Does the Selected Segment Within a Two-Legged Hopping Trial Alter Leg Stiffness and Kinetic Performance Values and...

Area of Science:

• Biomechanics
• Human Movement Science
• Sports Science

Background:

• Two-legged hopping is a common method for evaluating leg stiffness.
• Previous research has not clarified if the chosen hopping segment influences leg stiffness results.
• Understanding segment selection is crucial for consistent biomechanical analysis.

Purpose of the Study:

• To determine if the selected hopping trial segment affects leg stiffness values.
• To investigate the impact of segment selection on the individual variability (%CVind) of leg stiffness.
• To assess the influence of segment selection on kinetic performance metrics during hopping.

Main Methods:

• Elite female athletes and non-athletic women performed two-legged hopping at 130 bpm on a force plate.
• Leg stiffness was calculated using the resonant frequency method from vertical ground reaction forces (Fz).
• Four cumulative segments (1-10, 1-20, 1-30, 1-40 hops) and three 10-hop subranges were analyzed.

Main Results:

• No significant differences were found in leg stiffness values across different hopping segments (average 30.6–31.2 kN/m).
• Individual variability (%CVind) of leg stiffness remained consistent, averaging approximately 3% across segments.
• %CVind for kinetic performance metrics did not exceed 6.2%.

Conclusions:

• The choice of hopping segment does not significantly impact leg stiffness or its variability.
• A 10-hop segment, after excluding the first five hops for neuromuscular adaptation, is a robust and reliable data collection choice.
• These findings support consistent and efficient biomechanical data collection for leg stiffness analysis.