Power is the amount of energy generated per unit of time. In cycling terms, it applies to the amount of energy that is transferred to the pedals and it is measured in watts. Power has been acknowledged as the key factor in cycling performance for many years. The more power the better, though it’s not just about who produces the most watts……
When it comes to climbing, it also has to be related to the rider’s weight. The athlete who creates more power for their bodyweight will win the climb. The higher the watts per kilogram of bodyweight, the better the rider. For example, two riders are about to start a climb both have their SST (Steady State Threshold) at 200 watts & 160 bpm. Rider 1 weighs 60 kg (132lbs) whilst rider 2 weighs 70kg (154 lbs). Rider 1 has a power to weight ratio @ SST of 3.33 watts per kg, whilst Rider 2 produces only 2.85 watts per kg at SST. Rider 1 should be the first to the top by quite a long way.
When you first start training with a power meter you’ll notice that the power readings fluctuate a lot. This is normal. Power is a direct reflection of intensity so it will change rapidly and often. Set your screen to show 5-10 seconds average for most training rides. Heart rate is more stable and slower to change but is subject to variations on a daily basis much more easily by heat, fatigue, altitude, nutrition, etc. Think of heart rate as a guide to total physiological stress and power as the judge of exercise intensity at that moment. Therefore using the two together is best approach.
Many riders forget how important heartrate is once they buy a power meter and this is a huge mistake. For example, let’s say normally at 200 watts you are at 150 bpm but today you see your heartrate at 160 bpm at 200 watts. This is telling you that 200 watts is a lot harder on you today than usual. You need to know this. The higher HR is indicative that your body is under more stress to produce the desired power and that higher stress means more sugar than fat burned and a longer recovery required after the session. If you see this you need to decide on the correct course of action. Is the HR high due to sickness, stress, heat, dehydration or fatigue? Does it actually feel harder work than usual? Typically in this scenario, my advice would be to back off on the power and let the HR come back in to the desired zone for the session. Yes it might mean slowing down and an easier feeling workout but you might well thank me later when you don’t wake up sick the next morning or overly fatigued as the week progresses.
Pacing studies show that maintaining a constant power output is the most efficient way to success and economical energy expenditure. This is especially true for the long distance Triathlete whose bike portion of the race is in effect “setting you up” to have a strong run. When racing with the power meter in an endurance event, look to flatten out the course by easing off on the uphills and working harder downhill to give an even power average throughout.
After your ride, downloading your power data will tell you whether or not you did what you set out to do. The graphs should not have big surges during steady efforts. For example, if your ride is supposed to be 1hr in a 175-200w zone, try to stay in this power zone all the time. It is possible, though not desired, to fool yourself in to thinking that you did this by doing 50 mins @ 160 watts then a 10 min splurge at 250 watts to still give you an average in the zone. It easy to see though that for most of the ride you were really below zone and for 10 minutes way above it – this is obviously not what we are after!
Why FTP sucks ……..Personally, I steer clear of setting zones using FTP (Functional Threshold Power) field tests. The reason being that a “performance test” when you ride for say 20 mins and get an average power reading and then use that to set zones for other intensities is missing THE most important part of the equation and that is …. THE COST OF POWER. By this I mean, we need to know what type of energy you are using to create a power output. Let’s say in month 1 you climb a hill at 225 watts and it takes 20 minutes and you average 160 bpm. In month 2, eager to beat your last test you do the climb in 19.30 and average 230 watts with a HR average of 163 bpm. Are you fitter? Are you just more motivated? Were the conditions the same? Why were you faster? In truth, you don’t know and this is a problem if you are trying to hit peak performance. In this example, you have no idea what changed in your physiology. You don’t know the “metabolic cost” of the power you produced. This is why I always test my athletes in the lab taking lactate samples so that we know the true cost of a power output. We need to see the lactate response to a power number to really know what’s going on…..
……So, if the month 1 performance above gave an average lactate reading of 4.2 mmol and in month 2 gave 5.6 mmol, we’d know that the “improvement” was actually purely driven by motivation and suffering not by better conditioning. In fact you could say that the athlete actually was aerobically LESS efficient. This is a problem when trying to build the aerobic engine. However, if the athlete rode the hill at 225 watts both times and the heartrate decreased from 160 bpm in test 1 to 155 bpm in test 2, plus lactate dropped from 4.2 to 3.6 mmol then we’d know that the athlete was aerobically better conditioned, less stressed by the power effort and on the way to developing a better base.
Power is great but its only part of the equation. Training smart is everything in the long term and that means getting ALL the science on your side …..
POWER + HEARTRATE + LACTATE = KNOWLEDGE