And you certainly don’t have to be a professional athlete to benefit from the combination.

Supplementary training is part of the training routine for 42% of runners in Germany and the UK. The figure stands at 39% in Poland, 37% in Spain, 35% in France and 34% in Italy. Interestingly, the data reveal a consistent pattern across all the countries analysed: the more frequently people run, the more likely they are to include supplementary training. [1]Among runners who also do strength work, those completing up to four running sessions a week typically include at least one strength session. For runners doing five or more sessions a week, that number rises to two strength or functional sessions.

It makes sense. More running means more load on the body – and a greater need to strengthen the system that keeps you moving.

STRENGTH TRAINING CHANGES THE GAME

If you run – or are planning to start training regularly – and you’ve always ignored strength work or treated it as an optional extra, it may be time to rethink your approach.

That doesn’t mean spending hours in the gym every week. When it comes to strength training, smart programming matters more than sheer volume. The key is to make sure your strength sessions complement your running rather than compete with it.

Data from devices such as the Cheetah 2 Pro and Active 3 Premium can help you do that. The trick is knowing which metrics to watch and, just as importantly, how to interpret them.

Strength training plays by slightly different rules than running. That raises three important questions:

• Why does TL (Training Load) work so well for describing running load, but not necessarily strength-training load?
• Which metric can give you a better indication of whether your body is ready for another hard running session?
• What type of run makes sense before a strength workout – and what should you do afterwards?

WHY TL DOESN’T ALWAYS TELL THE FULL STORY AFTER STRENGTH TRAINING

If you’ve already had your fourth date with your training data, you’ll know that training load is estimated using factors such as workout duration and intensity. One of the metrics involved is EPOC (Excess Post-Exercise Oxygen Consumption), which describes the body’s increased oxygen demand after exercise.

For running, this can be a very useful way of estimating training load. The problem comes when we try to apply exactly the same logic to strength training.

Picture a one-hour gym session. You spend 60 minutes doing squats, lunges, deadlifts, calf raises and core exercises. You’re sweating, your muscles are working hard and, by the end of the session, your legs may feel as though they’ve completely run out of cooperation.

And yet your heart rate may spend much of the workout sitting in the two lowest zones, with only brief periods in the higher ones.

The result? Your TL, calculated largely from metrics related to your cardiovascular response, may end up lower than the TL from an easy recovery run of the same duration.

Does that mean you’re less fatigued after an hour of strength training than after an easy hour-long run?

Not necessarily.

You’re simply fatigued in a different way.

WHY CAN YOUR LEGS FEEL LIKE CONCRETE AFTER THE GYM?

Strength training can place a substantial load on your muscles and nervous system even when your heart-rate graph looks relatively unremarkable.

You might finish your workout, check your data and see a surprisingly modest training load. Then you head out for a run the next day – and suddenly your legs feel heavy, your stride has lost its spring and a pace that normally feels effortless requires much more work.

This is where HRV, or heart rate variability, can provide another useful piece of the puzzle.HRV is an indirect indicator of how your autonomic nervous system is responding to stress and recovery. In simple terms, lower-than-usual HRV can be associated with greater physiological stress, while higher values may indicate better readiness for exercise.

There’s an important caveat, though: HRV should never be interpreted based on a single reading in isolation.HRV naturally fluctuates from day to day. What matters far more than asking, “Is my HRV high?” is asking, “How does today’s HRV compare with my normal range?”