Story
Power and Jumping, What Gets You Higher
Last updated
In one pass Power is not the same as strength: it is force times speed, and it asks how much force you can bring to bear in a very short time.
Educational content, not medical advice — consult a clinician.
Story path
Chapter 1
Is power the same as strength?
Power is not the same as strength: it is force times speed, and it asks how much force you can bring to bear in a very short time. In a jump, only a fraction of a second passes between starting to push and leaving the ground. One ultrasound study analyzed the push-off as the last 350 milliseconds or so before take-off, while in a test where the joint does not move, muscle takes more than 300 milliseconds to reach its maximal force. So maximal strength is the ceiling, and how much of it you can use in a jump also depends on how fast the force rises, which is called the rate of force development.
This story is for basketball and volleyball players and anyone who wants to jump higher or run faster, and also for older people: getting up, taking a step, and catching yourself when you nearly fall all rely on producing force quickly too.
A step you can take today: next time you stand up from a chair or do a squat, make the upward part as fast as you can and keep the way down controlled.
If you feel a pop at the back of the ankle or below the kneecap while jumping or landing, and then cannot rise onto your toes or straighten your knee, suspect a tendon rupture: this is an emergency, so seek care promptly. If you get chest pain or tightness, or faint, during exercise, call emergency services now; see Does jumping hurt your knees?
This story is for basketball and volleyball players and anyone who wants to jump higher or run faster, and also for older people: getting up, taking a step, and catching yourself when you nearly fall all rely on producing force quickly too.
A step you can take today: next time you stand up from a chair or do a squat, make the upward part as fast as you can and keep the way down controlled.
If you feel a pop at the back of the ankle or below the kneecap while jumping or landing, and then cannot rise onto your toes or straighten your knee, suspect a tendon rupture: this is an emergency, so seek care promptly. If you get chest pain or tightness, or faint, during exercise, call emergency services now; see Does jumping hurt your knees?
Mechanism · Is there time to reach full force?
The rate of force development (RFD) describes how fast force rises once a muscle starts to contract. Aagaard 2002 writes that it determines how much force can be produced in the first 0–200 milliseconds of a contraction. The Maffiuletti 2016 review adds that a rapid rise in force in the first 300 milliseconds matters to athletes, and just as much to older people who need to catch themselves when they suddenly lose their balance.A jump falls squarely inside that window. Kurokawa 2001 used ultrasound to watch 8 men jump from a standstill and analyzed the push-off as the last 350 milliseconds or so before take-off, while in a test where the joint does not move, muscle needs more than 300 milliseconds to reach its maximal force. Following those two numbers, a jump is likely over before the muscle has had time to use all of its force; that is an inference, not something one study measured directly.
That is why strong people do not always jump high: maximal strength sets the upper limit, and the rate of force development decides how much of that limit a single push can use. The two are not unrelated, either. In Aagaard 2002, 15 men did 14 weeks of heavy strength training; their maximal strength rose from 291.1 to 339.0 newton-meters, and their rate of force development in the first 200 milliseconds of a contraction rose with it. The study had no separate untrained control group.
Chapter 2
How nerves make muscle fire faster
How fast you produce force depends first on your nerves: in the first few dozen milliseconds, how many muscle fibers they can call on at once, and how rapidly they fire. One motor nerve and the group of muscle fibers it controls together make up a motor unit. The Maffiuletti 2016 review sums up that the rate of force development depends mainly on nerve activation in the first 50–75 milliseconds of an explosive contraction, especially on how fast the motor units fire.
This part can be trained. In a small 1998 study of only 5 people, participants practiced fast ankle lifts for 12 weeks. The contraction time of the muscle itself did not change; the nerves did: motor units switched on earlier, reached a higher maximal firing rate, and fired more paired discharges only 2–5 milliseconds apart. Heavy strength training can also raise the rate of force development, again mainly by making activation faster. It is the same reason that, when you first start lifting, the strength you gain in the first few weeks comes mostly from the nerves (see Neural drive vs hypertrophy).
A step you can take today: when you do a strength movement, push the weight up as fast as you can and keep the lowering controlled.
This part can be trained. In a small 1998 study of only 5 people, participants practiced fast ankle lifts for 12 weeks. The contraction time of the muscle itself did not change; the nerves did: motor units switched on earlier, reached a higher maximal firing rate, and fired more paired discharges only 2–5 milliseconds apart. Heavy strength training can also raise the rate of force development, again mainly by making activation faster. It is the same reason that, when you first start lifting, the strength you gain in the first few weeks comes mostly from the nerves (see Neural drive vs hypertrophy).
A step you can take today: when you do a strength movement, push the weight up as fast as you can and keep the lowering controlled.
