Lifelong workouts benefit aging muscles in female athletes: Study

By Danielle Masterson

- Last updated on GMT

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Related tags Muscle athletes female athletes title ix

In just over two years, Title IX will celebrate its 50th anniversary. Since the landmark gender-equity law was passed, the number of girls playing high school sports has grown from 294,000 in 1971, to over 3 million in recent years.

The normalization of female athletics in the 1970s gave rise to a lifestyle shift that continues today, with the Title IX generation approaching 70 years of age. 

Susan Kleiner told NutraIngredients-USA that Title IX changed everything for females."There are many more women and girls in professional and recreational sports. When I started as a specialist in strength and power, I worked only with men for a decade. Now the girls who entered sports after Title IX and beyond are training with resistance training techniques no matter what sport they are in. It also gave permission for women who were pre-title IX girls to get into the game and really show ourselves how much we could push ourselves and how far we could go,"​ said Kleiner, a PhD nutritionist who advises high-profile female athletes. 

The Title IX milestone presented an opportunity for researchers to assess the effects of aging and lifelong exercise on the female athletes who have been working out consistently for the past 50 years, a topic that has not been well-studied.

Flexing research muscles 

“This is the first investigation to examine the effects of lifelong exercise on single-muscle fiber physiology in women,” ​said the authors of “Single-muscle fiber contractile properties in lifelong aerobic exercising women.”

The authors, who are researchers from Ball State University, wanted to examine the significance of exercise over a woman's total lifespan. Specifically, the team wanted to know how single-muscle fiber contractile properties of lifelong exercisers compare to non-exercisers the same age as well as how they compare to young exercisers.

Muscles vulnerable to time 

There are two general types of muscle fibers: slow-twitch and fast-twitch. Slow-twitch muscles help enable long-endurance workouts like distance running, while fast-twitch muscles fatigue quicker, but are useful in powerful bursts of motion like sprinting. Fast-twitch muscle fiber function tends to decline with age. 

The research team analyzed the type of muscle, as well as fiber size and function. To determine muscle mass, they measured the participant’s thighs. They also took blood and muscle-tissue samples. 

The women were divided into three groups.The ‘older exercisers’ (n=7) were over the age of 70 and had exercised moderately to vigorously consistently for almost 50 years. The second group, dubbed ‘the younger exercisers’ (n=10) had an average age of 25 and were also regularly physically active. The third group, called ‘the non-exercisers,’ (n=10)  was over the age of 70 and did not regularly exercise. 

Strength, size, power


The study, published in the Journal of Applied Physiology​, compared muscle strength, size and power. 

While the size of the individual slow-twitch fibers (endurance) was the same among the three groups, the researchers found that the older exercisers had more slow-twitch muscle fibers than the other two groups. 

The older exercisers also had more power in both the slow and fast-twitch muscle fibers compared with the non-exercisers. 

Both groups of older women had smaller fast-twitch fibers (power) compared to the younger exercisers. 

Nearly 50 years of moderate to vigorous aerobic exercise training resulted in enhanced slow-twitch fiber power primarily by increasing force production, whereas fast-twitch fiber power was preserved primarily by increasing contractile speed. These unique muscle fiber power profiles helped offset the effects of fast-twitch fiber atrophy and highlight the benefits of lifelong aerobic exercise for myocellular health,”​ the authors concluded. 

The authors also suggest future research on other modes of exercise such as resistance training, as well as exploring “the potential wide range of benefits across multiple physiological systems with lifelong exercise.”

Kleiner, the author of eight books, including The New Power Eating​, told us that good nutrition makes all the difference in performance. "I am more certain now than ever that good lifelong nutrition keeps an athlete in the game for much longer. It definitely extends a player’s career."

As for nutrition advice for older female athletes, Kleiner said not to succumb to the 'diet world' advice. "You still need to fuel your body. You want to eek every last bit out of the hormones that you have to keep your bones and muscles strong. That means you have to feed yourself well. Use your exercise to maximize what you can do. Do not think of training time as a weight loss or calorie deficit opportunity. Fuel your training to keep getting better. That is the ultimate win!"

Sports Nutrition Summit 

Influencers, the microbiome, protein, formulation challenges and opportunities, and female athletic consumers are just some of the topics that will take center stage at the NutraIngredients-USA Sports Nutrition Summit​ in San Diego, Feb 3-5, 2020. 

For more information and to register, please click HERE​.


Journal of Applied Physiology

Vol127 Issue 6 December 2019

“Single-muscle fiber contractile properties in lifelong aerobic exercising women”

Authors: K. Gries, et al

Related topics Research Healthy ageing

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