An Acute Throwing Episode Decreases Shoulder Internal Rotation

Abstract

Glenohumeral internal rotation (GIR) and total arc of motion (TAM) decrease, whereas external rotation (GER) may increase in throwing. Although decreased GIR has been documented after throwing, its time course for recovery and the effect of pitching role have not. We therefore asked (1) how much rotational change occurs after a single throwing episode; (2) do these changes return to baseline by the next throwing episode; and (3) does pitching role affect the amount of change that occurs? Forty-five pitchers, starters and relievers, were examined. GIR and GER measurements were taken at five time points (TP): before throwing (TP1); immediately after throwing (TP2); and 24 (TP3), 48 (TP4), and 72 (TP5) hours later. TAM was calculated as the combination of GIR and GER. GIR decreased from TP1 to TP5 and did not return to baseline. GER changed very little and TAM decreased at TP5. Relievers had greater GIR, GER, and TAM across all time points, but the amount of change over all time points was not different between groups. GIR was most affected over one 4-day throwing cycle after an acute throwing episode and was less than baseline 72 hours later. Pitching role did not affect the short-term changes. GIR changes should be expected after an acute throwing episode and conditioning and recovery programs should be used to modify the changes. Because GIR is dynamic, studies on GIR should specifically state when during the pitching cycle the measurement was obtained.