Evidence · What fast-force training changes
That 1998 study trained the muscle at the front of the shin that lifts the foot: the load was 30%–40% of maximal strength, each lift was done as fast as possible, and training lasted 12 weeks. Afterward, maximal strength and the speed of fast contractions had both gone up. When the muscle was tested with electrical stimulation, the time course of a single twitch had not changed, so the authors attributed the gain in speed mainly to the nerves. In fast contractions, motor units switched on earlier and reached a higher maximal firing rate, and the share of motor units firing paired discharges 2–5 milliseconds apart rose from 5.2% to 32.7%. With only 5 participants and no control group, this is a mechanism study, not a trial of effectiveness.Aagaard 2002 looked at heavy strength training: after 14 weeks, the amplitude of the muscle's electrical signal in the first 200 milliseconds of a contraction had risen by 22%–143%, and the authors suggest the faster force development can be explained by stronger neural drive. The Maffiuletti 2016 review brings the two lines together: explosive training and heavy strength training can both raise the rate of force development, mainly by making the muscle activate faster.
Fiber type plays a part too: type II fibers build force faster than type I fibers, and the fiber mix in a muscle varies widely from person to person. That explains some of the differences between people; what changed most clearly in the two studies above was how the nerves call on those fibers.
Chapter 3
How the tendon works like a spring
In the last instant of a jump, the hardest work often comes not from the muscle fibers but from the tendon, which is stretched first and then springs back. Kurokawa 2001 used ultrasound to watch the calf muscle during a jump from a standstill. For most of the time before take-off, the muscle fibers shortened and stretched the tendon tissue leading into the Achilles tendon, storing elastic energy. In the last 100 milliseconds or so, the fibers hardly shortened any more, yet the muscle and tendon together recoiled quickly and released the stored energy, with a higher peak power in that phase than the fibers produced themselves. This pattern of stretching first and then shortening is called the stretch-shortening cycle.
Dipping down first almost always gets you higher than pausing at the bottom and then jumping, but one study and one review both conclude that the main reason is that the dip lets the muscle build up its force before it starts pushing; elastic energy contributes only a small part.
Tendons do get stiffer and stronger under load, but at a slower pace than muscle: the training studies pooled in one all lasted at least 8 weeks (see Tendon Recovery). A step you can take today: start jump practice with small jumps and soft landings, and give your tendons time to catch up.
Dipping down first almost always gets you higher than pausing at the bottom and then jumping, but one study and one review both conclude that the main reason is that the dip lets the muscle build up its force before it starts pushing; elastic energy contributes only a small part.
Tendons do get stiffer and stronger under load, but at a slower pace than muscle: the training studies pooled in one all lasted at least 8 weeks (see Tendon Recovery). A step you can take today: start jump practice with small jumps and soft landings, and give your tendons time to catch up.
Evidence · Why dipping first gets you higher
Bobbert 1996 had 6 male volleyball players do two kinds of jump: dipping down and jumping straight away, and stopping at the same depth before jumping. Even when the body position at the start of the push was the same, the jump with the dip was 3.4 centimeters higher on average. After analyzing it with a model of the muscles and skeleton, the authors concluded that storing and reusing elastic energy could be ruled out; what the dip does is let the muscles reach a high level of activation and build up force before they start to shorten, so they can do more work in the first part of the push. A 2017 review reached a similar conclusion: the difference between the two jumps comes mainly from taking up the slack in the muscle and building up activation during the dip, and elastic energy may contribute only a little.This does not contradict the ultrasound study above. Kurokawa 2001 looked at jumps from a still squat and asked who does the work within one push, and the answer was that the tendon's recoil acts in the final phase; Bobbert 1996 asked why dipping first gets you higher. Both things happen in a jump.
Different kinds of training also change different things. Kubo 2007 had 10 people train one leg with jumps (repeated one-leg hops, and drop jumps, where you step off a box and spring straight back up) and the other leg with heavy calf training, for 12 weeks. The tendon got stiffer in the heavily loaded leg but not in the jumping leg; what changed in the jumping leg was the stiffness of the ankle during the landing, and its height rose more in all three kinds of jump. The authors conclude that the gains from jump training come from the mechanical properties of the muscle and tendon as a unit, not from changes in how the muscle is activated.
Chapter 4
What to train besides squats
Strength training such as squats raises the ceiling, and jump training works on fast force and springiness: the two fill different parts of the gap. Jump training, also called plyometric training, means exercises such as repeated jumps and jumping onto a box that use the stretch-shortening cycle. In a that pooled 26 studies, healthy people who did jump training raised the height of a jump with a dip by 8.7% on average.
Which part to work on first depends on which part you lack. In a randomized trial, 24 relatively weak men trained for 10 weeks: heavy squats and loaded jumps raised jump power about equally, but the maximal squat weight rose by 31.2% and 4.5% respectively. The authors concluded that for relatively weak people, working on strength first pays off more, and a review likewise says that without a fair amount of strength it is hard to have a lot of power. How to train strength itself is covered in Resistance training basics.
The following are only examples of the mechanism, not a training plan: squats and step-ups build strength, while jumping in place, jumping onto a low box and jumping rope train fast force. A step you can take today: if you are still fairly weak or not yet confident with squats, build your strength first; once you have a base, add a little jump practice.
Which part to work on first depends on which part you lack. In a randomized trial, 24 relatively weak men trained for 10 weeks: heavy squats and loaded jumps raised jump power about equally, but the maximal squat weight rose by 31.2% and 4.5% respectively. The authors concluded that for relatively weak people, working on strength first pays off more, and a review likewise says that without a fair amount of strength it is hard to have a lot of power. How to train strength itself is covered in Resistance training basics.
