Be honest — when was the last time you truly ran hard? Not tempo, not “comfortably tough,” but fast enough that your lungs burned and your legs felt like lead 20 seconds in?

For a lot of triathletes and endurance runners, the answer is “not often enough.” Most training sits in that safe middle ground — long, steady, predictable. It builds fitness, sure, but it doesn’t make you faster. If your short intervals aren’t really hard, they’re not doing their job.

The Comfort Zone Trap

Many age-group athletes blur the line between easy and hard. Threshold and endurance pace end up almost the same. You get great at running one speed — but breakthroughs never come. Sound familiar?

To lift your threshold pace, you need to lift your top-end speed first. That only happens when you push into intensities that feel uncomfortable, even messy, for short bursts. That’s where the real adaptation lives.

The Fix: Truly Hard Intervals

Stop treating interval sessions like controlled tempo runs. One session a week should be short, sharp, and full-gas — the kind of effort that forces your body to move efficiently when tired. Try:

• Hill Repeats: 8–10 × 30 seconds uphill, walk or jog down. Explosive, form-focused.
• 30/30s: 10–15 minutes alternating 30 seconds hard, 30 seconds float.
• Track or Flat Efforts: 8 × 200 m or 6 × 400 m fast, with equal jog recovery.

They should feel hard and put you on your limit. You’re training your stride, your rhythm, and your resilience, not just your lungs.

Why Speed Improves Form

Running fast fixes sloppy form. Short, intense efforts teach you to move with better posture, quicker cadence, and more snap through the hips. It’s almost impossible to hold lazy mechanics when you’re sprinting up a hill.

That improved economy trickles down to your endurance pace — you’ll feel smoother, lighter, and faster at every effort level.

How to Structure Your Week

For triathletes and time-poor runners, two to three runs a week can go a long way if they’re balanced:

• Session 1 – Short & Hard: hills, 30/30s, or track work. Go hard, recover well.
• Session 2 – Endurance: easy to steady, focus on aerobic development.
• Session 3 – Brick or Tempo: threshold running off the bike or mid-length tempo.
• Insert 20-30 second strides or ‘picks ups’ into endurance runs so your form gets attention on every run.

That one high-intensity session each week will do more for your speed and form than endless tempo miles ever could, especially if you have been plugging away it these types of runs for a long time with minimal gains.

The Takeaway

Are your short intervals hard enough? If not, you’re leaving speed on the table. The goal isn’t to suffer every run — it’s to add one truly hard, high-quality session that forces adaptation.

At Enduraprep, Coach Cronk helps triathletes and runners find that balance — training just hard enough, just often enough, to build the speed and efficiency that lasts all season.