To be successful in a chosen sport, athletes need to develop a variety of specific skills and physical attributes. In many sports, such as rugby union, athletes have limited time to train and develop each physical attribute before optimal recovery is compromised or injury risk is increased. It has been suggested that athletes may sometimes train with insufficient motivation or intensity to maximize their training time (23), and their training quality may suffer. Therefore, improving the quality of each training session (without extending the duration or increasing the volume) is a common goal for many athletes. Quality of training is vital to the success of the conditioning program and relates to the exercise stimulus required to make specific improvement (14). For example, attempting to maximize jump height or velocity during vertical jump training may lead to greater training quality and adaptation when compared to performing the same quantity of jumps performed with submaximal intent.
Psychological strategies may be a potential method for improving training quality and have been previously reported to improve performance of strength, power, and skill-based tasks (10,12,17,25). Psychological techniques can be classified as either intrinsic (e.g., self-talk, ‘psyching up’) or extrinsic (e.g., visual and verbal feedback [knowledge of results or performance], encouragement) and although the exact mechanisms for improvement are unclear, improvements may be because of a combination of enhanced neuromuscular activation, intent, focus of attention, levels of arousal, and improved skill performance and learning (10,12,16,17,25,31). ‘Psyching up’ has been shown to increase isokinetic bench press strength by 11.8% when compared to a mental distraction control (25). Additionally, Jung and Hallbeck (10) reported an increase in peak handgrip strength of approximately 5% when visual feedback or verbal encouragement was given. It should be noted that the strength improvements in the aforementioned investigations were assessed in testing sessions consisting of a single repetition or set, an approach that is atypical in resistance training where multiple sets and repetitions are performed consecutively (excluding one repetition maximum lifting) (20). Therefore, the effect of psychological strategies on resistance training performance still requires investigation.
Training quality can be affected by accumulated fatigue that occurs throughout a training session and may cause a reduction in exercise movement velocity (15). As such, the rate of work done (i.e., power) in the final sets may not be as high as in the initial sets, resulting in reduced training quality. Using psychological techniques Tod et al. (26) reported a significant increase (∼4.7%) in knee angular velocity during a vertical jump when athletes performed self-talk such as “I can jump high” before jumping. Verbal feedback is another psychological technique that might influence movement velocity when delivered to athletes throughout training sessions, although to date, such a possibility has yet to be explored. The finding that verbal feedback increases movement velocity during resistance training, thus allowing training quality to be maintained or improved, may yield practical implications for coaches and athletes.
Although strength is important and often assessed in practice, research indicates that power may be a better predictor of athletic performance (18). Numerous authors have reported increases in lower body power when psychological strategies were implemented (26,28,29). To date, only one study has investigated the acute effects of psychological methods on upper-body power (7). It was reported that the use of self-talk (labeled motivational self-talk) increased distance of an over head throw of a water polo ball in untrained swim class students compared to a no-talk (control) condition (7). It is however unknown whether verbal feedback can improve performance in upper-body power exercises in well-trained athletes. Therefore, the purpose of this investigation was to determine the effects of verbal feedback on upper-body power in a resistance training session consisting of multiple sets and repetitions in well-trained rugby athletes. We hypothesized that receiving feedback throughout a training session will improve training quality, observed as enhanced power output and velocity of each exercise set.
Experimental Approach to the Problem
To assess the effects of verbal feedback on mean peak power and mean peak velocity, 9 elite rugby union athletes were assessed using the bench throw exercise on 4 separate occasions each separated by 7 days. All testing sessions were conducted at 09:30 hours on the same day of the week. Athletes had been instructed to maintain a high level of hydration in the 24 hours leading up to each testing occasion. All athletes were provided with a standardized breakfast on all testing days, approximately 2 hours before training. Athletes were instructed to abstain from caffeine 12 hours before each testing session. Each athlete completed 2 sessions consisting of 3 sets of 4 repetitions of the bench throw with feedback provided after each repetition and 2 identical sessions where no-feedback was provided after each repetition. Each set was separated by 2 minutes of rest. Athletes were randomly split into 2 groups, which differed only in the order they received feedback or no feedback over the 4 testing occasions (Figure 1). Power and velocity were assessed using the bench throw exercise because of its common usage in power training programs and research studies and its ability to represent upper-body explosive performance (1,2). Multiple repetitions and sets were performed to be more representative of a typical training session. Peak power and velocity were selected as the dependent measures because they have been reported to have the greatest association with athletic performance (6).