The following are only examples of the mechanism, not a training plan: squats and step-ups build strength, while jumping in place, jumping onto a low box and jumping rope train fast force. A step you can take today: if you are still fairly weak or not yet confident with squats, build your strength first; once you have a base, add a little jump practice.
Evidence · How much higher jump training gets you
Markovic 2007 pooled randomized and non- in healthy people. After jump training, the height of a jump from a still squat rose by 4.7% on average, a jump with a dip by 8.7%, a jump with a dip and an arm swing by 7.5%, and a drop jump, where you step off a box and spring straight back up, by 4.7%. The author judged these gains statistically significant and practically meaningful.Read that number within its limits. The Kons 2023 umbrella review pooled 29 of jump training and concluded that it improves most related measures of fitness and sports performance; but only 5 of them compared against a control group, while the other 24 compared people with themselves before and after training, so the authors caution that the results should be read carefully.
The two kinds of training also change different parts of the body. In Kubo 2007, the study with one training method per leg, heavy training stiffened the tendon and raised jump height only in the jump from a still squat; jump training did not stiffen the tendon but did raise the stiffness of the ankle during the landing, and that leg jumped higher in all three kinds of jump.
kons-2023-plyometric-umbrella-review
Evidence · Strength first, or jumps first?
In Cormie 2010, every participant could squat with proper technique but was relatively weak. They were randomized to three groups: heavy squats (75%–90% of their maximal weight), all-out loaded jumps (0%–30% of their maximal weight), and a control group that did not train, for 10 weeks. Both training groups improved their jumping and their 40-meter sprint, with no significant difference between them: jump peak power rose by 17.7% and 17.6% respectively, but only the squat group made large gains in maximal strength. On that basis the authors argue that for relatively weak people, strength training brings about the same short-term gains in performance as power training, plus maximal strength in the long run, so it pays off more.The Cormie 2011 review writes this up as a principle: there is a basic relationship between strength and power, and without a fair amount of strength it is hard to have a lot of power; beyond that, training the weakest link in a given person brings the biggest gains. Suchomel 2016 reviewed more than 200 studies and concluded that greater strength is linked to better jumping, sprinting and changes of direction, and to a lower risk of injury.
Read the limits: Cormie 2010 had only 24 men and lasted only 10 weeks, and it cannot say what people who are already very strong should train first.
suchomel-2016-importance-strength
Chapter 5
Does jumping hurt your knees?
Jumping loads the tendons below the kneecap and at the back of the ankle, and that load is also what makes tendons stronger; what to guard against is landing too stiffly, and adding jumps faster than the tendons can adapt. On landing, the body has to stop its fall in an instant. In a randomized trial, jumping down from a 30-centimeter box produced a landing impact of about 4.5 times body weight on average; after participants were taught to bend the hips and knees together and land on the front of the foot first, it fell to about 3.6 times. A soft landing with the knees bent more deeply has a smaller impact, and the thigh and buttock muscles absorb more of the energy.
Pain between the kneecap and the shin is often linked to repeated running and jumping, and is commonly called jumper's knee (see Knee Pain). In a cohort of young volleyball players, the more hours they trained, the higher their risk of developing jumper's knee; this is an observed association.
A step you can take today: make your landings quieter, bending the hips and knees together to absorb them, and add jumps slowly, one change at a time.
If you feel sudden severe pain and a pop while jumping or landing, and then cannot rise onto your toes, cannot straighten your knee, or can feel a gap, suspect a tendon rupture: this is an emergency, so seek care promptly and do not train through it. If you get chest pain or tightness, or faint, during exercise, call emergency services now.
Pain between the kneecap and the shin is often linked to repeated running and jumping, and is commonly called jumper's knee (see Knee Pain). In a cohort of young volleyball players, the more hours they trained, the higher their risk of developing jumper's knee; this is an observed association.
A step you can take today: make your landings quieter, bending the hips and knees together to absorb them, and add jumps slowly, one change at a time.
If you feel sudden severe pain and a pop while jumping or landing, and then cannot rise onto your toes, cannot straighten your knee, or can feel a gap, suspect a tendon rupture: this is an emergency, so seek care promptly and do not train through it. If you get chest pain or tightness, or faint, during exercise, call emergency services now.
Evidence · How hard a landing hits, and softening it
Prapavessis 1999 had 91 healthy people jump down from a 30-centimeter box and land as softly as they could on a force plate. Those randomized to the instruction group were told to pay attention to how their hips and knees moved and to land on the front of the foot first; their peak landing impact fell from 4.53 to 3.57 times body weight. Those asked only to land more softly using the feel of their first jump barely changed (4.51 to 4.33 times). The authors suggest that a very high impact may be one of the triggers of injury.Devita 1992 compared soft and stiff landings in 8 female athletes dropping from a height of 59 centimeters: in soft landings the knee bent to 117 degrees on average, in stiff ones only to 77 degrees. The stiff landings had a larger ground reaction force; in soft landings the hip and knee muscles absorbed more energy, while in stiff ones the ankle absorbed more.
