Concurrent Repetitions Overestimate Hamstring:Quadriceps Ratios at Extended Knee Joint Positions: Implications for...

Area of Science:

• Biomechanics
• Sports Medicine
• Human Movement Science

Background:

• Isokinetic hamstring:quadriceps (H:Q) strength ratios are crucial for assessing muscle balance and injury risk.
• Concurrent repetition protocols, common in H:Q testing, may be influenced by the stretch-shortening cycle and axis misalignment.
• Isolated repetition protocols have been recommended to mitigate these confounding factors.

Purpose of the Study:

• To investigate the impact of concurrent versus isolated repetition protocols on H:Q strength ratios.
• To examine the influence of axis misalignment correction on H:Q ratios.
• To inform the development of more accurate screening protocols for muscle imbalance.

Main Methods:

• Fifteen healthy males performed isokinetic knee flexor and extensor tests at 60°/s using both concurrent and isolated repetition protocols.
• Sagittal plane kinematics were captured at 100 Hz to assess axis misalignment.
• Statistical parametric mapping was employed to compare the effects of protocol type and axis correction.

Main Results:

• Uncorrected data underestimated discrete conventional and functional H:Q ratios and all angle-specific ratios.
• Concurrent repetitions significantly overestimated the conventional H:Q ratio, particularly at more extended knee positions (24°-45°).
• Despite overestimations with concurrent trials, using uncorrected data from concurrent repetitions did not yield significantly different discrete or angle-specific H:Q ratios compared to corrected isolated repetitions.

Conclusions:

• Concurrent repetition protocols may increase the likelihood of false-negative injury risk assessments due to overestimation of H:Q ratios.
• The common practice of using uncorrected data from concurrent repetitions may not significantly impact discrete or angle-specific H:Q ratio outcomes when compared to corrected isolated repetitions.
• Clinicians and researchers should be aware of these protocol-specific differences when interpreting H:Q strength ratio data for injury risk screening.