Nine elite rugby union athletes from a Super 14 professional rugby team volunteered to take part in this study during the start of the competitive phase of their season (testing was performed in the month of March) (mean ± SD; age, 22.1 ± 2.1 years; height, 184.2 ± 7.7 cm; mass, 107.3 ± 13.2 kg; and maximal bench press strength, 135.9 ± 22.6 kg). Each athlete had undergone at least 2 years of intensive and regular resistance training. All athletes were informed of the experimental risks and benefits of the study and signed a consent document before the commencement of the study. The investigation was approved by an Institutional Review Board for use of Human participants (Auckland University of Technology Ethics Committee).
Peak velocity (m·s−1) was obtained by a GymAware® optical encoder (50-Hz sample period with no data smoothing or filtering; Kinetic Performance Technology, Canberra, Australia) and the numerical value (e.g., 2.38 m·s−1) was verbally provided to each participant after the completion of each repetition. Verbal feedback was provided at a volume slightly greater than normal conversation volume because of the additional noise created within the gymnasium. No other feedback or motivation (e.g., “come on” or “you can do it”) was provided. The no-feedback condition had only the repetitions counted aloud (i.e., “1, 2, 3, 4”) at the same volume as the feedback condition. The same encoder was also used to record the peak velocity and peak power of each repetition for later analysis (5). Briefly, GymAware® consists of a spring-powered retractable cord that passes around a pulley mechanically coupled to an optical encoder. The retractable cord is then attached to the barbell, and velocity and distance are calculated from the spinning movement of the pulley upon movement of the barbell. The encoder gave 1 pulse approximately every 3 mm of load displacement, with each displacement value time stamped with a 1-millisecond resolution. The mass of the bar (as entered into a personal digital assistant), the entire displacement (millimeters) of the barbell, and time (milliseconds) for the movement are used to calculate mean values for power (5).
A standardized warm-up consisting of 2 sets of 10 body-weight press-ups followed by 1 set of 5 explosive press ups with a clap was completed. Athletes then completed 3 sets of 4 repetitions of bench throw at a load of 40 kg within a Smith machine that was equivalent to 30% (±5%) of the group's mean maximal bench press. Athletes used a self-selected hand position and lowered the bar to a self-selected depth (1). Athletes then threw the bar vertically and explosively as possible, trying to propel the bar for maximal velocity (19). Each repetition began with an eccentric phase followed immediately by a concentric phase with no pause between the 2 phases. In both conditions, a 1-second pause occurred after the completion of each repetition (at the end of the concentric phase) so that verbal feedback or no feedback could be provided (obtained via GymAware®). Athletes rested for 2 minutes between all warm-up and training sets. Athletes were asked to rate their effort after each set; all reported maximal effort.
The first repetition from each set was excluded from analysis, because feedback could not be provided until after the completion of the first repetition. The repetitions for each set from the 2 feedback sessions were combined and averaged before analysis, as were the no-feedback repetitions. Mean peak power and mean peak velocity data of all 9 repetitions, and the mean for each set of 3 repetitions (set 1, 2, or 3) was used for analysis.
All data were log-transformed to reduce nonuniformity of error, and the effects were derived by back transformation as percent changes (9). Standardized changes in the mean of each measure were used to assess magnitudes of effects by dividing the changes by the appropriate between-participant SD. Standardized changes of <0.2, <0.6, <1.2, <2.0, and >2.0 were interpreted as trivial, small, moderate, large, and very large effects (8). An effect size of 0.2 was interpreted as the smallest worthwhile change. To make inferences about the true (large-sample) value of an effect, the uncertainty in the effect was expressed as 90% confidence limits. The effect was deemed unclear if its confidence interval overlapped the thresholds for small positive and negative effects (4). Intraclass correlations (r) and coefficient of variation % for the bench throw were assessed on 11 recreationally trained men and were r = 0.949 and 5.2%, and r = 0.957 and 3.1% for peak power and peak velocity, respectively.
A small increase of 1.8% (90% confidence limits; ±2.7%) in mean peak power of all repetitions was observed when feedback was received. When each set was compared individually, there was no difference in mean peak power between the first set in either condition. The mean peak power in the second set was 2.4% (±4.7%) greater when feedback was received when compared to the second set of the no-feedback condition and represented a small effect. There was also a small increase of 3.1% (±3.3%) in mean peak power of the third set in the feedback condition compared with no-feedback condition (Figure 2).
Mean peak velocity of all repetitions was 1.3% (±0.7%) greater when feedback was provided, and this represented a small effect. When each set was compared, a small improvement in mean peak velocity was observed in all 3 sets in the feedback condition compared to no-feedback. Increases in mean peak velocity were 1.3% (±1.1%), 1.1% (±1.1%), and 1.6% (±1.0%) for sets 1–3, respectively (Figure 3).
There were no clear differences between the change in power or velocity from set to set between either condition. However, the change in mean peak power from set 1 to set 2 in the feedback condition was nearing a clear difference compared to the no-feedback condition (2.5 ± 5.6%; effect size, 0.37 ± 0.83). Figure 4 illustrates the individual response in mean peak velocity and power to feedback and no-feedback conditions.
