Your form is breaking under load and your body is picking up the bill

The short answer: poor movement mechanics under load cause injuries over time. When your arches collapse, your ankles wobble or your knees cave in as the weight goes up or the miles stack up, the same tissues take a slightly wrong hit thousands of times. Nothing happens for weeks, then something flares up. The fix is to film your reps, find where the movement breaks down, and strengthen the weak link underneath it.

Most people think injuries are about doing too much. Sometimes they are. But a lot of the time the volume is fine and the movement is the problem. You can run the same weekly mileage with two different foot positions and get two very different outcomes.

What "poor mechanics under load" actually looks like

Load is anything that makes the movement harder: a heavier bar, a tired body at the end of a long run, a fifth set, a bad night's sleep. Mechanics are how well you hold your shape while that load is on. 

Here are the usual suspects:

• Collapsing arches. The foot flattens and rolls in every time you land or drive up out of a squat.
• Unstable ankles. The ankle wobbles side to side instead of staying stacked under your knee.
• Knees drifting inwards. Often a knock-on from the foot and ankle below.
• Hips dropping on one side. You see it in single-leg work and in the back half of a long run.

None of these feel dramatic in the moment. That is exactly why they get missed.

Why it catches up with you late

Think about a rep or a stride as a tiny withdrawal from your body's bank account. With good mechanics, the cost is spread across big, strong tissues that are built for it. With poor mechanics, the same cost lands on smaller structures that were never meant to cope on their own, like the sole of the foot, the Achilles or the inside of the knee.

One sloppy rep does nothing. A few thousand over a couple of months is where plantar fasciitis, sore shins and cranky knees come from. By the time it hurts, the pattern has been running for ages.

It also gets worse as you get tired. Your form at rep one is not your form at rep ten, and it is definitely not your form at mile eight. If you only ever check how things look when you are fresh, you are checking the wrong moment.

Step 1: Film it

You cannot fix what you cannot see, and what you feel is rarely what is actually happening. Your phone is all you need.

• Film from behind for squats, lunges, deadlifts and running. Feet and ankles are the story here.
• Film from the side for hinges and anything where your back position matters.
• Film your last few reps of a hard set, not the warm-up. That is where it falls apart.
• For running, do 30 seconds on a treadmill or a flat stretch late in a run, not at the start.

Watch it back at half speed. Look at the feet first, then knees, then hips. You will probably see something you did not expect.

Step 2: Spot the breakdown point

Do not try to fix everything at once. Find the first thing that goes wrong, and when it goes wrong.

Ask yourself:

1. Which joint moves first? Usually the foot or ankle, then the knee follows.
2. At what point does it happen? Rep six of eight, or the heaviest set, or the last couple of miles?
3. Is it the same on both sides? Most people have a weaker side that does the collapsing.

That tells you where your capacity runs out. If your arch caves on the last three reps, your working weight is a bit past what your foot and ankle can currently control. Fair enough, that is useful information, not a failure.

Step 3: Strengthen the weak link

Now you build the bit that is giving way. Keep it simple and do it consistently.

• Ankle stability work. Single-leg balance on a firm surface, then a slightly unstable one once that feels easy. Slow calf raises with a pause at the top.
• Foot strength. Short-foot drills (pulling the ball of the foot towards the heel without curling your toes) and barefoot carries or walks where it is safe.
• Single-leg strength. Split squats, step-ups and single-leg Romanian deadlifts. Two-legged lifts let your strong side hide the weak one. Single-leg work does not.
• Movement awareness. Pick one cue per exercise, like "tripod foot" or "knee tracks over the middle toes", and film again after a couple of weeks.

Put 10 to 15 minutes of this at the start of your sessions, when you are fresh enough to do it properly. Do not bolt it on at the end when you are knackered and your form is already gone.

Common mistakes

• Only checking form on light warm-ups. Mechanics fail under load, so test them under load.
• Adding weight or miles faster than your feet can cope. If the video shows a breakdown, hold the load steady until it cleans up.
• Chasing perfect form. You are after "good enough and repeatable", not a textbook picture.
• Ignoring the small stuff because nothing hurts yet. Pain is the last thing to show up, not the first.

What to do this week

Pick your two most important lifts or your usual run. Film the last set or the last few minutes. Find the first thing that moves out of line, and add two single-leg or ankle exercises to your next three sessions. Film again in two weeks and compare.

That is about an hour of effort in total, and it is a lot cheaper than three months off with a dodgy foot

- Patrick Moorshead  

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