Recent articles and updates [September 2025]
Heart rate variability (HRV), endurance coaching, training talk, wearables, entrepreneurship, and some ramblings.
Hi there 👋
I hope all is well.
Here’s a new recap of articles, research, and updates from the past month. I hope you’ll find the articles useful, and I would like to take the opportunity to thank you for your support.
Please feel free to comment below or in the articles should you have any questions, and I will follow up soon.
Take care!
The past two weeks, I set up a metabolic cart at my lab, and then took the opportunity for a good round of baseline testing, when not too busy enjoying the trails around Brisighella:
VO2max: ~65 ml/min/kg
Substrate utilization: fat oxidation rates between 0.8 and 1.2 grams per minute up to threshold intensity
Running economy: about 200 ml/kg/km for supershoes, 2-4% worse in regular shoes
First ventilatory and lactate threshold: around my recent 50 km race pace.
I am now doing a 2-month block with a few additional experiments in terms of training (hills, cross-training for both intensity and muscular endurance) and non-training-related stressors (heat).
HRV trending well again, which might signal a good moment to put more stress on the body (see my discussion here). But that’s a story for another day.
As mentioned earlier, athletes I personally coach can have access to these tools and my lab at no additional cost.
p.s. get coached.
Heart rate variability (HRV) 🫀
Heart Rate Variability (HRV) and Psychological Stress
I’ve recently come across two cases in which HRV data was tracking very well with psychological stress in athletes I coach, and I took the opportunity to discuss in this blog how effective morning HRV data can be, and how we can use it to make meaningful adjustments that will benefit our long-term health and performance.
Wearables ⌚️
On The Accuracy of Wearables for HRV
A few weeks ago week, a study by Joshua Hagen and his group caught my eye. The study, led by Michael Dial, looked at the accuracy of a few wearables in the context of measuring night heart rate and HRV data. As you know very well by now, there are better ways to track your physiological response, i.e. first thing in the morning (reasons covered in detail here, with yet another example from recent research here).
Wearables are however out there and despite measuring at a sub-optimal time, they could still provide accurate data, which just needs to be contextualized and interpreted differently. Do they? Learn more, here.
How Do You Track Sleep?
Some things are useful to track while others.. not so much. I have received this question a few times, given some of my work, hence here is an overview of my current thinking.
TrainingTalk 🏃🏻♂️
Winschoten 50 km: Training, Nutrition and Race Report
A few weeks ago, I ran the Winschoten 50 km, closing in 3h 43’ for a personal best over this course and distance (11 minutes better than last year).
In this blog, I cover the training and nutrition of the past three months, including periodization, key sessions, cross-training (cycling, strength), chronic diet, race week changes, heart rate variability (HRV), pacing, and more.
CoachCorner ⏱️
I’ve enjoyed this course on Strength and Conditioning for endurance athletes, even though my favorite on UESCA remains Bob Seebohar’s Nutrition course - covering lots of what I have discussed in my periodized nutrition blog (here).
Building 🛠️
Pranayama Protocols: Yogic Respiration (Resonant Frequency) and Chatushkona (Box Breathing)
Recently, I’ve been practicing a few Pranayama breathing techniques. My interest in pranayama has been revived by Alessandra, who is in her second year of yoga teacher training and is writing a thesis on breathing techniques.
Alessandra has been using HRV4Biofeedback to collect data during different protocols, and this time around, she recruited me to be part of her experiment. The practice led to the implementation of box breathing in the HRV4Biofeedback app, which you can find in the latest version of the app:
Interviews and Podcasts 🎙️
The Data-Driven Path to Aging Well with Marco Altini
A conversation with Dr. Kimberly Besuden, covering: What HRV actually measures (and what it doesn’t), The difference between stress and stress response, How aging athletes can use wearables the right way, Why stability > high numbers when it comes to HRV, The real keys to performance: sleep, nutrition, and recovery. See here.
Cuándo medir la variabilidad de la frecuencia cardíaca: ¿por la mañana, por la noche o de forma continua?
Something I recently wrote for Fissac and my Spanish-speaking friends, here.
Personal Coaching for Runners
If you are interested in working with me, please learn more here, and fill in the athlete intake form, here.
How to Show Your Support
No paywalls here. All my content is and will remain free.
As a HRV4Training user, the best way to help is to sign up for HRV4Training Pro.
Thank you for supporting my work.
That’s a wrap for this month. Thank you for reading and see you next month.
Recent Updates:
Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching. He is a certified ultrarunning coach.
Marco has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.
He is co-founder of HRV4Training, advisor at Oura, guest lecturer at VU Amsterdam, and editor for IEEE Pervasive Computing Magazine. He loves running.
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