REF-1720 · Bond et al., 2026 · Journal of Applied Physiology · Paper · PubMed

In 11 young men, wearing infrared-emitting clothing before, during and after one interval session (10 × 3 min) raised a few muscle signalling markers linked to mitochondrial biogenesis above a sham garment

Phosphorylated CaMKII right after exercise (P = 0.001 cytosolic, P = 0.003 nuclear) and NRF1 and TP53 mRNA (P ≤ 0.013) — with no difference in any angiogenesis marker; nothing was measured beyond 3 h, there was no fitness or performance outcome, and the funder, Kymira Ltd, is also one author's affiliation

Main caveat: 11 young men, training status not reported (VO2max 48.0 ± 4.6 mL/kg/min); one session per condition.
limited, mixed evidenceMeasured on non-athletes to trained athletesRead from the abstract only

Bond and colleagues at Loughborough University tested whether clothing made of infrared radiation-emitting fabric changes the muscle's signalling response to a hard interval session.

Eleven young men did the same session twice — ten 3-min intervals with 3 min at 25 W between them — once in the infrared-emitting garments and once in non-emitting sham garments, worn before, during and after exercise, in counterbalanced order and single-blind. Muscle biopsies were taken before, immediately after and 3 h after the session.

Phosphorylated CaMKII was higher right after exercise in the infrared condition, phosphorylated p38 MAPK rose from baseline only in that condition, and NRF1 and TP53 mRNA were higher than in the sham condition. None of the angiogenesis-related proteins or genes differed, although the hypothesis covered both pathways.

The authors conclude that the fabric augments some of the acute signalling linked to mitochondrial biogenesis, and state that whether this turns into greater long-term adaptation remains to be determined.

Participants

11 males, 22 ± 4 years, VO2max 48.0 ± 4.6 mL/kg/min.
Not in the abstract: training history, sport, body mass, how they were recruited.

Protocol

Session (done twice): 10 × 3 min at a power output equal to 60% of the difference between the gas exchange threshold and peak power output, with 3 min at 25 W between intervals.
Conditions: infrared radiation-emitting fabric (IREF) clothing vs non-emitting clothing (SHAM), worn before, during and after the session; repeated-measures, counterbalanced, single-blind.
Measurements: muscle biopsies at baseline, immediately after exercise and 3 h after; cytosolic and nuclear content of phosphorylated signalling proteins, and mRNA of genes linked to mitochondrial biogenesis and angiogenesis.
Not in the abstract: who made the garments and what they covered, how long they were worn before and after, the time between the two sessions, diet and prior-exercise control, whether blinding held, which muscle was sampled, effect sizes, and how many proteins and genes were tested.

Key Results

MarkerInfrared fabric vs sham
Phosphorylated CaMKII, cytosolic, immediately after exercisegreater with IREF, P = 0.001
Phosphorylated CaMKII, nuclear, immediately after exercisegreater with IREF, P = 0.003
Phosphorylated p38 MAPK, cytosolic and nuclearrose from baseline to post-exercise in IREF (P = 0.008 and P = 0.005) and not in SHAM — a change within each condition; no test between conditions is given in the abstract
NRF1 mRNAgreater with IREF immediately after exercise (P ≤ 0.013) and 3 h after (P = 0.002)
TP53 mRNAgreater with IREF immediately after exercise (P ≤ 0.013); at 3 h the abstract reports a difference for NRF1 only
Angiogenesis-related proteins and genesno difference between conditions for any target
The abstract gives P values only: no means, effect sizes or intervals, and no count of the targets tested, so how many comparisons the positive results were drawn from is unknown.

Practical Application

One hard interval session in infrared-emitting clothing left a few muscle signalling markers (phosphorylated CaMKII, NRF1 and TP53 mRNA) higher than the same session in a sham garment, in 11 young men (mean VO2max 48.0 mL/kg/min) — and that is all it shows. No fitness, mitochondrial or performance outcome was measured, and the authors themselves say that whether the acute change becomes more adaptation remains to be determined.
To "should I buy infrared kit to get more from my training?": the base has no trial showing that such clothing improves fitness or performance. This is one session, markers only, funded by a company that is also one author's affiliation. Nor does it show that the kit does not work: no fitness or performance outcome was tested. Wearing it because it is comfortable is a personal choice, not a training decision (the base's practice, SYNTH-83).
Inference, not tested here: a session's signal is brief and adaptation is the sum of many sessions plus recovery (PHYS-18), and a marker that moves does not show that the outcome moved (PHYS-44); read the result as a reason for a training study, not as a reason to change kit or training.
Half of the hypothesis did not hold: no angiogenesis-related protein or gene responded differently.

Limitations

11 young men, training status not reported (VO2max 48.0 ± 4.6 mL/kg/min); one session per condition.
Markers only, followed for 3 h: no protein content, mitochondrial function, VO2max or performance, and no training period.
Funding: the PubMed record lists Kymira Ltd as the funder, and one of the seven authors is affiliated with Kymira Ltd; the PubMed record carries no conflict-of-interest statement, and the abstract does not name the maker of the garments.
Single-blind: who was blinded, whether the participants could tell the garments apart and whether the people handling the samples knew the condition are not in the abstract.
P values without effect sizes; the number of proteins and genes tested and any correction for multiple tests are not in the abstract.
The p38 MAPK finding is a change within the infrared condition, not a tested difference between conditions.
Written from the abstract and the PubMed record; full text not read.
How this entry was checked and changed
Why this level

a crossover with fewer than 15 participants (B), one step down because every outcome is a signalling marker (rule 3); read from the abstract only