• Nagai T
• Schilaty ND
• Kunzer CM
• Greer A
• Bates NA
• McPherson AL

• Exercise Therapy / methods
• Hip
• Muscle Strength Dynamometer
• Open Access Document
• Reproducibility of Results

Hip abduction and external rotation muscular strength deficits are associated with various musculoskeletal conditions such as balance loss (falls), osteoarthritis, and lower extremity ligament strains. To countermeasure, a clamshell hip resistance exercise is commonly included as a part of preventive or rehabilitative programs. A simple and portable clamshell strength device was developed in attempt to encourage widespread hip strength assessments in clinics.

Objective: Examine test-retest reliability of hip clamshell strength using a portable device and validity with the hip abduction strength using the isokinetic dynamometer.

Methods: A test-retest reliability and validity study design at a sports medicine facility. Twelve young and healthy adults (8M/4F, 27.4yo, 180.1cm, 88.8kg) visited a sports medicine laboratory twice one week apart. Subjects performed maximum voluntary isometric contractions using both a portable clamshell strength device and isokinetic dynamometer. Average peak forces (Newtons) in right and left muscular strength with a clamshell strength device and hip abduction peak torques (Newton-Meters: Nm) with a dynamometer. Reliability and validity was analyzed using the intraclass correlation coefficients (ICC 3,1) and Pearson correlation coefficient (r), respectively.

Results: Clamshell strength was moderately reliable (ICC = 0.593-0.820) and valid (r = 0.545-0.584).

Conclusion: The current study found that a portable and inexpensive clamshell strength device was reliable and valid. This result encourages more hip strength testing at point-of-care clinics.

Author keywords: dynamometer, clamshell, gluteus medius, power, test-retest, reliability, validity

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