Simply smelling chocolate can boost your gym workout, according to a recent study that’s generated headlines around the world.
No eating, no calories, just smelling.
The journal claimed:
“Sniffing chocolate could make your leg day workout easier, even on an empty stomach.” Headlines followed, including:
“Sniff chocolate, do more reps without trying harder!” This came with the qualifier:
“We’re not even kidding. It’s a psychobiology thing.” But is all this too good to be true? Does the research check out? I’m an exercise scientist and here’s my verdict.
What the researchers did
The study recruited 23 young men who had been doing resistance training at least twice a week for the past two years. So, although they weren’t elite athletes, they were diligent gym-goers.
Resistance training is when you work your muscles against a load. This can be lifting weights, using machines, or using your own bodyweight.
In this study, the men used the leg extension machine. This is where you sit down, hook your shins under a padded bar, and straighten your knees against a weight (like a kicking motion).
In the study, each participant came into the laboratory three separate times after fasting overnight for roughly ten hours.
On each visit they sniffed a jar containing one of three things (in a random order) for 30 seconds: –a 90 per cent cocoa dark chocolate mixture –a 60 per cent cocoa milk chocolate mixture –plain distilled water (the control).
Then they jumped onto the leg extension machine and did as many sets of ten reps (repetitions) as possible at a weight that corresponded to 80 per cent of their ten rep maximum. That’s 80 per cent of the heaviest weight they could lift ten times. They sniffed the jar between each set.
They kept going until they felt they could not complete another set.
What they found
Across all the sets, the participants managed to complete roughly 18 more reps with dark chocolate and roughly nine more with milk chocolate, compared to sniffing water.
This means sniffing dark chocolate improved their performance by more than 25 per cent, which is quite substantial.
By comparison, we know from other studies that caffeine increases resistance training by about one repetition per set on average. This is much less than the current study found.
The participants also rated how hungry the smells made them feel compared to sniffing water. Dark chocolate made them feel less hungry, while milk chocolate didn’t impact their hunger. For what it’s worth, participants said milk chocolate smelt nicer than both water and dark chocolate.
The authors suggested that, because hunger competes for your attention, it can reduce your gym performance. So, the smell of dark chocolate might trick your brain into feeling fuller, allowing you to exercise harder.
The exact reason why dark chocolate had a larger effect than milk chocolate is unclear. But the authors suggest that the rich smell of dark chocolate might have been quite familiar to the participants, which could have made them feel fuller.
But there is one large limitation that needs to be acknowledged.
The study is described as a double-blind trial, which implies the participants don’t know which “intervention” they are getting. But the control was water, and water doesn’t smell. This means every participant probably knew which one was chocolate, and which was the control.
The main performance measure was also how many reps you could do before you decide to stop. This is not exactly a test of performance. It is a test of how hard you are willing to push yourself.
So it is highly likely the results were impacted by the participants’ knowledge of the study goals, and what the control condition was.
This may explain why the effect was even larger than what we would see with something like caffeine, when it probably shouldn’t be.
To be fair, the authors acknowledge these limitations in their paper. They also describe their study as “exploratory”. Nevertheless, their conclusions are oversold a bit. So we cannot say sniffing chocolate boosts your gym workout based on this study. (The Conversation)
