Sport
American football is a game of short, all-out plays, about 5 seconds long with about half a minute between them, and the positions ask very different things: linemen collide on every snap, while receivers and defensive backs sprint the furthest. Strength and power relative to body weight go with faster acceleration, and lifting, jumping and sprinting all help. The risks are just as clear: concussion is the commonest single injury in US college football, and in US high schools heat illness was over 11 times as common in football as in all other sports combined.
This guide covers what the game asks of your body, the common injuries, and the rules that protect young players: USA Football's limits on full contact in practice, the 14-day heat acclimatisation guidelines, tackling with the head up, and concussion rules in the US and the UK. It covers flag football too: far fewer head impacts, but not injury-free. It includes a 15-minute warm-up and a strength workout, with a 3D demo of every move.
In US college football, games produced about 36 injuries per 1,000 athlete-exposures (one player taking part in one game or practice), against about 4 in in-season practices. Concussion was the commonest single injury in 2014 to 2019.
Across studies, limits on full contact in practice went with about two-thirds fewer practice concussions. USA Football's 2021 youth recommendations: no full contact on consecutive days and no more than 30 minutes of it a day.
After 1976 rules banned spearing and tackling with the top of the helmet, permanent paralysis from neck injuries fell from 34 cases a year to 5. Head-down tackling is still the main cause of the rare injuries that remain.
In US states that made the 14-day heat acclimatisation guidelines compulsory, high-school pre-season heat illness was about half as common.
Tackle players aged 6 to 14 took about 15 times as many head impacts per session as flag players. But flag players still get hurt, and in one youth cohort they were injured more often than tackle players.
Every US state requires a young player with a suspected concussion to be removed from play and cleared by a healthcare professional before returning. In the UK, the British American Football Association (BAFA) backs the UK's grassroots concussion guidelines.
In televised US college games, a play lasted 5.2 seconds on average, with 36 seconds between plays when there were no stoppages and about 11 to 12 minutes between a team's series. So each play is an all-out effort, and recovering between plays matters over a whole game (our reading). The Compendium of Physical Activities gives competitive football 8.0 metabolic equivalents (METs) and flag or touch football 8.0, both measured values, or 4.0 at a light effort, an estimate.
In 33 college players tracked by GPS over 12 games, wide receivers and defensive backs covered the most distance and did the most sprinting, accelerating and braking. Linemen collide on almost every play, and they heat up faster and cool down more slowly than other players.
In 61 college players, sprint times depended on how fast players accelerated over the first 18 m and how well they held top speed. Strength and power went with speed only when measured relative to body weight, an association.
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The sites the studies point to:
A non-contact version in which tackles are made by pulling a flag from the hips; in Great Britain it's mostly 5 against 5. Collisions still happen: player collisions were the commonest cause of flag injuries seen in US emergency departments.
Strength and power for every position, sprint and change-of-direction work for backs and receivers, the neck and shoulders for contact, hamstrings and groins for sprinting, and conditioning that matches the game's short, repeated efforts rather than long runs.
Each study counted injuries its own way, so figures in different lines aren't comparable. Most studies come from the US.
The numbers, by group:
Boys' football had the highest concussion rate of any US high-school sport. Across studies of young tackle players, there were about 0.8 concussions per 1,000 athlete-exposures in high school and 1.2 at ages 5 to 15, and practices were a major source at every level. In players aged 8 to 12, the game rate was about 26 times the practice rate. About 15% of concussions kept players out for 30 days or more, and a concussion in the past year went with about twice the rate of another. Our concussion guide covers the graduated return.
They're rare: about 6 cases of permanent paralysis a year across US high-school and college football, mostly from defenders spear tackling with the head down, and about 0.7 serious brain injuries per 100,000 high-school players a year. Of players with a catastrophic brain injury, 59% had had an earlier head injury, often that season, and 39% were still playing with symptoms from it. We don't have a guide to spinal cord injury; our neck pain guide covers everyday neck pain.
