Niggle or injury? How sub-3 runners tell the difference

Every runner chasing sub-3 has asked the same question: is this just a niggle I can run through, or the start of something that could derail the whole block? It’s not always easy to tell, but learning the difference is one of the most important skills in serious marathon training.

A niggle is your body’s way of grumbling under load. It’s that stiff Achilles first thing in the morning that loosens once you’re moving. It’s the calf that feels ropey after a long run, or the knee that’s a bit sore on the stairs the day after hills. These things settle quickly, respond to basic strength and mobility, and don’t change your stride once you’re warmed up. Most sub-3 runners live with a rotating cast of these little complaints. I certainly do — three weeks out from Berlin marathon, I had a hamstring niggle during a hard 5K effort. You start to see 18 weeks of hard training evaporate in front of your eyes, and begin to pray it’s not a full-blown injury.

An injury is different. Pain that worsens as you run, lingers afterwards, or creeps into everyday life is a red flag. If it alters your gait, stops you from running smoothly, or grows sharper over consecutive days, you’re looking at something more serious. I had to call time on a competitive club race when an attempt at some intervals to test my strained hamstring required much more effort than usual. I could feel my other muscles trying to compensate and knew I was off-kilter. While letting my clubmates down at short notice was tough, I wouldn’t have been much use to them — and could have done a lot more damage.

The best way to decide is to grade what you feel:

• Green light: discomfort that fades during a run and doesn’t return. Safe to keep training, but note it down.
• Amber light: pain that stays with you throughout the run or comes back as soon as you stop. Time to back off intensity, cut mileage, and give it attention.
• Red light: pain that escalates mid-run, forces you to change stride, or sticks around in daily life. This is stop-and-fix territory.

Perspective is key. Missing two workouts feels huge in the moment, but it’s nothing compared to losing a whole season. I once felt like I had a bit of a “floaty knee” but decided to crack on with a long run anyway in order to, it shames me to say it now, defend a “local legend” segment on Strava. That caused me three weeks out, an expensive physio rehab series and — of course — the longer-term loss of the segment anyway. Your fitness lasts much longer than you think; aerobic gains are stubborn and don’t vanish overnight. What ruins campaigns isn’t caution, it’s pride and bloodymindedness.

A final word of warning: beware phantom niggles during taper. When training load drops, the body often uses the chance to repair itself, while nerves are sky-high and every twinge feels catastrophic. I find taper niggles often vanish in the caffeine and adrenaline-fuelled focus of race day. I remember being hugely paranoid about whether my right calf would hold up only to not think about it once throughout the entire marathon.

The art of sub-3 isn’t about never feeling pain. It’s about knowing when to push on, when to step back, and when to stop. Learn that judgement and you’ll give yourself the best chance of arriving on the start line ready to deliver.