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Neuromuscular training for youth athletes typically involves calisthenics, plyometric exercises, change of direction drills and speed training. Ample research has demonstrated that pre-pubertal athletes can significantly improve markers of performance with neuromuscular training despite experiencing minimal changes in muscle hypertrophy. However, the timing or sequencing of neuromuscular training may impact training adaptations. For example, when athletes train for neuromuscular development and aerobic fitness conditioning on the same day, there is potential for the interference effect to limit performance gains. This is an important consideration for coaches of youth athletes who typically do not have the luxury of holding separate sessions for specific training qualities on separate days due to time constraints. Therefore, it would be useful for coaches to know the optimal sequencing of training qualities when limited to a single training session ~3 times per week.
A new study published ahead of print in the Journal of Strength and Conditioning Research evaluated the sequencing effects of neuromuscular training and traditional tennis training on performance markers in elite youth tennis players. A total of 16 trained tennis players (~13 years old) were matched and randomly allocated to a group who performed neuromuscular training before tennis practice and a group who performed neuromuscular training after tennis practice. The neuromuscular training protocol was the same for both groups and involved maximal countermovement jumps, box jumps, drop landings, medicine ball throws, hurdle hops, depth-jumps, lateral bounds, acceleration/deceleration and change of direction drills. Workouts were performed 3 times per week for 5 weeks. Workouts were held either 30 mins before or after tennis practice. Before and after the training intervention, all subjects were tested for sprinting speed, 5-0-5 agility, countermovement jump, overhead medicine ball throw and tennis serve velocity.
The results showed that the group who performed neuromuscular training before tennis practice experienced small to moderate improvements in sprinting speed, agility, countermovement jump, overhead medicine ball throw and serve velocity (effect sizes ranged from 0.22 – 1.08). By contrast, the group who performed neuromuscular training following tennis practice experienced trivial or negative changes for all performance markers with agility showing the largest decrement. This study demonstrates that neuromuscular training can effectively improve markers of performance in youth tennis players when performed prior to tennis practice, but not after. Therefore, coaches should refrain from implementing this type of training after team practices.
Fernandez-Fernandez, J. et al. Sequencing Effects of Neuromuscular Training on Physical Fitness in Youth Elite Tennis Players. Journal of Strength and Conditioning Research. In press.
Coaches often include a combination of progressive plyometric training and resistance training into strength and conditioning programs for their athletes. Plyometric exercises are typically performed immediately following the warm-up and before strength training exercises. Alternatively, plyometrics are sometimes performed on the practice field, separate from strength training workouts. However, time constraints and limited availability to strength training equipment make it difficult for many teams to perform resistance training workouts. With the goal of enhancing athletic performance variables, it would be useful for coaches to know if coaches can still achieve desired training effects from plyometric exercises in the absence of resistance training.
A new study published ahead of print in the Journal of Strength and Conditioning Research compared the effects of progressive plyometric training and progressive resistance training on strength and performance markers. A sample of thirty healthy males, approximately 21 years of age were divided into a plyometric group (n=10) a resistance training group (n=10) and a control group (n=10). The training groups performed workouts twice per week for eight weeks with 72 hours between sessions while the control group abstained from exercise. The plyometric exercises included various hops, jumps, bounds and skips in various planes. The resistance training program involved squats, leg press, leg extensions, leg curls and calf raises. Intensity progressed from 70% to 80% of 1 RM while number of repetitions progressively decreased from 3 sets of 12 to 3 sets of 8. Before and after the training interventions, all subjects were tested for 1 RM back squat, vertical jump, broad jump, 20 m sprint and 505 agility.
The results showed that the plyometric group demonstrated significant improvements in broad jump, vertical jump and 1 RM back squat compared to the control group. The improvement in vertical jump observed in the plyometric group was also significantly greater than the improvement observed in the resistance training group. The only significant improvement observed in the resistance training group was for 1 RM back squat compared to control. No groups significantly improved sprint or agility performance. This study demonstrates the effectiveness of plyometric training for improving lower body explosive strength while also improving lower body maximal strength. It would appear that more specific training would be needed to improve speed and agility performance.
Whitehead, M. T., Scheett, T. P., McGuigan, M. R., & Martin, A. V. (2017). A Comparison of the Effects of Short-Term Plyometric and Resistance Training on Lower Body Muscular Performance. The Journal of Strength & Conditioning Research.
