Abstract
Objectives:
The rate of perceived exertion (RPE) is a commonly used subjective measure that measures an individual’s effort level. In baseball, RPE is utilized by pitchers most commonly during interval throwing programs (ITPs) as they recover from injury. An ITP that utilizes RPE is contingent on the ability of the pitcher to throw at the designed effort levels. Previous research has investigated RPE in high school and college pitchers during the long-toss portion of an ITP and reported at 75% RPE that ball velocity decreased to 86% of maximum and elbow varus torque only decreased 93% of maximum.1 On the mound, researchers have shown that there was not a proportionate decrease in ball velocity or elbow varus torque to perceived effort in college pitchers as well.2 While changes in maximum elbow varus torque have been reported, there is a lack of published data on the loading torque rate, as well as the cumulative elbow varus torque throughout a given pitch between different rates of perceived exertion. It was the goal of this study to analyze the difference in ball velocity, maximum elbow varus torque, loading torque rate, and cumulative elbow varus torque within pitchers pitching fastballs at 50%, 75%, and 100% RPE.
Methods:
Data were collected from 24 professional (PRO; 189± 5 cm, 91±7 kg) and 24 high school (HS; 183± 5 cm, 79±10 kg) pitchers. The PRO pitchers threw 5 fastballs at 100% RPE and 5 at 75% RPE and the HS pitchers threw 3 each at 50%, 75%, and 100% RPE. All throws were measured using a 3D motion capture system (480 Hz). The variables assessed were ball velocity, maximum elbow varus torque, loading torque rate (measured as the derivative of the torque curve), and cumulative elbow varus torque (measured as the area under the elbow varus torque curve) for each pitch. A linear mixed effects model was used to evaluate the within player relationship between RPE (100%, 75%, 50%) and ball velocity, maximum elbow varus torque, loading torque rate, and cumulative elbow varus torque. Significance was set at p<0.01.
Results:
Within a pitcher, significant reductions in ball velocity, maximum elbow varus torque, loading torque rate, and cumulative elbow varus torque were observed between RPE conditions (p<0.001) (Table 1 and 2); the magnitude of change for each metric varied compared to the magnitude of effort and per level.
When pitching at 75% RPE, PRO pitchers decreased ball velocity to 89% of maximum (35.2 ± 1.0 vs. 39.6 ± 0.7 m/s, respectively; p<0.001) and maximum elbow varus torque decreased to 78% (71.6 ± 4.0 vs. 92.1 ± 3.7 Nm, respectively; p<0.001). The loading rate decreased to 66% throwing at 75% RPE (521.6 ± 52.8 Nm/s vs. 786.7 ± 71.3 Nm/s, respectively; p<0.001) while cumulative elbow varus torque was reduced to 78% compared to 100% RPE (2449.6 ± 92.3 vs. 2890.1 ± 87.3 Nm, respectively; p<0.001).
At 75% RPE, HS pitchers showed a reduction in ball velocity to 92% of maximum (32.5 ± 0.6 vs 35.3 ± 0.3 m/s, respectively; p<0.001) and maximum elbow varus torque decreased to 84% (59.5 ± 2.3 vs 70.9 ± 3.3 Nm, respectively; p<0.001). Loading rate decreased to 76% (436.3 ± 49.5 vs 574.3 ± 46.1 Nm/s respectively; p<0.001), while cumulative elbow varus torque was reduced to 87% (2090.2 ± 83.4 vs 2403.0 ± 73.3 Nm respectively; p<0.001). At 50% RPE, HS pitchers reduced ball velocity to 86% of maximum (30.3 ± 1.1 vs 35.3 ± 0.3 m/s, respectively; p<0.001) and maximum elbow varus torque decreased to 74% (52.3 ± 3.6 vs 70.9 ± 3.3 Nm, respectively; p<0.001). Loading rate decreased to 64% of the value at 100% RPE (366.0 ± 39.6 vs 574.3±46.1 Nm/s, respectively; p<0.001), while cumulative elbow varus torque was reduced to 74% (1915.5 ± 115.5 vs 2403.0 ± 73.3 Nm, respectively; p<0.001).
Conclusions:
Decreases in RPE resulted in decreased ball velocity, maximum elbow varus torque, cumulative torque, ad torque loading rate. However, the magnitude of change was not proportional to percentage decrease in RPE, especially when looking at HS pitchers. PRO pitchers, likely influenced by increased experience, demonstrated a more accurate perception of exertion. In PRO pitchers, maximum elbow varus torque was found to be 78% of maximum value when pitching at 75% RPE, whereas, HS pitchers did not reach a similar reduction in this metric (74% of maximum value) until pitching at 50% RPE. Given that HS pitchers are not as adept at attenuating ball velocity and pitching load in relation to perceived effort; it is crucial to recognize that they may require different protocols than their PRO counterparts. Clinicians, players, and coaches at all levels, but especially at the HS level, should be cautious about relying on RPE and should consider more objective measures of pitching effort to better managing pitching effort, optimize rehabilitation, and reduce injury risk.