Side Effects of Gym: Real Risks vs Common Myths

The real side effects of the gym are mostly avoidable: strains and sprains from poor technique or dropped weights, rhabdomyolysis after an extreme first session, overtraining from too little rest, contaminated supplements, and the serious harms of anabolic steroids. The popular fears are mostly myths: lifting doesn't stunt height, women don't turn bulky by accident, muscle can't turn into fat, and resistance training is good for most hearts, not bad. Start gradually, rest, skip steroids, and see a doctor for the warning signs below.

Real risks vs myths at a glance

How common are gym injuries?

Less common than most people think. A 2017 systematic review of injuries in weight-training sports (weightlifting, powerlifting, bodybuilding, strongman and others) found:

• bodybuilding had the lowest rates, about 0.24 to 1 injury per 1,000 hours of training,
• strongman (4.5 to 6.1 per 1,000 hours) and Highland Games (7.5) had the highest,
• the shoulder, lower back, knee, elbow and wrist were the usual sites, mostly strains, tendinitis and sprains,
• overall, these sports "appear to have relatively low rates of injury compared with common team sports".

Those are competitive athletes lifting very heavy. Ordinary gym-goers get hurt in more ordinary ways. A US study of weight-training injuries seen in emergency departments from 1990 to 2007 found the most common diagnosis was a sprain or strain (46.1%), and the most common cause was weights dropping on the person (65.5%). Free weights were involved in 90.4% of cases.

So the biggest preventable risks are boring: a plate sliding off an unclipped bar, a dumbbell dropped on a foot, a rushed rep with too much weight.

Lower your risk:

• Learn the main lifts with a trainer before going heavy.
• Use collars on barbells and wear closed shoes.
• Add weight in small steps; work out training loads with the one-rep max calculator rather than guessing.
• Stop a set when your form breaks, not when you collapse.

What is rhabdomyolysis, and who gets it?

Rhabdomyolysis is the breakdown of muscle tissue that releases muscle contents into the blood. According to MedlinePlus, the protein myoglobin released from damaged muscle can harm the kidneys, and causes include severe exertion, severe dehydration, extremes of body temperature and some drugs. Acute kidney failure occurs in many people with it; early treatment lowers the risk of permanent damage.

It's rare, but gyms do see it. A 2021 case series described previously fit adults admitted to hospital after their first spin class, with a triad of muscle pain, weakness and dark, tea-coloured urine within a week. These were people doing an unaccustomed, intense session for the first time. Doing far too much, too soon is the pattern to avoid.

Lower your risk:

• Make your first few weeks easy, even if you feel you could do more.
• Drink fluids during and after hard sessions (MedlinePlus lists this as a prevention step). Check a sensible daily amount with the water intake calculator.
• Be careful in heat, after illness, or if you take medicines that list muscle side effects.

Normal next-day soreness is a different thing; see muscle soreness after the gym (DOMS) for how to tell them apart.

Can you overtrain?

Yes. The joint consensus statement of the European College of Sport Science and the American College of Sports Medicine says successful training needs overload but must avoid "excessive overload plus inadequate recovery". Short dips in performance that recover after rest are a normal part of training. When rest doesn't fix it, people slide into non-functional overreaching and, at the far end, overtraining syndrome, with fatigue, falling performance and mood disturbances.

The statement also lists things doctors check first, including eating too little (negative energy balance), not enough carbohydrate or protein, and iron deficiency. Crash dieting while training hard every day is a classic route there.

Lower your risk: take rest days, sleep, eat enough, and don't train the same muscles hard on back-to-back days. Our guide on how many rest days you need has a simple weekly layout.

Are gym supplements safe?

Some are fine, many are unnecessary, and the risk in India is often what's in the tub. The Citizens Protein Project (2024) analysed popular protein supplements sold in India and found most didn't meet their labelled protein content, while some showed signs of "protein/amino-spiking". It also reported fungal toxins, pesticide residues and heavy metals such as lead and arsenic in several products, and herbal extracts linked to liver injury.

You usually don't need a supplement at all. If you buy whey, our whey protein guide explains how to check the FSSAI licence and the label. Avoid "fat burners" and products promising rapid muscle gain, and tell your doctor about anything you take.

Why are steroids the biggest side effect risk?

