Could Popeye have drunk coffee?

Popeye devoured spinach to make his muscles strong. But his creators, like everyone else, were duped by a chemist’s miscalculation of this vegetable’s iron content. Could coffee have helped?

Many athletes drink coffee not just for a pick-me-up, but to help them perform. Sports scientists have explored caffeine’s exercise enhancing properties for more than a century.

More recently, the focus has shifted from aerobic exercises like cycling and running to caffeine’s effect on muscle strength, power and endurance.


Looking at the evidence

Studies have found varying effects of caffeine on muscle performance. One meta-analysis – larger analysis that pools all eligible studies together – found that caffeine increased the lower body’s muscle contraction ability by 7%. However, another meta-analysis found no effect. Part of the reason could be the type of tests that were used.

A new meta-analysis of ten studies has now reported that caffeine improves muscle strength and power using one-repetition maximum and vertical jump tests, respectively. Curiously, further analyses found that caffeine improved upper but not lower body strength.

Scientists are not clear exactly how coffee might enhance performance, but evidence suggests its effects could be multifactorial. It seems to revolve around caffeine’s stimulation of the nervous system. This likely explains why it helps people feel more alert. Caffeine may improve performance by enhancing muscle contraction and subduing perceived pain and exertion.

Maintaining muscle mass and strength is particularly important for healthy aging. Strength training programs tailored to individual needs, supplemented by protein and good nutrition, will alleviate risk of sarcopenia, falls, hospitalisation and associated decline.


Is coffee good for everyone?

It’s important to note that statistical analyses of research outcomes work on averages. Caffeine research shows notable variation in people’s response to it. This variation is apparent in research on its heart and cognitive benefits.

A study published last month reported that a large pooled analysis of several population-based studies showed caffeine intake was associated with decreased atrial fibrillation (abnormal heart rhythm that can impact heart function). Up to 6 cups of coffee a day was not linked with increased severity of abnormal heart rate overall. But around a quarter of patients reported that coffee did trigger atrial fibrillation.

People’s muscle function also shows varied response to caffeine. One study, for instance, reported that some participants’ back-squat performance decreased by 7% with caffeine intake while others increased by up to 10%. Authors concluded that, “Due to inter-individual variability in responses to caffeine consumption, it must be used in an individualized manner.”

The authors noted that people are likely to be caffeine ‘responders’ or ‘non-responders.’ In this they refer to genetic differences. People who are slow caffeine metabolisers lack a gene that is seen in fast caffeine metabolisers – you know, those lucky people who can have a coffee at midnight and still sleep soundly.

It turns out that positive links between coffee and heart health are seen in fast, but not slow, coffee metabolisers.

So if you know you can happily tolerate caffeine, indulging in a cuppa before exercise might help boost endurance and build muscle – perhaps not quite like Popeye but stronger and healthier nonetheless.



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