Faculty Sponsor Name

Garrett M. Hester

Additional Faculty

Trisha A VanDusseldorp, Exercise science and sports management, tvanduss@kennesaw.edu Yuri Feito, Exercise science and sports management, yfeito@kennesaw.edu

Abstract (300 words maximum)

Purpose: To determine sex differences in strength and contractile properties after isometric and dynamic fatiguing exercise of the plantar flexors. Methods: Recreationally active males (n=13, age=22.4±2.2 yrs) and females (n=15, age=20.9±2.4 yrs) performed a maximal isometric (2 min) and isotonic (120 reps at 30% peak torque) fatigue task on 2 separate visits. Before and after each fatigue task, participants performed a 3 sec maximal voluntary isometric contraction (MVIC) with tibial nerve stimulation being delivered during and immediately after the MVIC. Peak torque (PT; highest 250 ms) was obtained during the voluntary phase of the MVIC. Peak twitch torque (TTQ), rate of torque development (RTD; Δtorque/Δtime), and half relaxation time (HRT; time for TTQto decrease from peak to 50%) were calculated from the resting twitch after the MVIC. Voluntary activation (VA%; ability of the muscle to be fully activated) was calculated using a corrected interpolated twitch formula. Three-way (condition × sex × time) repeated measures ANOVAs were used for analysis. Results: Regardless of sex or condition, TTQ(-23.1%), RTD (-12.6%), HRT (+22.9%) were changed after fatigue (p<0.05), while VA% remained unchanged (p>0.05). Regardless of condition, PT was more reduced in males (-22.5%) compared to females (-19.2%)(p=0.017). Conclusions: Our findings indicate that the fatigue-induced decrease in strength was greater in males than females. While our findings do not identify the contributing physiological mechanism(s), changes at the peripheral level may be responsible.

Project Type

Oral Presentation (15-min time slots)

Share

COinS
 

Sex Differences in Plantar Flexor Strength and Contractile Properties after Isometric and Dynamic Fatigue

Purpose: To determine sex differences in strength and contractile properties after isometric and dynamic fatiguing exercise of the plantar flexors. Methods: Recreationally active males (n=13, age=22.4±2.2 yrs) and females (n=15, age=20.9±2.4 yrs) performed a maximal isometric (2 min) and isotonic (120 reps at 30% peak torque) fatigue task on 2 separate visits. Before and after each fatigue task, participants performed a 3 sec maximal voluntary isometric contraction (MVIC) with tibial nerve stimulation being delivered during and immediately after the MVIC. Peak torque (PT; highest 250 ms) was obtained during the voluntary phase of the MVIC. Peak twitch torque (TTQ), rate of torque development (RTD; Δtorque/Δtime), and half relaxation time (HRT; time for TTQto decrease from peak to 50%) were calculated from the resting twitch after the MVIC. Voluntary activation (VA%; ability of the muscle to be fully activated) was calculated using a corrected interpolated twitch formula. Three-way (condition × sex × time) repeated measures ANOVAs were used for analysis. Results: Regardless of sex or condition, TTQ(-23.1%), RTD (-12.6%), HRT (+22.9%) were changed after fatigue (p<0.05), while VA% remained unchanged (p>0.05). Regardless of condition, PT was more reduced in males (-22.5%) compared to females (-19.2%)(p=0.017). Conclusions: Our findings indicate that the fatigue-induced decrease in strength was greater in males than females. While our findings do not identify the contributing physiological mechanism(s), changes at the peripheral level may be responsible.