Understanding Overuse Injuries: Why They Happen and How to Train Around Them

Why overuse injuries are a capacity problem, not a luck problem. How tissue adaptation lags behind fitness. And the training, monitoring and recovery decisions that keep you on the start line of your course.

Overuse injuries are not bad luck. They are a capacity problem. To stay out of one: progress your weekly training load in steps your tissues can keep pace with (rough rule of thumb is no more than 10-15% increases week on week, with a lighter consolidation week every fourth or fifth), give loaded tissues at least 48 hours between hard impact sessions, train heavy compound and single-leg strength twice a week (this single intervention nearly halves overuse injury risk in pooled research), build a deep zone 2 aerobic base so movement quality holds longer under fatigue, and treat any pain that worsens during loading or persists past 48 hours as a signal to modify, not push through. Most overuse injuries are preventable. The unglamorous decisions above are what prevent them.

The rest of this article explains why overuse injuries happen, why the lower limb takes most of the damage in military populations, why fitness improves faster than the chassis that has to carry it, and the specific training and monitoring decisions that keep capacity ahead of demand across the months before a course.

The scene this usually plays out in

You were progressing well. The runs felt easier, the bergen sat better on your back, and the numbers in the gym were moving in the right direction. Then your shin started to ache on every footfall, or your knee began to complain on the descents, and within a fortnight you were limping out of sessions you used to finish comfortably. Nothing dramatic happened. There was no single moment you could point to. It simply crept up on you.

That is the defining feature of an overuse injury. Overuse injuries are not accidents. They are the predictable result of asking a tissue to do more than it has been prepared to do, repeatedly, before it has had the chance to adapt. For soldiers, selection candidates and tactical athletes, they are also the most common reason that good training plans fall apart. You rarely lose your place on a course because you were not fit enough. You lose it because something broke before the start date.

What is an overuse injury?

An overuse injury is damage that accumulates gradually from repeated loading without sufficient recovery between bouts. Every hard session creates a small amount of microtrauma in the loaded tissue. This is normal and, in fact, necessary. The repair process is what makes the tissue stronger. The problem arises when the rate of damage outpaces the rate of repair. Microdamage stacks up, the tissue cannot keep ahead of it, and what should have been a stimulus for adaptation becomes a stimulus for breakdown.

Left unchecked, that process moves through fairly predictable stages: a low-grade inflammatory response as the body tries to repair the area, then pain and reduced function, and eventually a structural change in the tissue itself, whether that is a stress reaction in bone, a degenerative change in a tendon, or irritation at a joint surface. Prolonged inflammation does not just signal damage. It can drive further damage if loading continues unaddressed.

The tissues most often affected in this population are the ones exposed to repetitive, cyclic, weight-bearing load: the bones, tendons and muscles of the lower limb. Running, jumping, and load carriage hammer these structures thousands of times per session. The most common presentations are medial tibial stress syndrome (shin splints), patellofemoral pain, Achilles and patellar tendinopathy, stress fractures of the tibia, metatarsals and femoral neck, and iliotibial band syndrome. Plantar heel pain and Achilles tendinopathy in particular tend to recur, which is why getting on top of them early matters.

The capacity-load framework: what's actually happening

The clearest mental model for overuse injuries is the capacity-load framework formalised by Bertelsen and colleagues (2017). Every tissue, bone, tendon, muscle, fascia, has a specific load tolerance. It can take a certain quantity of force, applied a certain way, a certain number of times, before it fails. Training raises that capacity. Loading consumes it. As long as your capacity is being built faster than your loading is consuming it, you adapt. As soon as the loading outpaces the capacity, you start accumulating damage.

Injury, in this model, is a load error meeting a capacity shortfall. Either the load was too large, applied too quickly, or stacked on top of insufficient recovery. Or the tissue's capacity was lower than the loading required, because of previous injury, deconditioning, fatigue, or simply because the tissue had not yet had time to adapt. Most injuries involve some combination of both.

The practical value of this model is that it stops the conversation being about luck or genetics. Both sides of the equation, capacity and load, are trainable. Every injury-reduction intervention discussed below acts on one or the other.

Why do the lower limbs take most of the damage?

