Is There a Gender Difference in How Runners Use Glycogen
Intuitively, it would be difficult to posit that male and female runners use glycogen differently at similar intensities in different environments and in similar muscles. Glycogen is stored sugar in the muscle (and liver) that is readily available for energy production. And fueling strategies center on ensuring sufficient glycogen through long training runs and races.
So some British researchers seemed to think it was possible since (1) running outdoors differs from treadmill running and (2) no prior studies looked at whether or not gender differences affect glycogen use or (3) or at how different muscles use glycogen under these criteria. They quantified glycogen use in the vastus lateralis (the muscle on the outer thigh) and the gastrocnemius (calf muscle) in 11 male and 10 female recreational runners, during and after a 10-mile road run (aerobic), an 8 x 800 m (very high intensity) and a 3 x 10 minute (moderately high intensity) outdoor track interval sessions.
A primer on cardio and substrate use: Aerobic, long-distance exercise uses a combination of fats and sugars (carbohydrates.) Middle-distance, moderately high intensity work uses more carbs than fats with higher production of lactic acid. Sprints are high intensity and produce more lactic acid because they don’t use sugars efficiently.
The results showed that steady-state running used higher amounts of glycogen overall, as expected.
Females generally don’t store as much muscle glycogen and therefore don’t use as much, which may lead to more lactic acid accumulation. And the calf seems to use more glycogen than the thigh muscle.
They conclude that the gender differences in glycogen usage probably should not impact fueling strategies for women other than to make sure you eat enough carbs.
For more on running physiology, read the following blog posts here, here, here, and here.
MSSE Sept. 2020
No Butts About It
All major body movements are initiated from the ground through feet, knees and hips. From there, the central core – the abdominals and lower back muscles – must brace accordingly to enable proper and sufficient upper body movements. But when it comes to running power and speed, the buck stops and starts at the gluteal muscles of the buttocks.
A Loughborough University (England) team studied the sizes of 23 lower body muscles using MRI. They looked at 5 elite sprinters (with personal bests of 9.99 seconds/100 meters), 26 sub-elite and 11 healthy, untrained males. The inclusion of elite runners differentiates this from prior studies with similar intents.
What they found was that the hip extensors (glutes and hamstrings) were ~32% larger in elite sprinters even compared to sub-elite ones who averaged only 1-1.25 seconds slower in the 100.
Interestingly, the calf muscles of elite and sub-elite sprinters were similar in size despite being renowned for that mystical force called ‘spring’, as in spring in your step.
Since 44% of the variability in performance was explained by the size of the glutes alone, it was almost serendipitous that elite sprinters glutes were 45% larger than those of the sub-elites. This suggests that not all big butts are bad. It simply depends on whether it’s muscle or fat.
MSSE Oct. 2020
We know cardio and even circuit training with machines or weights help the vascular system. Nut a July 2020 study in Journal of Physiology reports that young adults who did 5 sets of 45 second passive stretches, with 15 second rests, for their calf and thigh muscles 5/wk for 12 weeks had improved blood flow through each are through more dilated blood vessels. Harvard Heart Letter, Oct. 2020
A growing body of research is showing how physical well-being plays into mental well-being…and vice-versa. As reported in the journal Psychological Science, interventions that boosted an individual’s mood also boosted their “self-reported physical health.” One group of 25-75 year olds participated in a 12-week “positive psychological interventions” that “helped them identify personal values, strengths and goals.” The control group was put on a wait list. The intervention group showed increasing levels of well-being and fewer sick days throughout the study while the controls did not. Mind, Mood & Memory, Oct. 2020
A report from the American Heart Association in the Journal of the American Medical Association highlighted the role adults can play in helping children develop healthy, life-long dietary habits. These include: consistent timing of meals and snacks with an “appropriate structure around food”; let kids make choices for themselves from an array of healthy options; serve healthy or new foods alongside those kids already enjoy to encourage experimentation; eat and demonstrate enjoyment of foods especially healthy ones; learn your child’s hunger and fullness cues to reinforce appropriate timing of snacking and dining; avoid pressuring kids to eat more so they can develop their own sense of satiety and self-regulation. IDEA Fitness Journal Sept.-Oct. 2020