Every cell in the human body has a sex.  Consequently, males and females differ in anatomy and physiology resulting in marked sex differences in neuromuscular performance and fatigability. Typically, males outperform females in athletic performance after puberty across all age groups due to hormonal effects, primarily testosterone which is ~15-20 times greater in males from ~18 years of age (Handelsman et al., 2018). Sex differences in neuromuscular performance such a muscle strength and power range from 10-30% depending on the demands of the task and the muscle groups involved. Males have larger, stronger, and more powerful muscles particularly in the upper limb due to differences within the size and compositional area of the skeletal muscle fibers. In contrast, there are minimal sex differences in the ability to activate the available skeletal muscle during voluntary contractions prior to fatiguing tasks (Hunter, 2016).
While males are stronger and more powerful than females, the relative decrement in force or power during a fatiguing task of males is usually larger than for females, primarily during isometric and slow-velocity fatiguing contractions.  This sex difference in fatigability (relative, exercise-induced reduction in force or power) is not typically observed during fast-velocity contractions (Hunter, 2016; Senefeld et al., 2018). Multiple mechanisms are responsible for fatigability in both males and females that can include activation of the motoneuron pool from cortical and subcortical regions, synaptic inputs to the motor neuron pool via activation of metabolically-sensitive small afferent fibres in the muscle, muscle perfusion, skeletal muscle metabolism and altered crossbridge dynamics in the muscle fibres (Hunter, 2018). The greater fatigue resistance in females compared with males during isometric and slow velocity contractions however, is related to the sex differences in the fibre type proportional areas within the skeletal muscle and muscle perfusion (Hunter, 2016). Understanding the sex difference in neuromuscular fatigability has important implications for training and rehabilitation in males and females.
Despite more concerted efforts in the last ~15-20 years to include females in mechanistic studies, there is still inadequate inclusion of females and knowledge on the mechanisms for sex differences of fatigability and athletic performance. The sex bias of studying more males than females in both human and animal experiments in physiology and fatigability (Beery & Zucker, 2011; Hunter, 2016) has led to the false assumption that males and females respond similarly to interventions including fatiguing exercise. The field is ripe with opportunities to clarify and understand the sex differences in neuromuscular fatigability, athletic performance, and the underlying mechanisms during different tasks.