Study archive · page 29

Across 24 blinded crossover studies of real or simulated competition, acute caffeine intake increased high-intensity actions in intermittent sports such as team, racket and combat sports, including more sprints, accelerations, decelerations and body impacts. Caffeine also raised the success rate of sport-specific actions.

⚠What it shows: Strong for a supplement claim: results pooled from 24 trials where athletes took caffeine or a dummy in random order without knowing which, during real or simulated matches. The effects are modest rather than dramatic, and they will vary between sports and individuals.Meta-analysis · Int J Sports Physiol Perform

A meta-analysis of 14 randomised trials in 626 healthy adults found whey protein paired with resistance exercise increased lean body mass by 2.24 kg, while using whey to replace other calories was linked with a 4.20 kg drop in body weight and a 3.74 kg drop in body fat from baseline.

⚠What it shows: Reliable for the lifting result, weaker for the weight loss figures: results pooled from 14 trials in 626 healthy adults, and the weight and fat losses were measured against people's own starting points rather than a comparison group. Whey also failed to significantly beat other protein sources when compared head to head.Meta-analysis · J Am Coll Nutr

A meta-analysis of 7 randomised trials covering 402 people found taurine supplements, taken alone or combined with exercise training, did not significantly improve cognitive scores; the pooled evidence does not support taurine as a cognition enhancer.

⚠What it shows: A useful debunk resting on a thin base: results pooled from just 7 trials covering 402 people, mixing those with and without cognitive impairment, found no overall benefit. The one positive signal came from a subgroup combining taurine with medication and needs confirming before it means anything.Meta-analysis · Int J Food Sci Nutr

An umbrella review pooling 72 randomised trials found curcumin supplementation lowered LDL cholesterol by 5.84 mg/dL and triglycerides by 13.15 mg/dL, both clinically meaningful reductions; total cholesterol fell and HDL rose too, but by amounts too small to matter clinically.

⚠What it shows: A big evidence base with a wobble: results pooled from 72 trials, but the trials disagreed with each other a great deal, so exact effect sizes are uncertain. Benefits were clearest in people with metabolic conditions such as type 2 diabetes, using enhanced-absorption forms for at least 8 weeks.Meta-analysis · Nutr Rev

Across 21 controlled trials in highly trained athletes, melatonin supplementation at doses of 5 mg to 100 mg improved antioxidant status, inflammatory response and markers of muscle and liver damage. Its direct effect on sports performance remains unproven.

⚠What it shows: Encouraging for recovery markers but not proof of performance: a sweep of 21 controlled trials in highly trained athletes found better blood markers, yet doses ranged widely from 5 mg to 100 mg and no direct performance benefit was demonstrated. Findings in elite athletes may not transfer to everyday exercisers.Systematic review · Nutrients

A meta-analysis found unilateral resistance training was no more effective than ordinary bilateral training at improving sprint-type horizontal movement, despite the popular specificity argument for single-leg work. Both approaches improved performance, and combining strength with plyometric training showed the largest effects for bilateral work.

⚠What it shows: A fair verdict from results pooled from several trials in healthy people, and both training styles clearly worked. The trials differed in who they tested and how they trained, so the ideal mix for any one athlete or sport is still an open question.Meta-analysis · Sports Med

Resistance training produces clearly greater muscle growth than aerobic training, according to a meta-analysis of 21 studies. The gap showed up at the whole-muscle level and inside both slow-twitch and fast-twitch muscle fibres.

⚠What it shows: Strong evidence: results pooled from 21 studies of good or moderate quality, and they agreed with each other remarkably well. Every measurement came from the thigh muscles, so other muscle groups are an educated guess.Meta-analysis · Sports Med

Neuromuscular electrical stimulation produced virtually identical strength gains to conventional strength training across 19 randomised studies in healthy people, when training volume was matched between methods.

⚠What it shows: A trustworthy null: results pooled from 19 studies in healthy people, all matching the amount of training work between methods, found gains statistically indistinguishable. It covers strength only, so muscle size and sport performance remain open questions.Meta-analysis · J Strength Cond Res

Resistance training substantially improved handball players' maximal strength, muscle power and ball-throwing velocity across 18 pooled studies of 275 players, though it did not significantly improve isokinetic strength.

