Most athletes focus on muscle mass as they age. The research says that's only part of the picture.
New data published in The Proceedings of the National Academy of Sciences (PNAS 2026) shows that mitochondrial decline plays a central role in age-related performance loss. And crucially, it's not inevitable. Exercise can reverse it, even later in life.
The key finding: when mitochondrial function was blocked, the benefits of training disappeared. This tells us mitochondrial adaptation is the mechanism, not just a side effect of training.
Train consistently. Train hard enough to matter. The biology responds.
Share this with an athlete who thinks decline is just part of getting older.
#EndureIQ #endurancetraining #health #Mitochondria #triathlon #TSS #fitness #science #sportsscience
Two athletes. Same VO2max. Same workout. Both adapt. But to completely different things.
The difference is VLamax.
VLamax is your maximal glycolytic rate. Think of it like: V = Velocity/Rate, La = Lactate, Max = Maximum. It represents how fast your body produces lactate during hard efforts, and it has a large effect on which energy system actually contributes to the work.
Low VLamax Athlete
*Aerobic, efficient, diesel
*Strong steady-state power
*Greater fat oxidation
High VLamax Athlete
*Explosive, glycolytic, punchy
*Strong sprint ability
*Higher carbohydrate reliance
An athlete with low VLamax doing high-intensity intervals (30/30s or 40/20s) heavily recruits glycolytic pathways, and thus creates a strong signal to increase VLamax, leading to unwanted changes that will lower lactate threshold and increase lactate production at lower wattage. They might respond better to longer intervals that allow them to reach a high percentage of VO2max without stimulating VLamax.
An athlete with high VLamax doing the exact same session will also respond quite differently. Their glycolytic system might dominate before the aerobic system is properly challenged, meaning they never reach a high percentage of VO2max. The body adapts to what it actually experienced, not what the session was designed to do.
Both of which may, or may not be the desired training response. As always, "Context, before Content".
By repeatedly doing these types of sessions without understanding, you may be unknowingly training the glycolytic system with the goal of increasing VO2max, causing your lactate threshold to drift downward, carbohydrate reliance to increase, and fat oxidation to drop.
The same workout can lead to a completely different internal response.
This is why intervals have to be specific to your goals and your physiology.
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#endureiq #endurancetraining #cyclingphysiology #vo2max #vlamax #triathlon #triathlontraining #trainingphysiology #hiit #lactate #sportsscience #performancecycling
Pro cyclists are now targeting 90 to 120g+ of carbohydrate per hour on demanding stages.
A decade ago, 60g was considered high. 😅
Our latest Training Science Summaries breaks down why the key shift isn't just about amount of carb but the timing. And why riders have moved intake onto the bike and away from before and after stages.
Stage racing doesn't give you time to recover. Less than 24 hours between efforts. Fueling should be viewed as part of an integrated strategy that supports both performance and recovery. Especially in multi-day contexts.
The principle applies beyond professional cycling. Match your carbohydrate intake to the demands of the session. Easy days don't need high availability. Hard days and racing do.
Save this one for race week.
#EndureIQ #RaceNutrition #CarbIntake #TrainingScience #CyclingPhysiology #Triathlon #EnduranceNutrition #GutTraining #TSS
April is now behind us, and we’re super excited to bring you another episode of TSS 🎉
TSS is where Dr. Dan Plews and Dr. Ed Maunder review 10 studies and break them down with practical applications for anyone interested in coaching, sport science, or training.
This month they cover a huge variety of topics:
* Race nutrition & fuelling strategies
* Mitochondrial function & muscle mass
* Heat & altitude for enhanced adaptation
* Rapid weight loss drugs
* Blood flow & carbohydrate timing during exercise
* Sprint training & muscle glycogen depletion
* Exercise & back health, good or bad?
* Menstrual cycle data & substrate use during exercise
* Exercise training & impulse control
* How mitochondrial function declines with age
If you’re interested in TSS, don’t miss out. For a very small monthly investment you’ll get access to genuinely informative content. Check out the link in bio.
Last post I talked about the Norwegian 4×4. The most (over) hyped interval session on the internet. Intensity x duration interactions are key.
The comments came in. And they weren’t wrong, all three formats have value within the right context. Context before content, always. But those comments reminded me of the perfect follow-up study.
If you’re using all three formats across a training block, does the sequence matter?