Because that is where the load goes. British Army research has repeatedly found that the large majority of musculoskeletal injuries in recruits, in the region of 80%, occur in the lower limb (Sharma et al. 2015; Anderson et al. 2016). A more recent systematic review and meta-analysis of military recruit populations (Robinson et al. 2023) confirmed that lower-limb injuries remain the dominant injury class globally, with overuse mechanisms accounting for roughly half of all musculoskeletal injuries during basic training. The pattern has not shifted, because the demands have not shifted. Marching, tabbing and running under load are unavoidable parts of the job.

Ground reaction force is central to this. Every time your foot strikes the ground, the ground pushes back with a force equal to and opposite your own. Add a loaded bergen, increase the speed, or run downhill, and that force climbs. Carry the load for long enough and a second problem appears: fatigue erodes your ability to manage the force. A 2022 study in Applied Ergonomics (Wills et al. 2022) found that after two consecutive days of military load carriage, participants showed a measurable reduction in ankle plantarflexor torque, meaning the calf and ankle complex became less able to absorb and redirect ground reaction force. The load did not change. The body's ability to cope with it did.

Downhill running deserves special mention. Eccentric loading on the descents produces far higher per-step impact than level running, and is one of the most common triggers for patellofemoral pain, quadriceps tendinopathy and shin issues in selection candidates training on hills. If your course route involves descents, your training has to include them, and your downhill capacity has to be built before the volume is.

It is worth being honest about the evidence on biomechanical risk factors. Much of the research linking factors such as ground reaction force, limb asymmetry and abnormal joint angles to injury was collected after the injury occurred, which makes cause and effect difficult to untangle. The asymmetry you measure in an injured runner may be a result of the injury rather than its cause. One of the few prospective studies to measure ground reaction force before injury found that those who went on to be injured did indeed display higher forces beforehand (Kiernan et al. 2018), which is a useful signal, but a single finding is not a law. Treat these as contributing factors to manage, not as a diagnosis.

Why does tissue lag behind fitness?

This is the mechanism most people miss, and it is the one that causes the most damage. Your aerobic system adapts quickly. Within a few weeks of consistent training your heart, blood and muscles become noticeably more capable, the runs feel easier, and your perceived effort drops. The structural tissues, the bones and tendons that have to survive every footfall, adapt far more slowly.

The engine adapts in weeks. The chassis takes months.

This mismatch is dangerous precisely because it feels good. Your fitness tells you that you can do more, so you do more, while the tissue that has to tolerate that work is still weeks or months behind. Bone is the clearest example. After a sudden, non-gradual jump in training, the early phase of bone remodelling can actually leave the bone temporarily more vulnerable, and stress reactions tend to appear in roughly the six to eight week window when remodelling has not yet caught up with the new demand (Warden et al. 2014). Tendon behaves similarly. It begins responding within a fortnight, but meaningful gains in stiffness and load tolerance take months of progressive loading, not weeks (Magnusson & Kjaer 2019).

Table 1. Different tissues adapt on very different timelines. Programme to the slowest tissue, not the fastest. The runner who feels great in week three is often the same one limping by week eight, because they trained the speed at which the engine adapted, not the speed at which the chassis did.

Why do overuse injuries happen in practice?

The single most common trigger is a rapid increase in training load. When the work you are doing this week is much greater than the work your body has grown accustomed to over the preceding weeks, injury risk rises. This is intuitive, and it is supported by a large body of work on training load and injury, including the International Olympic Committee consensus statements on the subject (Soligard et al. 2016; Schwellnus et al. 2016).

You may have heard a specific version of this rule, often phrased as a sudden jump of more than 50% over your recent average roughly doubling your injury risk, expressed through the acute to chronic workload ratio (ACWR). It is worth being clear about where that idea now stands. The ratio was a useful way of drawing attention to load spikes, but it has been heavily criticised on conceptual and statistical grounds (Impellizzeri et al. 2020; Lolli et al. 2019), and it should not be treated as a precise predictor you can calculate your way to safety with. Injury is multifactorial. No single number captures it.

