Receiving real-time feedback during training helps users learn to lift with intent, leading to improved performance even after the feedback is no longer provided.
Summary
In sport-specific training we aim for an increase in power. An important variable in power training is the intention of lifting as fast as possible in the concentric phase. Coaches often try to give verbal encouragement to help the athletes to lift with intent, but most studies show a lack of success doing so. In this study the author compared verbal subjective feedback to visual objective feedback, wanting to find out if adding visual feedback would increase lifting velocity. The second scope of the study was to look at what would happen when the feedback was removed. The findings can give coaches an edge when using feedback as a tool. Adding visual objective feedback on lifting velocity gave a statistically significant improvement in performance. Acute augmented visual feedback increased mean propulsive velocity in the squat compared to not receiving feedback, thereby acting as a performance enhancing tool for resistance training. Even after the feedback was removed, squat velocity remained high, suggesting a lasting effect on performance.
Introduction
Maximizing potential gains of resistance training (RT) is in interest of all strength-training individuals. Especially for athletes invested in improving every detail to improve their sport. The use of augmented feedback in velocity-based training (VBT) has shown to be beneficial for strength, speed, and power (Argus et al., 2011, Harries et al., 2012, Keller et al., 2014, Zhang et al., 2021). Augmented feedback (AugFb) is feedback from an external source on knowledge of the result, for example information about movement outcome, or knowledge of performance, for example movement execution Using feedback, not only from a trainer, but from an objective measure is a potentially overlooked way of improving resistance training both acute and over time. Studies showes on motivation, competitiveness and perceived workload (Weakley et al., 2019; Weakley et al., 2020).
In a systematic review by Weakley et al. (2023) an overview of the chronic and acute effects of feedback, and recommend the use of high-frequency, visual feedback as most effective for both acute and chronic outcomes in performance, and particularly effective for increasing motivation and competitiveness.
However, whether the increased performance when adding feedback is a lasting effect is not established. Keller et al. (2014) found that adding feedback increased acute jump performance, but when the feedback was removed, the jump-height dropped. From this study, Weakley et al. (2023) claimed that "removing feedback causes performance to return to pre-feedback levels". The author wanted to examine how the effect of removing feedback the squat. To examine this question, a study was conducted comparing two groups with and without feedback and measuring performance before, during and after feedback was given.
Study Design
The design was set to have one test group doing one set of squats without feedback, a second set with acute visual feedback, and finally a third set without feedback, while a control group doing three sets of squats without feedback. Other variables were made similar by using a standardized protocol for verbal encouragement for each participant. Performance was measured as lifting velocity in m/s (mean propulsive velocity of center of mass) and visual feedback was given after each rep on a large screen using Alphatek's system.
The sample consisted of 29 healthy adults, 12 female and 17 male, from age 20 to 55 (mean ±SD; age: 28.17 ± 8.0 years), with squatting experience from 1 to 20 years (mean ±SD; 5.4 ± 4.2 years). A criterion of squatting minimum once per week over the last year was chosen to ensure familiarity with the movement. Participants were recruited as an easy accessible convenience sample from gyms in Norway and randomly put in either the test or control group.
Each participant performed their sets of squats either with or without feedback with a standardized pause of 3 minutes, and load estimated to be around 60% of their 1RM. All participants were told that the researcher would see their velocity from all sets, ensuring no difference between groups in the feeling of being evaluated, as this is known to increase performance. The researcher monitored the velocity of these sets to ensure that velocity was in the power zone (0.50 m/s to 1.0 m/s), aiming to start the experiment at 0.60 to 0.70 m/s.
After the data collection, data was analyzed in SPSS with inferential statistics, running both paired sample t-tests and independent t-tests. In the process of analyzing, change from set to set was evaluated to understand the effect of adding and removing feedback.
Statistics
Paired Sample T-Tests
Paired samples t-test was conducted to investigate whether in-group changes in velocity were significant. In Table 1 paired samples statistics for each set and each group are presented with means and SD for reference, and Table 2 shows test results.
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Independent Sample T-Test:
Independent samples t-test was run to analyze the between-group differences. For this test, a new variable for the difference between sets was computed. These difference variables are described in Table 6. The change between FG sets 1 & 2 was then compared with the change in CG set 1 & 2 to establish the effect of adding feedback in the sample. To investigate the research question of what happens when feedback is removed the change between FG sets 1 & 3 was compared with the change in CG sets 1 & 3.