Various forms of stretching have long been an integral component to the pre-training warm-up routine. Teams would often line up in rows on the field and count out their ~15 seconds stretches in unison, starting from their upper body and moving progressively to their lower body. However, the effects of static stretching on strength and power performance were called into question. This sparked a line of research that aimed to determine if athletes should static stretch before training and competing. It’s been demonstrated that excessive static stretching (e.g., holding stretches for > 60 s) may cause acute reductions in force and power output of the stretched muscles. However, factors such as stretching type, proximity to training/competition and inclusion of an active warm-up following stretching need to be considered, as these may modify the effects of static stretching on performance.
A new study published ahead of print in the Journal of Strength and Conditioning Research compared the effects of various stretching protocols on jumping and sprinting performance in a team of soccer players. In a randomized, cross-over design, 12 male soccer players (17-18 years old) performed four stretching interventions and a control condition followed by range of motion (sit and reach test) squat-jump, countermovement-jump and 30 m sprint testing. Subjects performed two familiarization sessions to learn the stretching protocols. The interventions involved 3 sets of 30 second active stretching (holding elongated stretch position), ballistic stretching (oscillating stretch every second), passive stretching (partner-assisted technique causing a more intense stretch) and proprioceptive-neuromuscular facilitation (PNF) stretching using the hold-relax technique of the lower limbs. All stretching was supervised or assisted by a physical therapist. The control condition involved passive rest for the same time duration.
The results showed that all four of the stretching interventions significantly improved range of motion in the sit and reach test compared to control. Both passive stretching and PNF stretching protocols resulted in decrements in jump height, peak power and relative power during both the squat-jump and countermovement jump (mean reductions ranged from -1.33 to -5.98%). By contrast, the effects of passive and ballistic stretching on jump performance were trivial. While no significant differences were detected for sprinting speed, the control condition had the fastest sprint times and the PNF stretching resulted in the slowest sprint time (very large effect size). Therefore, it appears that 3 sets of 30 seconds of active or ballistic stretching can improve range of motion without adversely affecting performance. However, passive and PNF stretching should be avoided prior to training due to the observed reductions in jumping performance.
de Paula Oliveira, L., Vieira, L. H. P., Aquino, R., Manechini, J. P. V., Santiago, P. R. P., & Puggina, E. F. (2017). Acute Effects Of Active, Ballistic, Passive And Proprioceptive Neuromuscular Facilitation Streching On Sprint And Vertical Jump Performance In Trained Young Soccer Players. The Journal of Strength & Conditioning Research.
With the development of practical sleep-monitoring devices, empirical evidence has steadily emerged from research that supports what coaches have known all along; sleep quality affects performance. Valuing sleep pays off in how athletes feel, how they train and how they perform. Therefore, coaches need to take a proactive role in addressing sleep quality with athletes and educating them on how to get more restful sleep. It would also be useful for coaches to understand how various factors might affect sleep quality. For example, proximity to competition may result in heightened levels of anxiety which may make it difficult for athletes to fall asleep. Additionally, training loads must also be considered given that moderate levels of exercise tend to enhance sleep quality while excessively high training loads can reduce sleep quality. Ultimately, more research in this area is needed to guide coaches and their athletes.
A new study published ahead of print in the European Journal of Sport Science evaluate sleep quality and quantity in gymnasts and their relationships with training load and performance. A sample of 26 elite female gymnasts ranging in age from ~12-18 years participated in the study. Total sleep time, sleep efficiency (the ratio of time spent asleep versus time spent in bed) and training load derived from session rating of perceived exertion (sRPE) were retrospectively analyzed. Performance level was inferred from coaches rankings of athletes in addition to World Championship qualification ranking. Data were retrospectively analyzed to establish associations between markers of sleep quality, performance and training load.
The results showed that when evaluated as a group (n = 26), total sleep time was lower during the week compared to weekends (Effect Size, ES = -1.12). The youngest athletes (<13 years) tended to have the highest total sleep time and sleep efficiency. A higher training load was associated with lower total sleep time on the subsequent night. For the World Championship competitors, total sleep time was lower on the night before qualifications relative to average total sleep time throughout the World Championship competitions (ES = -0.95). Interestingly, total sleep time was significantly related with coach ranking (r = -0.86) where athletes with greater total sleep tended to have better rankings. In contrast, athletes experiencing higher training loads tended to have a worse World Championship (r = 0.83) and coach (r = 0.89) ranking. Therefore, it appears that excessive training loads may be hindering sleep quality and performance in athletes.
