Many people choose to take a caffeinated, protein-based supplement before working out – and new (often expensive) products are hitting the shelves every day. Previous studies have demonstrated the positive effects of such multi-ingredient pre-workout formulations (PREW) on strength, power output, muscular endurance, and muscle mass. However, a new double-blind, randomised control trial published in the Journal of the International Society of Sports Nutrition has suggested they may not be any more effective than a carbohydrate-only supplement.
What Did the Study Find?
The 43 middle-aged, physically active individuals who completed the study were randomly assigned to one of two groups: the caffeinated, protein-based pre-workout supplement group or the carbohydrate-only supplement group. Each group took 30g of their assigned supplement, mixed with 400ml of water, 15 minutes before each workout session. Measurements of fat and fat-free mass, waist and hip circumferences, muscle thickness, strength, power output, and muscle endurance performance were collected before and after a six-week resistance training programme performed three times per week.
While the caffeinated, protein-based pre-workout group showed a significant reduction in waist circumference, no significant differences between groups were identified for isometric force, countermovement jump, medicine ball throw, and upper and lower body muscle endurance performance – all of which improved in both groups.
Caffeine – known for its thermogenic (increases body temperature and metabolic rate) and ergogenic (performance-enhancing) effects on endurance and strength, has become the predominant ingredient in pre-workout supplements in recent years. Yet these results suggest that some of these supplements may not prove any more beneficial for resistance training gains than carbs alone.
What Does This Mean for Us?
The researchers had actually predicted that compared to a carbohydrate-only supplement, a caffeinated, protein-based PREW would likely further stimulate fat loss and lead to a more favourable body composition and better performance outcomes. Partly because previous studies conducted in middle-aged adults identified beneficial effects of caffeinated PREW containing protein and fortified with amino acids in maximising resistance training outcomes.
It would make sense to think that the ingredients in a caffeinated, protein-based pre-workout supplement would facilitate more gains than carb-only, with the former typically leading to a reduced perception of effort. However, this study suggests that carbohydrates – widely thought of as the ‘king of fuel’ – are just as effective.
The global sports nutrition industry is worth a lot of money – in 2024, Euromonitor valued it at $28 billion. So, any scientific research on specific products and ingredients is welcomed – particularly because supplements are not regulated in the way food products are. With new products popping up all the time on the supplement shelves – often accompanied by aggressive marketing about their alleged effects – it is crucial we educate ourselves about their benefits (or lack thereof).
However, this certainly doesn’t mean all caffeinated pre-workout supplements don’t promote additional resistance training benefits. It is just one study – and a relatively small one at that. The researchers themselves highlight several limitations to the study, including the lack of a standardised diet and the fact participants already drank three to five coffees or teas a day, which may have affected the results.
The Bottom Line
Along with the limitations mentioned above, this study only looked at middle-aged adults, and the researchers flag that more studies with larger sample sizes and longer-term investigations are needed.
When it comes to performance supplementation, everyone is different, and what works for somebody else might not work for you. Also, this study doesn’t show that the supplement is ineffective, just that it’s no more effective than a carb-only pre-workout supplement.
However, in a largely unregulated industry and with social media feeds more saturated with information than ever, this study shows that it’s always worth doing your research and checking in with experts and medical professionals before taking something new. In reality, some products and ingredients may not be quite as effective as we initially thought.
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Hannah Bradfield is a Senior Nutrition Writer across Women’s Health UK and Men’s Health UK. An NCTJ-accredited journalist, Hannah graduated from Loughborough University with a BA in English and Sport Science and an MA in Media and Cultural Analysis.
She has been covering sports, health and fitness for the last five years and has created content for outlets including BBC Sport, BBC Sounds, Runner’s World and Stylist. She especially enjoys interviewing those working within the community to improve access to sport, exercise and wellness. Hannah is a 2024 John Schofield Trust Fellow and was also named a 2022 Rising Star in Journalism by The Printing Charity.
A keen runner, Hannah was firmly a sprinter growing up (also dabbling in long jump) but has since transitioned to longer-distance running. While 10K is her favoured race distance, she loves running or volunteering at parkrun every Saturday, followed, of course, by pastries. She’s always looking for fun new runs and races to do and brunch spots to try.