Anabolic steroids are man-made versions of male hormones. They're the one gym "shortcut" with a long list of documented harms. The NHS lists:

• in men: reduced sperm count, shrunken testicles, breast development, severe acne,
• in women: facial and body hair growth, a deeper voice, period problems,
• in both: liver or kidney problems or failure, fluid retention, aggression, mood swings and paranoia,
• in teenagers: premature ageing of the bones and restricted growth,
• addiction, with withdrawal symptoms such as fatigue, low mood and joint pain.

The NHS adds that "cycling" or "stacking" steroids hasn't been shown to reduce these harms. If a trainer offers injections or "special tablets", walk away. If you're already using them, see a doctor; stopping suddenly can cause withdrawal.

Myth: does the gym stop height growth?

No. A review in the British Journal of Sports Medicine on youth resistance training states there is "no evidence that resistance training will negatively impact growth in height during childhood and adolescence". It also notes that growth-cartilage injury hasn't been reported in any prospective youth training study with professional guidance. Most youth lifting injuries in case reports were accidents, linked to poor supervision, technique or loads.

The rule for under-18s is supervision, not avoidance: a qualified coach, sensible loads and good technique. Ironically, the thing that can genuinely restrict a teenager's growth is steroids, as above.

Myth: will lifting make women bulky?

No, not by accident. A 2020 meta-analysis found women and men on the same programme gained muscle size at a similar relative rate, and women made larger relative gains in upper-body strength. The difference is hormones: an Endocrine Reviews paper notes that after puberty men's circulating testosterone is more than 15 times women's, which largely accounts for the sex gap in muscle mass and strength. Our guide to weight training for women covers this in more detail.

Myth: does muscle turn into fat when you stop?

It can't; they're different tissues. What happens is that muscle fibres shrink when you stop training. In a 2024 study, people trained one arm for 10 weeks and then stopped for 16 weeks. Fibre size went down, but the extra nuclei the muscle had gained stayed put, and the previously trained arm had larger fibres after retraining. Fat gain after quitting comes from eating the same while moving less.

Myth: is the gym bad for your heart?

For most people, the opposite. The American Heart Association's 2023 scientific statement says resistance training is "a safe and effective approach for improving cardiovascular health in adults with and without cardiovascular disease". It reports:

• about a 15% lower risk of death from any cause and 17% lower risk of cardiovascular disease in adults who do resistance training,
• maximum benefit at roughly 30 to 60 minutes a week,
• resting blood pressure falls of about 4/2 mm Hg in healthy adults over 40, and about 6/5 mm Hg in people with high blood pressure,
• signs of reduced heart blood flow and abnormal rhythms occurring less often during resistance exercise than aerobic exercise.

That doesn't mean everyone should start heavy deadlifts tomorrow. If you have heart disease, chest pain on exertion, or blood pressure that isn't controlled, get medical clearance and a supervised start.

When should you see a doctor?

Get help the same day if you have:

• dark, cola or tea-coloured urine with severe muscle pain, swelling or weakness after exercise,
• chest pain, pressure or tightness, fainting, or a racing or irregular heartbeat during training,
• sudden severe pain with a pop, rapid swelling, or a joint that gives way.

Book a regular appointment if you have:

• pain in one spot that lasts more than a week or keeps coming back,
• constant tiredness, poor sleep and dropping performance despite rest,
• any effects after using steroids or "fat burners".

Check with a doctor before starting if you're pregnant, have diabetes on medication, heart disease, high blood pressure, kidney disease, or a recent injury or surgery.

The short version

• Gym injuries are mostly strains, sprains and dropped weights; learn technique and progress slowly.
• Rhabdomyolysis is rare but serious; don't go all-out in your first sessions, and watch for dark urine.
• Overtraining comes from too much load and too little rest or food.
• Many supplements are unnecessary and some are mislabelled; steroids carry serious, documented harms.
• Lifting doesn't stunt height, make women bulky by accident, turn muscle into fat or harm most hearts.

Useful links

• Keogh and Winwood (2017): injury epidemiology across weight-training sports
• Kerr et al. (2010): weight-training injuries in US emergency departments
• MedlinePlus: Rhabdomyolysis
• ECSS/ACSM consensus on overtraining syndrome (2013)
• NHS: Anabolic steroid misuse
• Faigenbaum and Myer (2010): youth resistance training safety
• American Heart Association (2023): resistance exercise and cardiovascular health

This is general information, not medical advice.