The jumper's knee study is Visnes 2013: 141 volleyball students aged 16 to 18 were followed for 4 years, and 28 of them developed jumper's knee. Each extra hour of volleyball training came with an of 1.72, and boys had 3 to 4 times the risk of girls. It is an observational study: it shows that training volume and jumper's knee go together, and cannot on its own show which jumps caused it.
Children can do jump training too. A systematic review of 7 studies found that children aged 5 to 14 clearly improved their running and jumping after jump training, and that it was safe when parents consented, the children agreed to take part, and safety rules were built in; all 7 studies, though, were of low quality. How children should train at each stage of growth is covered in Youth & adolescent training.
johnson-2011-plyometric-young-children
Red flag · Signs to stop and seek care now
The signs below are not ordinary soreness; they need action right away. This site does not diagnose; if they appear, stop first.Sudden severe pain while jumping or landing, with a pop you hear or feel, and then being unable to push off or rise onto your toes, or feeling a gap: suspect a tendon rupture (an Achilles rupture, for example). This is an emergency: seek care promptly, and do not try to train through it.A pop when you injure your knee, after which the knee gives way, cannot hold you up or will not straighten: it may be a torn ligament, tendon or meniscus, so seek care promptly.Sudden chest pain or tightness during or after exercise that feels like pressure or squeezing, may spread to the arm, neck or jaw, and comes with breathlessness or a cold sweat: it may be a heart emergency, so call emergency services now.Fainting during exercise: call emergency services now.
Pain between the kneecap and the shin that keeps coming back, often after repeated running and jumping, may come from the patellar tendon; how to adjust the load so it heals is covered in Knee Pain. If it has not improved within a few weeks, see a doctor.
Chapter 6
Does power still matter with age?
Yes. Power declines earlier and faster with age than strength does, and getting up, climbing a step and catching yourself when you nearly fall all depend on it. A cross-sectional study compared healthy people aged 65 to 89: for each year of age, static strength was 1%–2% lower and leg power about 3.5% lower, and leg power relative to body weight was linked both to how fast people could stand up from a low chair and to how high a step they could climb onto. A review lists power as an important predictor of limited mobility in older people. The nerves play a part as well: in fast ankle lifts, people aged 71 to 84 built force 48% more slowly than young adults, and their motor units fired 27% more slowly.
Training power does not require jumping. In a that pooled 20 randomized trials, healthy adults over 60 who lifted the weight as fast as possible and lowered it slowly during strength training improved their everyday physical function slightly more than with ordinary strength training; the certainty of this evidence is low.
A step you can take today: stand up from a chair as quickly as you can, and sit back down slowly. If you have known heart disease, or have had chest pain, unexplained breathlessness, or fainting during exertion, see a doctor for an assessment before you start. If you get sudden chest pain or tightness during or after exercise, or faint while exercising, call emergency services now.
Training power does not require jumping. In a that pooled 20 randomized trials, healthy adults over 60 who lifted the weight as fast as possible and lowered it slowly during strength training improved their everyday physical function slightly more than with ordinary strength training; the certainty of this evidence is low.
A step you can take today: stand up from a chair as quickly as you can, and sit back down slowly. If you have known heart disease, or have had chest pain, unexplained breathlessness, or fainting during exertion, see a doctor for an assessment before you start. If you get sudden chest pain or tightness during or after exercise, or faint while exercising, call emergency services now.
Evidence · Is fast-force training safe in later life?
Balachandran 2022 pooled 20 randomized trials with 566 healthy older adults living in the community (mean age 70.1, 65% women) and compared two kinds of strength training: one lifting and lowering under control as usual, the other lifting as fast as possible and lowering under control. In the 13 trials that measured physical function, the fast-lifting groups improved slightly more (a standardized mean difference of 0.30), and the certainty of this evidence is low; the authors call for larger, higher-quality trials.On safety, neither group reported serious adverse events; but 14 of the 20 trials did not report adverse events completely, and most trials lasted only 12 weeks with small samples, so that statement carries limited weight. The speed in these studies means doing the lifting part of a strength exercise fast, not asking older people to jump.
The age figures need careful reading too. Skelton 1994 was a cross-sectional comparison, not a study following the same people over time, so a figure such as 3.5% a year is a difference between people of different ages; and only in men did power fall clearly faster than strength, while in women the difference did not reach statistical significance. Why muscle is lost with age, and how strength training resists it, is covered in Elderly resistance training.