⚠What it shows: Points firmly in one direction, but treat the size of the effect with suspicion: results pooled from 18 studies of 275 players disagreed with each other a great deal, and favourable results appear likelier to have been published. The direction of the benefit is more trustworthy than its magnitude.Meta-analysis · Int J Environ Res Public Health

Pooled results from 38 randomised trials suggest soluble fibre supplements improved every standard blood fat measure in people with type 2 diabetes: triglycerides fell by 16.97 mg/dL, LDL cholesterol by 11.14 mg/dL, total cholesterol by 13.87 mg/dL, and HDL cholesterol rose by 1.74 mg/dL.

⚠What it shows: Strong as supplement evidence goes: results pooled from 38 trials, all in people with type 2 diabetes, and all four blood fat measures moved the same way. The improvements are modest, and it is not yet known whether they translate into fewer heart problems.Meta-analysis · Prostaglandins Other Lipid Mediat

Endurance training and combined endurance-strength training improved blood sugar control and cholesterol more than strength training alone in overweight and obese adults, in a meta-analysis of 46 trials. Combined training also beat endurance alone on insulin resistance and triglycerides.

⚠What it shows: Solid but not settled: results pooled from 46 trials in overweight and obese adults, but the trials disagreed with each other quite a bit, so the exact size of each advantage is uncertain even if the overall direction looks consistent.Meta-analysis · Int J Environ Res Public Health

Across 34 randomised trials covering 1391 adults with type 2 diabetes plus overweight or obesity, aerobic exercise improved blood glucose, glycated haemoglobin, insulin resistance, body fat, waist size and cholesterol compared with standard treatment alone.

⚠What it shows: Strong direction, fuzzy sizes: results pooled from 34 trials in 1391 middle-aged and older adults with type 2 diabetes and excess weight, and most improvements were modest. The authors themselves flag considerable uncertainty in several of the outcomes.Meta-analysis · J Diabetes Complications

Garlic supplementation reduced triglycerides, total cholesterol, LDL cholesterol, diastolic blood pressure, BMI and waist circumference versus placebo across 19 randomised trials of 999 adults with metabolic disorders.

⚠What it shows: Worth noting, not a prescription: results pooled from 19 trials of 999 adults with metabolic problems favoured garlic across six risk markers, but the studies disagreed with each other considerably. There are also signs that trials with negative results may never have been published, which would flatter the picture.Meta-analysis · BMC Complement Med Ther

Pooled trial data in resistance-trained men and women found a ketogenic diet did not significantly change one-rep max squat (106 participants) or bench press (119 participants) compared with other diets. The reviewers add that a single max lift may not capture performance in longer hypertrophy-style sessions.

⚠What it shows: Solid as far as it goes: results pooled from several trials of trained lifters, but only 106 people for squat and 119 for bench, so a small effect either way could be missed. The authors also flag that a one-rep max is a blunt tool for judging how a full training session actually goes.Meta-analysis · Nutrients

Pooled trials in adults with overweight or obesity found fibre supplements modestly improved blood sugar control on average, cutting HbA1c by 0.13% and fasting insulin by 0.82 μIU/mL, but effects split sharply by fibre type: one subgroup saw LDL cholesterol rise by 9.03 mg/dL and another saw systolic blood pressure rise by 3.85 mmHg.

⚠What it shows: Trust the headline averages, treat the fibre-type splits with more care: results pooled from 34 trials in 1804 adults with overweight or obesity, but the subgroup comparisons rest on fewer studies and the trials often disagreed with each other. The surprising unfavourable shifts in cholesterol and blood pressure need confirming before anyone rewrites the fibre rulebook.Meta-analysis · Nutr Rev

A meta-analysis of 13 randomised trials in adults aged 60 and over found soy protein interventions improved muscle mass over time and matched animal protein and other comparators on body composition, strength and physical function.

