The athletic shoulder (ASH) test: reliability of a novel upper body isometric strength test in elite rugby players

Key points

1. 01The ASH test measures isometric shoulder strength in three prone arm positions (I at 180 degrees, Y at 135 degrees, T at 90 degrees) by pushing into a force platform.
2. 02Day-to-day reliability was excellent across all positions (ICC 0.94 to 0.98).
3. 03Measurement error was below 10% in every position except the non-dominant arm I-position (CV 11.3%).
4. 04A change larger than the minimal detectable change (about 13 to 26 N) is needed before a real difference can be confirmed.
5. 05The test is portable, quick (under 6 min for all positions, both arms) and may help guide return to play and monitor recovery from fatigue.

How it was conducted

Design

Test-retest reliability study on consecutive days

Participants

18 elite male rugby players (age 22.4 plus or minus 4.6 years, body mass 95.5 plus or minus 13.4 kg)

Test positions

Prone isometric pushes at three abduction angles, I (180 degrees), Y (135 degrees) and T (90 degrees), each arm

Equipment

Pasport PS-2141 vertical axis force platform, three 3 s maximal trials per position with 20 s rest

Outcomes

Net peak force (NPF); reliability via ICC, CV, SEM and minimal detectable change (MDC)

What they found

• Interday reliability for mean NPF was excellent in all positions, ICC 0.94 to 0.98.
• Standard error of measurement ranged 4.8 to 10.8 N.
• Coefficient of variation was below 10% in all positions (5.0% to 9.9%) except the non-dominant arm I-position (CV 11.3%).
• Minimal detectable change at 90% confidence (MDC90) ranged 13.3 to 25.9 N (MDC% 10.7 to 20.1).
• Reliability was higher using the mean of three trials (ICC 0.94 to 0.98) than the maximum of three trials (ICC 0.89 to 0.98).
• Net peak force was highest in the I-test, then Y-test, then T-test.

Limitations

• Small sample of only 18 participants from a single group of elite male rugby players, so results may not apply to other populations.
• Test order was not randomised, so reliability cannot be fairly compared between the three positions.
• Validity, sensitivity to fatigue and the link to injury or rehabilitation outcomes were not tested and remain to be established.
• Small increases in force from day 1 to day 2 may reflect a learning effect or extra recovery time despite prior familiarisation.

Why it matters

For patients

For an injured athlete, this test offers an objective, repeatable way to track shoulder strength recovery during rehabilitation and inform return-to-play decisions.

For clinicians

Practitioners can treat ASH test changes greater than about 13 to 26 N (depending on position) as a real change, but should establish individual baselines and confirm clinimetrics in their own population.

For readers

A practical reliability study showing a quick force platform shoulder test repeats well in elite athletes, though its real-world usefulness still needs further validation.