Women are constantly overwhelmed with diet, health and lifestyle advice, yet are rarely the sole focus of exercise science research.
A new University of Otago – Ōtākou Whakaihu Waka study is changing this, investigating the impact of post-exercise protein supplementation on pre-menopausal women.
Led by Marc Murray, who completed the study as part of his PhD in the School of Physical Education, Sport and Exercise Sciences, researchers aimed to build on earlier research about how exercise and protein influence Insulin-like growth factor 1 (IGF-1). IGF-1 is a hormone that possesses anabolic effects, relating to protein synthesis, which play a role in muscle development and repair.
Marc Murray
"Using pre-menopausal women as our study participants made a lot of sense, as they remain underrepresented in exercise science research," Mr Murray says.
"While there are studies involving women, particularly in post-menopausal or clinical contexts, the physical activity guidelines for healthy adults have been mainly derived from male-dominant or mixed-sex studies.
"This gap may overlook sex-specific responses in exercise adaptations and any post-exercise protein supplementation responses, where hormones like estrogen and progesterone may influence protein turnover and needs, and exercise outcomes."
Twenty-seven healthy, untrained, pre-menopausal women aged between 18 and 50 took part in Otago's study, which was recently published in the journal Nutrients.
For 12 weeks they completed two upper body resistance sessions and three high-intensity interval cycle sessions each week.
After each training session, half of the participants were given a whey protein drink (24g), while the others were given an equicaloric, low protein (3g) drink.
By the end of the study, the participants had made "significant gains" in their strength and lean mass, without a change in body weight, but post-exercise protein supplementation made little difference and no differential IGF-1 response.
"The effects of post-exercise protein intake on protein synthesis are well-documented in the literature and based on that, we did expect that post-exercise protein supplementation would increase changes in muscle mass and strength, although our results didn't show this," Mr Murray says.
"Twelve weeks of training in the grand scheme of things isn't very long and it may also be likely that a longer period is needed to see differential effects of post-exercise protein intake on muscle development and associated strength gains."
Participants' diets and the timing of the training sessions (prior to normal meal times) may have also played a role, so women should not discount a possible positive effect of protein supplementation, particularly if protein intake from the daily diet is suboptimal.
"There is value in taking protein supplements post-workout as they provide a convenient and accessible way to meet protein intake requirements particularly if you are busy or finding it difficult to meet the recommended intake from your meals," he says.
"Our study was not without limitations, and I would be interested in seeing the outcome of post-exercise protein supplementation in studies over a longer timeframe, especially considering how great the overall improvement in strength was in the women.
"We also don't know if greater amounts of protein in the supplementation might have made a difference."
Mr Murray says the study shows untrained women tolerate physical activity recommendations that are largely based on male data.
"Within just three months, there were significant gains in strength and lean mass across all our participants, demonstrating a strong effect of training," he says.
"There remains a need for more research on women specific physiological responses. We and others are just starting to extend that knowledge base after years of under-representation in health research."