Dumortier, J., Mariman, A., Boone, J., Delesie, L., Tobback, E., Vogelaers, D., & Bourgois, J. G. (2017). Sleep, training load and performance in elite female gymnasts. European Journal of Sport Science, 1-11.
Access to more affordable technologies such as accelerometers and linear position transducers that sync with mobile phones and tablet devices has lead to an increase in the monitoring of bar speed in the weight room. In turn, a substantial increase in research on how bar speed can be practically implemented for athletes has been developed. Some coaches use a specific velocity drop-off points (e.g., 10%) as the threshold for terminating a set in effort to maintain high quality repetitions. Others use barbell velocity to predict 1RM via simple linear regression equation. Bar velocity is also used by some coaches to assess fatigue and recovery status by evaluating bar speed during a standardized movement with a standardized load. What remains to be determined is what variables explain or contribute to bar speed and more importantly, how bar speed relates with performance markers such as sprinting speed.
A new study published ahead of print in the Journal of Strength and Conditioning Research evaluated relationships between bar speed characteristics during the back squat with anthropocentric, training experience and athletic performance variables. A sample of 21 collegiate athletes (13 football players and 8 softball players) from an NAIA institution participated in the study. Anthropmetry, including size, stature and femur length and training history (years of training with the back squat and recent frequency of use) was acquired at the laboratory. Sprinting speed over 36.6. m was evaluated on an outdoor football field and the best time from two attempts was recorded. Following the sprint, all subjects were tested in the barbell back squat for 1 RM. During the squat, a linear position transducer (Tendo Unit) was used to measure peak and average velocity and power.
The results showed that average concentric barbell velocity during the back squat 1 RM did not significantly relate with any anthropometric, performance or training experience variables. In contrast, peak concentric barbell velocity during the back squat 1 RM was significantly related with 36.6 m sprint speed (r = -0.612). However, relative strength (1RM squat / body mass) (r = -0.720) and relative peak power during the squat (r = -0.779) were both stronger predictors of 36.6 m sprinting speed than average or peak concentric velocity markers. Therefore, coaches may be able to use relative strength or peak relative power during the back squat as a surrogate for speed testing. Moreover, this study might also suggest(and in line with previous research) that improving lower-body relative strength and power will improve sprinting speed.
Fahs, CA. et al. An Analysis of Factors Related to Back Squat Concentric Velocity. Journal of Strength and Conditioning Research. In press.
There are many instances in team sports where matches are held every day or every other day. This occurs during tournament play as well as congested match fixtures. Competitions are considerably more taxing on players than practices, often resulting in greater soreness and muscle damage. Therefore, it is reasonable for coaches to be concerned about player recovery status after 1 or 2 consecutive games in a row. Accordingly, it would be useful for coaches and sports medicine personnel to understand the physiological and biomechanical changes that players experience from repeated match exposure. This would enhance monitoring protocols, facilitate recovery interventions and influence player substitution. As a result, teams may experience less injuries and hopefully achieve more successful match outcomes.
A new study published ahead of print in the Journal of Strength and Conditioning Research assessed the physiological, psychometric and biomechanical responses to simulated soccer matches across a five day period. A sample of 10 semi-professional male soccer players performed 90-minute treadmill-based soccer match simulations in laboratory controlled conditions three times with 48 hours separating each trial. The trials were held at the same time of day, corresponding to regular match times. Heart rate, oxygen consumption, electromyography of the biceps femoris muscle and blood lactate were measured throughout the standardized soccer simulation protocol. Before and after each trial, knee flexor peak torque was evaluated. Perceived muscle soreness was rated before and after each training session.
The results showed that heart rate, blood lactate and oxygen consumption progressively increased throughout each session, but did not differ between sessions. This indicates that effort and intensity drifts upward throughout a match. Biceps femoris electromyography was significantly higher during the first half of each trail relative to the second half. In addition, biceps femoris activity was lower in trial two and three compared to trial one. Peak knee flexor torque was significantly lower in trial three compared with trial one. Thus, the decreased muscle function as a result of fatigue may increase hamstring injury risk. Finally, muscle soreness was significantly higher at trial three compared with trial one. Clearly, neuromuscular performance appears to be affected from frequent competition simulations. Therefore, coaches should closely monitor playing time in starters to limit fatigue accumulation as injury risk may be heightened.
