Marathon Science

This is how I fueled a full training week about six months back.

This was a heavy, high-volume block, often running and lifting more than once a day.

Total daily carbohydrate and protein is the lever I pay the most attention to. Research is starting to suggest timing is probably a second lever, behind total daily intake.

But it earns more weight in a heavy block like this, when you’re running and lifting more than once a day and have to refuel for the next session. This is where I like to supplement my real food approach with carb and protein supplement to hit my daily energy needs.

On easy or shorter runs, roughly 60 to 75 minutes or under, I personally don’t find I need a gel to run well.

Once a run gets long, around 11 to 12 miles plus, or turns into quality work, I’ll fuel it.

During big blocks in and post race nutrition supplementation and mixes can help me hit my daily energy targets, which matter for recovery.

Of course to support the quality of the session itself, so I get as big a training stimulus as possible. And fueling well, especially keeping it up toward the end, may help me recover faster and start topping up my stores for the next session.

Long runs I also use to practice fueling, so my body’s used to it on race day. I reach for a BETA Fuel gel and its dual-source 1:0.8 blend, which can help raise how much carbohydrate I’m able to absorb.

When I have a second run the same day, or a hard session the next day. I get carbs in soon after, because the window before the next quality session is short.

On doubles I lean on BETA Recovery, with its dual-source carbs and protein, to help restock muscle and liver glycogen before the next session.

On Saturday I take a BETA Fuel Drink Mix after my one run. I get carbohydrate in as soon as possible, to start replenishing my glycogen stores in both muscle and liver before my quality session on Sunday.

A big goal of my training is to use nutrition to support my quality sessions, so I get a training stimulus.

Six supplements clear the evidence bar for cycling performance. The rest of the marketed shelf doesn’t.

Whitfield et al. applied the Australian Institute of Sport framework to a UCI-commissioned review in IJSNEM and named six Group A supplements with a sound evidence base: caffeine, creatine, sodium bicarbonate, beta-alanine, dietary nitrate, and glycerol.

Each lever is different. Caffeine acts on the central nervous system. Creatine refills the rapid-energy system. Sodium bicarbonate buffers acid outside the cell. Beta-alanine builds buffer inside it. Nitrate cuts the oxygen cost of submaximal work. Glycerol holds onto fluid in long, hot events.

The protocols are specific. Caffeine 3 to 6 mg/kg, one hour pre. Creatine 20 g/day for 7 days or 3 g/day for 28. Sodium bicarbonate 0.3 g/kg, 1 to 3 hours pre, enteric capsules for GI. Beta-alanine 4 to 6 g/day for 4-plus weeks, slow-release tablets. Nitrate 8 to 16 mmol, 1.5 to 2 hours pre. Glycerol 1.0 to 1.5 g/kg with 15 to 30 mL/kg water, 1 to 1.5 hours pre. Test in training first.

Scope caveats matter. Most underlying research used Tier 2-3 men in cycling protocols. Nitrate shows no ergogenic effect at a VO2max at or above 65 ml/kg/min, and current literature doesn’t support a positive nitrate effect in women.

One caveat travels with all six. A 2022 review of 50 supplement surveys found 28% of products contained undeclared substances. A 2025 Australian survey found 35% of 200 products contained WADA-banned substances. The authors point to HFL, HASTA, NSF, and Informed Sport for third-party testing.

Huge thanks to Whitfield, Egan, Del Coso, Derave, Saunders, and Burke for this review.

Whitfield et al. (2026), International Journal of Sport Nutrition and Exercise Metabolism.
doi:10.1123/ijsnem.2025-0111

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Same pace. Same power. No alarms on the watch.

Then my Stryd Duo data told a different story.

Nineteen miles at marathon pace, three tempo blocks built in. Warmup ran even at 51/49. When pace dropped to 6:23-6:59, Leg Spring Stiffness Balance peaked at 52 to 53% on the left. In each tempo block. Three for three.

Small asymmetries are common. My April baseline at marathon pace runs within 1% on LSS (L 8.5 / R 8.4), and GCT Balance sits at 50/50.

What mattered on March 29 wasn’t the asymmetry itself. It was the change from baseline. An old difference getting stronger plus a new one showing up.

Reading that signal takes triangulation: Duo data, how the legs feel, recent training context. My right hip had been niggly for weeks. Two of three checks pointed toward compensation.

I swapped the next quality session for an easy bike. Protective, not corrective.

Comment GYM and I’ll DM you the Calf Gym Strength Plan. Targeted work for the symmetric single-leg capacity your long runs actually test.

Most runners are already eating more sodium than they need. Adding more during exercise often does nothing for performance.

McCubbin (2025) reviewed decades of research on sodium in athletes (Monash University, Performance Nutrition). The picture that emerges challenges how the endurance world talks about salt.

