Determining meaningful changes in hip abductor muscle strength obtained by handheld dynamometry

Area of Science:

• Kinesiology
• Biomechanics
• Musculoskeletal Health

Background:

• Assessing isometric hip abductor muscle strength is crucial for evaluating lower limb function.
• Handheld dynamometers (HHDs) are commonly used for muscle strength testing.
• Quantifying measurement error, such as minimal detectable change (MDC), is essential for reliable strength assessments.

Purpose of the Study:

• To quantify the minimal detectable change (MDC) for isometric hip abductor muscle strength in healthy adults using a handheld dynamometer (HHD).
• To establish a threshold for determining a true change in hip abductor strength beyond measurement error.

Main Methods:

• Ninety healthy volunteers (45 males, 45 females) aged 22-70 years participated.
• Isometric hip abductor force was measured bilaterally using a digital HHD in a supine position.
• Measurements were normalized to body weight (BW); intratester reliability was assessed using ICC(3,1).

Main Results:

• High intratester reliability was found with an ICC(3,1) of 0.96.
• The standard error of measurement (SEM) was 2 Newtons.
• The MDC(95) was determined to be 5.4% BW for males and 5.3% BW for females.

Conclusions:

• The MDC(95) provides a reliable threshold to differentiate true changes in isometric hip abductor strength from measurement variability.
• These findings are valuable for clinicians and researchers using HHDs to monitor hip abductor strength.
• Changes in strength below the MDC(95) should be interpreted as within the margin of error.