A stinger, or burner, is a sudden burning or tingling down one arm after a hit to the neck or shoulder, from a stretched or pinched nerve. In the National Football League (NFL), 3.7% of players had one each season and three-quarters missed no time; in college, about 1 in 5 were repeats. Neck muscle strains ran at about 1 per 10,000 athlete-exposures, mostly from contact. Our pinched nerve in the neck guide covers arm symptoms that don't settle.
Knee ligament injuries and ankle sprains were among the injuries most concentrated in games. Football had the highest rate of anterior cruciate ligament (ACL) tears of any US college men's sport, mostly from contact. Our ACL injury, MCL sprain (the medial collateral ligament, on the inside of the knee), meniscus tear, sprained ankle and chronic ankle instability guides cover treatment.
In the NFL, a quarter of players strained a hamstring, groin, calf or thigh muscle each year, and the 2 weeks of training camp produced 19% of the strains that cost time. A third of players with a hamstring injury hurt it again. Our hamstring strain, groin strain and quad strain guides cover recovery.
Sprains of the acromioclavicular (AC) joint at the top of the shoulder were among the injuries most concentrated in games, and our AC joint guide notes that half of US college AC joint sprains happened in football. Lower back injuries ran at 2.7 per 10,000 athlete-exposures in college, and 60% of players were back within a day. Our AC joint, shoulder dislocation, broken collarbone, back pain and turf toe guides cover these.
In US high schools, the heat illness rate in football was 11.4 times that of all other sports combined, and 60% of cases came in August. In college, the risk was highest in the first 14 days of pre-season, especially the first 7, and on days with a wet-bulb globe temperature (a heat index that includes humidity and sun) of 27.8°C or more. The heat section below covers prevention.
US high-school and college football averaged about 12 deaths a year, about 1 per 100,000 players, and causes other than a blow, such as heart problems, heat and sickle cell trait, were twice as common as injuries. Sudden cardiac arrest was the commonest cause of deaths not caused by a blow.
No warm-up programme has been tested on injuries in American football. Most of the evidence on contact limits and coaching comes from observational studies, and each note says what kind of study it is.
Across studies, strategies that limited contact in practice went with about two-thirds fewer practice concussions. After Wisconsin's high-school rule limiting how much and how long players could hit in practice, practice concussions fell from 0.76 to 0.33 per 1,000 athlete-exposures, while game concussions didn't change. In one high school, a statewide limit cut head impacts by 42% a season, most in linemen.
As a 2022 review describes it, a high-school limit of 75 minutes of full contact a week in the season's second week, and 60 minutes from week 3, was followed by 54% fewer practice concussions. These are before-and-after studies, so other changes may have played a part.
USA Football's coaching course covers equipment fitting, tackling technique, drills with less player contact, and concussion, heat and cardiac emergencies, taught through a league's player safety coach. In 2,108 players aged 5 to 15, leagues using it together with Pop Warner's practice contact rules had about an eighth of the practice injuries of leagues using neither, and leagues using the course alone about a third; game injuries fell only where the practice rules were also in place.
In high schools, practice and game injuries were lower with a player safety coach, and concussions were 4.1 against 6.0 per 100 players with the course. None of these studies was randomised, and USA Football funded two of them. Nearly half of youth coaches missed the safety coach's clinic.
Most neck fractures came from hits with the top of the helmet and the neck straight. Since 1976, US high-school and college rules ban spearing and tackling helmet-first, and permanent paralysis fell from 34 cases a year to 5. The National Athletic Trainers' Association (NATA) says keeping the head up and making contact with the shoulder or chest lowers the risk, that the rules are rarely enforced, and that coaches should spend more practice time on correct technique.
In 3,000 game tackles reviewed by Texas researchers, head-up tackles with the inside shoulder were the most successful, though most coaches who replied to their survey taught a riskier head-across technique. In a laboratory study in 24 young players, practising a head-up tackle cut hard head accelerations.