Results
Adding feedback
Mean velocity in the first set for the test group was .643 m/s, while mean velocity in the control was .654 m/s. In the second set the test group received feedback and increased significantly to .675 m/s (p = .007), while the control had a significant drop to .629 (p = .032). This is illustrated in the graph below. This finding supports other research indicating an increase in performance by adding acute visual feedback.
Removing real-time feedback
In set 3 there was no significant change in mean velocity in the test group at .672 m/s ( p = .754). Mean velocity in the control group had another significant decrease in velocity to .601 m/s ( p = .039). The change from set 2 to set 3 is illustrated below. Although practitioners have reported their thesis of this effect, other research has not yet shown this particular matter.
These findings imply that the performance-enhancing effect of visual feedback transfers to the set after, and possibly to other exercises and the rest of the workout. How long this effect lasts is not known.
Control group vs Test group
Comparing set 1 and set 3 in each group, the test group had a significant increase with a p-value of .013, while the control had a significant loss in velocity with a p-value of <.001. The graph below shows difference in velocity in both groups from set 1 to set 3.
Difference between the two groups
When comparing the difference in set 1 and 2, and 1 and 3 between the groups, there was a significant difference with p-value of 0.001 in set 1-2, and a significant result with a p-value of <0.001.
Discussion
First, the study findings show adding feedback gives a statistically significant improvement in performance, both from the baseline of same individuals and compared to a control group. Acute augmented visual feedback increases mean propulsive velocity in the squat compared to not receiving feedback, thereby acting as a performance-enhancing tool for resistance training, and likely other areas. Second, it shows that the benefits of using acute visual feedback lasts beyond the initial set given feedback to.
The practical implication of increasing an athlete's performance on every repetition in every set is possibly massive by maximizing potential gains, not to mention improving motivation, enjoyment and autonomy in the task. Receiving objective feedback on performance can be a huge motivator for increasing effort for athletes as you receive acute reward for the intensity of effort. This reward might be what teaches people to lift with intent or effort, and the physiological activation, also known as the post-activation potentiation, might be part of the reason for the increased performance.
Using feedback improves later performance as well as acute, which means it can be an effective tool for athletes and others, ensuring quality of training even when he or she cannot be present, by providing valuable feedback directly to the athlete.
References
Argus, C. K., Gill, N. D., Keogh, J. W., & Hopkins, W. G. (2011). Acute effects of verbal feedback on upper-body performance in elite athletes. Journal of strength and conditioning research, 25(12), 3282–3287.
Harries, S. K., Lubans, D. R., & Callister, R. (2012). Resistance training to improve power and sports performance in adolescent athletes: a systematic review and meta-analysis. Journal of science and medicine in sport, 15(6), 532–540.
Keller, M., Lauber, B., Gehring, D., Leukel, C., & Taube, W. (2014). Jump performance and augmented feedback: immediate benefits and long-term training effects. Human movement science, 36, 177–189.
Liverød, J. A. (2023). The effect of adding and removing feedback: Visual augmented feedback improves movement velocity even when feedback is no longer provided (Bachelor`s Thesis). University of Stavanger, Department of social sciences.
Weakley, J., Cowley, N., Schoenfeld, B., Read, D., Timmins, R., García Ramos, A., & McGuckian, T. (2023). The Effect of Feedback on Resistance Training Performance and Adaptations: A Systematic Review and Meta-analysis. Sports Medicine. 1-15. https://doi.org/10.1007/s40279-023-01877-2
Weakley, J., Wilson, K., Till, K., Banyard, H., Dyson, J., Phibbs, P., Read, D., & Jones, B. (2020). Show Me, Tell Me, Encourage Me: The Effect of Different Forms of Feedback on Resistance Training Performance. Journal of strength and conditioning research, 34(11), 3157–3163.
Weakley, J. J. S., Wilson, K. M., Till, K., Read, D. B., Darrall-Jones, J., Roe, G. A. B., Phibbs, P. J., & Jones, B. (2019). Visual Feedback Attenuates Mean Concentric Barbell Velocity Loss and Improves Motivation, Competitiveness, and Perceived Workload in Male Adolescent Athletes. Journal of strength and conditioning research, 33(9), 2420–2425.
Zhang, X., Li, H., Bi, S., Luo, Y., Cao, Y., & Zhang, G. (2021). Auto-Regulation Method vs. Fixed-Loading Method in Maximum Strength Training for Athletes: A Systematic Review and Meta-Analysis. Frontiers in physiology, 12, 651112. https://doi.org/10.3389/fphys.2021.651112 This Article is written by: Josefine Adele Liverød — Psychology and sports scientist