When half marathon training goes wrong

Training blocks fail in recognisable ways, and the single most useful skill is telling them apart. Doing too much, doing too little, doing the wrong thing, and being injured all feel similar from the inside — tired, slow, and vaguely guilty — and they need opposite responses.

• Doing too much — Easy runs have got slower at the same effort, sleep is worse rather than better, motivation has gone flat, and the legs feel heavy from the first mile rather than the last. This is the failure that most resembles laziness from the inside, which is why people respond by training harder and make it worse. The response is a genuinely easy week — not a rest day bolted onto the same week.
• Doing too little — Missed weeks, sporadic sessions, and long runs that are much harder than the plan says they should be because the base under them was never built. The response is not to catch up. Catching up is how people convert this failure into the first one and then into the fourth.
• Doing the wrong thing — Every run at the same middling effort — too hard to recover from, too easy to develop speed. Very common in people training alone without a watch discipline. The response is polarising: make the easy runs genuinely conversational and put the hard work in one clearly hard session.
• Injured, or becoming so — Pain that is localised rather than general, that is worse at the start of a run than in the middle, that changes your gait, or that persists after the run. This is the one where continuing is a decision with consequences, and where a physiotherapist rather than a training plan is the right next step.

Once you know which failure you are in:

1. 1

   Step 1: Stop trying to recover the plan

   The plan was a guess made before it met your life. A block with three good weeks and one missed one is a good block. Rewriting the remaining weeks to make the total add up is the single most common way people injure themselves in the last month.

   You will know it worked when: The plan serves you rather than the other way round.

2. 2

   Step 2: Protect the long run above everything

   If time is short, the long run is the session that matters most for a half marathon and the midweek sessions are the ones to lose. Reduce their number rather than shortening the long one.

   You will know it worked when: The specific adaptation the distance needs.

3. 3

   Step 3: Make easy easy

   If you cannot hold a conversation, it is not an easy run. Most amateur runners improve more from slowing their easy days than from any other single change, and it also fixes the heavy-legs problem within a fortnight.

   You will know it worked when: Recovery that actually happens between sessions.

4. 4

   Step 4: Take a real down week

   Not a rest day. A week at roughly half the volume, with the intensity removed rather than the distance. Fitness is not lost in a week and the accumulated fatigue that has been masking it will lift.

   You will know it worked when: You find out what fitness you actually have.

5. 5

   Step 5: Reset the goal rather than the training

   If the block has genuinely gone, the honest move is to change the race target — finish rather than a time, or a later race. This is a much better outcome than arriving injured at a time goal that stopped being realistic six weeks ago.

   You will know it worked when: A race you can run.

The rule that covers pain specifically: a general ache that is symmetrical and eases as you warm up is usually training. Something sharp, one-sided, that changes how you run or that is worse the day after is worth having looked at rather than reasoned about. Nothing on this page is a substitute for a physiotherapist, and a half marathon is not worth a chronic injury.