After the Ivy League, a group of US universities, moved the kickoff line forward 5 yards and the touchback line from the 25 to the 20-yard line in 2016, touchbacks rose from 18% to 48% of kickoffs and concussions on kickoffs fell from about 11 to 2 per 1,000 kickoff plays, in a before-and-after study.
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The one randomised trial of braces in football:
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In 1,396 US military cadets playing tackle football, preventive knee braces cut knee injuries only in defensive players. In college players the trend was small and not clear, and across 6 studies the results were inconsistent, two finding more knee injuries in braces. They aren't recommended for uninjured knees.
Catastrophic head injuries have stayed low since modern helmets arrived in the early 1970s. But in 2,081 high-school players, concussion rates didn't differ by helmet brand, age or reconditioning. When the NFL made padded caps compulsory in practice for linemen, tight ends and linebackers, concussions in those positions fell, but not for impacts to the helmet shell, so the padding can't explain the fall on its own.
Across sports, people without mouthguards had over twice the risk of mouth and face injuries. For concussion the evidence is mixed: across collision sports, wearers had about a quarter fewer concussions, but in high-school football, custom-fitted mouthguards went with more concussions than off-the-shelf ones, an association. Wear one for your teeth and jaw.
Popular measures without good evidence in football:
Across 15 studies, people whose back-squat strength rose most also gained most sprint speed, about 3% on average, though these studies weren't of footballers. In 289 college players tested over 8 years, bench press rose about a third and squat a little more across a playing career, while 40-yard sprint time didn't change: strength keeps improving, and speed is harder to shift.
In 20 college players training 4 days a week for 15 weeks, squat strength rose with both Olympic-style lifting and powerlifting, and the Olympic lifters gained more jump height; sprint and agility didn't differ. In 47 college players, adding jump squats to an off-season programme improved squat and clean strength more than no jump squats, with no difference in jumping, sprinting or agility. Both trials were small.
Plays last about 5 seconds, so conditioning means short, repeated efforts with recoveries, scaled by position (our reading). Experts reviewing heat-stroke deaths in football advise conditioning specific to each position, no conditioning tests or repeated sprints unsuited to linemen, changes for the heat, and never using exercise as punishment. The first 7 days of any new training block are the riskiest: in the NFL, training camp produced 19% of the leg muscle strains that cost time.
Neck training builds neck strength, and our strength workout includes it. Whether a stronger neck prevents concussion is unproven: across team sports the link was small and very low certainty. Head-up tackling and contact limits have the better evidence.
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No performance trials have been done in flag football. It's sprinting, cutting and stopping without contact, so sprint and landing training from other field and court sports is the closest guide (our reading). Girls' flag has brought ACL tears without contact, and warm-ups with strength and landing work halve ACL injuries in other sports.
Off-season: 3 or 4 strength and power sessions a week, as in the college trials, plus sprint and change-of-direction work once or twice a week (our suggestion). Summer and pre-season: build up gently, with the first week back treated as a way back in, and follow the heat acclimatisation rules.
In season: 1 or 2 shorter strength sessions a week, early in the week, with no heavy legs, Nordic lowers or hard jumping in the 48 hours before a game (our suggestion), and full contact within USA Football's or your state association's limits. Young players: USA Football sets practice length and frequency by age, and the National Health Service (NHS) asks children for an average of at least 60 minutes of activity a day, across a variety of activities.
These are the rules as each body publishes them. Leagues, schools and US states set their own versions, so check yours.
For US youth football, all game types with contact:
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The National Federation of State High School Associations (NFHS) strongly recommends full contact in no more than 2 to 3 practices a week, and suggests no full contact on consecutive days, no more than 30 minutes a day and 60 to 90 minutes a week. Tackling should be taught without contact, then with bags and controlled contact, before full-speed drills; only one session a day has full contact during pre-season doubles; and heat rules come first. Each state association sets its own rules.