The underlying principle, however, has survived the criticism intact: avoid sharp, unaccustomed spikes in load, and build your capacity gradually over time. In fact, the more important half of that principle is the part people ignore. A high level of fitness built up gradually is protective, not dangerous. Gabbett's work on what he called the training-injury prevention paradox showed that athletes carrying high chronic workloads, accumulated sensibly over time, tend to be more robust and less injured than those training at low workloads (Gabbett 2016). The danger is not hard training. The danger is hard training your tissues have not been prepared for.

Recovery is the other side of the same coin. Microtrauma needs time to repair, and the demands of heavy load carriage in particular can linger. Research on the physiological cost of load carriage suggests that some effects remain present well beyond 72 hours after a hard session, depending on its intensity and duration (Faghy et al. 2022). Stacking another heavy session on top of incomplete recovery is one of the most reliable ways to convert a stimulus into an injury. Sleep matters here too. Restriction of sleep below 7 hours a night for several consecutive nights measurably increases injury risk in athletic populations (Milewski et al. 2014); the same effect compounds in selection candidates running sleep-deprived sessions on principle.

What other factors contribute to overuse injuries?

Load is the headline, but several other factors influence how that load is distributed and tolerated. Four are worth understanding because each one points to something you can train.

Movement quality. Poor movement patterns and limited range of motion concentrate force in places that are not built to absorb it. This matters most under fatigue, because when you are tired the body abandons whatever it was consciously trying to do and defaults to its most ingrained pattern. Weak control of the muscles around the knee, for example, allows greater forward shear at the joint during ground contact, loading the supporting structures more than they should be. The pattern you grind in when fresh is the one your body falls back on when wrecked.

Limb asymmetry. A difference in strength, girth or mobility between left and right is common and, on its own, has not been shown to reliably reduce performance or cause injury. What it can do is concentrate stress. If one limb is less able to absorb ground reaction force, that limb takes a greater share of the strain over thousands of repetitions. Worth addressing, not worth panicking over.

Aerobic shortfall. Most candidates don't think of aerobic fitness as injury prevention, but it is one of the most under-recognised risk factors in this population. Fatigue is when movement quality collapses and force absorption fails. A deeper aerobic base delays the onset of that fatigue. The longer you hold sound movement, the longer the chassis stays protected.

Environment and footwear. Hard surfaces such as roads raise ground reaction force compared with softer ground. Worn or inappropriate footwear removes shock absorption you were relying on. Wet or icy conditions reduce traction, which forces the stabilising muscles to work harder and fatigue sooner. For anyone preparing in the conditions typical of UK selection courses, sensible footwear choices, sensible route selection and looking after the feet themselves are not minor details. They are part of the training plan.

Table 2. The main contributors to lower-limb overuse injury and the training response to each.

How do you tell an overuse injury from normal training discomfort?

Most training produces some level of soreness, especially after harder sessions or new stimuli. The skill is in telling diffuse, training-driven discomfort apart from the specific signal of an overuse injury starting. The table below sets out three stages of escalation and the appropriate response at each.

Table 3. The escalation continuum for overuse symptoms. Stage 1 can be trained through with modifications. Stage 2 calls for direct modification. Stage 3 calls for help, not heroism.

Three honest rules around symptoms.

• Pain that sharpens during loading is not training pain. It is a signal. Modify the session.

• Pain present 48 hours after a session is not soreness. It is unrepaired damage. Reduce the load before the next session.

• Pinpoint bone pain in a runner is a stress fracture until proven otherwise. If you can point at a specific spot on your tibia, foot or femur and it hurts when you hop on that leg, stop running and get scanned. Continuing through bone stress symptoms is the single most common way candidates lose their course place permanently.

How do you train to reduce overuse injuries?

The goal is simple to state and harder to hold to: build the capacity of the tissue faster than you build the demand placed on it. When capacity stays ahead of demand, you adapt. When demand outruns capacity, you break. Everything below serves that one idea.

Progress load gradually and periodise it

Increase volume, intensity and frequency in steps your tissues can keep pace with, and avoid the sharp jumps that cause most of the trouble. The old rule of capping weekly increases at 10% was never an exact law, but as a practical heuristic for selection-preparation-level runners and tabbers it sits in the right ballpark. 10-15% week-on-week, with a consolidation week (drop volume by 30-40%) every fourth or fifth week, gives the tissue time to catch up before the next push.