The purpose of this investigation was to determine the acute effects of verbal feedback on upper-body power in a resistance training session consisting of multiple sets and repetitions in well-trained athletes. Small improvements in bench throw mean peak power and mean peak velocity were observed when verbal feedback was received immediately after each repetition. These results contribute to the current body of knowledge in several ways. First, to our knowledge, only one other investigation has examined the effects of psychological strategies on upper-body power (7). Indeed, the previous investigation examined the effects of feedback on a relatively complex skill-based task (overhead water polo throw), whereas the current investigation examined the effects on a simpler task (bench throw). Second, this was the first investigation to examine the effects of feedback in well-trained athletes using assessment procedures typical of a traditional resistance training session, that is, consisting of multiple sets and repetitions. As such, the current investigation addresses a deficit in the strength and conditioning literature.
Receiving verbal feedback improved mean peak power and velocity of the training session by 1.8 and 1.3%, respectively. The greatest benefit when receiving feedback appears to be in the latter sets of training. Indeed, when each set was analyzed separately, improvements were greatest in the final set (3.1% mean peak power; 1.6% mean peak velocity). These findings suggest that receiving feedback improved the rate of work done and therefore the overall quality of the training session, especially as the training session progresses. If these improvements can be made during 1 training session, the long-term effects of repeating these “higher quality” sessions may result in enhanced training adaptations and potentially better performance (11,18,30). Although the benefits gained may appear small, it should be noted that previous literature has reported 5% improvements in upper-body power in elite rugby league athletes over a 4-year period (3). As such improvements of ∼3.1% in a single session are a positive and worthwhile finding.
Performance improvements were smaller than previously reported in studies investigating the effects of psychological strategies in muscular force (10,12,17,25,26,28). Differences may be because of the level of participants and musculature recruited. It is commonly accepted that well-trained individuals routinely recruit a greater percent of muscle than their untrained counterparts (13,21,27). Therefore, in untrained individuals, there may be greater potential for feedback and other psychological strategies to enhance muscular activation, which may lead to greater performance improvements. The smaller improvements in this study may also be because of the muscle group involved (i.e., upper vs. lower body), whereby the larger muscle mass of the lower body may have greater scope for improvement.
The mechanisms for improvements as a result of feedback were not assessed in this investigation. Previously, authors have speculated that improvements from psychological interventions such as feedback may be because of a combination of enhanced neuromuscular activation, intent, focus of attention, levels of arousal, and improved skill performance and learning (10,12,16,17,25,31). Further research should attempt to identify the mechanisms that lead to performance improvements with specific feedback because this may allow the nature of the feedback to be altered to further augment the acute response.
Interestingly, there appeared to be a small increase in mean peak power and velocity from set 1 to set 2 in both conditions (Figures 2 and 3). It is possible that either the warm-up before the first set was not adequate to prepare the athletes for maximal effort or, although not measured in the current investigation, there may have been potentiating effects provided from the first training set. Postactivation potentiation is the phenomenon in which acute muscle force output is enhanced as a result of contractile history and is typically evident after maximal or near maximal lifting (22). However, it is possible that the lighter load performed with maximal intent may have provided some potentiating effects. Indeed, Thompsen et al. (24) reported increased standing long jump distance after performing a dynamic warm-up wearing a weighted vest of only 10% bodyweight when compared to performing the same warm-up without additional weight. Although in this study both groups tended to produce greater mean peak power on set 2 than set 1, we observed a small but unclear difference (effect size = 0.37 ± 0.83) in mean peak power between the conditions, suggesting the possibility that the increase in mean peak power across the first 2 sets was greater in the feedback than no-feedback condition (Figure 2). It may therefore be suggested that in addition to postactivation potentiation, the greater improvements in power for the feedback group may have been in part because of potentiating effects of receiving feedback.
The use of verbal feedback resulted in acute increases in upper-body mean peak power and velocity. However, it is unknown whether providing acute feedback to athletes across multiple training sessions will provide continuous acute adaptations in performance over a longer training phase, or if adaptation will diminish with repeated use. Future research should investigate the chronic training effects of receiving feedback to determine any long-term use benefits.
Providing feedback during the performance of a typical power training exercise improves the rate of work done (i.e., power output) and hence the quality of training of well-trained athletes, in which even small improvements in power are often difficult to achieve. Based on our findings, conditioning coaches and athletes should consider the use of specific feedback (i.e., velocity) during a resistance training session to improve performance and maximize training quality.
The Waikato Rugby Union and the Tertiary Education Commission provided finical support by way of scholarship for the primary author. The results of the present study do not constitute endorsement by the National Strength and Conditioning Association.
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