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As described in the study that evaluated them: no full-speed head-on blocking or tackling drills with players lined up more than 3 yards apart, and contact for no more than a third of practice time. Pop Warner's current rulebook may differ.
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Under BAFA, contact football below senior level starts at under-16 (ages 13 to 15, 5 against 5) and continues at under-19 (ages 16 to 18). Adult-grade helmets are compulsory and youth-grade helmets aren't allowed. Youth flag football runs at under-11 (from age 7), under-14 and under-17.
No study has shown an age at which tackling becomes safe. In 42 retired NFL players, those who started tackle football before 12 did worse on thinking and memory tests in later life, but later studies of former high-school players and 4,376 college athletes found no such link, and a 2021 review judged all the studies at high risk of bias. Chronic traumatic encephalopathy (CTE), a brain disease linked with repeated head impacts, was found in 110 of 111 donated brains of former NFL players, a selected group that can't give a rate.
Our reading: fewer head impacts are better, and flag football cuts them sharply.
In 524 boys aged 6 to 14 wearing sensors in their mouthguards, tackle players took about 15 times as many head impacts per session as flag players and 23 times as many hard ones. Smaller studies agree, though individual flag impacts can still be hard.
In 3,794 players in US school grades 2 to 7, flag players were injured more often than tackle players, with no clear difference in serious injuries or concussions. At youth flag tournaments, a third of injuries were to the head, face or neck, and girls had about three times the boys' rate. In US emergency departments, collisions were the commonest cause; children most often hurt their heads and adults their fingers, and in women and girls sprains and strains were commonest.
Among 24 girls aged 13 to 18 who needed knee surgery after flag football injuries in California, 21 had ACL tears, 21 of the 24 injuries happened without contact, and only 2 had done an ACL prevention programme. Warm-ups with strength and landing work halve ACL injuries in other sports.
In 1,504 adult players in a contact flag league, a rule banning pockets, self-fitting mouthguards, ankle braces for players with repeated sprains and an injury leaflet were followed by 54% fewer injuries than in the two previous seasons, mainly fewer hand and wrist injuries caught in pockets. The comparison was with earlier seasons, not a randomised group.
The NATA-led task force's guidelines for US high schools, for every athlete, including late arrivals:
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An expert consensus kept the 14 days and asked for at least 10 sessions in the heat, 60 to 90 minutes of training a day, sessions of no more than 2 hours in the first week and 2.5 hours in the second, no double sessions before day 7 and never on consecutive days, hard conditioning either on its own or at the start of practice, conditioning-only sessions indoors or in the cool of the morning or evening, and no punishment sessions. The rules apply to everyone, whatever their level, sex or summer training.
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In US high-school football, pre-season heat illness was 55% lower in states and years where the guidelines were compulsory (0.42 against 0.72 per 10,000 athlete-exposures). But in a 2017 survey only 3.9% of programmes followed all 17 guidelines, and only 27.5% had all six heat-stroke preparations in place, such as a tub of iced water ready before practice. In Georgia, a 5-day acclimatisation period with practices of no more than 2 hours, and limits by heat index, was followed by much less heat illness.
In recent reports, every heat-stroke death in US high-school and college football happened in a conditioning session, and linemen were 97% of those who died. US sports medicine organisations ask that the first 7 days of any new training block be treated as a transition, with limits on how much and how hard players train, especially in the first 4 days, workouts approved by a qualified strength and conditioning coach, and exercise never used as punishment.
For trained medical staff, NATA's position statement: exertional heat stroke means confusion or collapse with a core temperature over 40.5°C; immerse the player up to the neck in cold, stirred water at once, aiming to cool them below 38.9°C within 30 minutes of collapse, then send them to hospital. Cooling that fast went with no deaths in more than 2,000 cases. For everyone else, the NHS's advice is in the warning signs below: call 999 for heatstroke and cool the person while you wait.
