Pace, speed and the three-way relationship
Runners think in pace — minutes per kilometre or mile — while cyclists and treadmills think in speed. They are reciprocals of each other, which is why a small pace improvement at fast speeds is much harder than the same improvement at slow ones. Going from 6:00/km to 5:30/km is a 30-second gain; going from 3:30 to 3:00 is the same 30 seconds and vastly harder.
Training paces from one race result
A recent race gives you a reasonably reliable basis for the rest of your training. Rough guidance relative to current 5K pace:
- Easy runs — 75–90 seconds per km slower. These should feel conversational, and they are most of your weekly volume.
- Marathon pace — around 30–40 seconds per km slower than 5K pace.
- Threshold / tempo — roughly 15–20 seconds per km slower; comfortably hard, sustainable for about an hour.
- Interval / VO₂max — around 5K pace, in repeats of 3–5 minutes.
The most common training error is running easy days too fast, which leaves you too tired to run hard days hard. The polarised approach — genuinely easy easy, genuinely hard hard — is well supported by research.
Building the endurance the pace depends on
A pace target is an output, not a plan. What produces it is a few weeks of unglamorous consistency, governed by three rules that almost every coaching system shares.
- The 80/20 rule. Roughly 80% of weekly volume should be genuinely easy and 20% genuinely hard. Most amateurs run 100% in the middle — too fast to recover from, too slow to drive adaptation.
- The 10% rule. Increase weekly mileage by no more than about 10%. Most running injuries are load errors, not technique errors.
- Down weeks. Every fourth week, cut volume by 20–30%. Adaptation happens during recovery, not during the session.
| Session | Effort | What it builds |
|---|---|---|
| Easy run | Full conversation possible | Aerobic base, capillaries, fat use |
| Long run | Easy, extended | Endurance, glycogen storage |
| Tempo | Comfortably hard, ~1 hour | Lactate threshold |
| Intervals | Hard, 3–5 min repeats | VO₂max, running economy |
| Strides | Fast, 20 s, relaxed | Turnover and form |
Two more things that quietly cost time: cadence — most efficient runners land between 170 and 185 steps per minute, and overstriding at a low cadence brakes you on every step — and heat, which costs roughly 2–3% per 5°C above about 15°C. Adjust race expectations for the forecast rather than blaming yourself afterwards.
Even splits, negative splits and the wall
The table above assumes an even pace throughout, which is close to how most world records are actually run. Two adjustments in practice:
- Negative splits — running the second half slightly faster — produce the best results for the vast majority of runners, and starting 5–10 seconds per km slower than target feels absurdly easy and pays off later.
- Marathon fade is a glycogen problem, not a willpower problem. Most runners store enough for about 30 km at race pace, which is precisely where the wall lives. Fuelling from early in the race is the standard answer.
Also worth knowing: heat, hills and wind all cost real time. Roughly 2–3% slower per 5°C above about 15°C is a common rule of thumb.