Complex training: The effect of exercise selection and training status on postactivation potentiation in rugby league players

This study compared the postactivation potentiation (PAP) response of the hex bar deadlift (HBD) and back squat (BS) exercises. The PAP response between different levels of athletes was also compared. Ten professional and 10 amateur rugby league players performed 2 experimental sessions. Participants performed a countermovement jump (CMJ) before and 2, 4, 6, 8, 10, 12, 14, and 16 minutes after a conditioning activity (CA) that contained 1 set of 3 repetitions at 93% 1 repetition maximum of either HBD or BS. A force platform determined peak power output (PPO), force at PPO, velocity at PPO, and jump height of each CMJ. Surface electromyography (EMG) of the vastus lasteralis, rectus femoris, tibialis anterior, and gastrocnemius medialis of each participant's dominant leg was recorded during each CMJ. A further 10 participants performed a control trial without a CA. The HBD expressed PAP between 2 and 6 minutes post-CA, whereas the BS did not. The HBD exhibited a significantly (p ≤ 0.05) greater PAP response than the BS for PPO. There were no significant (p > 0.05) differences between stronger and weaker players. There were no significant (p > 0.05) changes in the EMG variables. These results suggest that HBD is a suitable CA for eliciting PAP in stronger and weaker athletes. Strength and conditioning coaches should consider the CA and time frame between the CA and the plyometric exercise for optimal PAP responses

Sources of Variability in Musculo-Articular Stiffness Measurement

The assessment of musculo-articular stiffness (MAS) with the free-oscillation technique is a popular method with a variety of applications. This study examined the sources of variability (load applied and frequency of oscillation) when MAS is assessed.Over two testing occasions, 14 healthy men (27.7±5.2 yr, 1.82±0.04 m, 79.5±8.4 kg) were measured for isometric maximum voluntary contraction and MAS of the knee flexors using submaximal loads relative to the individual's maximum voluntary contraction (MAS%MVC) and a single absolute load (MASABS).As assessment load increased, MAS%MVC (coefficient of variation (CV) = 8.1-12.1%; standard error of measurement (SEM) = 51.6-98.8 Nm-1) and frequency (CV = 4.8-7.0%; SEM = 0.060-0.075 s-1) variability increased consequently. Further, similar levels of variability arising from load (CV = 6.7%) and frequency (CV = 4.8-7.0%) contributed to the overall MAS%MVC variability. The single absolute load condition yielded better reliability scores for MASABS (CV = 6.5%; SEM = 40.2 Nm-1) and frequency (CV = 3.3%; SEM = 0.039 s-1).Low and constant loads for MAS assessment, which are particularly relevant in the clinical setting, exhibited superior reliability compared to higher loads expressed as a percentage of maximum voluntary contraction, which are more suitable for sporting situations. Appropriate sample size and minimum detectable change can therefore be determined when prospective studies are carried out. © 2013 Ditroilo et al

Physiological responses to pedaling on a water stationary bike at different immersion heights

Only a few studies[1-4] have investigated oxygen consumption (V’O2) and heart rate (HR) responses to pedaling on a stationary bike in water (WSB), while literature is still lacking on the effects elicited by variations in immersion depth. 14 subjects (8 M, 6 F, age 30±6y, weight 67±14kg, BMI 22.8±2.3kg/m2, fat mass 21,4±3%) performed 2 testing sessions and 2 exercise sessions: i) dry-land incremental exercise test (cycle-ergometer) to age-predicted maximum HR (HR); ii) underwater (hip-height) incremental exercise test (on a WSB) to exhaustion; iii/iv) two 2-stage (18-minutes each) underwater pedaling exercises on a WSB (Aqquatix S.r.l., Italy) at 2 different immersion heights (armpit/hip). Breath-by-breath V’O2 and beat-by-beat HR were recorded continuously throughout dry-land sessions. The intensities of the exercise sessions were 45%-55% (stage#1) and 70%-80% (stage#2) of the underwater V’O2 peak (a metronome was set at the V’O2 peak pedaling rate). A repeated-measures (2 exercise intensities) 2-way (armpit/hip heights) ANOVA was performed on each variable and the Bonferroni test was used for post-hoc comparisons. Compared to the hip-height condition, pedaling immersed at the armpit level elicited significantly lower V’O2 and HR (significant solely at high-intensity for HR) responses, either exercising at high (25.5±4.6 vs. 29.1±4.8 mL∙kg-1∙min-1; 127±14 vs. 140±19 beats∙min-1) or low (17.9±3.6 vs. 20.1±3.6 mL∙kg-1∙min-1; 105±16 vs. 110±15 beats∙min-1) intensity. While peak V’O2 didn’t differ significantly between dry-land and underwater tests (36.2±5.4 vs. 38.8±5.8 mL∙kg-1∙min-1), mean HRs at both intensities and both water heights were significantly lower when expressed as percentage of the HR resulting from the underwater test to exhaustion, rather than applying the 220-age prediction equation.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Repeated sprint ability and muscular responses according to the age category in elite youth soccer players

