Determining the Corticospinal Responses to Single Bouts of Skill and Strength Training Mason, J, Frazer, AK, Jaberzadeh, S, Ahtiainen, JP, Avela, J, Rantalainen, T, Leung, M, and Kidgell, DJ. Determining the corticospinal responses to single bouts of skill and strength training. J Strength Cond Res 33(9): 2299–2307, 2019—Neuroplastic changes in the primary motor cortex accompany performance improvements following motor practice. Recent evidence suggests that the corticospinal responses to strength and skill training are similar, following both a single session and repeated bouts of training, promoting discussion that strength training is a form of motor learning. However, these findings are limited by the lack of a light-load strength training group. Therefore, the aim of the current study was to determine whether a single session of heavy-load strength training, light-load strength training or skill training differentially modulates the corticospinal pathway. Transcranial magnetic stimulation was used to assess the excitatory and inhibitory circuitry of the motor cortex following a single session of skill training, and following a single session of light-load and heavy-load strength training. Following a single session of training, participants in all groups experienced comparable increases in corticospinal excitability (ranging from 38 to 46%, all p < 0.05); however, disparity was observed in the inhibitory responses. Corticospinal inhibition was reduced in all 3 single-sessions, although to a greater magnitude in the heavy-load and skill-training sessions (22 and 18% respectively, compared with 11% following light-load training, all p < 0.05). Short-interval intracortical inhibition was reduced immediately following single sessions of heavy-load strength training (40% p < 0.05) and skill training (47% p < 0.05), but remained unchanged the following light-load strength training session. It appears that the corticospinal responses to single sessions of different types of strength and skill training are task-dependent. These findings reinforce the notion that strength training, at least when heavily-loaded, can be considered a form of motor learning, potentially because of the sensory feedback involved. |
The Competition-Day Preparation Strategies of Strongman Athletes Winwood, PW, Pritchard, HJ, Wilson, D, Dudson, M, and Keogh, JWL. The competition-day preparation strategies of strongman athletes. J Strength Cond Res 33(9): 2308–2320, 2019—This study provides the first empirical evidence of the competition-day preparation strategies used by strongman athletes. Strongman athletes (n = 132) (mean ± SD: 33.7 ± 8.1 years, 178.2 ± 11.1 cm, 107.0 ± 28.6 kg, 12.8 ± 8.0 years general resistance training, 5.9 ± 4.8 years strongman implement training) completed a self-reported 4-page internet survey on their usual competition-day preparation strategies. Analysis of the overall group and by sex, age, body mass, and competitive standard was conducted. Ninety-four percent of strongman athletes used warm-ups in competition, which were generally self-directed. The typical warm-up length was 16.0 ± 8.9 minutes, and 8.5 ± 4.3 minutes was the perceived optimal rest time before the start of an event. The main reasons for warming up were injury prevention, to increase activation, and increase blood flow/circulation, temperature, and heart rate. Athletes generally stated that competition warm-ups were practiced in training. Dynamic stretching, foam rolling, and myofascial release work were performed during warm-ups. Warm-up intensity was monitored using the rate of perceived exertion, perceived speed of movement, and training load (as a percentage of 1 repetition maximum). Cognitive strategies were used to improve competition performance, and psychological arousal levels needed to increase or be maintained in competition. Electrolyte drinks, caffeine, and preworkout supplements were the commonly used supplements. These data will provide strongman athletes and coaches some insight into common competition-day preparation strategies, which may enhance competition performances. Future research could compare different competition-day preparation strategies in an attempt to further improve strongman competition performance and injury prevention. |