What athletes typically eat:

○ Australian male endurance athletes: about 3,869 mg/day
○ Female endurance athletes: about 3,176 mg/day
○ National guidelines: under 2,400 mg/day

The kidneys handle the surplus. McCubbin (2019) fed athletes double their normal intake for three days. Only about 21% was retained. By contrast, Goulet (2018) gave a single dose four hours before exercise and about 77% was retained. The mechanism: kidneys adjust how fast they clear sodium within about two hours. Days of loading get cleared. One dose, taken close to the start, sticks around.

So when does sodium during exercise matter? The modelling (a fluid-sodium model from the review) suggests three conditions need to line up:

○ The athlete can replace more than 70% of fluid losses
○ They tolerate that fluid volume
○ It’s practical within event rules

Typically this means ultra-endurance events and prolonged team-sport in heat. Below the 70% fluid-replacement threshold, blood sodium rises naturally as you lose more water than salt. Adding sodium at low fluid replacement can push blood sodium too high.

For everyone else, the evidence points to “season to taste.” Sodium during exercise doesn’t appear to influence performance unless it also drives greater fluid intake.

One caveat: most of these studies used non-elite, predominantly male, non-weight-bearing athletes. Generalising to elite runners and females is less certain.

Huge thanks to McCubbin for this work.

Paper: https://doi.org/10.1186/s44410-025-00011-9

Also Fueling Endurance Podcast one of the best ones out there.

Speed, hills, and cadence change which leg tissues take the most damage. Cadence was the only lever that helped all three. Same kilometers, different tissues take the hit.

Van Hooren et al. (2024) modeled tissue loads at the knee, shin, and Achilles in 19 recreational runners. Treadmill, 1-minute bouts, modeled not directly measured.

Faster running lowered total stress per km on every tissue because there were fewer steps. The model predicted damage on the knee rose at the same time. Shin and Achilles damage trended upward but did not reach statistical significance.

Damage uses load raised to a tissue exponent. A step twice as hard counts about 128x as much for bone, more than 600x for tendon. Fewer-but-harder steps can raise damage even when total stress falls.

I’m not a huge fan of changing running form when their is no pain or injury but sometimes manipulating cadence, surface and speed can be important when coming back from injury.

Cadence at about 6% above preferred (roughly +10 steps/min) was the only lever linked to lower modeled damage on all three tissues at the same running speed.
How to cue it: set a metronome at your current cadence × 1.06. Or filter your music library by BPM. Hold the new cadence on easy runs first.

Knee: the authors suggest raising cadence and avoiding large volumes of downhill running.

Achilles: cut fast-interval volume first. Then raise cadence and cut uphill volume.

Shin: raise cadence first. Cutting uphill volume also lowers modeled damage.

Observational modeling, not a training trial. n = 19 recreational runners, treadmill. Knee loading lacks in-body reference data. Framework, not prescription. “Run faster to reduce injury load” is the framing the authors warn against.

Huge thanks to Van Hooren, van Rengs, and Meijer for this work.
Van Hooren et al., Scand J Med Sci Sports, 2024.

doi:10.1111/sms.14570

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Eight days of taurine raised whole-body sweat loss by about 26 to 27% in the heat.

Naddafha, Stout, and Evans (Nutrients, 2026) reviewed the small human trial base on taurine and heat tolerance. The pooled studies put trained-to-active adults on cycling and walking protocols at 35 to 37.5 °C.

The pattern across trials is consistent. Acute dosing at ~50 mg/kg, 1.5 to 2 hours pre-exercise, may lift end-exercise sweat rate by about 12.7% and drop final core temperature from 38.5 to 38.1 °C. Cycling time to exhaustion went up by roughly 10%. Eight days at ~50 mg/kg/day appears to recruit 22 to 32% more active sweat glands. In one trial, the heat-balance ceiling shifted upward from ~21.7 to ~25.0 mmHg.

The authors suggest taurine may act in the hypothalamus, lowering the temperature at which the brain turns on sweating. Animal work supports this. Direct human confirmation is missing.

The catch is real. The evidence base is small: about 2 to 3 primary trials, n=11 to 15 per trial, mostly young trained men, cycling and walking, not running. More sweat means more fluid and sodium to replace. Taurine may also dampen perceived exertion in a way that masks physiological strain. It won’t help if sweat can’t evaporate, or if you’re already fully heat-acclimated.

Where this matters: racing in heat without full acclimation. Promising, but preliminary.

Huge thanks to Naddafha, Stout, and Evans for this careful review.

Source: Naddafha S, Stout JR, Evans C. Nutrients, 2026.
doi:10.3390/nu18040592

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New research: stiffer runners are typically more economical. But there’s no universal optimum.

