .106) in the postingestion phase. Symptom severity decreased with DEL (4.6 ± 2.8 arbitrary units) compared with GEL (7.0 ± 2.6 arbitrary units; p = .001) and was lower with ENT (2.8 ± 1.9 arbitrary units) compared with both GEL (p < .0005) and DEL (p = .044) NaHCO3. Blood bicarbonate anion concentration increased in all NaHCO3 conditions compared with the placebo (p < .0005), although this was lower with ENT than with GEL (p = .001) and DEL (p < .0005) NaHCO3. Changes in blood potential hydrogen were reduced with ENT compared with GEL (p = .047) and DEL (p = .047) NaHCO3, with no other differences between the conditions. Ingestion of ENT NaHCO3 attenuates GI disturbances for up to 3 hr postingestion. Therefore, ENT ingestion forms may be favorable for those who report GI disturbances with NaHCO3 supplementation or for those who have previously been deterred from its use altogether.

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Hunter S. Waldman, Brandon D. Shepherd, Brendan Egan and Matthew J. McAllister

In the present study, our team aimed to investigate the effects of acute ingestion of a ketone salt (KS) supplement on the cognitive performance in healthy college-aged males during a dual-stress challenge (DSC). Following a peak oxygen uptake test and DSC familiarization, 16 males completed a DSC while cycling at 60% of their respective peak oxygen uptake after ingesting either a commercially available racemic (D- and L-)β-hydroxybutyrate (β-OHB) KS (0.38 g/kg body mass) or a placebo, using a triple-blinded, crossover, and counterbalanced design. The participants consumed the KS or placebo at −60 and −15 min prior to the start of the DSC. Heart rate, rating of perceived exertion, and blood β-OHB and glucose were sampled throughout. The DSC consisted of a mental arithmetic challenge and a modified Stroop Color Word, which alternated every 2 min for 20 min. Upon completion of the DSC, responses for correct, incorrect, and no responses were recorded for the mental arithmetic challenge and Stroop Color Word. Blood β-OHB was elevated with KS by −15 min and remained so throughout (p < .001), peaking at 0.76 ± 0.32 mM. Blood glucose was lower with KS compared with the placebo at −15 and 10 min by 9% and 5%, respectively (both ps < .05). There were no differences between the treatments for heart rate, rating of perceived exertion, mental arithmetic challenge, or Stroop Color Word. Overall, this study suggests that KSs are not effective aids for enhancing cognitive performance during a DSC, which might partially be explained by the inability of currently available commercial KS supplements to elevate β-OHB blood concentrations above ∼1.0 mM.

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Yann Le Mansec, Jérôme Perez, Quentin Rouault, Julie Doron and Marc Jubeau

Purpose: To evaluate the effects of muscle fatigue on badminton performance during a smash stroke. Methods: In total, 17 young, well-trained players completed 20 forehand smashes twice (prefatigue and postfatigue protocol), and both speed and precision of the strokes were measured. The fatigue protocol consisted of 10 series of 10 maximal countermovement jumps (3-s rest in between) followed by 8 lunges. Perception of effort and countermovement-jump performance during each series were also measured to assess fatigue. Results: Shuttlecock speed decreased moderately (−3.3%) but significantly after the fatigue protocol (P < .001, ηp2=.671). Precision significantly decreased after the fatigue protocol (−10.3%, P = .001, ηp2=.473). The decrease in precision was mainly due to an increased number of faults (P = .006, ηp2=.378, d z = 0.756) and to a decrease in accuracy (P = .066, ηp2=.195, d z = 0.478). Conclusion: The present study showed that fatigue impairs performance during specific badminton skills. Moreover, by showing a slight decrease in speed and a large decrease in accuracy of the shuttlecock when fatigue is experienced, the present study suggested that, as previously observed in other racket sports, the speed of the missile appears to be the key factor used by the players to win the rally. Coaches and physical trainers should therefore develop interventions aiming to limit the negative impact of fatigue on badminton strokes.