Carrying one sickle cell gene isn't sickle cell disease. But in US college football, players with the trait had 37 times the risk of dying during exertion, mostly in intense conditioning. After the National Collegiate Athletic Association (NCAA) required athletes to know their status, or sign a waiver, and educated coaches and staff, these deaths fell by about 89% in the top division; it isn't clear which part did it. The NHS says carriers don't have the disease and can't develop it, and anyone can ask their GP for a blood test. Our reading: knowing your status is a reason to build up gradually and stop when you can't keep going, not a reason not to play.
Since 2007, 57 US college athletes in 9 team outbreaks had exertional rhabdomyolysis, a serious breakdown of muscle, and 51 went to hospital; new, unaccustomed exertion was the commonest cause. In one college team, it followed a workout of 100 back squats, more often in players who took longer, went to failure or did extra. The signs, and what to do, are in the warning signs below.
Every US state and Washington, DC, has a law for children and teenagers in sport: education, immediate removal of a player with a suspected concussion, and clearance by a healthcare professional (a doctor, in some states) before returning. The laws require that clearance rather than setting a minimum number of days. Fourteen states explicitly ban returning on the same day, eight require a graduated return, and who may clear a player varies by state.
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BAFA backs the UK concussion guidelines for grassroots sport: if in doubt, sit them out; NHS 111 or a healthcare professional within 24 hours; a graduated return to activity, education or work, and sport; and no return to competition before day 21. Our concussion guide covers the stages.
Of 94 US high-school and college players with a catastrophic head injury, 59% had had an earlier head injury, most of those in the same season, and 39% were playing with symptoms from it.
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The NFL and NCAA have their own concussion protocols, which this guide doesn't cover. Players in those programmes follow their medical team.
Built on the site's warm-up guide and the shape of the FIFA 11+ (editorial): no warm-up programme has been tested on injuries in American football. The doses for the leg swings, stretches, lunges, bridges and pull-aparts are the site's dynamic warm-up's, and the neck holds are England Rugby's Activate warm-up's. It works for flag players too.
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The movement on the figure: Acceleration wall drill
The strength workout's main lifts and the warm-up's landing and speed drills. Each has a 3D demo.
3D demoHang power cleanAdvanced · A barbell
3D demoWeighted jump squatAdvanced · A barbell
3D demoBarbell back squatAdvanced · A barbell
3D demoBarbell bench pressIntermediate · A barbell + A bench or box
3D demoDumbbell Romanian deadliftIntermediate · A dumbbell
3D demoRear-foot-elevated split squat (Bulgarian split squat)Intermediate · A bench or box
3D demoNordic curlAdvanced · An anchor point
3D demoIsometric neck holds (four-way)Beginner · No equipment
3D demoFace pullIntermediate · A band
3D demoFarmer's carryBeginner · A dumbbell + A kettlebell
3D demoAcceleration wall drillBeginner · A wall
3D demoSingle-leg hop and stickIntermediate · No equipment
3D demoSnapdown to athletic landingBeginner · No equipment
3D demoShuttle runsAdvanced · No equipmentThe first two are new: the warm-up and a strength session. The rugby workouts share football's contact demands; the others cover hamstrings, the neck, power, lifting technique, knee control for flag players, and light exercise after a concussion.
A 15-minute American football warm-up: jog, skips and shuffles, leg swings and lunges, bridges and band walks, neck holds, landings, accelerations and turns.
15 minBeginner16 movesCardio machine, A wallA 55-minute gym session for American football: hang cleans or jump squats, back squats, bench press, Romanian deadlifts, rows, Nordics, neck work and carries.
55 minIntermediate16 movesA band, A barbellA 55-minute gym session for rugby: jump squats and chest throws, heavy squats, bench press, Romanian deadlifts, rows, Nordic lowers, shoulder and neck work.