Effects of Citrulline Malate and Beetroot Juice Supplementation on Blood Flow, Energy Metabolism, and Performance During Maximum Effort Leg Extension Exercise Trexler, ET, Keith, DS, Schwartz, TA, Ryan, ED, Stoner, L, Persky, AM, and Smith-Ryan, AE. Effects of citrulline malate and beetroot juice supplementation on blood flow, energy metabolism, and performance during maximum effort leg extension exercise. J Strength Cond Res 33(9): 2321–2329, 2019—Citrulline malate (CitMal) and beetroot juice (BEET) are increasingly popular ergogenic aids, but few studies have rigorously investigated their effects on resistance exercise performance and underlying mechanisms. The current randomized, double-blind, crossover study evaluated the effects of CitMal and BEET supplementation on blood flow, metabolic efficiency, and performance during maximal isokinetic leg extension exercise. After familiarization, 27 recreationally active men (age: 22 ± 4 years) completed 3 visits in which subjects ingested a treatment beverage (CitMal [8 g], BEET [400-mg nitrate], or placebo [PLA]), followed by a 2-hour rest period, warm-up, and 5 sets of 30 concentric leg extensions. Before and after exercise, ultrasound was used to measure diameter (aDIAM) and blood flow (aBF) of the superficial femoral artery, along with cross-sectional area and echo intensity of the vastus lateralis. Plasma analytes (lactate, nitrate/nitrite [NOx], and urea nitrogen [BUN]) were also assessed at these times, and indirect calorimetry was used to measure energy expenditure and respiratory exchange ratio before and during exercise. Resting NOx values were higher in BEET (233.2 ± 1.1 μmol·L−1) compared with CitMal (15.3 ± 1.1, p < 0.0001) and PLA (13.4 ± 1.1, p < 0.0001). Postexercise NOx values, adjusted for resting differences, were higher in BEET (86.3 ± 1.2 μmol·L−1) than CitMal (21.3 ± 1.1, p < 0.0001) and PLA (18.1 ± 1.1, p < 0.0001). No other variables were affected by treatment (all p > 0.05). While BEET increased NOx, neither treatment was found to enhance performance, blood flow, metabolic efficiency, nor the hormonal response to leg extension exercise. |
The Effect of 2 Weeks of Inactivated Probiotic Bacillus coagulans on Endocrine, Inflammatory, and Performance Responses During Self-Defense Training in Soldiers Hoffman, JR, Hoffman, MW, Zelicha, H, Gepner, Y, Willoughby, DS, Feinstein, U, and Ostfeld, I. The Effect of 2-Weeks of Inactivated Probiotic Bacillus coagulans on Endocrine, Inflammatory and Performance Responses During Self-Defense Training in Soldiers. J Strength Cond Res 33(9): 2330–2337, 2019—The effect of 2 weeks of inactivated Bacillus coagulans (iBC) ingestion on performance and inflammatory cytokines was examined during a self-defense course in soldiers. Sixteen male soldiers were randomly assigned to either iBC (n = 8) or placebo (PL; n = 8) in this double-blind study. Participants were garrisoned on base and participated in the same training tasks. Assessments were conducted in a single day before (PRE) and after the supplementation period (POST). During each testing session, participants were assessed for vertical jump power (VJP), muscle endurance, simulated casualty drag, and 2 100-m shuttle runs. Resting blood measures for testosterone, cortisol, creatine kinase, and inflammatory cytokines were also assessed. Mann-Whitney analysis of change (Δ) scores indicated no significant change (p's > 0.05) in any of the performance or blood variables. However, a trend (p = 0.089) was noted in the Δ score for VJP in iBC compared with PL. In addition, trends were observed in the change in IL-10 (p = 0.057) and IFNγ (p = 0.057). Magnitude based inferential analysis indicated that changes in VJP and simulated casualty drag were likely beneficial (90.7 and 80.4% likelihood effect, respectively) for iBC. In addition, iBC supplementation very likely augmented IL-10 concentrations, but was possibly negative for changes in IL-6, and likely negative for changes in TNFα and IFNγ. Changes in all other performance and blood markers were unclear. Results indicated that 2 weeks of iBC supplementation appeared to be beneficial for maintaining power and short-term speed performance, while attenuating the inflammatory response during intense training in a military self-defense course. |
