Spirulina supplementation improves oxygen uptake in arm cycling exercise
Authors: Tom Gurney, Owen Spendiff
DOI / Source: https://doi.org/10.1007/s00421-020-04487-2
Date: 05 September 2020
Reading level: Intermediate
Why This Matters for Freedivers
If spirulina can raise hemoglobin even a little, it may help with oxygen transport—basically giving you a slightly “bigger oxygen taxi fleet.” This study also hints that some supplements can reduce heart rate and oxygen cost at a fixed workload, which (in theory) could support longer, calmer efforts in training—but it’s not freediving-specific, so treat it as a “promising clue,” not a guarantee.
Synopsis
This paper tests a simple but interesting idea: can one week of spirulina supplementation make exercise feel “cheaper” for the body?
The researchers used a double-blind crossover design with 11 healthy young men who weren’t trained in arm cycling. For 7 days they took either 6 g/day spirulina or a placebo, then swapped after a washout period. After each supplement phase, they did two 30-minute arm-cycling bouts at 55% of their VO₂max, followed by an incremental test to fatigue. The team continuously measured oxygen uptake (VO₂), heart rate, and respiratory exchange ratio (RER), and measured hemoglobin from a finger-prick before exercise.
The headline findings were: - Hemoglobin increased after spirulina compared to placebo (about a ~10 g/L bump in this group). - During the 30-minute submax sessions, oxygen uptake was lower with spirulina, and heart rate was lower too—meaning the same work rate demanded less from their cardio-respiratory system. - RER didn’t change significantly overall (so the “fuel mix” didn’t clearly shift), although the authors discuss a possible trend toward slightly more fat use later in the steady work. - During the incremental test, VO₂ at the point of fatigue was higher with spirulina, but time to fatigue wasn’t significantly different.
So what does that mean in plain terms. In these participants, spirulina seemed to nudge the body toward being a bit more efficient at a steady workload (lower VO₂ and HR), and to reach a slightly higher oxygen uptake at the end of a hard ramp test—without clearly extending how long they lasted. The authors suggest a few possible reasons, with the most practical being the hemoglobin increase (more oxygen-carrying capacity) plus potential effects on blood flow / nitric oxide pathways, but they also note that the exact mechanism isn’t nailed down here.
For freedivers, the most useful angle isn’t “spirulina will make you dive deeper.” It’s the concept that small shifts in blood oxygen-carrying capacity and cardiovascular strain can show up quickly, even in a short intervention—and that’s exactly the kind of lever freedivers care about when trying to stay calm and economical.
Abstract
Purpose Spirulina has previously been reported to improve high-intensity exercise performance and hemoglobin. However, spirulina’s effect on arm cycling exercise has yet to be investigated. The purpose of this study was to investigate the responses of spirulina supplementation on hemoglobin and on oxygen uptake, RER and HR during seated arm cycling exercise.
Methods In a double-blinded randomized crossover design, eleven males untrained in arm cycling ingested 6 g/day of spirulina or placebo for seven days. Seated on the Arm Crank Ergometer, each participant performed a baseline VO₂max test, and then after supplementation, 2×30-min submaximal exercise bouts corresponding to 55% of their VO₂max, followed by an incremental test to fatigue. A seven-day wash-out period was required between conditions. Oxygen uptake, RER and HR were measured continuously during exercise and hemoglobin measured prior to exercise after both conditions.
Results Spirulina significantly increased Hb in comparison to placebo. After spirulina supplementation, during the 30-min exercise bouts, oxygen uptake and HR were significantly lower, while RER was not significantly different. In comparison to placebo, spirulina significantly increased oxygen uptake at time of fatigue. Time taken to fatigue was not different.
Conclusion Spirulina supplementation significantly reduces oxygen uptake and HR during arm cycling submaximal exercise, allowing for an increased oxygen uptake during an incremental test to fatigue.