55 minIntermediate15 movesA band, Medicine ballEngland Rugby's and World Rugby's Activate warm-up, the manual's adult sample phase: running, balance, partner holds, hops, sprints and neck holds.
25 minBeginner15 movesCardio machine, A wallThe Nordic hamstring and Copenhagen adduction programmes from the football trials: a 10-week build, three adductor levels, then once a week in season.
15 minIntermediate6 movesA wall, An anchor pointDeep neck holds and shoulder-blade strength in under 20 minutes: one of the best-supported kinds of exercise for a stiff, sore neck.
18 minBeginner11 movesA band, An anchor pointAn advanced jump training session: pogo hops, box jumps, split squat jumps, broad jumps and depth jumps.
30 minAdvanced8 movesA bench or box, A stepBarbell strength workout A: back squats and bench presses in sets of five, plus rows. Workout B (squat, overhead press, deadlift) is a separate session.
40 minBeginner6 movesA band, A barbellWorkout B of the beginner strength program: back squats, overhead presses and deadlifts in sets of five, plus chin-ups, with the safety pins set.
55 minBeginner10 movesA band, A barbellA 25-minute practice session for the squat: find your depth on a chair, groove the bodyweight squat with pauses, then load it with a slow goblet squat.
25 minBeginner8 movesA wall, A bench or boxA 30-minute session from the hip hinge to your first deadlift: hinge practice, kettlebell deadlifts, slow Romanian deadlifts, a light bar and a carry.
30 minBeginner9 movesA kettlebell, A dumbbellA 30-minute practice session for the bench press: shoulder blade work, push-ups and dumbbell presses, then the empty bar with the safety arms set.
30 minBeginner7 movesA band, A dumbbellA 20-minute warm-up that trains your knees to track over your toes: side-hip strength, squats and lunges with alignment practice, balance and quiet landings.
20 minBeginner10 movesA wall, A bandA 20-minute light session after a concussion: a symptom check, 10 to 15 minutes of easy cycling or walking, gentle bodyweight moves and a cool-down.
20 minBeginner8 movesCardio machine, A bench or boxFor the off-season: three or four strength sessions a week suit the college trials' frequency; drop to one or two in season.
A 12-week beginner barbell program: squat every session, alternate bench and row with press and deadlift, and add weight each time until it stalls.
3 training days50 minBeginner4 days a weekA 4-day upper/lower split: two upper body and two lower body gym days, each muscle trained twice a week, with sets, reps and progression.
4 training days50 minIntermediate3 days a weekFor after about 8 weeks of a beginner plan: three full-body sessions a week, one heavy, one moderate and one light, in a gym or at home, for 12 weeks.
3 training days50 minIntermediate3 days a weekA beginner gym plan: three full-body sessions a week, alternating workouts A and B, with sets, reps, rest and an 8-week progression.
3 training days45 minBeginnerThe PAR-Q+ (Physical Activity Readiness Questionnaire for Everyone) asks about a heart condition or high blood pressure, chest pain, dizziness or losing consciousness, other long-term conditions and their medicines, a bone or joint problem that activity could make worse, and being told to exercise only under supervision. If you answer yes to any, check with your doctor or a qualified exercise professional first. If you're over 45 and not used to hard exercise, ask a qualified exercise professional before the hardest sessions, and delay if you're ill.
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A concussion in the past year went with about twice the rate of another in high-school players, and players with catastrophic head injuries had often been playing with symptoms. No contact until you're cleared under your rules: a healthcare professional's clearance under US state law, or the UK guidelines' graduated return with no competition before day 21.
About 1 in 5 college stingers were repeats, and some players had a brief loss of feeling or strength in their arms and legs from a temporary spinal cord injury. Get assessed before contact (our suggestion); our pinched nerve in the neck guide covers arm symptoms that last.
If you don't know your status, the NHS says you can ask your GP for a blood test. Carriers can play: build up conditioning gradually, drink plenty, and stop at once if you can't keep going (our suggestion).