Page, R. M., Marrin, K., Brogden, C. M., & Greig, M. (2017). The physical response to a simulated period of soccer-specific fixture congestion. The Journal of Strength & Conditioning Research. In press.
The majority of research evaluating recovery status in American football players has evaluated endocrine markers, biochemical markers (i.e., creatine kinase) and subjective ratings of well-being. However, little attention has been given to cardiovascular markers. Football is often thought of as a predominantly anaerobic sport which may cause some to under appreciate the importance of having a well developed cardiovascular system for meeting the physical demands of training. Moreover, the cardiovascular system plays an important role in facilitating recovery between intermittent bouts and in the post-exercise period. A popular marker of cardiovascular recovery among sports teams is resting heart rate variability (HRV). HRV reflects autonomic regulation of the heart with specific parameters representing parasympathetic influence. It is thought that cardiovascular homeostasis is attained following exercise when parasympathetic indices of HRV return to baseline values.
A new study published ahead of print in the Journal of Strength and Conditioning research evaluated resting HRV throughout spring camp among a group of NCAA Division 1 football players. The primary aim of the study was to determine if HRV returned to baseline between consecutive day training sessions. Twenty-five players were grouped according to playing position: receivers and defensive backs (Skill), running backs, linebackers and tight-ends (Mid-Skill) and linemen. HRV was recorded approximately 90 minutes before practices using a validated pulse-wave finger sensor synced to an iPad. Baseline HRV was compared with HRV following ~20 hours of recovery, prior to the next day training session. Training load was quantified via tri-axial accelerators. The parameter used in this study was total PlayerLoad.
The results showed that at the group level, HRV returned to baseline among Skill by next day training. HRV values trended back toward baseline for Mid-Skill, though considerable inter-individual variability was observed. For linemen, HRV values were significantly below baseline. This was observed despite the fact the linemen experienced significantly lower PlayerLoad values than Skill and Mid-Skill players. Changes in HRV were significantly related with body mass (r = -0.62) where larger players experienced the largest HRV reductions. The authors speculate that these findings may have important implications for the competitive season. Because linemen showed inadequate cardiovascular recovery between sessions, this may make them more susceptible to autonomic nervous system imbalance (an indicator of overtraining) during more intensive periods.
Flatt, AA. et al. Heart rate variability and training load among NCAA division 1 college football players throughout spring camp. Journal of Strength and Conditioning Research. In press.
It can take anywhere from 48 to 96 hours for full recovery to take place following a match. However, there are many instances in which athletes are not given adequate recovery time between competitions. Tournament-play and congested match fixtures often require athletes to compete on consecutive days, or sometimes twice in the same day. As such, coaches place a high premium on effective recovery modalities that can accelerate the restoration of performance in athletes. Foam rolling is a form of self massage that aims to reduce muscle “tightness” by stimulating the golgi tendon organ, thereby causing muscle to relax. Post-competition foam rolling has generated a lot of attention due to anecdotal reports of improving perceptual recovery markers. However, little research exists evaluating the effects of foam rolling on performance recovery in elite level athletes.
A new study published ahead of print in the Journal of Strength and Conditioning Research compared the effects of post-training foam rolling versus passive rest on next-day performance markers in a team of professional soccer players. Eight-teen soccer players provided ratings of soreness and recovery as well as performed baseline performance testing (counter-movement jump, t-test, 5 & 10 m sprint and sit and reach test) prior to an intense soccer training session. Following the training session, subjects were randomly allocated to a foam rolling group or a passive recovery group. The foam rolling group spent 20 minutes rolling out their quadriceps, hamstrings, gluteals, adductors and gastrocs in a standardized manner using a dense roller. The passive rest group sat quietly for 20 minutes, serving as the control condition. Perceptual recovery markers and performance were re-evaluated ~24 hours later.
The results showed that of the performance metrics, no significant difference between groups was observed for counter-movement jump and sprint times. However, agility performance (t-test) demonstrated significantly better restoration to baseline in the foam rolling group compared with the passive rest group (ES = 1.06). Perceptual ratings of recovery and soreness levels were not substantially different between days for the foam rolling group whereas significant decrements were observed for these variables among the passive rest group. Collectively, these results indicate that foam rolling post-training can minimize subsequent-day perceived fatigue and muscle soreness while mitigating reductions in agility performance. Given that foam rolling is an easy to implement and inexpensive intervention, coaches should consider encouraging athletes to foam roll post-training when enhanced recovery is desired.
