Tooth et al. (2023)

Effectiveness of a Shoulder Injury Prevention Program in Volleyball

This study examined the effectiveness of a shoulder injury prevention program in volleyball players

Significant differences were found in favor of the intervention group who followed, BUT…

The study reports findings that should not have been interpreted

Introduction

Volleyball players frequently undertake repetitive motions such as serving, which can place considerable strain on their shoulders. Over time, these repetitive actions can result in injuries. According to research, specialized programs can avoid approximately 50% of sports injuries. While there have been successful shoulder injury prevention programs for handball players, there hasn’t been a verified program for volleyball players until now. As a result, the goal of this study was to develop and evaluate a shoulder prevention program specifically for volleyball players. The idea is to give coaches a new tool to help them reduce injuries in their players.

 

Methods

The study engaged eight teams, totaling 93 players. Four teams (50 players) were assigned to the prevention group, while the other four teams (43 players) were blindly assigned to the control group.

Shoulder injury prevention program
From: Tooth et al., Phys Ther Sport (2023)

 

The study’s preventive program is known as the “Liège University Program.” It is intended to be integrated into volleyball players’ warm-up routines, replacing the traditional warm-up. The program lasts about 24 minutes in total and is broken into three sections: running exercises (3 minutes), preventative exercises (18 minutes), and a final exercise (3 minutes).

The program’s major emphasis is on strengthening, plyometric, and proprioception exercises. These exercises focus largely on the shoulder, but they also incorporate other portions of the body and the kinetic chain to enhance balance and functional movement. The program includes exercises such as shoulder external rotator strengthening with Theraband, core stability exercises, shoulder and ankle proprioception exercises, shoulder proprioception with Theraband, passing exercises, external rotators plyometric exercises, and push-ups. To accommodate varied ability levels, the program also offers workouts of differing complexity levels.

Shoulder injury prevention program 2
From: Tooth et al., Phys Ther Sport (2023)

 

Results

The risk of injury was compared between the intervention group (those who followed the prevention program) and the control group (those who did not follow the program). The results showed that the incidence of injuries was lower in the intervention group compared to the control group. Specifically, the prevention group had an incidence of 5.1 injuries per 1000 playing hours, while the control group had an incidence of 7.1 injuries per 1000 playing hours. This difference in injury incidence led to a RR of 0.71 (95% CI 0.476 – 1.08).

When shoulder injuries were considered specifically, 26.8% of the control group injured their shoulder, while only 12.8% did in the intervention group. This led to a RR of 0.47 (95% CI 0.193 – 1.173). Two-thirds of those sustaining a shoulder injury had a history of shoulder injury.

In male players, the risk of shoulder injuries was significantly lower in the prevention group compared to the control group, with a risk ratio of 0.253 (95% CI 0.057 – 1.118). This was calculated from the 31.6% of players in the control group sustaining a shoulder injury versus 8% of those in the intervention group.

The severity of the injuries was significantly different between both groups, with the intervention group sustaining less severe injuries and injuries with a minor impact on performance.

The main outcomes of this study were focused on assessing the feasibility and compliance of the prevention program for shoulder injuries in volleyball players. They found that not all participants were fully adherent to the exercises. While the recommendation was to complete the program twice per week, only 16.67% of the participants engaged more than 1.5 times per week in the prevention exercises.

 

Questions and thoughts

The intervention group sustained 5.1 injuries per 1000h playing hours while those in the control group sustained 7.1 injuries per 1000h. This difference in injury incidence was statistically significant if you look at the corresponding p-value. This is also what the authors report, thereby indicating that the prevention program had a positive impact in reducing the risk of injuries in volleyball players. I cannot understand why this could have been published since the confidence interval spans the null value as it contains “1”. Based on the 95% confidence interval, this reduction in injuries per 1000 hours of play is not statistically significant, in contrast to what was published here. The correct interpretation of a statistical test is of utmost importance when a study gets published and flaws like these misuse the noncorrect interpretation of findings to arrive at a publication. You could say they made an error in their interpretation, however of the 3 so-called significant risk ratios, none was interpreted correctly. In all cases, the confidence interval spanned the null value and was not significant, but the authors still reported statistical significance.

Physiotherapists can play a crucial role in educating volleyball players about the importance of injury prevention programs and guiding them in implementing appropriate exercises. Based on the outcomes of this study, the prevention program led to an absolute risk reduction of (7.1-5.1=) 2 injuries per 1000 hours of play. This may not be worth the effort of implementing this into a club’s program.

Am I saying that no prevention programs should be followed? Certainly not. But we must acknowledge that not every situation is predictable. One may twist his ankle whilst stepping out of a car despite engaging in stability training regularly. But the prevention programs that should be implemented into practice better make real differences, otherwise, it just costs a lot of time and money.

One of the reasons this program did not prevent more injuries could have been the suboptimal adherence and compliance to the program. The duration and content of the program may need to be adjusted to improve compliance and meet the specific needs of the players and trainers.

 

Talk nerdy to me

The risk ratio compares the risk in one group to the risk in another. However, there is a catch. Consider two studies: one in which the risk is 0.2% and 0.1% in two groups, and another in which the risk is 90% and 45%. Both trials would provide the same risk ratio of 2, implying that the intervention group faces twice the risk. However, the first study found only a minor increase in risk (0.1%), whereas the second found a far larger increase (45%). As a result, publishing merely the risk ratio can make the effect appear more significant in the first scenario and less important in the second. It is critical to study the actual numbers to understand the exact impact. Indeed, if you compare 7.1 injuries to 5.1 injuries per 1000 hours of play, is this program worth the effort?

All players from the same club were allocated to the same intervention group. This was to ensure no crossover of information from the prevention program was shared with the control group.

 

Take home messages

Based on the results of this study, it can be concluded that the prevention program for shoulder injuries in volleyball players does not seem to show promise in terms of feasibility and adherence, nor risk reduction of (shoulder) injuries in volleyball players.

 

Reference

Tooth C, Schwartz C, Croisier JL, Gofflot A, Bornheim S, Forthomme B. Prevention of shoulder injuries in volleyball players: The usefulness and efficiency of a warm-up routine. Phys Ther Sport. 2023 Nov;64:97-103. doi: 10.1016/j.ptsp.2023.09.006. Epub 2023 Sep 30. PMID: 37812954. 

Additional references

Szumilas M. Explaining odds ratios. J Can Acad Child Adolesc Psychiatry. 2010 Aug;19(3):227-9. Erratum in: J Can Acad Child Adolesc Psychiatry. 2015 Winter;24(1):58. PMID: 20842279; PMCID: PMC2938757. 

Tan, S. H. and Tan, S. B. (2010). The correct interpretation of confidence intervals. Proceedings of Singapore Healthcare, 19(3), 276-278. 

George A, Stead TS, Ganti L. What’s the Risk: Differentiating Risk Ratios, Odds Ratios, and Hazard Ratios? Cureus. 2020 Aug 26;12(8):e10047. doi: 10.7759/cureus.10047. PMID: 32983737; PMCID: PMC7515812. 

 

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