Sylta et al. (2016) tested exactly this with 63 well-trained cyclists over 12 weeks. Three groups, identical total load, different organisation:
INC: Long to short (4×16 → 4×8 → 4×4) DEC: Short to long (4×4 → 4×8 → 4×16) MIX: Randomly rotated
All groups improved significantly across VO2 max, 40-min power, peak power, and power at 4 mmol/L lactate. No significant differences between groups. But the MIX group underperformed on nearly every outcome and had the highest non-responder rate (44% vs 13% in INC). Structured sequencing wins. Small margins matter.
So which way should you sequence? Think non-specific to specific.
If your event is threshold-dominated, think HYROX or close to an hour of sustained effort, progress shorter to longer, building tolerance at the intensity your event demands.
If your event is VO2 max-dominant, think 2km rowing, start longer to build the aerobic ceiling then compress duration and sharpen intensity closer to race day. Time at race-specific intensity improves movement economy, and efficiency is a key determinant of performance.
📖 Sylta et al. (2016). The effect of different high-intensity periodization models on endurance adaptations. MSSE.
The Norwegian 4×4 protocol seems to have become the holy grail of interval training. Every fitness influencer seems to believe it’s the best way you improve VO2max. 4 min at 90–95% max heart rate, four reps, twice a week.
However, The science doesn’t back the hype.
Seiler et al. (2013) compared three effort-matched interval protocols in trained cyclists over 7 weeks:
* 4 × 4 min @ ~94% HRmax — 16 minutes of total work
* 4 × 8 min @ ~90% HRmax — 32 minutes of total work
* 4 × 16 min @ ~88% HRmax — 64 minutes of total work
The 4×4 group trained the hardest. Highest heart rates. Highest blood lactate. Highest RPE — significantly higher than both other groups across every session of the entire 7-week block.
And when it came to improving VO2 max? The 4×4 was the only group that failed to produce a statistically significant improvement.
The 4×8 group,slightly lower intensity, twice the accumulated work duration, improved VO2 max, power at VO2 max, and power at 4 mmol/L blood lactate significantly. Every single athlete in that group showed moderate to large gains. The 4×4 showed the smallest and most variable response.
Intensity and duration are not independent variables, they interact. The adaptive signal your body receives isn’t determined by intensity alone. It’s shaped by the combination of how hard you go and how long you sustain work at that intensity. The key is to get the right balance to drive adaptation while maintaining consistent training ✊.
📖 Seiler, S., Jøranson, K., Olesen, B. V., & Hetlelid, K. J. (2013). Adaptations to aerobic interval training: Interactive effects of exercise intensity and total work duration. Scandinavian Journal of Medicine & Science in Sports, 23(1), 74–83. /10.1111/j.1600-0838.2011.01351.x
In case you missed the March TSS — we covered 10 of our favourite sports science studies, some brand new, some classics.
We got into ketone esters and post-workout timing for training adaptations, why overtraining happens when you ignore training stress and how to avoid it, and whether one bad night of sleep actually matters.
We looked at GLP-1 medications and why they work better paired with structured exercise, the effect of the menstrual cycle and reproductive life stages= on HRV, and a fresh take on carbohydrate fuelling guidelines.
We also covered carbohydrate mouth rinsing, the overlooked upper body technique that could level up your cycling, what makes super shoes super, and — one of our favourite topics — whether an afternoon nap is actually good for you.
Check it out via the link in bio. $7.50 for some of the best sports science out there — perfect for coaches and students wanting to stay current! ✊🙌
OCEANSIDE 70.3 — SEASON OPENER. What a way to kick off the 70.3 season!
First up, a massive shoutout to John Whitehead, one of Dr. Dan Plews’ personal one-on-one coached athletes, who absolutely delivered at Oceanside 70.3 — finishing 2nd overall in the 60-64 age group in a time of 4:49, complete with a personal best run split (by one second — but a PB is a PB! ).
And then there’s George Berar, who opened his season in style with an outstanding race AND secured his spot at World Championships. 🌍 That’s how you start a season. 🔥🔥🔥
One of the most common questions I get as a coach: “How far below the top of Zone 2 should my endurance sessions be?”
My answer? There’s no such thing as training stress without Intensity and duration. 🎯
At Endure IQ & ENDUROX, we deliberately build a wide Level 2 training zone. And here’s why:
Banging out training at the top of your Zone 2 every session, regardless of how long you’re out there, is a fast track to undesirable excessive fatigue.
As you get fitter, the top of your L2 can actually feel surprisingly fast and hard from a muscular output point of view. A 30-minute run at the top of L2 vs. a 2-hour run at the top of L2? Completely different training load and overall stress.
Two hours running at the ceiling of Zone 2 will leave you cooked. 🔥
📍 Short sessions? You can sit near the top of L2.
