Validity and Reliability of Handheld Dynamometry to Assess Isometric Hamstrings and Quadriceps Strength at Varying...

Area of Science:

• Biomechanics
• Sports Medicine
• Clinical Assessment

Background:

• Hamstring injuries are common in sports, particularly at lengthened muscle positions.
• Assessing knee muscle strength in these positions is crucial for injury risk evaluation.
• Handheld dynamometry (HHD) is a practical clinical tool for measuring isometric muscle strength.

Purpose of the Study:

• To evaluate the validity and reliability of HHD for measuring isometric knee muscle strength at diverse muscle lengths.
• To compare HHD measurements with an isokinetic dynamometer across various hip and knee flexion angles.

Main Methods:

• Concurrent validity and test-retest reliability were assessed.
• Thirty healthy participants performed isometric strength tests using HHD and an isokinetic dynamometer.
• Measurements were taken in six different hip and knee flexion positions.

Main Results:

• HHD demonstrated good to excellent reliability and moderate to high validity in most tested positions.
• An exception was noted for hamstring strength in a seated, knee-extended position (30° hip flexion).

Conclusions:

• HHD is a valid and reliable tool for clinical assessment of knee muscle strength in healthy adults at various lengths.
• HHD is not recommended for measuring hamstring strength in lengthened positions (hip flexed, knee extended).
• Further research is needed to confirm these findings in athletic populations.