The ExtRA Capacity Test: Reliability, validity and normative data of a new clinical tool for assessing shoulder...

Introduce The ExtRA Capacity Test, a measure for assessing shoulder muscle performance. Assess its reliability, validity and present normative scores in a large sample of asymptomatic adults.

Cross-sectional observational study with test-retest.

Community.

Volunteers (n = 344, age 20-90 years).

The ExtRA Capacity Test involves two capacity tests completed to a 30 beats per minute metronome: maximal scapular plane lateral raises to 90° abduction with 2.5 kg of external load, and maximal external rotations in unsupported prone lying with the shoulder at 90° abduction. Reliability was assessed in 30 asymptomatic participants, tested by two raters over two sessions, one week apart, using Bland-Altman analysis to determine mean bias and 95 % limits of agreement (LoA) as measures of error. Criterion validity was evaluated in 20 participants using Pearson correlation to examine the relationship between ExtRA and isokinetic dynamometry measures. A normative dataset was also established from 344 asymptomatic individuals across a range of ages, physical activity levels, and both sexes.

The intra-rater and inter-rater agreement for the ExtRA Capacity Test was assessed in a sample of 30 participants. The 95 % LoA for abduction and external rotation measurements ranged from 2.9 to 13.1 repetitions. In a sample of 20 participants, the abduction test showed good/moderate correlation with muscle strength measures but not with the external rotation test. Older age, female sex and not achieving the WHO activity guidelines have a negative impact on ExtRA performance.

Within the caveats discussed in this paper, ExtRA can be considered a reasonably reliable tool for assessing shoulder strength and control in a clinical setting. The normative database will help clinicians set rehabilitation or return-to-play targets based on sex, age, and physical activity level. CONTRIBUTIONS OF PAPER.