Post-Workout Collagen Doesn’t Boost Muscle Connective Tissue Synthesis
Researchers tested whether 30g of hydrolyzed collagen taken after resistance training would increase protein synthesis in muscle connective tissue in 45 young adults (~23 years old).
Participants performed leg presses and extensions, then received collagen, collagen-matched amino acids, or placebo.
Despite significant increases in circulating glycine and proline (confirming absorption), neither supplement increased connective tissue, muscle fiber, or skin protein synthesis rates at rest or after exercise.
The disconnect between amino acid availability and tissue response suggests that glycine/proline supply isn’t the limiting factor for connective tissue remodeling in muscle, at least short-term. PubMed Study Link
My Thoughts
This is a well-designed study that challenges some popular assumptions in the running community that collagen can help recovery and/or build muscle. But, this study shows this may be unlikely.
The key nuance here: muscle contains relatively little collagen (~1-6% of dry weight) compared to tendons (~66%). So while this study found no benefit for muscle connective tissue, it doesn’t rule out effects on more collagen-rich tissues like tendons or cartilage, which we saw evidence of in a previous post.
For runners dealing with Achilles issues or joint concerns, longer-term collagen supplementation combined with targeted loading may still have merit.
Your Liver Recovers Faster Than Your Muscles After Hard Training
Researchers used ultra-high-field MRI to track both muscle and liver glycogen in 12 well-trained cyclists (VO2max ~67 ml/kg/min) after glycogen-depleting exercise.
One condition consumed 10g carbs/kg bodyweight over 12 hours (that’s ~700g for a 70kg athlete), the other fasted.
The findings were striking: liver glycogen fully replenished within 6 hours, exceeding pre-exercise levels by 42%.
Muscle glycogen? Only reached 69% of baseline after 12 hours despite aggressive carb intake.
Without carbohydrates, both stores remained depleted. PubMed Study Link
My Thoughts
This study reframes how we should think about recovery fueling for back-to-back training days.
If you’re doubling up on hard sessions, your liver bounces back quickly, but your leg muscles are playing catch-up for much longer than 12 hours.
For runners doing morning and evening workouts, or racing on consecutive days, this explains why that second session can feel so much harder even after “eating well.”
The practical takeaway: if you have less than 24 hours between demanding sessions, prioritize carbs immediately post-exercise (that 1.2g/kg/hour window matters) but also manage expectations. Your muscles may still be underfueled regardless of how well you eat.
Six Weeks of Breathwork Slashed Anxiety Scores by 24%
Researchers randomized 107 adults (mean age 41) to either six weekly 90-minute online Conscious Connected Breathwork (CCB) sessions or a waitlist control. CCB involves continuous rhythmic breathing without pauses between inhale and exhale.
Anxiety scores dropped from 43.87 to 33.31 in the breathwork group, a 10.56-point reduction with a large effect size (Cohen’s d = 1.44). The control group barely budged (43.00 to 41.11). PubMed Study Link
My Thoughts
Race anxiety and pre-run nerves are real for a lot of recreational runners.
This study caught my attention because the effect size was huge and the intervention was accessible. Six weekly sessions delivered online produced meaningful anxiety reduction that stuck.
For runners who struggle with performance anxiety before races, structured breathwork might be worth exploring as part of your mental toolkit.
The caveat: this wasn’t tested specifically in athletes, and “conscious connected breathwork” is more intensive than simple box breathing. But the principle that deliberate breathing practice can meaningfully shift anxiety levels has strong support here.
