Improve Your Endurance

Why: The ACSM says gradual progression of intensity and volume may reduce the risks of exercise. Sudden jumps in distance or intensity, especially after a break, raise the chance of injury and of burning out.

Who it applies to: Anyone starting or restarting, and people with a new race goal.

Try instead: Build up over weeks, repeat a week when needed, and use the talk test to keep most sessions easy.

Why: The consensus statement on overtraining describes overload plus inadequate recovery as the route to non-functional overreaching and overtraining syndrome. The NHS Couch to 5K plan builds in rest days between runs.

Who it applies to: Motivated beginners and regular athletes who feel guilty about rest.

Try instead: Keep most sessions easy, plan hard days apart, and take rest days.

Why: MedlinePlus describes rhabdomyolysis as the breakdown of muscle tissue that releases harmful contents into the blood and often damages the kidneys. It lists severe exertion such as marathon running and severe dehydration among causes, and dark, red or cola-coloured urine, muscle aching and weakness among symptoms.

Who it applies to: Anyone doing a much harder or longer session than usual, especially in the heat or when dehydrated.

Try instead: Build up gradually, drink fluids after strenuous exercise, and contact a medical professional promptly if you have these symptoms.

Why: The AHA statement notes that vigorous exercise can acutely increase the risk of sudden cardiac death and heart attack in susceptible people, particularly the unfit. These symptoms are a reason to stop.

Who it applies to: Everyone, including experienced athletes.

Try instead: Stop, rest, and get urgent medical care for chest pain or pressure, fainting, severe breathlessness or new palpitations.

Why: The NHS notes a high risk of heat exhaustion or heatstroke during hot weather or exercise, and advises avoiding extreme exercise on very hot days and the midday sun.

Who it applies to: Outdoor runners, cyclists and hikers, children, older adults and people with long-term conditions.

Try instead: Train in cooler hours, slow down, carry fluids and stop at the first signs of dizziness, nausea or confusion.

Why: The consensus statement on overtraining lists dietary caloric restriction, insufficient carbohydrate or protein, iron deficiency and magnesium deficiency among factors that can contribute to the picture. It also reminds readers that persistent fatigue needs a medical look.

Who it applies to: Athletes cutting weight, skipping meals or eating very little before long sessions.

Try instead: Eat regularly and enough to support your training; ask a doctor or dietitian if you are worried. If restricting food feels hard to stop, seek support.

Eating disorders and disordered eating →

Why: The overtraining consensus advises excluding infection and organic disease when performance falls and fatigue lingers. Hard sessions on top of unresolved illness make recovery harder.

Who it applies to: Anyone who feels ill, or has been unwell recently.

Try instead: Rest until you feel well, then return gradually.

Return to Your Routine After Illness → Return to Exercise After a Break →

Why: The IOC consensus statement says only a few supplements (including caffeine, creatine, buffering agents and nitrate) have good evidence of benefit, that responses vary widely, that an inadvertent banned substance in a supplement is a known risk, and that a full nutritional assessment should come before supplement use.

Who it applies to: Anyone tempted by powders, tablets or blends promising extra endurance.

Try instead: Put effort into training, sleep and food first. If you compete under anti-doping rules, get expert advice before using any supplement.

Energy supplements and adrenal claims → Medicine interactions →

Why: The World Anti-Doping Agency Prohibited List bans anabolic agents (including anabolic steroids and SARMs), erythropoietins and agents affecting red-cell production, and growth hormone in sport. We did not review health-risk studies for them and give no instructions.

Who it applies to: Anyone competing under anti-doping rules, and anyone tempted by black-market products.

Try instead: Improve endurance through training, recovery and nutrition. If you have a medical reason to use a prescribed hormone or blood medicine, your doctor decides, and athletes should check anti-doping rules.

Why: An AHA scientific statement notes that large exercise volumes and vigorous intensities are associated with potential cardiac maladaptations, and that the relationship with physical activity often follows a U- or reverse J-shaped curve. The overtraining consensus describes the cost of too little recovery.

Who it applies to: Highly motivated exercisers.

Try instead: Aim for steady, sustainable training and look after recovery.

Why: The nitrate meta-analysis found a clear benefit for time to exhaustion but only a small, non-significant effect on time trials. Effects were seen more often in inactive to recreationally active people.

Who it applies to: Social media and shop promotions for sports supplements.

Try instead: Treat supplements as small extras, trial them in training and do not expect them to replace a training plan.

Why: Training advice in the sources separates easy aerobic work from occasional vigorous or very vigorous sessions. Doing everything at the same medium-hard effort tends to leave you tired without a clear training signal.

Who it applies to: Recreational runners and cyclists who chase pace every session.

Try instead: Keep most sessions at a talking pace, and make the hard ones few and clearly hard.

Why: The NHS and ACSM recommend strengthening on at least 2 days a week, and a meta-analysis found strength training improved running economy in highly trained runners.

Who it applies to: Endurance athletes who feel strength work is for someone else.

Try instead: Add two short, regular strength sessions.

Why: The nutrition review for distance runners advises a personalised and practised plan because of the risk of gut discomfort, and the IOC statement advises trialling any performance supplement in training before using it in competition.

Who it applies to: Anyone preparing for a race or long outing.

Try instead: Rehearse your plan on long training sessions.

Partly supported. In a meta-analysis of 28 trials in healthy adults aged 18 to 45, interval training gave a possibly small extra VO2max gain over continuous endurance training, and both gave large gains compared with no exercise. It does not show that intervals are better for older adults, people with health conditions or for every sport.

Not supported. An AHA statement notes potential cardiac maladaptations with large volumes and vigorous intensities, and the overtraining consensus describes performance falling when overload is not matched by recovery.

Partly supported. A meta-analysis found a moderate benefit for time to exhaustion but only a small, non-significant benefit for time trials, with effects seen more often in less-trained people.

Supported with caveats. An umbrella review of 21 meta-analyses found caffeine ergogenic for aerobic endurance with mostly moderate-quality evidence, but studies were mainly in young men and caffeine has side effects.

Possible but unproven. A meta-analysis of 4 trials found an average gain of 3.00 mL per kg per minute, but with wide uncertainty, high heterogeneity and few studies.

Not as a rule. The ACSM says drinks with electrolytes and carbohydrate can have benefits over water alone under certain circumstances, and that fluid plans should be customised because sweat rates differ.

Banned in sport and not an option on this site. These substances appear on the WADA Prohibited List.