Explosive neuromuscular performance of males versus females

Abstract

The purpose of the study was to investigate sex-related differences in explosive muscular force production, as measured by electromechanical delay (EMD) and rate of force development (RFD), and to examine the physiological mechanisms responsible for any differences. The neuromuscular performance of untrained males (n = 20) and females (n = 20) was assessed during a series of isometric knee extension contractions; explosive and maximal voluntary efforts, as well as supramaximal evoked twitches and octets (eight pulses at 300 Hz). Evoked and voluntary EMD were determined from twitch and explosive contractions. The RFD was recorded over consecutive 50 ms time windows from force onset during evoked and explosive contractions, and normalized to maximal strength. Neuromuscular activity during explosive voluntary contractions was measured with EMG of the superficial knee extensors normalized to maximal M-wave. Muscle size (thickness) and muscle-tendon unit (MTU) stiffness were assessed using ultrasonic images of the vastus lateralis at rest and during ramped contractions. Males and females had similar evoked and voluntary EMD. Males were 33% stronger (P < 0.001) and their absolute RFD was 26-56% greater (all time points P < 0.05) compared with females. Muscle size (P < 0.001) and absolute MTU stiffness were also greater for males (P < 0.05). However, normalized RFD was similar for both sexes during the first 150 ms of the explosive voluntary contractions (P > 0.05). This was consistent with the similar normalized twitch and octet RFD, MTU stiffness and agonist EMG (all P > 0.05). When differences in maximal strength were accounted for, the evoked capacity of the knee extensors for explosive force production and the ability to utilize that capacity during explosive voluntary contractions was similar for males and females.

Reliability of Panoramic Ultrasound Imaging in Simultaneously Examining Muscle Size and Quality of the Hamstring Muscles in Young, Healthy Males and Females

“…These findings may have been expected given the males' greater body mass and height, which have been shown to account for a significant portion of the variance in muscle size (Engel-Hoek et al 2012;Kawakami et al 1993). Moreover, our results are in agreement with those reported by previous authors, who demonstrated greater US CSA and/or MT values in males versus females for the biceps brachii (Arts et al 2010;Caresio et al 2014), vastus lateralis (Caresio et al 2014;Hannah et al 2012), rectus femoris (Caresio et al 2014), biceps femoris (Blackburn et al 2009), triceps brachii (Ichinose et al 1998;Kanehisa et al 1994), lateral gastrocnemius (Chow et al 2000), soleus (Chow et al 2000) and tibialis anterior (Arts et al 2010;Caresio et al 2014) muscles. For measurements of EI, however, previous US studies have revealed contrasting findings regarding differences between genders for the muscles of the upper and lower extremities (Arts et al 2010;Caresio et al 2014;Verhulst et al 2011).…”

Peak power is reduced following lengthening contractions despite a maintenance of shortening velocity

“…A potential key component that may contribute to the impaired power production following lengthening contractions is the rate of torque development (RTD) (Andersen and Aagaard 2006). The reduction in MVC following fatigue or lengthening contractions is associated with impaired RTD (Behrens et al 2012;Crameri et al 2007;Hannah et al 2012), and this would be manifested during dynamic contractions such that the ensuing angular velocity and power production will be reduced when the contractile torque equals and then exceeds the specific isotonic load.…”

“…Because torque production and RTD are impaired substantially following lengthening contractions (Behrens et al 2012;Crameri et al 2007;Hannah et al 2012), we hypothesized that there would be a greater loss of power at higher loads during dynamic shortening actions. However, due to less reliance on RTD to achieve the requisite isotonic load at a lower percentage of MVC, shortening velocity will be less impaired than at higher loads.…”

Neural, biomechanical, and physiological factors involved in sex-related differences in the maximal rate of isometric torque development

“…Based on the work of Hannah et al (2012), it was hypothesized that maximum isometric strength would account for sex-differences in the maximum rate of torque development in the TA, because males and females are more comparable in maximum isometric strength in the lower limb. Studying mechanisms behind sex-differences in distal muscles that are responsible for balance and explosive activity can guide specific training interventions or rehabilitation techniques.…”