Relations between the inflection point on the force-time curve and force-time parameters during static explosive grip

Area of Science:

• Biomechanics
• Human Physiology
• Sports Science

Background:

• Muscle contractile speed varies individually during static explosive contractions.
• These differences are observable in the force-time curve's developmental phase.
• Understanding these dynamics is crucial for performance evaluation.

Purpose of the Study:

• To determine the properties and reliability of the force-time curve's inflection point during static explosive grip.
• To statistically divide static explosive grip into two distinct phases.
• To examine the relationship between the inflection point and other grip parameters.

Main Methods:

• Measured static explosive grip data twice in 32 healthy young men (15.5 ± 0.8 years).
• Utilized a two-phase regression model to identify the inflection point.
• Analyzed parameters including time to reach maximal force, integrated area, and quotient values.

Main Results:

• The inflection point occurred at 0.3 seconds, representing 80% of maximal grip force, with good reliability (ICC=.77–.95).
• Inflection point parameters correlated significantly with time to 90% maximal force and integrated areas (r=-.78 to .88, p<.05).
• These parameters did not correlate with maximal grip force, suggesting different underlying physiological factors.

Conclusions:

• The identified inflection point is a reliable and useful parameter for evaluating static explosive grip.
• The developmental phase and maximal force may be influenced by distinct physiological factors.
• This research provides valuable metrics for assessing explosive muscle function.