Ezequiel, R. et al. The Effects of Foam Rolling as a Recovery Tool in Professional Soccer Players. Journal of Strength and Conditioning Research. In press.
One of the primary drivers of skeletal muscle adaptations is total resistance training volume. Provided that the volumes fall within the recovery capacity of the individuals, the magnitude of the stimulus will be greater with higher volume. When it comes to recovery from training however, total volume may not be the only factor we need to consider. For example, coaches need to be mindful of how sore athletes get from training during the in-season to minimize performance decrements during competitions. Apart from sets, reps and training intensity, a key variable that must be considered is proximity to muscular concentric failure during sets. However, the effects of training to failure versus volume matched work not to failure on the time course of recovery has received little investigation.
A new study published ahead of print in the European Journal of Applied Physiology investigated the time course of recovery following varying resistance training protocols that differed based on total volume and proximity to muscular failure. A group of 10 resistance-trained males performed 3 different training protocols on 3 separate occasions in a randomized order. The three protocols involved squats and bench press with 1) 3 sets of 5 with a 10 RM load, 2) 6 sets of 5 with a 10 RM load and 3) 3 sets of 10 with a 10 RM load. Neuromuscular performance, including counter-movement jump height and barbell velocity with standardized loads (e.g., 1 m/s and 75% of 1RM) was evaluated before and up to 72 hours post-training for each workout. Biochemical markers of muscle damage were also measured.
The results showed that training to muscular failure (3×10 with 10 RM) negatively effected acute neuromuscular recovery (counter-movement jump and barbell velocity performance in the squat and bench press) significantly more than the other protocols. Moreover, at 24 and 48 hours post-exercise, the non-failure protocols demonstrated significantly faster restoration of neuromuscular performance. Markers of muscle damage (e.g., creatine kinase) were greater at 24 and 48 hours in responses to the training to failure protocol compared with the non-failure protocols. Therefore, if athletes have important competitions in the upcoming 24-48 hours, training to muscular failure should be avoided as it will delay recovery.
Morán-Navarro, R., Pérez, C. E., Mora-Rodríguez, R., de la Cruz-Sánchez, E., González-Badillo, J. J., Sánchez-Medina, L., & Pallarés, J. G. (2017). Time course of recovery following resistance training leading or not to failure. European Journal of Applied Physiology, 1-13.
Increases in training load are often used by coaches to stimulate adaptations in athletes. Overload periods are common in periodized training structures and often precede a taper leading into competition. Despite being exposed to the same training schedule, not all athletes respond the same way to intensified training. Some athletes will respond well and improve performance while others may become fatigued and present with overuse issues. Baseline fitness level, stress, sleep quality and dietary factors may contribute to the individuality in training responses. It would be useful for coaches to have an objective physiological marker that they can use to evaluate how athletes are responding. This would enable coaches to identify those responding poorly to training and thus can modify training loads accordingly for them. Heart rate variability (HRV) is an objective, physiological marker that can be acquired daily via smartphone applications and is emerging as a useful training status marker among sports teams. While HRV has been shown to identify positive from negative responders based on performance changes, it is unknown whether HRV relates at all with overuse injuries.
A new study published ahead of print in the Journal of Sports Science and Medicine monitored incidence of overuse injuries, changes in training load and heart rate variability in a small sample of high level competitive CrossFit athletes. Training load was quantified via the session rating of perceived exertion method. From this, the exponentially-weighted moving average for the acute to chronic workload ratio was derived to determine when training loads were high. Vagally-mediated heart rate variability was measured daily by the athletes with a commercially available smartphone application. A brief questionnaire was emailed to each subject once per week to assess overuse injuries. The observation period spanned a sixteen week training cycle.
The results showed that there was a significant interaction effect between the weekly HRV average and acute to chronic workload ratio on reported overuse injuries the subsequent week. There was a substantially greater risk of overuse issues when individuals demonstrated lower HRV during a high load training week. In contrast, when athletes were able to maintain HRV within baseline ranges during a high load week, less overuse injuries were reported. Therefore, when monitoring HRV responses in athletes during intensified training, coaches should follow-up with athletes demonstrating reduced values to ensure overuse issues aren’t occurring.
Marco Altini, Sean Williams, Matthew Watson, Daniel Rowland, Thomas Booton, (2017) Heart Rate Variability is a Moderating Factor in the Workload-Injury Relationship of Competitive CrossFit™ Athletes. Journal of Sports Science and Medicine (16), 443 – 449.