The research on triathlon injury is unflattering. Studies of overuse injury incidence report ranges from 37 to 91 percent depending on the population and how it is measured, and in some cohorts three quarters of athletes picked up an overuse problem across a season.
The knee is the most common site, at around a quarter of all overuse problems, followed by the lower leg and the lower back. And the vast majority of overuse injuries in this sport, somewhere between half and ninety percent depending on the study, are associated with running.
That is the whole picture in three numbers. Most injuries are overuse. Most are running. Most are at the knee or below.
The Window Where They Are Made
In my experience they are not created randomly across a block. They cluster in one place.
Somewhere around weeks twelve to twenty, your cardiovascular fitness has improved substantially. You can hold a pace comfortably that you could not manage in month one. Your legs feel capable. So you extend the long run, add a fourth run, and push a bit harder because you can.
What has not kept pace is your connective tissue. Tendons, ligaments and bone adapt over months rather than weeks, and there is no sensation that tells you they are behind.
So you have an engine capable of driving a chassis that is not ready, and the gap between them is where the achilles, the IT band, the shin and the plantar fascia are broken.
The Rules That Actually Prevent It
Ramp running volume slowly, and separately
Ten percent a week is the usual guidance and it is roughly right. What matters more is that you only increase one thing at a time. If you extend the long run, do not also add a session. If you add a session, do not also add intensity.
Most injuries I see come from two changes made in the same week, where neither would have caused a problem alone.
Cap the long run
Two to two and a half hours is enough for an Ironman marathon. Longer runs in training produce diminishing returns and rising risk.
The Ironman marathon is trained by weekly accumulation and by running off the bike, not by rehearsing the distance. Plans that have you running thirty-two kilometres are producing injuries.
Move volume to the bike
The most underused injury-prevention tool available. Cycling gives you aerobic load at almost no structural cost. If you want more hours, the bike is where they belong. If you are carrying extra weight or have a history of running injuries, this is not optional.
Lift, properly
Two thirty-minute sessions a week. Not circuits, not endless single-leg work with tiny weights. Loaded, progressive resistance work: a squat, a hinge, a step-up or split squat, a calf raise, a carry.
Stronger tissue tolerates more load. This is the single most effective intervention in the list and it is universally the first thing cut when the week gets busy.
Calf raises specifically deserve a mention. The achilles is one of the most common serious injuries in this sport and progressive heavy calf work is one of the best-supported protective measures for it.
Take the recovery weeks
Every third or fourth week at roughly half volume with the intensity removed. Adaptation happens in those weeks. Athletes who skip them because they feel fine are the ones getting injured in month five.
The Signals to Actually Act On
The difference between a niggle and an injury is usually how long you ignored it.
Pain that is present at the start of a session and disappears as you warm up is usually manageable, but it deserves attention rather than dismissal. Pain that appears during a session and gets worse as you continue is a stop signal. Pain that is present the next morning when you get out of bed is telling you something has been damaged rather than merely irritated. Pain that changes how you move is a hard stop, because a compensating gait creates a second injury somewhere else.
My rule for athletes: a niggle that is still present after seven days means the running stops until it is not. Seven days off in February costs you nothing. Six weeks off in May costs you the race.
The Non-Training Causes
Two things cause injuries that never appear in a training log.
Under-eating. Insufficient energy availability impairs bone remodelling and tissue repair directly. A meaningful proportion of the stress reactions and stubborn tendon problems I see are not load problems at all. They are fuelling problems presenting as load problems, and they do not resolve until the eating changes.
Bike fit. Knee pain on the bike is very often a saddle height or cleat position problem rather than a training problem, and no amount of strength work will fix a position that is wrong. If you have knee pain that appears on the bike specifically, get fitted before you do anything else.
The Bottom Line
Most triathlon injuries are overuse, most come from running, and most are created in the window where your fitness has outrun your structure.
Change one variable at a time. Cap the long run at two and a half hours. Put extra volume on the bike. Lift twice a week and do your calf raises. Take the recovery weeks. Eat enough. And treat a seven-day niggle as a stop rather than a nuisance.
