The run is where triathlon races are won and lost. It is the final leg, the moment where fitness meets fatigue, and the place where all your preparation either pays off or falls apart. Everyone wants to run faster off the bike, but there is a good chance you are doing things in training that are actively working against that goal.
These are five of the most common mistakes, ones that most triathletes make at some point, and the fixes that actually produce results.
1. Focusing on Pace During Sessions
Pace is the metric most runners default to, and it makes sense on the surface. You want to run faster, so you track how fast you are running. The problem is that pace is an outcome, not a control variable.
Your running pace on any given day is influenced by fatigue, heat, humidity, terrain, how well you slept, and a dozen other factors. Chasing a specific pace when your body is not ready for it leads to overreaching on easy days and underperforming on hard days. You end up training in a mediocre middle zone that does not develop the fitness qualities you actually need.
The fix: Start looking at heart rate instead of pace. Heart rate tells you what your body is actually experiencing internally, regardless of external conditions. It keeps easy days genuinely easy and ensures hard days are hitting the right physiological targets. Over time, your pace at any given heart rate will improve, and that is a far more meaningful measure of fitness than chasing numbers on a watch.
2. Doing Too Much Work Above Threshold
This is the big one. Most triathletes, especially those looking to improve their run, default to hammering high-intensity sessions. Tempo runs, threshold intervals, VO2 max repeats. It feels productive because it hurts, and there is a widespread belief that suffering equals improvement.
The reality is that too much above-threshold work creates more problems than it solves. It accumulates fatigue rapidly, increases injury risk, and does not build the aerobic base that sustains performance over race distances. A fast 5 km time trial means nothing if you cannot maintain your form 15 kilometres into a half-marathon off the bike.
The fix: Train just below threshold instead of above it. Spending more time in the upper aerobic zone, around and just below your first lactate threshold (LT1), builds the metabolic engine that sustains race-day performance. Use VO2 max and high-threshold sessions sparingly and strategically rather than as the backbone of your run training.
3. Running on the Track Multiple Times Per Week
Track sessions are a staple of running programs, and they have their place. But doing them multiple times per week is a common mistake for triathletes. Track running is high-impact, high-intensity, and performed on a surface that encourages speeds most triathletes do not need in racing.
Multiple track sessions per week dramatically increases your injury risk while providing diminishing returns. The speed you develop on the track rarely translates directly to triathlon performance, where the demands are fundamentally different from pure running events.
The fix: Limit yourself to one track or structured speed session per week. Make it count, execute it with purpose, and let the rest of your running volume support your aerobic development and durability.
4. Doing More Running Off the Bike
Brick sessions, running immediately after cycling, are often prescribed in triathlon training because they simulate race conditions. The logic seems sound. However, loading up on brick sessions comes at a cost. Running off the bike is harder on your body, increases injury risk, and often means the quality of the run is compromised because you are already fatigued from the ride.
More is not better here. Excessive brick sessions accumulate fatigue without proportionally improving your ability to run well off the bike on race day.
The fix: Swap to one brick session per week. Make it purposeful, with clear targets for both the bike and the run portions. The rest of your run training should be standalone sessions where you can focus on quality and proper execution without carrying bike fatigue into every run.
5. Drinking Only Water During Sessions
This one applies to all three disciplines, but it has a particularly damaging effect on the run. Many athletes show up to training sessions with a bottle of water and nothing else. They might take a gel before a long run, but during the session itself, it is water only.
This is the equivalent of driving your car on a long trip without filling up the fuel tank because it is just a casual drive. Your body needs fuel to perform and adapt. Training on water alone depletes your glycogen stores, impairs the quality of your session, and slows recovery. Over weeks and months, this chronic underfuelling undermines your ability to train consistently and limits your adaptation.
The fix: Consume carbohydrates and sodium during all sessions, not just long ones and not just races. This fuels the work, supports recovery, and trains your gut to handle nutrition under stress, which is exactly what you need it to do on race day.
You would not drive your car without fuel just because it is an easy drive. So do not do it in your training sessions.
Putting It All Together
None of these fixes are complicated on their own. The challenge is implementing all of them consistently within a training plan that balances the demands of three disciplines. Each change reinforces the others: training to heart rate keeps your intensity honest, sub-threshold work builds your engine without breaking you down, limiting track and brick sessions manages your injury risk, and proper fuelling supports all of it.
Your triathlon run split is not limited by your talent. It is limited by how intelligently you train for it. Fix these five things and the improvement will follow.