The aim of this study was to analyse the influence of age category on the performance and muscle response after a Repeated Sprint Ability (RSA) test in elite youth soccer players. 62 soccer players from three different age categories (Under 14 [n = 21], Under 16 [n = 20], and Under 18 [n = 21]) were selected to participate in this study. Players completed an RSA test (7 × 30 m) with a 20-s recovery between sprints. The muscular response to an electrical stimulus before and after the test of both the biceps femoris (BF) and the rectus femoris (RF) were evaluated using tensiomyography. A two-way ANOVA was used to analyse the differences in RSA parameters in each of the four distance-intervals (0–5; 5–25; 25–30; 0–30 m) between sprint and age category. The U14 age category (5.30 ± 0.30 s) showed higher mean sprint times than U16 (4.62 ± 0.20 s) and U18 (4.46 ± 0.17 s) throughout the entire test (p 0.05), although the delay time (Td) of the muscle was significantly lower after the RSA test in U16 players (−1.53 ms, CI95%: −2.607 to −0.452; ES: 0.38) and U18 players (−1.11 ms, CI95%: −2.10 to −0.12; ES: 0.22). In conclusion, this study revealed an increase in physical performance and muscle response variability after a repeated sprint ability test in the U16's and over. The fatigue induced by the RSA test did not show differences depending on the age of the players, although muscle mechanical properties were altered after the RSA test in U16 and U18 soccer players. Physical performance and muscle response can be complementary variables in managing fatigue according to the age category in soccer players.Sin financiación3.367 JCR (2019) Q1, 20/81 Physiology1.211 SJR (2019) Q2, 52/186 Physiology, 31/107 Physiology (medical)No data IDR 2019UE

The effect of accommodating resistance on the post-activation potentiation response in Rugby League players

This study examined the post-activation potentiation (PAP) response of two conditioning activities (CA), the hexbar deadlift (HBD) and back squat (BS), combined with accommodating resistance; this adds a percentage of the total resistance during the exercise. Twenty amateur rugby league players performed two experimental trials and a control trial without a CA. Participants performed a countermovement jump (CMJ) before and 30, 90, and 180 seconds after one set of three repetitions of each CA at 70% 1 repetition maximum (RM), with up to an additional 23% 1RM from accommodating resistance. Peak power output (PPO), force at PPO, velocity at PPO and jump height were calculated for each CMJ. Surface electromyography (EMG) of the vastus lasteralis (VL), rectus femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GM) were also measured. Repeated-measures analysis of variance revealed no significant (p > 0.05) PAP response for either exercise condition when comparing CMJ variables to baseline values, nor were there any significant (p > 0.05) differences between exercise conditions. However, individualized recovery intervals (baseline vs. maximum potentiation response) demonstrated significant (p ≤ 0.05) improvements in PPO (3.99 ± 4.99%), force at PPO (4.87 ± 6.41%), velocity at PPO (4.30 ± 5.86%), jump height (8.45 ± 10.08%), VL EMG (20.37 ± 34.48%), BF EMG (22.67 ± 27.98%), TA EMG (21.96 ± 37.76%) and GM EMG (21.89 ± 19.65%). Results from this study must be interpreted with caution; however, it is conceivable that athletic performance can be acutely enhanced when complex training variables are individualized

Tibial impacts and muscle activation during walking, jogging and running when performed overground, and on motorised and non-motorised treadmills.

Purpose To examine tibial acceleration and muscle activation during overground (OG), motorised treadmill (MT) and non-motorised treadmill conditions (NMT) when walking, jogging and running at matched velocities. Methods An accelerometer recorded acceleration at the mid-tibia and surface EMG electrodes recorded rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA) and soleus (SL) muscle activation during OG, MT and NMT locomotion whilst walking, jogging and running. Results The NMT produced large reductions in tibial acceleration when compared with OG and MT conditions across walking, jogging and running conditions. RF EMG was small-moderately higher in the NMT condition when compared with the OG and MT conditions across walking, jogging and running conditions. ST EMG showed large and very large increases in the NMT when compared to OG and MT conditions during walking whilst SL EMG found large increases on the NMT when compared to OG and MT conditions during running. The NMT condition generated very large increases in step frequency when compared to OG and MT conditions during walking, with large and very large decreases during jogging and very large decreases during running. Conclusions The NMT generates large reductions in tibial acceleration, moderate to very large increases in muscular activation and large to very large decreases in cycle time when compared to OG and MT locomotion. Whilst this may decrease the osteogenic potential of NMT locomotion, there may be uses for NMTs during rehabilitation for lower limb injuries