References · 25
- Kurokawa, S., Fukunaga, T., & Fukashiro, S. (2001). Behavior of fascicles and tendinous structures of human gastrocnemius during vertical jumping. Journal of Applied Physiology, 90(4), 1349-1358. Ultrasonography of the medial gastrocnemius in eight male subjects doing squat jumps (no countermovement). From 350 to 100 ms before toe-off the muscle-tendon length was almost constant while fascicles shortened by 26% and tendinous structures were stretched by 6%, storing 4.9 J of elastic energy; in the last 100 ms, 'although fascicles generated force quasi-isometrically, MTC shortened rapidly by 5.3%, releasing prestored elastic energy with a higher peak positive power than that of fascicles.' Conclusion: 'the compliance of tendinous structures, together with no yielding of muscle fibers, allows MTC to effectively generate relatively large power at a high joint angular velocity region during the last part of push-off' (abstract, PMID 11247934). 10.1152/jappl.2001.90.4.1349
- Maffiuletti, N. A., Aagaard, P., Blazevich, A. J., Folland, J., Tillin, N., & Duchateau, J. (2016). Rate of force development: physiological and methodological considerations. European Journal of Applied Physiology, 116(6), 1091-1116. Narrative review. Rate of force development '(1) seems to be mainly determined by the capacity to produce maximal voluntary activation in the early phase of an explosive contraction (first 50-75 ms), particularly as a result of increased motor unit discharge rate; (2) can be improved by both explosive-type and heavy-resistance strength training in different subject populations, mainly through an improvement in rapid muscle activation; (3) is quite difficult to evaluate in a valid and reliable way' (abstract, PMID 26941023). Full text (PMC4875063): a rapid rise in force in the initial phase of a voluntary contraction (0-300 ms) 'is vital not only to the trained athlete but also to the elderly individual who needs to counteract sudden perturbations in postural balance'; maximal torque in isometric contractions is reached only after more than 300 ms; the rate of tension development is faster in type II than type I fibres, and fibre type composition varies widely between individuals; older adults (71-84 years) showed a 48% slower RFD and a 27% lower motor unit discharge rate at the onset of ballistic ankle dorsiflexions than young adults (about 20 years). 10.1007/s00421-016-3346-6
- Aagaard, P., Simonsen, E. B., Andersen, J. L., Magnusson, P., & Dyhre-Poulsen, P. (2002). Increased rate of force development and neural drive of human skeletal muscle following resistance training. Journal of Applied Physiology, 93(4), 1318-1326. 'The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0-200 ms).' 15 male subjects measured before and after 14 weeks of heavy-resistance strength training (38 sessions): maximal isometric quadriceps strength rose from 291.1 to 339.0 N·m; contractile RFD rose at 30, 50, 100 and 200 ms after contraction onset (for example from 1,601 to 2,020 N·m/s at 30 ms); normalized to MVC, RFD rose 15%; EMG amplitude rose 22-143% and rate of EMG rise 41-106% in the first 200 ms. Conclusion: 'increases in explosive muscle strength (contractile RFD and impulse) were observed after heavy-resistance strength training. These findings could be explained by an enhanced neural drive, as evidenced by marked increases in EMG signal amplitude and rate of EMG rise in the early phase of muscle contraction' (abstract, PMID 12235031). 10.1152/japplphysiol.00283.2002
- Balachandran, A. T., Steele, J., Angielczyk, D., Belio, M., Schoenfeld, B. J., Quiles, N., Askin, N., & Abou-Setta, A. M. (2022). Comparison of power training vs traditional strength training on physical function in older adults: a systematic review and meta-analysis. JAMA Network Open, 5(5), e2211623. 20 RCTs, 566 healthy community-living adults aged 60 or older (mean 70.1 years, 65% women), comparing power training (lifting weights fast and lowering under control) with traditional strength training. Power training was associated with better physical function in 13 RCTs (n = 383; SMD 0.30, 95% CI 0.05-0.54), low-certainty evidence. Full text (PMC9096601): 'There were no serious adverse events reported for either group'; adverse events were insufficiently reported in 14 of 20 RCTs; most trials were short (12 weeks) and small. Conclusion: 'PT was associated with a modest improvement in physical function compared with traditional strength training in healthy, community-living older adults. However, high-quality, larger RCTs are required to draw more definitive conclusions' (abstract, PMID 35544136). 10.1001/jamanetworkopen.2022.11623
- NHS. (2025). Heel pain (page last reviewed 24 October 2025). Sudden sharp pain in the heel, swelling, a popping or snapping sound during the injury and difficulty walking may be a heel fracture or a ruptured Achilles tendon; pain in the back of the heel, ankle and calf may be Achilles tendonitis. Do not try to diagnose the cause yourself. Contact NHS 111 urgently if you have severe heel pain after an injury, feel faint, dizzy or sick from the pain, have an ankle or foot that has changed shape or is at an odd angle, heard a snap, grinding or popping noise at the time of injury, are not able to walk, are not able to walk on your tiptoes, are not able to walk up the stairs, or have swelling and bruising in your calf and ankle. www.nhs.uk/symptoms/foot-pain/heel-pain