After a long or heavy load carriage session, give the relevant tissues at least 48 hours before loading them hard again. Structure the wider plan so that intensity and volume rise and fall in a deliberate rhythm rather than climbing relentlessly. Periodisation is not a complication. It is how you keep capacity ahead of demand over months rather than days.

Get stronger, and train the brakes

Strength training is the most evidence-backed injury-reduction tool available, and it is routinely underused by endurance-focused candidates who worry it will slow them down. A large meta-analysis found that strength training reduced overuse injuries by close to half, with a dose-response relationship, meaning more appropriately programmed strength work tended to mean fewer injuries (Lauersen et al. 2018). Strength improves not just how much force you can produce but how much you can absorb. That second quality is what protects you, because absorbing ground reaction force is exactly what fails under load and fatigue.

Eccentric strength, the ability to control a load as it lengthens the muscle, is particularly relevant for the calf, quad and hamstring, and is the quality you lean on every time you control a descent. Practically, that means heavy slow-tempo work on calf raises (single-leg, weighted, 3-4 second descent), tempo squats and split squats, Nordic hamstring curls, and direct posterior chain work.

For a fuller treatment of why strength does not slow down endurance performance (it tends to do the opposite), the dedicated Strength Training Does Not Make You Slow article on the website covers the mechanism and the evidence base in detail.

Build a genuine aerobic base

Low-intensity aerobic work, the kind that sits in zone one and two and feels almost too easy, does two useful things at once. It builds the aerobic engine that delays the onset of fatigue, and because fatigue is when movement quality collapses and force management fails, a deeper aerobic base indirectly protects the structures. It also lets you accumulate training volume at a tissue cost far lower than constant hard running. Much of the injury risk in this population comes from trying to make every conditioning session hard. Most of them should not be.

The Slow Down to Speed Up article on the website covers zone 2 in full, with practical heart-rate ranges and session structures.

Treat mobility and movement as daily maintenance

Mobility work earns its place when it is treated as routine hygiene rather than an occasional event. The aim is to own usable range of motion and to groove sound movement patterns in a controlled setting, because under fatigue the body reverts to whatever it has practised most. Where it is available, a basic movement assessment can identify a glaring asymmetry or restriction worth targeting. Where it is not, honest attention to how you move when you are tired tells you most of what you need to know.

Ten focused minutes a day, repeated across weeks, outperforms occasional hour-long sessions. Address what limits you in your job: ankle dorsiflexion for the descents, hip extension for the marches, thoracic rotation for the bergen carry, shoulder mobility for the load.

Monitor load practically, not obsessively

ACWR's collapse as a precise predictor does not mean monitoring is useless. It means the monitoring needs to be practical. A simple weekly journal tracking three things will catch the spikes that matter: total running and tabbing minutes per week, average session RPE (rate of perceived exertion, 1-10), and how you felt waking up each morning across the week. Any week that doubles your running minutes, or stacks four consecutive 8-out-of-10 sessions, or leaves you waking sore and flat for three mornings in a row, is the kind of week worth modifying down.

Bertelsen's framework gives the conceptual scaffold here. You are watching for loading that exceeds the structure's capacity. Most of the time, your body tells you. Sleep, mood, soreness localisation and morning stiffness are decent proxies. Honest tracking beats elaborate calculation.

Look after the feet

The feet sit at the bottom of the chain and absorb everything above them. Blisters, hot spots and macerated tissue that go unmanaged become limp-inducing pain that changes your gait, which changes the loading on the knee, hip and back. Foot care is durability work, not vanity. The Foot Care for Tabbing article on the website covers the practical detail.

Run all of this concurrently

None of these levers work in isolation. They work because they are run concurrently: strength, aerobic development, load carriage and mobility consolidated into a coherent plan rather than fighting each other for space. Concurrent training is the principle the Stoic Conditioning programming is built on, and it is the difference between arriving at a course built up and arriving at it broken down. The dedicated Concurrent Training article on the website covers how to fit strength, aerobic and intensity work in the same week without interference.

When to modify, when to push, when to see a physio

Most overuse symptoms sit in stage one (manageable niggle) or stage two (modifiable signal). Three principles for navigating them honestly.