Masson, Millet, and Kerhervé just published a narrative review in Sports Medicine synthesizing studies on stiffness and running through March 2025.

The headline finding is consistent. Higher whole-body stiffness is linked to better running economy. Kubo et al. (2010) reported plantar-flexor tendon stiffness correlated with 5000 m time at r = 0.76. Arampatzis et al. (2006) found the most economical runners had a stronger calf and a stiffer Achilles tendon.

Then the picture gets more nuanced.

“Stiffness” isn’t one thing. Whole-body, joint, muscle-tendon, and tissue-level stiffness have different units and measurement methods. They don’t always change together.

More important: most runners naturally settle on stiffness, contact time, and stride frequency that follow an inverted-U curve. Too low and too high are both detrimental. The authors note that an “individually defined optimal stiffness” hasn’t been systematically researched.

Two practical signals:

→ Long-term: 6 to 14 weeks of plyometric or combined strength training improved tendon stiffness and running economy.

→ Warm-ups: a plyometric warm-up improved economy, and the change tracked rising leg stiffness. In male well-trained runners, greater flexibility from static stretching was linked to worse economy and shorter distance in a 30-minute run. The same protocol didn’t change economy in female runners.

Most cross-sectional data is correlational. Stiffer runners may already be more economical for other reasons, like training history or anatomy.

The takeaway isn’t “be stiffer.” Each runner likely sits on their own inverted-U. The biggest movers are weeks of plyometric or strength work.

Huge thanks to Masson, Millet, and Kerhervé for this work.

Paper: https://doi.org/10.1007/s40279-026-02406-7

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training

New research: a ketone monoester did not improve exercise capacity at the modern 120 g/h fueling target. It also reduced how efficiently the body used those carbs by about 10%.

Martyn et al. (2026, Journal of Applied Physiology) ran a single-blind crossover RCT in 8 trained male cyclists (VO2max ~66 mL/kg/min). Each rode three trials: placebo, 120 g/h CHO, and 120 g/h CHO + 75 g ketone monoester (KME). The ride was 3 hours at 95% of lactate threshold, followed by an exhaustion test at 150% LT.

Three metabolic shifts moved together with KME, all in the same direction:

Mean blood glucose: 4.4 vs 4.9 mmol/L
Exogenous CHO oxidation: 1.35 vs 1.50 g/min
Oxidation efficiency: 67% vs 75%

Then the capacity test. Time to exhaustion was 349 s on CHO and 319 s on CHO + KME. Median gap of 17 seconds, P = 0.48. Effectively a tie. Both far outperformed placebo (75 s).

Why the disconnect? The authors suggest KME slowed the rate at which ingested carbs reached the bloodstream. By the start of the capacity test, blood glucose and whole-body CHO oxidation had equalized between the two CHO conditions. Carb availability wasn’t the limiter at that moment.

KME also reduced markers of fat breakdown (NEFA, glycerol). The marketed “more fat oxidation” effect didn’t show up here.

For the trained male cyclist already fueling near 120 g/h: this study doesn’t support adding KME for a capacity edge. It also fits a growing body of literature that ketone esters do not improve prolonged endurance performance. Whether the reduced CHO oxidation efficiency matters for longer events, harder finishes, or higher CHO intakes is an open question this study did not test. Translating to women, runners, or fasted exercise would need more evidence.

Huge thanks to Martyn et al. for this work. Paper: https://doi.org/10.1152/japplphysiol.01072.2025

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New research says endurance athletes need more protein on recovery days than on training days. The repair bill comes due after the work, not during it.

Witard, Hearris, and Morgan reviewed a decade of metabolic studies in Sports Medicine. In endurance-trained men, indicator amino acid oxidation (IAAO) data point to about 1.8 g/kg/day on a standard training day, about 1.95 g/kg/day on a low-carb training day, and over 2.0 g/kg/day on a recovery day. Endurance athletes habitually eat about 1.5 g/kg/day. The training-day target is roughly 2.3 times the RDA for sedentary adults.

After a hard endurance session, early evidence suggests a per-meal dose of about 0.5 g/kg supports myofibrillar repair. For a 70 kg runner, that’s roughly 35 g. Worth flagging: this estimate comes from a single dose-response study in trained cyclists and triathletes, with a wide confidence interval (0.26 to 0.72 g/kg). The post-endurance dose is about twice the post-strength dose.

Where the evidence is still thin: no IAAO study has been done specifically in female endurance athletes, the luteal-phase guideline is extrapolated from team-sport data, no IAAO study has covered masters athletes over 65, and most cited studies recruited cyclists or triathletes rather than runners.
Huge thanks to Witard, Hearris, and Morgan for this review.

Witard, Hearris, and Morgan (2025), Sports Medicine.