- NHS. (2023). Knee pain (page last reviewed 21 December 2023). Pain between the kneecap and shin, often caused by repetitive running or jumping, may be tendonitis. A knee that is unstable, gives way when you try to stand or cannot be straightened, perhaps with a popping sound during the injury, may be a torn ligament, tendon or meniscus or cartilage damage. Get advice from 111 now if the knee is very painful, you cannot move it or put any weight on it, it is badly swollen or has changed shape, it locks, gives way or painfully clicks, or you have a very high temperature with redness or heat around the knee. www.nhs.uk/symptoms/knee-pain
- NHS. (2026). Heart attack: symptoms. Symptoms can include chest pain that may feel like crushing or squeezing on the chest and may spread to the arm, neck and jaw; feeling short of breath; feeling or being sick; feeling like indigestion; sweating; and pale, blue or grey skin. Call 999 for chest pain that feels tight or like squeezing, or that spreads to the arms, neck or jaw, with severe difficulty breathing, or if someone becomes unresponsive. A heart attack needs emergency treatment in hospital (page last reviewed 31 March 2026). www.nhs.uk/conditions/heart-attack/symptoms
- NHS. (2026). Fainting (page last reviewed 17 August 2026). Fainting is when you pass out for a short time; it is not usually serious, but anyone who has fainted should see a GP to find out what might have caused it. Causes can include standing up too quickly (which could be a sign of low blood pressure), not eating or drinking enough, being too hot, being very upset or in severe pain, heart problems, and taking drugs or drinking too much alcohol. Call 999 if someone is not breathing, cannot be woken up within 1 minute, has not fully recovered or has difficulty with speech or movement, has chest pain or a pounding, fluttering or irregular heartbeat (palpitations), has seriously hurt themselves before or after fainting, is shaking or jerking (a seizure), fainted while exercising, or fainted while lying down; do not drive yourself to A&E. If you feel about to faint: lie down with your legs raised, or if you cannot, sit with your head lowered between your knees; drink some water; cross your legs while standing up or rock up and down on your toes; clench your fists. If you see someone faint: check whether they respond by gently shaking their shoulders and asking loudly; if not, shout for help and tilt back the head and lift the chin; listen for breathing for at least 10 seconds; if they are breathing normally, lay them on their back and raise their legs (on their side if pregnant, especially over 28 weeks); they usually wake up within 30 seconds. www.nhs.uk/conditions/fainting
- Van Cutsem, M., Duchateau, J., & Hainaut, K. (1998). Changes in single motor unit behaviour contribute to the increase in contraction speed after dynamic training in humans. The Journal of Physiology, 513 Pt 1, 295-305. Five subjects trained the ankle dorsiflexors for 12 weeks with fast dorsiflexions against 30-40% of maximal strength. Training raised maximal voluntary contraction and the speed of ballistic contraction; 'This last enhancement was mainly related to neural adaptations since the time course of the muscle twitch induced by electrical stimulation remained unaffected.' During ballistic contractions motor units 'were activated earlier and had a greater maximal firing frequency'; the share of sampled units firing brief 2-5 ms doublets rose from 5.2% to 32.7%. Conclusion: 'It is likely that earlier motor unit activation, extra doublets and enhanced maximal firing rate contribute to the increase in the speed of voluntary muscle contraction after dynamic training' (abstract, PMID 9782179). 10.1111/j.1469-7793.1998.295by.x
- Moritani, T., & deVries, H. A. (1979). Neural factors versus hypertrophy in the time course of muscle strength gain. American Journal of Physical Medicine, 58(3), 115-130. A small training study, not a randomized trial: 7 young men and 8 women, 8 weeks of isotonic strength training. Neural factors accounted for the larger share of the initial strength gain; after the first 3 to 5 weeks hypertrophy became the dominant factor. The abstract gives no percentage split between neural and hypertrophic contributions (abstract, PMID 453338). pubmed.ncbi.nlm.nih.gov/453338
- Bobbert, M. F., Gerritsen, K. G., Litjens, M. C., & Van Soest, A. J. (1996). Why is countermovement jump height greater than squat jump height? Medicine & Science in Sports & Exercise, 28(11), 1402-1412. Six male volleyball players; even with the same body position at the start of push-off, countermovement jump height was on average 3.4 cm greater than squat jump height. 'The greater jump height in CMJ was attributed to the fact that the countermovement allowed the subjects to attain greater joint moments at the start of push-off.' 'According to simulation results, storage and reutilization of elastic energy could be ruled out as explanation for the enhancement of performance in CMJ over that in SJ. The crucial contribution of the countermovement seemed to be that it allowed the muscles to build up a high level of active state (fraction of attached cross-bridges) and force before the start of shortening, so that they were able to produce more work over the first part of their shortening distance' (abstract, PMID 8933491). 10.1097/00005768-199611000-00009
- Van Hooren, B., & Zolotarjova, J. (2017). The difference between countermovement and squat jump performances: a review of underlying mechanisms with practical applications. Journal of Strength and Conditioning Research, 31(7), 2011-2020. 'Countermovement jump performance is almost always better than SJ performance, and the difference in performance is thought to reflect an effective utilization of the stretch-shortening cycle.' Conclusion: 'the difference in performance may primarily be related to the greater uptake of muscle slack and the buildup of stimulation during the countermovement in a CMJ. Elastic energy may also have a small contribution to an enhanced CMJ performance. Therefore, a larger difference between the jumps is not necessarily a better indicator of high-intensity sports performance' (abstract, PMID 28640774). 10.1519/JSC.0000000000001913