Almost all heat-stroke deaths were linemen in conditioning, and the first days back are the riskiest. After heat stroke, NATA advises 7 to 21 days of rest, normal blood tests and a doctor's clearance before a supervised, gradual return.
Sudden cardiac arrest caused over half of the football deaths not caused by a blow. The NHS says to call 999 if someone faints while exercising, and to see a GP after fainting: do that before you play.
The NHS says it may take up to 16 weeks to return fully to some sports. Our shoulder dislocation guide suggests young players in collision sports ask about surgery.
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The NHS advises against sports with a risk of falling or bumping your tummy, so no contact. Talk to your midwife or GP about flag football or non-contact training, and see our pregnancy guide.
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Flag football means far fewer head impacts, USA Football sets practice length by age, and in the UK contact football starts at under-16. Supervised strength training is safe for children, as our children's guide explains.
The NHS says to call 999 if someone has hit their head and:
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Stop playing: if in doubt, sit them out, and don't return that day. Under the UK's grassroots concussion guidelines, they should be assessed within 24 hours by a healthcare professional or NHS 111 (the NHS's urgent advice line), with no competition before day 21. In the US, state law requires a healthcare professional's clearance before returning. Contact NHS 111 straight away if they're being sick, feel dizzy or take medicine that thins the blood.
Severe neck pain after a hit is a red flag needing urgent medical assessment, by ambulance if necessary, and a player with a suspected neck injury should only be moved by trained healthcare professionals. Burning or tingling in an arm that doesn't settle within minutes, or symptoms in both arms or the legs, need urgent assessment too (our suggestion).
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Heat exhaustion (tiredness, dizziness, a headache, feeling or being sick, heavy sweating with pale, clammy skin, cramps, a high temperature, intense thirst or feeling irritable) needs a cool place, fluids and cooling the skin. Call 999 if they're still unwell after 30 minutes of rest, cooling and fluids, or have a very high temperature, hot skin that isn't sweating, a fast heartbeat or breathing, confusion, a fit or loss of consciousness; wrap them in a cool, wet sheet or sponge them with cold water while you wait. Where trained staff and a tub of cold water are ready, immersion comes first.
Call 999 if someone faints or collapses while exercising, or has chest pain that doesn't go away, spreads to the arms, neck, jaw, stomach or back, or comes with sweating, feeling sick, light-headedness or breathlessness. Tell the ambulance crew if the player carries sickle cell trait, which went with deaths during intense conditioning (our suggestion).
Dark, red or cola-coloured urine, much less urine than usual, or weak, very painful or tender muscles in the days after a hard session can be rhabdomyolysis: get medical help the same day.
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Go to A&E (accident and emergency) if you can't move your arm, or the shoulder looks out of place or has changed shape. For a suspected broken collarbone, go to A&E if the shoulder has changed shape or swollen very quickly, bone is through the skin, or you have difficulty breathing or chest pain.
Call 999 or go to A&E if you heard a crack, the injured part has changed shape or points at an odd angle, it's numb or tingling, or the skin is blue, grey or cold. Get help from NHS 111 if it's very painful, very swollen or bruised, or you can't put weight on it or walk more than a few steps.
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A broken tooth needs a dentist: keep any piece in milk or saliva. Go to A&E for an eye hit at high speed, a change in your sight or severe eye pain, and for a nosebleed that won't stop or clear fluid from the nose. For a cut, press on it with a clean cloth; call 999 or go to A&E if the bleeding won't stop.
Limiting full contact in practice went with about two-thirds fewer practice concussions, and in Wisconsin game concussions didn't rise. In one college programme, live-contact practices produced 7 times the injuries of non-contact ones.
In high-school players, concussion rates didn't differ by helmet brand, age or reconditioning, and padded helmet covers couldn't explain the fall in NFL practice concussions on their own.
