Study Sheds Light on the Best Indicators of Fatigue in Baseball Pitchers

Knowing when an athlete has reached his or her limit is a key element of coaching. A new study examined the best ways to determine fatigue in baseball pitchers.

When training or competing it’s a good idea for athletes and coaches to monitor fatigue. One problem with doing so is that some kinds of fatigue aren’t easy to detect, especially amongst younger athletes. To shed light on this issue, researchers conducted a study published recently in the Journal of Strength and Conditioning Research that looks at ways you might not have thought of to monitor fatigue.

As a coach, I teach my clients to focus on alternative methods of fatigue detection. But determining fatigue in throwing maneuvers can be especially tricky for athletes of any age. Because of the ballistic nature of throwing, it’s a particularly dangerous activity to partake in while fatigued. Repeatedly training during fatigue not only ruins form in the long term, but also increases the chance of injury.

One reason throwing fatigue can be tough to assess is because there are varying kinds of fatigue that affect throwing and different metrics by which to measure them. In the new study, the researchers examined a few kinds of fatigue, and determined how several different methods of measurement interacted with each.

One way to measure fatigue that’s used in the majority of athletic studies is a subjective assesment, which means the athletes report how they feel. In this case, the players reported how sore their arms got from throwing. The researchers also used several objective measures, including a proprioception test, which measured awareness of arm position, a throwing accuracy test, and velocity tests. These measurements were performed before and after either a throwing workout or a running workout. Here’s how each of these measurements played out:

  • Arm Soreness: Not surprisingly, arm soreness proved to be a good measure of arm fatigue specifically, as it increased significantly more after the throwing workout than the running.
  • Proprioception: Proprioception test results didn’t change before or after exercise, and the researchers concluded the test was not an accurate measure of fatigue. This result is fortuitous, considering the testing machine the researchers used is not widely available.
  • Throwing Accuracy: Throwing accuracy was another indicator of arm fatigue. However, it was only altered by the throwing workout and remained unchanged after the running workout.
  • Velocity: Velocity was reduced by both workouts at pretty much the same rate. The reduction only came out to about one or two miles-per-hour, on average. Despite the small difference, the researchers pointed out that this means a decrease in throwing velocity correlates more with general fatigue than arm fatigue.

The researchers suggested that pitchers report on arm soreness at every opportunity. Also, when possible, coaches should use a ball tracking system to determine accuracy. If you don’t have that technology, refer to the pitcher’s and catcher’s assessments of accuracy in between innings. Combined with velocities, these tests could provide valuable information.

Regardless of the type of fatigue, this study sheds light on an otherwise difficult issue that coaches and athletes of many sports face. Fatigue increases the risk of injury, so try to develop metrics to help you determine when an athlete needs rest.


1. Jonathan Freeston, et. al., “Indicators of Throwing Arm Fatigue in Elite Adolescent Male Baseball Players: A Randomized Crossover Trial,Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000395

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