⚠What it shows: Reassuring rather than dramatic: a sweep of 13 trials in adults over 60, every one using soy at widely varying doses, so it says nothing about pea, rice or blended plant proteins. Effects on strength and function were limited across the board.Meta-analysis · Nutrients

MRI studies show knee cartilage thickness and volume dip by roughly 3.3% to 4.9% immediately after running, but the changes appear transient, with some measures back to baseline within 91 minutes and existing cartilage defects unchanged within 48 hours. Reviewers concluded a single bout of running does not appear detrimental to knee cartilage.

⚠What it shows: Reassuring but far from settled: a sweep of 24 imaging studies covering 446 knees, and the authors rate the certainty of the evidence as very low, with only a third of studies at low risk of bias. It also only examined single runs, so it says nothing about years of training or people with existing knee problems.Meta-analysis · Osteoarthritis Cartilage

Pooled data from ten trials in 892 adults with knee osteoarthritis found high-intensity strength training was no better than lighter training or routine care for knee pain, function, stiffness or quality of life, with a comparable rate of adverse events.

⚠What it shows: A null you can actually use: results pooled from ten trials in 892 adults with knee osteoarthritis found lighter strength work matched heavy training on almost every measure, including safety. The comparison lumped lighter training together with routine care, so it cannot rank those two against each other.Meta-analysis · Am J Phys Med Rehabil

In a small 8-week trial, 29 women aged 40 to 70 with knee osteoarthritis improved similarly in pain, function, strength and fear of movement whether they did closed chain exercises in water or on land. Only the 40-metre walk test favoured the land group.

⚠What it shows: Useful but small: a trial of 29 women assigned at random to pool or land sessions for 8 weeks, so it cannot speak for men or for longer-term joint outcomes. Both groups improved, and only one walking test told them apart.Study · Health Sci Rep

A meta-analysis of 57 randomised trials in 3194 adults found that at least 12 weeks of moderate aerobic exercise raised protective apolipoproteins, lowered harmful ones and improved atherogenic lipid ratios, markers thought to predict heart risk better than a standard cholesterol panel.

⚠What it shows: A solid evidence base: results pooled from 57 trials in 3194 previously inactive adults, though the individual marker shifts were small in absolute terms. Whether those shifts translate into fewer heart attacks was not tested.Meta-analysis · Sports Med

Inspiratory muscle strength training lowered systolic blood pressure by an average of 7.93 mmHg and diastolic by 3.80 mmHg across pooled results from 12 randomised trials, and the analysis judged these effects conclusive.

⚠What it shows: About as solid as this field gets: results pooled from 12 trials in 386 people across five countries, plus a further statistical check suggesting the blood pressure findings are unlikely to be overturned. The trials were short though, so nobody knows whether the effect lasts beyond 3 months.Meta-analysis · J Clin Hypertens (Greenwich)

Pooled results from seven randomised trials suggest beetroot juice supplementation reduces the muscle damage marker creatine kinase and improves strength, jump performance and soreness threshold after damaging exercise, while inflammation markers stay unchanged.

⚠What it shows: Promising but not settled: results pooled from seven trials, and the trials disagreed with each other on several outcomes, so the exact size of the benefit is uncertain. Inflammation markers did not move, which muddies the simplest explanation for how it works.Study · Ann Med Surg (Lond)

Across 7 trials in 370 older adults, exercise training improved muscle oxygenation, with resistance training enhancing oxygen extraction and blood vessel function, endurance training improving microvascular blood flow and oxidative capacity, and walking helping those with narrowed leg arteries.

⚠What it shows: Encouraging but thin: a sweep of all the studies turned up only 7 trials covering 370 older adults, some healthy and some with narrowed leg arteries. Programmes varied so much in length and intensity that no single best prescription emerges.Systematic review · Arch Gerontol Geriatr

Exercise training improved executive function in adults with depression across 14 randomised trials of 1201 people, with the largest gains in reasoning and planning. Benefits appeared for aerobic exercise at moderate to vigorous intensity, done three or more times a week for at least 13 weeks.

⚠What it shows: Solid enough to take seriously: results pooled from 14 trials of 1201 adults with depression all point the same way, though the overall gains were small. It also cannot say whether sharper thinking translates into relief from depression itself.Meta-analysis · Sports Med