Test-retest reliability and discriminative ability of forward, medial and rotational single-leg hop tests

Key points

1. 01All four hop tests showed excellent reliability with ICCs ranging from 0.93 to 0.98
2. 02The smallest detectable difference was 7-11% of mean hop distance, so roughly a 10% improvement reflects a true change
3. 03Fewer ACL-reconstructed participants passed the 90% limb symmetry cut-off on medial (40.6%) and rotational (46.9%) tests compared to forward hops (59.4-62.5%)
4. 04Medial and rotational hop tests expose asymmetries that forward tests can miss, making them useful additions to return-to-sport assessment
5. 05An absolute limb symmetry index is recommended over the classic index to avoid masking individual asymmetries

How it was conducted

Design

Cross-sectional reliability and discriminative ability study with two cohorts

Reliability participants

16 non-injured recreational athletes (8 female, 8 male; mean age 22.4 years), tested twice one week apart

Discriminative cohort

32 ACL-reconstructed participants (4 female, 28 male; mean age 24.4 years; 6 months postoperative, hamstring autograft)

Tests performed

Single hop for distance (SH), triple hop for distance (TH), medial side triple hop for distance (MSTH), and 90-degree medial rotation hop for distance (MRH)

Primary outcomes

Intraclass correlation coefficients (ICC), standard error of measurement (SEM), smallest detectable difference (SDD), and limb symmetry index (LSI)

What they found

• ICC values ranged from 0.93 to 0.98 across all hop tests and both legs
• SEM ranged from 2.6-4.1% of mean hop distance; SDD ranged from 7.2-11.3% of mean hop distance
• No significant test-retest differences in hop distances were found for any test (all P > .05)
• In non-injured athletes, 93.8% passed the 10% absolute limb symmetry cut-off for SH and TH, but only 68.8% passed for MSTH and MRH
• Operated leg distances were significantly lower than non-operated leg for all hop tests in ACL group (all P < .001)
• ACL group LSI (mean SD): SH 89.4% (11.9), TH 87.8% (18.3), MSTH 85.2% (19.2), MRH 86.6% (13.6)
• Proportion of ACL participants passing the 90% LSI cut-off: SH 62.5%, TH 59.4%, MSTH 40.6%, MRH 46.9%

Limitations

• Reliability was tested only in 16 non-injured participants, limiting generalizability to injured or clinical populations
• ACL-reconstructed group was predominantly male (28 of 32) and used only hamstring autografts, reducing applicability to females and other graft types
• Rehabilitation was not controlled in the ACL group, introducing variability in recovery status
• Hop tests are performed in a closed, predictable environment and do not capture neurocognitive demands or fatigue present in sport

Why it matters

For patients

Athletes recovering from ACL reconstruction may benefit from being assessed with medial and rotational hop tests, as these are more likely to uncover persistent leg weakness or asymmetry that forward hop tests can miss.

For clinicians

Adding MSTH and MRH to return-to-sport protocols is justified by their excellent reliability and greater sensitivity to limb asymmetry; a roughly 10% change in hop distance represents a true performance shift when retesting.

For readers

This study provides first-reported reliability data for multidirectional hop tests and offers practical cut-offs, though larger and more diverse samples are needed before firm return-to-sport thresholds can be established.