Fibion Blog • Gender Differences in Muscle Growth • Timo Haikarainen

Gender Differences in Muscle Growth

Do Women Really Gain Muscle Mass as Fast as Men

Gender Differences in Muscle Growth

Gender differences in strength training –series 3/6

It is often said that for women it is almost impossible to gain muscle mass. So is this really true? Well it’s very simple – it’s just not true! Several studies indicate that in the early stages of training muscle mass increases in women as fast as in men, if the exercise intensity is just high enough (Staron et al., 1994).

This may be related to the fact that fast Type II muscle fibers, that have greater growth potential, are smaller in non-trained women than in men and therefore possess lot of potential for growth. The size difference of fast muscle fibers may be related to boy’s more vigorous physical activities in the childhood. Also men’s higher testosterone levels might have an impact, as it is believed that testosterone affect fast twitch muscle fibers more.

In recent years, however, some research findings have emerged that have shown muscle growth being slower in women also in the early stages of training. In addition, individual differences in women in muscle growth are likely to be larger than in men (Häkkinen et al., 1992). When progressing further in the training, difference between men and women in gains of muscle mass start to increase. The main reason is believed to be testosterone as men’s levels are tenfold or even more. Despite this, testosterone in women is not negligible hormone. Although women have less testosterone, it´s effects can be relatively higher than in men. Larger individual differences in gains in muscle mass in women may be due to varying testosterone levels between individuals, differing hormone responses during training, different estrogen-testosterone ratios, genetic differences and psychological factors (like aggressiveness and concentration to training).

In the next blog we are researching gender differences related to the most neglected part of strength training – adapatation of connective tissues.

Timo Haikarainen
Timo Haikarainen

Personal Trainer

Fibion Guest Blogger


Connecting sport science research with practical applications

Timo started his coaching and instructing career in 1990s in martial arts, athletics and fitness exercise. From year 2002 he has worked as a gym instructor, personal trainer, and sport coach. Between 2002 and 2008 Timo studied biology of physical activity in University of Jyväskylä, where he graduated majoring in Sport Coaching and Fitness Testing. During the years Timo has accumulated over 15 000 hours of personal training. Practical coaching continues still active even though during last 6 years expert work and education as well as media work in TV and magazines take a big share of his time. Timo is educating personal trainers and gym instructors at SAFE Education, SATS Finland and Sport Center Pajulahti. Timo’s own sport background comes from martial arts, athletics and strength training.