📍 Long sessions? Drop into the middle or lower end of L2. Even dipping into L1 is totally fine for really long days.
Self-regulation within larger a Zone 2 band allows you to manage your week, recover properly, and, most importantly, stay consistent.
Remember, consistency is always the absolute key ✊
Ironman Taupō holds so many special memories for me. Wishing the best of luck to everyone racing tomorrow — enjoy every second out there.
A few memories from my journey on this course:
2013 – My first ever Ironman. Finished in 9:23, 2nd in the age group, and learned the brutal lesson of what Ironman is really all about.
2015 – (No photo sadly!) Came back and managed to win the age group overall and break 3 hours for the marathon for the first time. Chased down cramping @fitter.co.nz in the last 5 km…🤩😘
2017 – First time breaking 9 hours on an exceptionally windy and tough day (those who raced that year will remember). Another sub-3 marathon. 10th Overall.
2018 – 8:35 and an age group course record. 9th overall. My coached athletes @terenzo1 and @janvberkel taking 1 and 4 overall. We had a great time training together for that!
2022- 8:50 on a hard day weather wise. A return to Ironman after 4 years, and I managed to take the tape in a AG only race.
And some great 70.3 memories too — wins in 2020 and again in 2023.
Taupō really is one of the best Ironman races on the planet. Have an incredible day out there tomorrow and enjoy the experience. Race smart, take chances and let’s go!! 🔥🔥YIEW!
A recent editorial in the International Journal of Sports Physiology and Performance (Skorski-Forster & Daniel, 2025) explores how social media is reshaping sports science and coaching — and why that shift comes with real risks.
Their central concern is clear: The same features that make social media powerful also make it fragile.
Speed, brevity, and reach reward simple messages over nuance. Complex findings get flattened into single numbers, bold claims, and polished graphics. Uncertainty, limitations, and context are easily lost.
The authors emphasise that misinformation doesn’t usually arise from bad intent. Well-meaning practitioners may share partial interpretations. Researchers may oversimplify for attention. Bias quietly steers conclusions. Perhaps we’re all guilty of that.
But social media also shifts the meaning of authority.
Credibility is often inferred from follower count, production quality, or confidence of delivery rather than methodological expertise.
In sports science and coaching, this creates space for influencers with little or no formal qualifications to speak with the same perceived authority as trained researchers and experienced practitioners.
Persuasive does not equal accurate. Confident does not equal competent.
When complex evidence is filtered through personalities who lack training in research design, statistics, or critical appraisal, nuance collapses.
Social media has democratised access to sports science and coaching knowledge. But perhaps democratisation without standards can quietly turn confidence into counterfeit expertise. 🤷♂️ Interesting article and full reference is below.
Reference: Skorski-Forster, S., & Daniel, L. (2025). Scientific integrity in the age of visibility: The role of academics in navigating social media discourse. International Journal of Sports Physiology and Performance. �
One thing that really stood out to me at HYROX Auckland the other week was just how many people are now tattooed. I don’t have any tattoos myself, which probably puts me in the minority these days—but it did get me thinking. What do tattoos actually do to heat dissipation and sodium loss?
There’s a 2017 study showing that tattooed skin had higher sodium concentrations in sweat and reduced water loss at the skin level. That combination could matter for thermoregulation, because if you’re losing less water through the skin, you may not dissipate heat as effectively, and overheating becomes more likely.
Now, if you believe sodium loss is directly linked to cramping (that’s certainly not me 😃), then in theory this could increase cramp risk. That said, sodium does play a role in intra/extracellular fluid shifts, so it’s still something worth thinking about.
Important caveat: that 2017 work used simulated sweat conditions.
A follow-up study in 2019 looked at a more realistic exercise model—4 × 5-minute cycling intervals—and found no difference in sweat rate or sodium concentration between tattooed and non-tattooed skin.
So where does that leave us? Jury’s still out. It’s possible that heavily tattooed individuals may see meaningful changes in sodium loss or skin excretion under certain conditions. This may in turn affect heat tolerance. But for the odd, smaller tattoo, the real-world exercise data doesn’t seem to scream major “problem.”
References:
Luetkemeier, M. J., Hanisko, J. M., & Aho, K. M. (2017). Skin tattoos alter sweat rate and Na⁺ concentration. MSSE, 49(7), 1432–1436.
Rogers, E., Irwin, C., McCartney, D., Cox, G. R., & Desbrow, B. (2019). Tattoos do not affect exercise-induced localised sweat rate or sodium concentration. JSMS, 22(11), 1249–1253.