Exploratory Research in Sport and Exercise Science

Quantitative exploratory research implies a flexible examination of a dataset with the purpose of finding patterns, associations, and interactions between variables to help formulate a hypothesis, which should then be severely tested in a future confirmatory study. In many fields, including sport and exercise science, exploratory research is not openly reported. At the same time, experts agree that most of the research we conduct is indeed exploratory, and that exploration is a crucial step in scientific knowledge generation. Using a flowchart, we review how data are typically collected and used, and we distinguish exploratory from confirmatory studies by arguing that data-driven analyses, where the Type I and Type II error rate cannot be controlled, is what characterises exploratory research. Even if a study tests a hypothesis in an error-controlled manner, often it also includes exploratory analyses on the data. We ask which factors increase the quality and value of exploratory analyses, and highlight large sample sizes, uncommon sample compositions, rigorous data collection, widely used measures, observing a logical and coherent pattern across multiple variables, and the potential for generating new research questions as the main factors. Finally, we provide guidelines for carrying out and transparently writing up an exploratory study

The benefits of preregistration and Registered Reports

Practices that introduce systematic bias are common in most scientific disciplines, including toxicology. Selective reporting of results and publication bias are two of the most prevalent sources of bias and lead to unreliable scientific claims. Preregistration and Registered Reports are recent developments that aim to counteract systematic bias and allow other scientists to transparently evaluate how severely a claim has been tested. We review metascientific research confirming that preregistration and Registered Reports achieve their goals, and have additional benefits, such as improving the quality of studies. We then reflect on criticisms of preregistration. Beyond the valid concern that the mere presence of a preregistration may be mindlessly used as a proxy for high quality, we identify conflicting viewpoints, several misunderstandings, and a general lack of empirical support for the criticisms that have been raised. We conclude with general recommendations to increase the quality and practice of preregistration

The effectiveness of two novel techniques in establishing the mechanical and contractile responses of biceps femoris

Portable tensiomyography (TMG) and myotonometry (MMT) devices have been developed to measure mechanical and contractile properties of skeletal muscle. The aim of this study was to explore the sensitivity of the aforementioned techniques in detecting a change in passive mechanical properties of the biceps femoris (BF) muscle as a result of change in knee joint angle (i.e. muscle length). BF responses were assessed in 16 young participants (23.4 ± 4.9 years), at three knee joint angles (0°, 45° and 90°), for maximal isometric torque (MIT) along with myo-electrical activity. Contractile and mechanical properties were measured in a relaxed state. Inter-day reliability of the TMG and MMT was also assessed. MIT changed significantly (p < 0.01) across the three angles, so did stiffness and other parameters measured with MMT (p < 0.01). Conversely, TMG could detect changes only at two knee angles (0° and 45°, p < 0.01), when there is enough tension in the muscle. Reliability was overall insufficient for TMG whilst absolute reliability was excellent (coefficient of variation < 5%) for MMT. The ability of MMT more than TMG to detect an inherent change in stiffness can be conceivably exploited in a number of clinical/therapeutic applications that have to do with unnatural changes in passive muscle stiffness

The Effect of Complex Training on Muscle Architecture in Rugby League Players

PURPOSE: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on muscle architecture in rugby league players during a 6-week mesocycle. METHODS: Twenty-four rugby league players competing in the British University & Colleges Sport (BUCS) Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk), which involved alternating high-load resistance exercise with plyometric exercise in the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Muscle thickness (MT), pennation angle, and fascicle length (Lf) were assessed for the vastus lateralis (VL) and gastrocnemius medialis using ultrasound imaging. RESULTS: Both TCT and VRCT groups significantly improved VL MT and VL Lf compared with control (all P < .05). Standardized within-group changes in MT and Lf (Cohen dav ± 95% CI) were moderate for TCT (dav = 0.91 ± 1.0; dav = 1.1 ± 1.1) and unclear for VRCT (dav = 0.44 ± 0.99; dav = 0.47 ± 0.99), respectively. Differences in change scores between TCT and VRCT were unclear. CONCLUSIONS: VRCT and TCT can be utilized during the competitive season to induce favorable MT and Lf muscle architecture adaptations for the VL. TCT may induce greater muscle architecture adaptations of the VL, whereas VRCT may be of more practical value given the shorter intracontrast rest interval between resistance and plyometric exercises