Research has previously elucidated the impact of post-exercise carbohydrate nutrition and environmental conditions on muscle glycogen re-synthesis with several studies questioning the value of sports nutrition products and the difference in the body's response to carb-rich food compared to carb gels. However, research has minimally considered the implications of glycogen recovery in females as well as males.
The current study from the University of Montana (UM), led by UM Research Professor and veteran endurance athlete Brent Ruby, aimed to determine the effects of varied mixed macronutrient feedings on glycogen recovery and subsequent exercise performance in both sexes.
Ruby hopes these results - published in the European Journal of Applied Physiology - will help female athletes, as well as men, make better-informed choices about their refuelling programs.
"Endurance athletes love to talk about how hard they train and how special their diet is," Ruby said. "But we need to take a deep breath. It doesn't have to be complicated. As long as you are getting adequate carbohydrates, your diet can be as diverse as you want it to be.
"There's been a great deal of research into what sets the stage for muscle recovery after exercise. But women have been poorly represented in these studies. It is common to only study men and then make broad recommendations, which is wrong."
Ruby's team looked at muscle recovery between male and female recreational athletes using potato products and sports supplements. Eight men and eight women participated in the study, which involved 90 minutes of intense cycling followed by rest, recovery and refueling and a 20-kilometer time trial.
Two carbohydrate feedings (1.6 g kg−1) of either sport supplements or potato-based products were delivered at zero and two hours post-exercise. Muscle biopsies (glycogen) and blood samples (glucose, insulin) were collected during the recovery, then subjects completed a 20 km cycling time trial.
The researchers found no difference between sexes or trials for glycogen recovery rates and time trial performance was not affected by the different diets.
Simplify strategies
The authors conclude that this study adds weight to a previous study undertaken by Cramer et al in 2015, which concluded that a McDonald's Happy Meal is just as effective for exercise recovery as commercial nutrition products.
The current report's authors conclude that recommendations given by coaches and trainers can be simplified and diversification of dietary strategies may enhance carbohydrate compliance and sustainability of energy intake.
The report states: "As long as an adequate amount of carbohydrate (1.6 g kg−1) is provided at multiple intervals during recovery, the source of macronutrients for men and women may be diverse and need not be limited to exclusively commercial sport nutrition products. Variation in recovery food sources may enhance carbohydrate compliance, contributing to sustainable recovery dietary design.
"The uniformity and flexibility of these recommendations simplify and potentially decrease the cost of recovery feeding plans, a notion that may be particularly important for recreational athletes who may be susceptible to commercial marketing."
Discussing the lack of difference in response seen in males and females, the report states that consumers should be wary of sex-specific marketing messages for recovery products.
The report states: "Sex similarities in glycogen re-synthesis contradict suggestions that women require unique recovery feeding recommendations when compared to men (Black et al. 2019; Rehrer et al. 2017), indicating that consumers and athletes should be wary of sex-specific marketing related to carbohydrate-rich recovery products. Like Tarnopolsky et al. (1997), the current study found no significant difference between men and women in peak oxygen uptake when normalised for fat-free mass."
The authors concede there were several limitations to their study as they did not consider protein, fat, micronutrient, or specific amino acid needs that may differ between sexes. The study also used a fasted state, but athletes usually train and compete in a fed state, so additional research using alternate feeding strategies may be warranted.
Source: European Journal of Applied Physiology
Ruby. B., et al
"Males and females exhibit similar muscle glycogen recovery with varied recovery food sources"
https://doi.org/10.1007/s00421-020-04352-2