Load-Carriage Conditioning Elicits Task-Specific Physical and Psychophysical Improvements in Males Wills, JA, Saxby, DJ, Glassbrook, DJ, and Doyle, TLA. Load-carriage conditioning elicits task-specific physical and psychophysical improvements in males. J Strength Cond Res 33(9): 2338–2343, 2019—Load carriage is a requirement of many military roles and is commonly used as an assessment of soldier physical readiness. Loaded, compared with unloaded, walking tasks elicit increased physical demands, particularly around the hip joint, which can exceed the initial capacity of military personnel. This study aimed to identify and characterize physical performance responses to a lower-limb focused physical training program targeted toward load-carriage task demands. Fifteen healthy male civilians (22.6 ± 1.5 years, 1.82 ± 0.06 m, and 84.1 ± 6.9 kg) completed a 10-week physical training program consisting of resistance training and weighted walking. A load-carriage task representing the Australian Army All Corps minimum standard (5 km at 5.5 km·h−1, wearing a 23-kg torso-borne vest) was completed before and on completion of the 10-week training program. Heart rate and rating of perceived exertion measures were collected throughout the load-carriage task. The performance measures of countermovement and squat jumps, push-ups, sit-ups, and beep test were performed before, mid-way, and on completion (weeks 0, 6, and 11) of the 10-week training program. Psychophysical performance, as measured by rating of perceived exertion, significantly decreased (p < 0.05) during the load-carriage task after training, demonstrating improvements in psychophysical responses. The training program resulted in significant increases in squat jump maximal force, push-ups, sit-ups (p < 0.05), and estimated maximal oxygen uptake (p < 0.05). Physical performance improvements and positive physiological adaptations to a load-carriage task were elicited in males after completing a 10-week training program. Military organizations could use this evidence-based training program to efficiently train soldiers to improve their load-carriage capacity. |
A Genome-Wide Association Study of Sprint Performance in Elite Youth Football Players Pickering, C, Suraci, B, Semenova, EA, Boulygina, EA, Kostryukova, ES, Kulemin, NA, Borisov, OV, Khabibova, SA, Larin, AK, Pavlenko, AV, Lyubaeva, EV, Popov, DV, Lysenko, EA, Vepkhvadze, TF, Lednev, EM, Leońska-Duniec, A, Pająk, B, Chycki, J, Moska, W, Lulińska-Kuklik, E, Dornowski, M, Maszczyk, A, Bradley, B, Kana-ah, A, Cięszczyk, P, Generozov, EV, and Ahmetov, II. A genome-wide association study of sprint performance in elite youth football players. J Strength Cond Res 33(9): 2344–2351, 2019—Sprint speed is an important component of football performance, with teams often placing a high value on sprint and acceleration ability. The aim of this study was to undertake the first genome-wide association study to identify genetic variants associated with sprint test performance in elite youth football players and to further validate the obtained results in additional studies. Using micro-array data (600 K–1.14 M single nucleotide polymorphisms [SNPs]) of 1,206 subjects, we identified 12 SNPs with suggestive significance after passing replication criteria. The polymorphism rs55743914 located in the PTPRK gene was found as the most significant for 5-m sprint test (p = 7.7 × 10−7). Seven of the discovered SNPs were also associated with sprint test performance in a cohort of 126 Polish women, and 4 were associated with power athlete status in a cohort of 399 elite Russian athletes. Six SNPs were associated with muscle fiber type in a cohort of 96 Russian subjects. We also examined genotype distributions and possible associations for 16 SNPs previously linked with sprint performance. Four SNPs (AGT rs699, HSD17B14 rs7247312, IGF2 rs680, and IL6 rs1800795) were associated with sprint test performance in this cohort. In addition, the G alleles of 2 SNPs in ADRB2 (rs1042713 & rs1042714) were significantly over-represented in these players compared with British and European controls. These results suggest that there is a genetic influence on sprint test performance in footballers, and identifies some of the genetic variants that help explain this influence. |
