Knowledge for your cycling training.

FTP (Functional Threshold Power) is an estimate of the highest power you can sustain for a long time, often described as about an hour. The usual test is twenty minutes all-out; 95% of that is your FTP. It is a practical approximation of your threshold, not a measurement of it: for an individual rider the difference from the physiological boundary can be as much as thirty watts. Use it mainly to repeat the same test and follow your progress.

Usually not with yet another block of intervals. With the riders I coach, the brake is more often in three other places: endurance rides that go too hard, no real progression from week to week, and zones that do not match your own thresholds. Train in blocks with a purpose, keep your easy rides truly easy, and give a build long enough to work.

Most apps calculate your zones as a percentage of your FTP. That is an estimate of an estimate: where your first threshold sits relative to your FTP differs from rider to rider. It is more accurate to anchor your zones on measured thresholds, LT1 and LT2, from a lactate test, with the heart rate at each boundary as well.

By zone 2 most riders mean easy endurance riding below your first threshold (LT1). Well-trained riders spend most of their hours there: in studies between 70 and 95% of their training time. It builds your aerobic base and you recover from it well. Be aware that which power counts as 'zone 2' depends on your zone model. If your zones are a percentage of your FTP, your easy rides often end up slightly too hard.

That is not settled yet. One recent meta-analysis found that polarized training raises VO2max more, especially in well-trained athletes, but found no difference in time-trial performance. A second found no difference between polarized and pyramidal on either. Sweet spot, tempo between your two thresholds, is not bad in itself; the problem starts when you end up there without meaning to. That is why I choose the split per rider and per period.

There is no fixed number. More hours help, but only if you can recover from them alongside work, family and sleep. What matters more is what you do with your hours: training in focused blocks, with a season that builds towards something, gets more out of the same hours than simply piling up kilometres. That holds at ten hours a week just as much as at twenty.

TSS (Training Stress Score) sums up the duration and intensity of a session in one number, and the fitness line in your training platform is a calculation on those scores. It is handy for summing up a week, but sessions with the same TSS can ask very different things: two easy hours at 71% of your FTP and one full hour at your FTP both come to about 100 TSS. So always read your power next to your heart rate and how hard the session felt.

Look at the conditions first: heat and fluid loss push your heart rate up, and during a long ride it creeps up slowly even when your power stays the same (cardiac drift). If it is not that, poor sleep, stress or a cold coming on can play a part. One ride says little; watch the pattern over several days, and how the session felt.