Shoulder Internal and External Rotator Strength Reliability and Validity in Healthy Adolescent Athletes.

International journal of sports physical therapy · 2026 · Other · PT
Katie Sloma, Garrett Robbins, John Arvesen, Ashley Erdman, Alex Loewen, Joshua Riesenberg, Ava Davis, Henry Ellis, Philip Wilson, Sophia Ulman

Handheld dynamometry gives a usable number for shoulder internal rotator strength in teen athletes (prone or supine), but its external rotator readings are unreliable in every position tested. Do not use HHD external-rotator numbers to clear a young athlete back to throwing.

Key findings

1

For internal rotators, HHD in the prone position agreed best with Biodex (ICC 0.81 dominant, 0.84 non-dominant), followed by supine (ICC 0.76 both arms); seated was weakest (ICC 0.59 both arms).

2

For external rotators, HHD showed poor agreement with Biodex in all three positions (ICC 0.28–0.43 dominant, 0.29–0.38 non-dominant), and HHD values were significantly higher than Biodex in every position (p < 0.001, r = 0.48–0.87).

3

The minimal detectable change for internal-rotator strength in the prone position was 18.3 Nm (dominant) and 16.7 Nm (non-dominant); changes smaller than this are within measurement error.

MethodologyResultsClinical Relevance

Single-blind randomized controlled trial. Sixty-four participants were randomized across two intervention arms and assessed at twelve weeks for the primary outcome…

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