Fitness Characteristics of Elite and Subelite Male Ice Hockey Players: A Cross-Sectional Study Vigh-Larsen, JF, Beck, JH, Daasbjerg, A, Knudsen, CB, Kvorning, T, Overgaard, K, Andersen, TB, and Mohr, M. Fitness characteristics of elite and subelite male ice hockey players: A cross-sectional study. J Strength Cond Res 33(9): 2352–2360, 2019—The purpose was to evaluate fitness profiles in elite (age 23.5 ± 4.4 years) and subelite (age 19.4 ± 3.1 years) male ice hockey players. Twenty teams from the best (n = 164) and second-best (n = 132) Danish ice hockey division were assessed in-season using a field-test battery consisting of off-ice measurements of countermovement jump (CMJ) performance and body composition, as well as performance tests on the ice. These included the submaximal and maximal Yo-Yo intermittent recovery ice hockey tests, level 1 (Yo-Yo IR1-IHSUB and Yo-Yo IR1-IHMAX), the 5-10-5 pro-agility test, and a straight-line sprint test. Elite players were heavier (85.7 ± 8.1 vs. 80.8 ± 10.0 kg, p ≤ 0.05) and had a higher skeletal muscle mass (41.9 ± 3.9 vs. 38.8 ± 4.7 kg, p ≤ 0.05) than subelite players. Moreover, elite players elicited a superior CMJ (50.1 ± 6.1 vs. 44.9 ± 5.4 cm, p ≤ 0.05), agility (4.76 ± 0.17 vs. 4.96 ± 0.22 seconds, p ≤ 0.05), and sprint (4.49 ± 0.16 vs. 4.71 ± 0.19 seconds, p ≤ 0.05) performance. Finally, elite players outperformed subelite players in Yo-Yo IR1-IHSUB (79.7 ± 6.8 vs. 88.0 ± 5.4% HRmax, p ≤ 0.05) and Yo-Yo IR1-IHMAX tests (2,434 ± 414 vs. 1,850 ± 499 m, p ≤ 0.05). Top elite teams performed. 1.1 and 7% better than bottom elite teams on the agility and CMJ test (p ≤ 0.05), whereas differences approached significance for sprint (p = 0.08) and Yo-Yo IR1-IHMAX (p = 0.08) performance in favor of top-tier teams. No differences were observed between forwards and defensemen. In conclusion, elite-level ice hockey requires a high level of fitness in terms of muscle mass and explosive strength, as well as a well-developed high-intensity intermittent exercise capacity. In addition, these demands seem to apply for both forwards and defensemen. |
Strength and Conditioning Practices in Adolescent Rugby Players: Relationship With Changes in Physical Qualities Weakley, JJS, Till, K, Darrall-Jones, J, Roe, GAB, Phibbs, PJ, Read, DB, and Jones, BL. Strength and conditioning practices in adolescent rugby players: relationship with changes in physical qualities. J Strength Cond Res 33(9): 2361–2369, 2019—Adolescent rugby players benefit from the implementation of resistance training. However resistance training practices and how they influence short-term physical change is unknown. Therefore, the purpose of this study was to quantify resistance training practices, evaluate physical development, and relate these changes to resistance training variables across 12 weeks in adolescent rugby union players. Thirty-five male adolescent rugby union players participated in the study with subjects completing an anthropometric and physical testing battery before and after a 12-week in-season mesocycle. Subjects recorded resistance training frequency, exercises, repetitions, load, minutes, and rating of perceived exertion for each session using weekly training diaries during the 12-week period. Paired sample t tests and Cohen's d effect sizes were used to assess change, whereas Pearson correlation coefficients assessed relationships between variables. Resistance training practices were variable, although significant (p ≤ 0.05) improvements in body mass, countermovement jump (CMJ) height, front squat, bench press, and chin-up strength were observed. Resistance training volume load had moderate to strong relationships with changes in CMJ (r = 0.71), chin up (r = 0.73), and bench press (r = 0.45). Frequency of upper and lower-body compound exercises had significant moderate to large relationships with changes in CMJ (r = 0.68), chin up (r = 0.65), and bench press (r = 0.41). Across a 12-week in-season period, adolescent rugby union players have varying resistance training practices, although anthropometric and physical characteristics seem to improve. Given the observed relationships, increased volume loads through the implementation of free-weight compound exercises could be an effective method for improving physical qualities in young rugby players. |