• Modify before you stop. Complete rest is rarely the right answer. Reduce the aggravating load, swap impact work for non-impact aerobic work, maintain strength, and let the area recover under reduced demand.

• Treat persistent symptoms early. Stage two symptoms that don't resolve within 7-10 days of modification are stage three until proven otherwise. Book a physio. Tendinopathies, in particular, respond far better to early intervention than to weeks of pushing through.

• Suspect bone stress in pinpoint pain. Hopping on the affected leg reproduces pain. Pain at night. Pain on simple daily tasks. These are red flags. See a sports medicine doctor and get an MRI. Running through tibial or metatarsal stress reactions is how you turn an 8-week problem into a 6-month one.

This is general information, not individual medical advice. If symptoms persist or worsen, see a qualified physiotherapist or sports medicine doctor.

Bottom line

Overuse injuries are not bad luck. They are a capacity problem. They happen when the demand you place on a tissue rises faster than the tissue's ability to tolerate it, and they cluster in the lower limb because that is where the repetitive, weight-bearing load of military training is concentrated. The mismatch is made worse by the fact that fitness improves quickly while bone and tendon adapt slowly, so the body that feels ready to do more is often not yet built to.

The fixes are not exotic. Progress load in steps your tissues can follow. Get strong enough to absorb force as well as produce it. Build an aerobic base deep enough to delay fatigue. Keep your movement honest. Respect recovery after the hard sessions. Treat early signs as early signs. Do that consistently and you keep capacity ahead of demand, which is the whole game.

The candidate who arrives at the start line is almost always the one who trained patiently, not the one who trained hardest.

Overuse injuries: frequently asked questions

How do I know if I have an overuse injury or just normal soreness?

Normal training soreness is diffuse, eases as you warm up, and settles within a day or two. An overuse injury tends to be localised to a specific point, often worsens with the very activity that caused it, and persists or returns session after session. Pain that sharpens during loading, rather than easing, is the clearest warning sign that you are dealing with more than soreness.

How much should I increase my training each week?

There is no single safe number. The old rule of 10% a week was always a guideline rather than a law. The practical principle is to increase in steps your body can keep pace with (10-15% weekly increases for most), build in a consolidation week every fourth or fifth week, and avoid sudden spikes after time off. If a jump in load leaves you sore for days or aching in a specific spot, it was too much, regardless of what any percentage suggested.

Does strength training really reduce overuse injuries?

Yes, and it is one of the best-supported interventions there is. Pooled research has found that strength training can cut overuse injuries by roughly half, with greater benefit from appropriately programmed work (Lauersen et al. 2018). It helps because it improves your ability to absorb force, not just produce it, and force absorption is what fails under fatigue and heavy load.

How long should I rest after a heavy load carriage session?

Give the loaded tissues at least 48 hours before another hard, high-impact session, and bear in mind that the physiological cost of heavy load carriage can persist beyond 72 hours depending on duration and intensity (Faghy et al. 2022). That does not mean total rest. Low-intensity aerobic work or mobility can fit comfortably in the gap. Stacking hard impact on incomplete recovery is how a stimulus becomes an injury.

Are some people just more prone to overuse injuries?

Prior injury, low baseline fitness, rapid increases in load, and chronic sleep restriction all raise risk, and they tend to compound. The encouraging part is that the largest contributors are the ones you control: how quickly you progress, how strong you are, how deep your aerobic base is, how well you sleep, and how seriously you take recovery. Build those and you move a long way out of the high-risk group.

Should I train through an overuse injury?

Training straight through the painful activity usually makes an overuse injury worse, because the loading that caused it continues to outpace repair. That is not the same as complete rest, which is rarely necessary. The usual answer is to reduce the aggravating load, maintain fitness through activities that do not provoke symptoms, address the underlying cause through targeted strength and mobility work, and seek physiotherapy input if it is not settling within a couple of weeks of modification.

Are stress fractures different from other overuse injuries?