- Bohm, S., Mersmann, F., & Arampatzis, A. (2015). Human tendon adaptation in response to mechanical loading: a systematic review and meta-analysis of exercise intervention studies on healthy adults. Sports Medicine - Open, 1(1), 7. 27 studies (37 interventions of at least 8 weeks, 264 healthy adults aged 18-50, Achilles or patellar tendon): stiffness SMD 0.70, Young's modulus SMD 0.69, cross-sectional area SMD 0.24, all significant. Stiffness adaptation depended on loading intensity but not on contraction type; 'Although not significantly different, SMD was higher for interventions with longer duration (≥12 weeks).' Conclusion: 'tendons are highly responsive to diverse loading regimens. However, the data strongly suggests that loading magnitude in particular plays a key role for tendon adaptation in contrast to muscle contraction type' (abstract, PMID 27747846). 10.1186/s40798-015-0009-9
- Magnusson, S. P., Langberg, H., & Kjaer, M. (2010). The pathogenesis of tendinopathy: balancing the response to loading. Nature Reviews Rheumatology, 6(5), 262-268. Mechanical loading upregulates collagen expression and synthesis in tendon: 'This increase in collagen formation peaks around 24 h after exercise and remains elevated for about 3 days. The degradation of collagen proteins also rises after exercise, but seems to peak earlier than the synthesis.' 'Despite the ability of tendons to adapt to loading, repetitive use often results in injuries, such as tendinopathy'; microrupture and material fatigue are suggested injury mechanisms, implying one or more weak links in the structure (abstract, PMID 20308995). 10.1038/nrrheum.2010.43
- Heinemeier, K. M., Schjerling, P., Heinemeier, J., Magnusson, S. P., & Kjaer, M. (2013). Lack of tissue renewal in human adult Achilles tendon is revealed by nuclear bomb 14C. The FASEB Journal, 27(5), 2074–2079. Bomb-pulse 14C in 28 forensic Achilles tendon core samples and 4 muscle samples: the tendon core retained 14C levels matching the atmosphere several decades before sampling, showing very limited tissue turnover, while muscle showed continuous turnover (abstract, PMID 23401563). 10.1096/fj.12-225599
- Markovic, G. (2007). Does plyometric training improve vertical jump height? A meta-analytical review. British Journal of Sports Medicine, 41(6), 349-355. Meta-analysis of randomised and non-randomised controlled trials in healthy individuals (26 studies). Pooled improvement in jump height with plyometric training: squat jump 4.7% (95% CI 1.8 to 7.6), countermovement jump 8.7% (7.0 to 10.4), countermovement jump with arm swing 7.5% (4.2 to 10.8), drop jump 4.7% (0.8 to 8.6); effect sizes 0.44, 0.88, 0.74 and 0.62. Conclusion: 'PT provides a statistically significant and practically relevant improvement in vertical jump height with the mean effect ranging from 4.7% (SJ and DJ), over 7.5% (CMJA) to 8.7% (CMJ). These results justify the application of PT for the purpose of development of vertical jump performance in healthy individuals' (abstract, PMID 17347316). 10.1136/bjsm.2007.035113
- Cormie, P., McGuigan, M. R., & Newton, R. U. (2010). Adaptations in athletic performance after ballistic power versus strength training. Medicine & Science in Sports & Exercise, 42(8), 1582-1598. Relatively weak men (n = 24) randomized to heavy strength training (back squats at 75-90% of 1RM), ballistic power training (maximal-effort jump squats at 0-30% of 1RM) or control, three sessions a week for 10 weeks. Jump and sprint performance improved in both training groups with no significant difference between them (jump peak power: strength 17.7%, power 17.6%; 40-m sprint: 2.2% and 3.6%); squat 1RM rose 31.2% with strength training versus 4.5% with power training. Conclusion: 'Improvements in athletic performance were similar in relatively weak individuals exposed to either ballistic power training or heavy strength training for 10 wk... The ability of strength training to render similar short-term improvements in athletic performance as ballistic power training, coupled with the potential long-term benefits of improved maximal strength, makes strength training a more effective training modality for relatively weak individuals' (abstract, PMID 20139780). 10.1249/MSS.0b013e3181d2013a
- Cormie, P., McGuigan, M. R., & Newton, R. U. (2011). Developing maximal neuromuscular power: part 2 - training considerations for improving maximal power production. Sports Medicine, 41(2), 125-146. Narrative review. 'First, a fundamental relationship exists between strength and power, which dictates that an individual cannot possess a high level of power without first being relatively strong. Thus, enhancing and maintaining maximal strength is essential when considering the long-term development of power.' 'Ballistic, plyometric and weightlifting exercises can be used effectively as primary exercises within a power training programme that enhances maximal power'; plyometric exercises should involve stretch rates and loads similar to the sport. 'A training programme that focuses on the least developed factor contributing to maximal power will prompt the greatest neuromuscular adaptations and therefore result in superior performance improvements for that individual' (abstract, PMID 21244105). 10.2165/11538500-000000000-00000
