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NEW: Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations

Nuzzo, James L.


Journal of Strength and Conditioning Research 37(2):p 494-536, February 2023. | DOI: 10.1519/JSC.0000000000004329 SDC


PURPOSE

To summarize the literature on sex differences in numerous strength training–related variables and outcomes including muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training.


CONCLUSIONS:

o Male subjects become notably stronger than female subjects around age 15 years.

o Sex differences in adults regarding strength are more pronounced in upper-body vs. lower-body muscles and in 

   concentric vs. eccentric contractions.

o Greater male than female strength is due to greater muscle mass and type II fiber areas and not because of higher 

   voluntary activation.

o Males participate in strength training more often than women.

o Males are motivated more by challenge, competition, social recognition, and the desire for increased muscle size and 

   strength.

o Males have greater preference for competitive, high-intensity, and upper-body exercise. Females are motivated more by 

   improved attractiveness, muscle “toning,” and body mass management.

o Females have greater preference for supervision in lower-body exercises.

o Regarding intrasexual competition, mate selection, and the drive for muscularity, they are likely the fundamental 

   reasons for exercise behaviors in males and females.

o Males and females increase muscle size and strength after weeks of strength training, but females experience greater 

   relative strength improvements depending on age and muscle group.

o Males experience a higher rate of strength training injury.

o No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.


IN PLAIN ENGLISH:

Due to obvious natural differences in genetic make-up, specifically muscle mass, skeletal structure, and hormonal factors – along with innate motivations and societal influences - males and females differ in strength training ability and underlying motivations to do it.

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