Yes, in one important respect: they involve structural damage to bone and almost always require complete cessation of impact loading until the bone has remodelled (typically 6-12 weeks depending on site and severity). Pinpoint bone pain, pain on hopping, and pain that worsens through a session rather than easing are red flags. Continuing to load a stress reaction can turn it into a full fracture and a much longer rehabilitation. If you suspect a bone stress injury, see a sports medicine doctor for assessment. Cycling, swimming and pool running can usually maintain aerobic fitness without loading the bone.

Does running technique matter for injury prevention?

Some elements matter and the rest is mostly noise. The evidence on specific running form changes (forefoot vs heel strike, increased cadence, stride length adjustments) is mixed, with small effects in some studies and none in others. What appears more consistently relevant is being able to maintain your usual mechanics under fatigue. That is more a function of strength and aerobic capacity than of conscious form coaching. Build the engine and the chassis. Form tends to look after itself.

What about deloading. When and how should I take it?

A consolidation week (often called a deload) should be planned, not earned through symptoms. The standard approach is to drop weekly volume by 30-40% every fourth or fifth week, while maintaining intensity on the residual sessions. This allows accumulated fatigue to clear, tissue to consolidate, and the next training block to start from a recovered baseline rather than a debt. Candidates who only deload when they feel broken are usually deloading too late.

References

Anderson K, Grimshaw P, Kelso R, Bentley D. Musculoskeletal lower limb injury risk in army populations. Sports Medicine - Open, 2:1-9, 2016.

Bertelsen ML, Hulme A, Petersen J, et al. A framework for the etiology of running-related injuries. Scandinavian Journal of Medicine & Science in Sports, 27(11):1170-1180, 2017.

Faghy MA, Shei RJ, Armstrong NCD, White M, Lomax M. Physiological impact of load carriage exercise: current understanding and future research directions. Physiological Reports, 10(21):1-15, 2022.

Gabbett TJ. The training-injury prevention paradox: should athletes be training smarter and harder? British Journal of Sports Medicine, 50(5):273-280, 2016.

Impellizzeri FM, Woodcock S, Coutts AJ, Fanchini M, McCall A, Vigotsky AD. Acute:chronic workload ratio: conceptual issues and fundamental pitfalls. International Journal of Sports Physiology and Performance, 15(6):907-913, 2020.

Kiernan D, Hawkins DA, Manoukian MAC, McKallip M, Oelsner L, Caskey CF, Coolbaugh CL. Accelerometer-based prediction of running injury in National Collegiate Athletic Association track athletes. Journal of Biomechanics, 73:201-209, 2018.

Lauersen JB, Andersen TE, Andersen LB. Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis. British Journal of Sports Medicine, 52(24):1557-1563, 2018.

Lolli L, Batterham AM, Hawkins R, et al. Mathematical coupling causes spurious correlation within the conventional acute-to-chronic workload ratio calculations. British Journal of Sports Medicine, 53(15):921-922, 2019.

Magnusson SP, Kjaer M. The impact of loading, unloading, ageing and injury on the human tendon. Journal of Physiology, 597(5):1283-1298, 2019.

Milewski MD, Skaggs DL, Bishop GA, et al. Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopaedics, 34(2):129-133, 2014.

Robinson J, et al. Epidemiology of musculoskeletal injury in military recruits: a systematic review and meta-analysis. BMJ Military Health, 2023.

Schwellnus M, Soligard T, Alonso JM, et al. How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. British Journal of Sports Medicine, 50(17):1043-1052, 2016.

Sharma J, Greeves JP, Byers M, Bennett AN, Spears IR. Musculoskeletal injuries in British Army recruits: a prospective study of diagnosis-specific incidence and rehabilitation times. BMC Musculoskeletal Disorders, 16(1):1-7, 2015.

Soligard T, Schwellnus M, Alonso JM, et al. How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. British Journal of Sports Medicine, 50(17):1030-1041, 2016.

Warden SJ, Edwards WB, Willy RW. Optimal load for managing low-risk tibial and metatarsal bone stress injuries in runners: the science behind the clinical reasoning. Journal of Orthopaedic & Sports Physical Therapy, 51(7):322-330, 2021.

Wills JA, Saxby DJ, Glassbrook DJ, Doyle TLA. Multiday load carriage decreases ability to mitigate ground reaction force through reduction of ankle torque production. Applied Ergonomics, 2022.