REF-1598 · Starling et al., 1996 · Medicine & Science in Sports & Exercise · Paper · PubMed

In ten competitive male cyclists, five days of inosine at 5,000 mg a day did not change Wingate power or the work done in a 30-min self-paced ride compared with placebo, time to fatigue in a constant-load supramaximal sprint was shorter on inosine (99.7 vs 109.7 s), and blood uric acid rose. From the abstract

Main caveat: Ten men; written from the abstract.
limited evidenceMeasured on trained to highly trained athletesRead from the abstract only

Starling and colleagues gave ten competitive male cyclists inosine (5,000 mg a day) and placebo for five days each. After each period the riders did a Wingate test, a 30-min self-paced performance ride scored by the work done, and a constant-load supramaximal sprint held to fatigue. Blood was drawn before and after each supplement period and after each test.

Uric acid was higher after inosine than after placebo, and 2,3-DPG did not change. Wingate peak and end power, fatigue index and work did not differ between treatments, nor did work in the 30-min ride; the supramaximal sprint lasted longer on placebo.

The authors conclude that inosine taken for several days does not seem to improve aerobic performance or short-term power on the bike and may impair performance in some tests.

Participants

n = 10 competitive male cyclists. Age, body mass and fitness are not given in the abstract.

Protocol

Supplements: inosine 5,000 mg a day or placebo, five days each (crossover).
Tests after each period: Wingate test (WIN); 30-min self-paced ride, total work (END); constant-load supramaximal sprint to fatigue (SPN). Whether the three tests fell on one day is not stated.
Blood: before and after each supplement period and after each test (uric acid, 2,3-DPG, lactate).

Key Results

MeasureInosinePlaceboDifference
Wingate peak power (W/kg)8.5 ± 0.38.4 ± 0.3not significant
Wingate end power (W/kg)7.0 ± 0.36.9 ± 0.2not significant
Wingate fatigue index (%)18 ± 218 ± 2not significant
Wingate work (kJ/kg per 30 s)0.45 ± 0.020.45 ± 0.02not significant
Lactate after the Wingate (mmol/L)12.2 ± 0.512.9 ± 0.6not significant
Work in the 30-min ride (kJ/kg)6.1 ± 0.36.0 ± 0.3no difference
Lactate after the 30-min ride (mmol/L)8.4 ± 1.09.9 ± 1.3no difference
Supramaximal sprint, time to fatigue (s)99.7 ± 6.9109.7 ± 5.6longer on placebo, P < 0.05
Lactate after the sprint, 14.8 ± 0.7 and 14.6 ± 0.8 mmol/L, did not differ between treatments (the abstract's order, read as placebo then inosine).
Uric acid was higher after inosine (P < 0.05); no values are given. 2,3-DPG did not change.
The abstract does not say whether the ± values are SD or SEM.

Practical Application

Inosine is not worth taking for performance: in ten competitive male cyclists, five days at 5,000 mg a day changed neither Wingate power nor a 30-min ride against placebo, shortened a supramaximal sprint to fatigue by 10 s (99.7 vs 109.7 s), and raised blood uric acid.
The base holds no other inosine trial; this one is small and old, and it found no benefit on any of its three tests.
Inference, not tested here: a supplement that raises uric acid is a poor choice for anyone with gout or a history of kidney stones, a question for their doctor.
Not from this paper; the base's own practice: products outside the short evidence-backed list are not added (SYNTH-67).

Limitations

Ten men; written from the abstract.
Randomisation and blinding come from MEDLINE indexing, not from the abstract; no washout between periods is described in either.
One dose for five days; no longer use.
Uric acid is reported only as higher; no values and no safety outcome.
With three tests and several measures, one significant difference could be chance (inference).
Published in 1996.
How this entry was checked and changed
Why this level

a crossover with fewer than 15 participants (n = 10) on performance outcomes, numbers reported; randomisation and blinding rest on the indexing only, and no washout is described