Review questions whether carb-loading helps once placebo and in-race fuelling are controlled
A thin week: I could verify few papers inside the window, so this edition adds dated items from the prior 30 days, all read through your half-marathon lens (nutrition and heat physiology). I found no verified neuroscience or climate-science paper this week.
The 30-second version
A Sept 2026 review in IJSNEM finds carb-loading evidence weak once blinding and in-race carbohydrate are considered.
A Eur J Sport Sci study (10 men) finds perceived strain tracks heat strain but can't replace measurement.
Blueberry 'faster half marathon' headlines rest on a nine-runner, industry-funded trail trial in IJSNEM.
01IJSNEM · Sept issue
Carb-loading's benefit is unproven once placebo and in-race fuelling are controlled
Design: a critical review of 14 published carbohydrate-loading studies (not a new trial). Only two were double-blind, placebo-controlled; only four gave carbohydrate during exercise. Both double-blind studies, which also gave in-exercise carbohydrate, found no performance benefit.
The other two in-exercise-carbohydrate studies showed a benefit of moderate size, Cohen's d about 0.35, which the authors say is comparable to effects reported for placebo nutrition interventions. Limits: few studies, mixed test types (time-to-exhaustion vs time trial), and it concerns ~90-240 minute efforts. I worked from the abstract; funding and conflict statements were not available to me. Consult a qualified professional before changing diet or training.
Bottom line: weak, mostly indirect evidence; it doesn't show carb-loading fails, only that its benefit is unproven when fuelling during exercise and blinding are handled properly.
In heat, how hard it feels tracks body strain, but isn't interchangeable
Design: randomized crossover trial in 10 healthy, active, non-heat-acclimated men (mean age 29), cycling 60 minutes in hot-dry and warm-humid conditions with equal wet-bulb globe temperature. A perceptual strain index (from effort and thermal sensation) correlated very strongly with physiological strain indices (r = 0.94-0.98).
But agreement was loose: limits of agreement ran from -2.8 to 4.2 arbitrary units, so the authors say the measures are not interchangeable. Limits: ten men, cycling not running, indoor lab. Date caveat: the Exa index lists Sep 9; the Wiley listing shows Oct 1, so the exact online date is unconfirmed. Funding not found. Heat illness is serious; consult a qualified professional about hot-weather training.
Bottom line: small lab study, modest evidence; feeling-based strain is a rough screen for heat stress, not a safety measurement.
Claim checked: 'blueberries improve half-marathon time' overreaches a nine-runner trial
Runner's World coverage (Sep 24) of an IJSNEM study, plus a UFV release (Sep 14). The study was a double-blind, placebo-controlled crossover in nine recreational trail runners: seven days of freeze-dried blueberry powder vs placebo before a simulated 22.2 km trail race. Race time was faster with blueberries (p = .003); the university says about seven and a half minutes, and Runner's World reports 2:37:05 vs 2:44:30 (4.2%). Heart rate and perceived exertion did not differ.
Limits: n = 9, one trail course, no road or half-marathon test; the dose was about three cups of berries daily by the researchers' calculation. The US Highbush Blueberry Council funded it. Earlier lab studies by the same authors found no differences. I could not open the journal page; I used the abstract and press accounts.
Claim checked: partly supported for trail racing in nine runners; not shown for half marathons, and industry funding warrants caution.