Reliability of the Load-Velocity Relationship and Validity of the PUSH to Measure Velocity in the Deadlift Chéry, C and Ruf, L. Reliability of the load-velocity relationship and validity of the PUSH to measure velocity in the deadlift. J Strength Cond Res 33(9): 2370–2380, 2019—This study investigated the reliability between load and mean velocity, mean propulsive velocity, peak velocity, mean power, and peak power in the deadlift. Also, we looked at the validity of an inertial sensor (PUSH) and a linear-position transducer (Tendo) to measure velocity variables. Ten strength-trained men (23.4 ± 1.3 years) were involved in three 1 repetition maximum (1RM) testing sessions, separated by at least 72 hours. The protocol used 6 different lifting intensities, comprising 20, 40, 60, 80, 90, and 100% of 1RM. Reliability of the load-velocity and load-power relationship was assessed by comparing velocity and power measurements from session 2 and 3 for each relative %1RM. The validity of tested devices was analyzed regarding to each relative intensity by comparing results from each instrument to a reference instrument (GymAware). The findings revealed that intermediate intensities (ranging from 60 to 90% of 1RM) seem to be reliable. Furthermore, extreme points of the load-velocity curve (20, 40, and 100% of 1RM) were found to be less reliable and should therefore be used with caution when implemented as part of autoregulating strategies. Tendo produced measurements that were highly correlated with GymAware and thus, constitutes a valid and cheaper alternative. By contrast, measurements from the PUSH presented a low level of precision and accuracy. Therefore, PUSH cannot be considered as a valid tool to measure velocity variables in the deadlift. |
Acute Neuromuscular and Endocrine Responses to Two Different Compound Exercises: Squat vs. Deadlift Barnes, MJ, Miller, A, Reeve, D, and Stewart, RJ. Acute neuromuscular and endocrine responses to two different compound exercises: squat vs. deadlift. J Strength Cond Res 33(9): 2381–2387, 2019—Anecdotally, it is believed that the deadlift exercise brings about greater levels of central fatigue than other exercises; however, no empirical evidence exists to support this view. In addition, little is known about the acute endocrine response to heavy deadlift exercise and how this may differ from other similar compound exercises. Therefore, the aim of this study was to identify and compare the acute, neuromuscular and endocrine responses to squat and deadlift exercises. Ten resistance-trained males completed 8 sets of 2 repetitions at 95% of 1 repetition maximum. Maximum voluntary isometric contraction (MVIC) force of the quadriceps, along with measures of central (voluntary activation [VA] and surface electromyography) and peripheral (electrically evoked control stimulus) fatigue were made before and 5 and 30 minutes after exercise. In addition, salivary testosterone and cortisol were measured at these same time points. MVIC was reduced after the completion of both exercises (p = 0.007); however, no difference between exercises was evident. Similarly, although VA changed over time (p = 0.0001), no difference was observed between exercises. As a measure of peripheral fatigue, force from the control stimulus changed over time (p = 0.003) with a greater decrease evident after the squat (p = 0.034). Electromyography was reduced over time (p = 0.048) but no difference was seen between exercises. No change was seen in testosterone and cortisol. Although a greater absolute load and larger volume load were completed for the deadlift, no difference in central fatigue was evident between the 2 compound exercises. The greater peripheral fatigue observed after squat exercise may be due to the greater work completed by the quadriceps with this exercise. These results suggest that separate periodization, tapering, and programming considerations may be unnecessary when using the squat and deadlift to develop muscular strength. |
Πέμπτη 29 Αυγούστου 2019
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