In high-school football, custom mouthguards went with more concussions than off-the-shelf ones, an association, and the evidence on mouthguards and concussion is mixed. Their protection for teeth and jaws is clear.
No study has shown that tackling early protects players later. Flag players take far fewer head impacts, and in ice hockey, learning to body check earlier didn't protect players either.
Flag players were injured more often than tackle players in one youth cohort, youth flag tournaments had about 5 injuries per 1,000 athlete-exposures, and girls' flag has brought ACL tears without contact.
Recent heat-stroke deaths in football happened in conditioning, almost all in linemen. Experts advise conditioning specific to each position, changes for the heat and never exercise as punishment, and compulsory acclimatisation rules went with half the heat illness.
The link between neck strength and concussion was small and very low certainty. Train the neck for strength, and rely on head-up tackling and contact limits for concussion.
Studies of preventive knee braces were inconsistent, and two found more knee injuries in braces. Lace-up ankle braces, though, cut ankle injuries by 61% in a high-school trial.
Squats, Romanian deadlifts, bench press and rows for strength, jump squats or Olympic-style lifts for power, Nordic lowers for hamstrings, and shoulder and neck work. In college players, Olympic-style lifting added jump height and jump squats improved squat strength more than a standard programme, and across studies gains in squat strength went with faster sprints. Our strength workout puts these together.
USA Football recommends no full contact on consecutive days, no more than 30 minutes of it a day, no more than 75 minutes a week in pre-season and 60 in season, and at most one full-contact game a week. US high schools follow their state association's rules, built on national guidance of full contact in no more than 2 or 3 practices a week.
No study has shown an age at which tackling becomes safe. Flag players aged 6 to 14 took about 15 times fewer head impacts than tackle players, and studies of early tackling and later brain health disagree. In the UK, contact football starts at under-16, from age 13, with flag from 7.
It's much safer for heads, with far fewer head impacts, but it isn't injury-free: in one youth cohort flag players were injured more often than tackle players, and girls' flag has brought ACL tears without contact. A mouthguard and a warm-up with landing and turning work help.
Follow the 14-day acclimatisation guidelines: one practice a day for the first 5 days, helmets only on days 1 and 2, full kit and contact from day 6, and rest in a cool place between sessions. US states that made them compulsory had about half the pre-season heat illness. Know the signs of heat exhaustion and heatstroke, and call 999 for heatstroke.
A sudden burning or tingling down one arm after a hit to the neck or shoulder, from a stretched or pinched nerve. Most players miss little or no time, but about 1 in 5 college stingers were repeats. Symptoms that don't settle, or that affect both arms or the legs, need urgent assessment.
Catastrophic head injuries have stayed low since modern helmets arrived in the early 1970s, but in high-school players concussion rates didn't differ by helmet brand, age or reconditioning. Tackling with the head up and limits on contact in practice have better evidence for preventing concussion.
In the US, every state requires immediate removal of a young player with a suspected concussion and a healthcare professional's clearance before returning, rather than a set number of days. In the UK, BAFA follows the grassroots concussion guidelines: if in doubt, sit them out, NHS 111 or a healthcare professional within 24 hours, and no competition before day 21.
Carriers have one copy of the sickle cell gene; they don't have the disease and can't develop it. But in US college football, players with the trait had a much higher risk of dying during intense conditioning, so knowing your status, building up gradually and stopping when you can't keep going all matter.
For strength and power, with conditioning that matches the game's short, repeated efforts, not long runs or sprint tests. Almost all heat-stroke deaths in football were linemen in conditioning sessions, so experts advise conditioning specific to each position, extra care in the heat and never using exercise as punishment.
Exercise education for people who play sport, not a personal prescription or a diagnosis, and clinical review of these pages is pending. Check with a GP or physiotherapist before hard training if you have a heart condition, chest pain, dizziness or an injury that isn't settling, and stop for sharp or increasing pain. Health disclaimer.
