Athletes who play sports requiring repetitive, forceful, overhead movements such as baseball, volleyball, or handball players, have been shown to be at a somewhat high risk of shoulder injury. Some studies have shown that 5-12% of athletes report they have had moderate or high reduction in training volume or performance levels due to some kind of shoulder problem (Clarsen). Many things have been proposed as potential causes, or risk factors, for shoulder pain/injury in these athletes, but there has been little consensus in the scientific literature to clearly define what may put an athlete at increased risk for a shoulder injury.
Let’s first discuss what constitutes an injury, because even that can be debatable. Your first thought might be that an injury would involve some kind of a torn muscle, tendon or ligament, or some kind of problem in the joint such as an injury to the labrum. These very well may be involved in an injury, but as you’ll see in a minute, these alone may not actually be significant in terms of looking at injury. For our purposes, we’ll consider a shoulder injury to be any pain or weakness in the shoulder that prevents or limits the athlete’s ability to participate in their sport, or training for their sport.
Now, we’ll look at why anatomical differences such as rotator cuff or labrum tears may not be indicative of an “injury” in our terms. A study in the American Journal of Sports Medicine in 2019 found that partial-thickness rotator cuff tears alone are not correlated with shoulder pain OR weakness in college baseball players. Read that again – college baseball players who were found to have partial thickness tears in the supraspinatus and/or infraspinatus did not show any correlation with shoulder pain or weakness. Another study in 2002 found that almost 80% of participants (who were MLB pitchers WITHOUT SHOULDER PAIN) demonstrated some abnormality (tear, fraying, etc) of the shoulder labrum. There is a whole host of additional research that has come out recently demonstrating poor correlation between abnormal imaging findings and increased pain or decreased function. We’ll be diving more into that research in a couple weeks. These findings are important for a ton of reasons, but the takeaway that I want to drive home for overhead athletes is that even if you have imaging proof of some abnormality in your shoulder, it doesn’t necessarily mean that you have to either have surgery or give up your sport. Athletes can still perform at very high levels even with these abnormalities.
Now that that’s settled, what are the risk factors that we’ve found for shoulder injury? A systematic review in 2018 found these as some of the top risk factors for shoulder injuries in overhead sports:
- Acute to chronic workload spikes of >60% over one week
- Chronic high workloads
- Decreased shoulder external rotation range of motion
Additionally, the introduction of a strength and conditioning program was shown to decrease the risk of substantial shoulder injury in handball players.
ACUTE TO CHRONIC WORKLOAD RATIO
Monitoring your acute to chronic workload ratio has gained a lot of popularity in recent years, and does appear to be a valuable tool in mitigating injury risk for athletes. Tracking this ratio involves looking at your training volume over the course of one week (Acute workload) and comparing it to your training volume over the previous 4 weeks (Chronic workload). You then divide the acute workload by the chronic workload, which will give you the Acute:Chronic workload ratio. In regards to shoulder injuries, one risk factor was found to be a jump in acute:chronic workload ratio of >60% in one week. A scenario where this may be a big factor is when you look at someone coming out of the off season and instead of gradually increasing their workload, they jump in full steam ahead.
How To Calculate Acute:Chronic Workload Ratio
There are a few ways to calculate your workload depending on what type of training you are doing. If you’re a distance runner, you can track this ratio using miles ran. If you’re a powerlifter, you can track the amount of weight lifted per workout, per muscle group. If you’re a pitcher, you can track the number of pitches thrown. Some sports can be a little more difficult to quantify, but the good news is there is one way that you can track your workload that can apply to any activity. That is by using your own Rating of Perceived Exertion (RPE). Using RPE, you simply rate how difficult your workout was on a 10 point scale (10 is extremely difficult, 0 is minimal difficulty), then multiply that number by the number of minutes in your workout. For example, let’s say you work out for 75 minutes, and rate it as a 6/10 difficulty. Your workload for that day would be 75 minutes x 6 = 450. You can then track this each day for a week to get your acute workload.
CHRONIC HIGH WORKLOADS
This one requires a little more nuance than the one above. To a certain extent, chronic high workloads have been found to be protective against injury, but there is a breaking point where a high workload becomes too much.
DECREASED SHOULDER EXTERNAL ROTATION RANGE OF MOTION
The final modifiable risk factor for shoulder injuries in overhead athletes was found to be a decrease in shoulder external rotation range of motion. This makes sense as you have to have a lot of shoulder external rotation for most overhead movements that athletes make. If you lack that range of motion, then you will repetitively overstress the tissues limiting that range of motion.
STRENGTH AND CONDITIONING TO REDUCE INJURY RISK
One study on handball players found that the addition of regular strength and conditioning was correlated with reduced risk of substantial injury. This probably seems like common sense to most people – get your muscles and tendons stronger, and you’re less likely to get hurt. Listed below are some exercises that we like to use with our overhead athletes to help improve cuff and scapular strength, especially working into the overhead ranges of motion, where these athletes spend a lot of their time. Strength and conditioning is also a way that you can slowly build up your chronic training workload in the offseason or when rehabbing from an injury to allow you to return to full participation without the added injury risk of returning when you have not been training properly.
BFR IMPLEMENTATION AND BENEFITS
One tool that can really help manage your workload, while allowing you to continue to make gains in strength, hypertrophy, and cardiovascular fitness is blood flow restriction training. We highlighted the BFR cuffs by Saga Fitness in a few of the videos above. If you want to know more about the research behind these cuff, we’d love to talk to you about them, the research is pretty incredible, and we’d love to help you get started on a program that would incorporate BFR. The Saga cuffs in particular are really cool. They automatically calibrate to the appropriate pressure for you, and you can control the pressure through an app on your phone! Check out the link below if you’re interested, and you’ll get a 15% discount!
- Asker M, Brooke HL, Waldén M, et alRisk factors for, and prevention of, shoulder injuries in overhead sports: a systematic review with best-evidence synthesis British Journal of Sports Medicine 2018;52:1312-1319.
- Clarsen B, Bahr R, Heymans MW, et al. The prevalence and impact of overuse injuries in five Norwegian sports: Application of a new surveillance method. Scand J Med Sci Sports 2015;25:323–30.
- Clarsen B, Bahr R, Andersson SH, et al. Reduced glenohumeral rotation, external rotation weakness and scapular dyskinesis are risk factors for shoulder injuries among elite male handball players: a prospective cohort study. Br J Sports Med 2014;48:1327–33.
- Mihata, T., Morikura, R., Hasegawa, A., Fukunishi, K., Kawakami, T., Fujisawa, Y., … Neo, M. (2019). Partial-Thickness Rotator Cuff Tear by Itself Does Not Cause Shoulder Pain or Muscle Weakness in Baseball Players. The American Journal of Sports Medicine, 036354651987814. doi:10.1177/0363546519878141
- Miniaci, A., Mascia, A. T., Salonen, D. C., & Becker, E. J. (2002). Magnetic Resonance Imaging of the Shoulder in Asymptomatic Professional Baseball Pitchers. The American Journal of Sports Medicine, 30(1), 66–73. doi:10.1177/03635465020300012501