- Kubo, K., Morimoto, M., Komuro, T., Yata, H., Tsunoda, N., Kanehisa, H., & Fukunaga, T. (2007). Effects of plyometric and weight training on muscle-tendon complex and jump performance. Medicine & Science in Sports & Exercise, 39(10), 1801-1810. Ten subjects trained the plantar flexors for 12 weeks, plyometric training (hopping and drop jumps) on one leg and weight training (80% of 1RM) on the other. 'Tendon stiffness increased significantly for WT, but not for PT. Conversely, joint stiffness increased significantly for PT, but not for WT. Whereas PT increased significantly jump heights of SJ, CMJ, and DJ, WT increased SJ only. The relative increases in jump heights were significantly greater for PT than for WT'; muscle activation during jumping changed no differently between legs. Conclusion: 'the jump performance gains after plyometric training are attributed to changes in the mechanical properties of muscle-tendon complex, rather than to the muscle activation strategies' (abstract, PMID 17909408). 10.1249/mss.0b013e31813e630a
- Prapavessis, H., & McNair, P. J. (1999). Effects of instruction in jumping technique and experience jumping on ground reaction forces. Journal of Orthopaedic & Sports Physical Therapy, 29(6), 352-356. Randomized controlled trial in 91 non-impaired subjects who jumped from a 300 mm box and tried to land as softly as possible on a force plate. Those given instructions to focus on hip and knee joint motion and a forefoot landing reduced peak ground reaction force from 4.53 to 3.57 times body weight; those asked only to use the experience of their first jump did not (4.51 to 4.33). Conclusion: 'High ground reaction forces may be a precipitating factor associated with an injury, where the site of tissue damage would benefit from decreased forces. These findings support the use of instructions related to joint motion to reduce landing forces' (abstract, PMID 10370919). 10.2519/jospt.1999.29.6.352
- Devita, P., & Skelly, W. A. (1992). Effect of landing stiffness on joint kinetics and energetics in the lower extremity. Medicine & Science in Sports & Exercise, 24(1), 108-115. Eight female athletes landed from a 59 cm fall with soft (on average 117 degrees of knee flexion) and stiff (77 degrees) landings. 'The stiff landing had larger GRFs'; 'The hip and knee muscles absorbed more energy in the soft landing (hip, -0.60 vs -0.39 W.kg-1; knee, -0.89 vs -0.61 W.kg-1), while the ankle muscles absorbed more in the stiff landing (-0.88 vs -1.00 W.kg-1)' (abstract, truncated at 250 words, PMID 1548984). 10.1249/00005768-199201000-00018
- Visnes, H., & Bahr, R. (2013). Training volume and body composition as risk factors for developing jumper's knee among young elite volleyball players. Scandinavian Journal of Medicine & Science in Sports, 23(5), 607-613. Four-year prospective cohort of 141 healthy elite volleyball students aged 16-18; 28 developed jumper's knee. Boys had three to four times the risk of girls; volleyball training had an odds ratio of 1.72 (1.18-2.53) for every extra hour trained, and match exposure an odds ratio of 3.88 (1.80-8.40) for every extra set played per week; body composition did not differ. Conclusion: 'male gender, a high volume of volleyball training and match exposure were risk factors for developing jumper's knee' (abstract, PMID 22260424). 10.1111/j.1600-0838.2011.01430.x
- Skelton, D. A., Greig, C. A., Davies, J. M., & Young, A. (1994). Strength, power and related functional ability of healthy people aged 65-89 years. Age and Ageing, 23(5), 371-377. Cross-sectional study of 50 healthy men and 50 healthy women evenly spread across ages 65-89. 'The differences in isometric strength and leg extensor power over the age range were equivalent to losses of 1-2% per annum and approximately 3 1/2% per annum, respectively. The decline of explosive power was faster than the decline of knee extensor strength in men (p = 0.0001), but not significantly so in women (p = 0.08). Power standardized for body weight influenced chair rise time and step height' (abstract, PMID 7825481). 10.1093/ageing/23.5.371
- Reid, K. F., & Fielding, R. A. (2012). Skeletal muscle power: a critical determinant of physical functioning in older adults. Exercise and Sport Sciences Reviews, 40(1), 4-12. Review: 'Muscle power declines earlier and more precipitously with advancing age compared with muscle strength. Peak muscle power also has emerged as an important predictor of functional limitations in older adults.' The authors' working hypothesis is that lower extremity muscle power is 'a more discriminant variable for understanding the relationships between impairments, functional limitations, and resultant disability with aging' (abstract, PMID 22016147). 10.1097/JES.0b013e31823b5f13
- Riebe, D., Franklin, B. A., Thompson, P. D., Garber, C. E., Whitfield, G. P., Magal, M., & Pescatello, L. S. (2015). Updating ACSM's recommendations for exercise preparticipation health screening. Medicine & Science in Sports & Exercise, 47(11), 2473-2479. ACSM roundtable: 'there is considerable evidence that exercise is safe for most people and has many associated health and fitness benefits; exercise-related cardiovascular events are often preceded by warning signs/symptoms; and the cardiovascular risks associated with exercise lessen as individuals become more physically active/fit.' The new screening model rests on current activity level, the presence of signs or symptoms or known cardiovascular, metabolic or renal disease, and the desired exercise intensity (abstract, PMID 26473759). 10.1249/MSS.0000000000000664