Training With Power: What’s it all about?

What good is a watt? What is actual work done? Should you be training with a power meter? Read on for Training with Power and how it can be used to maximize your training and your success.

There was a time when the only way to know what the actual work done on your bike was, called for the athlete to be tested in a laboratory setting at a university or sports performance facility on a cycle ergometer. This gave the athlete an idea of where their physiological parameters such as VO2 max and lactate threshold were, but how was the athlete to implement this data into their workouts and training?

For years using heart rate training was considered the gold standard, an athlete would be tested in the laboratory and be given ranges that corresponded to specific energy systems in the body such at aerobic energy system, fast glycolysis or lactate threshold energy system. The athlete then went out and trained according to these ranges and often found they were mostly successful but there was a fundamental flaw to heart rate training and that is the fluctuation in heart rate from interval to interval, day to day or week to week. The workload that was done at 150 beats per minute last week may not reflect the same workload of 150 beats per minute next week or even on the next interval. In fact the heart rate that the athlete tested at in the lab or on a field test may not even reflect a truly accurate heart rate for the test done.

To understand this a little better we must first examine what causes heart rate to fluctuate. In our day to day lives variables such as nutritional status, hydration levels, stress levels and sleep status can cause our heart rate to vary. When we train and these variables present themselves they can have an even greater effect on heart rate, causing an undesired increase or decrease in heart rate that does not necessarily reflect work performed. With training, an additional variable must be closely considered and that is the level of fatigue. With fatigue we may see an increase or even decreases in our achievable heart rate. This fatigue may be acute fatigue experienced in the same workout such as interval to interval or over the course of a long ride or it could be chronic fatigue developed over days, weeks or months of training. No matter where the fatigue originates it factors into our heart rate and if we consider all of the above mentioned variables we see that heart rate can vary greatly based on factors that are not necessarily related to the actual work we are doing. As an example you may have a set of 15 minute intervals at 160 bpm heart rate but for some reason you cannot get your heart rate above 153 bpm, you feel like you are working hard but your heart rate will just not respond, so does this mean you’ve lost fitness and the training session was pointless? No, in fact it might have been a great training session but your heart rate was just not responding for whatever reason. It’s quite possible that you may have been working much harder than you needed to be to elicit a training response causing more fatigue than necessary or you may have just been tired and you were never able to get your workload (power) up to a level that it needed to be to elicit a response but you kept going, trying harder and harder to hit that target heart rate only to dig yourself deeper and deeper into a hole. The message here goes back to the simple concept that 150 bpms is not always 150 bpms, is not always 150 bpms, there are so many variables that influence heart rate that you can never really be sure you are doing the appropriate level of intensity for the given day’s training. Can heart rate work well enough to see results, yes it can but your training time is too valuable to be unsure about what you are doing and thanks to technology there is now a much better way to measure what you are doing on the bike. This of course is the power meter and where the heart rate monitor falls short the power meter more than makes up for.

The power meter has given us the opportunity to take data that was once only available in the lab out into the field. What makes a power meter so great is that it gives a true representation of actual work done. What is 200 watts today is 200 watts tomorrow and there are no variables that can influence power like there are with heart rate, the number is concrete. And unlike heart rate which has a delayed response to a change in workload the change in power is instantaneous as it is a measure of force application to the crank or hub as wells as the velocity/distance that those pedals travel (applied in cycling as cadence).

The athlete and coach can now see what the actual work performed was in watts and kilojoules for a specific workout session or race. What’s so great about all of this actual “work performed”? Simple; workout and race analysis, feedback, progression indices, specific race demands and the ability to accurately monitor fatigue. With a power meter a coach can now see exactly what your workout session or race looked like and can offer feedback. Were you going too hard on an interval set or an endurance ride or were you not going hard enough? Were you unable to complete a set of intervals, was this due to fatigue from prior training sessions or were the first couple of intervals done at a greater than desired power level causing premature fatigue? Was the training session executed to the level it needed to be to elicit the desired response? Keep in mind these variables hold true throughout the training continuum from interval sessions to recovery rides. In race situations you can gauge where your level of intensity truly is and develop better race strategy based off of this information (should I attack or sit right here?), even better you get data on what the energy system and nutritional demands (your kilojoules expenditure is a rough equivalent of your caloric expenditure) were and can better prepare for that very race the following season or subsequent races of similar character. Over the course of many seasons the athlete can collect data on races and courses and use that data to objectively prepare for the next time they race it. For example if and athlete were to race on the Ironman Lake Placid course with their power meter and expend 3200 kilojoules at an average power of 190 watts and a heart rate average of 155bpm, the athlete and coach can then take that data and understand the demands of the course both from an energy expenditure (how many calories did you really burn out there…how many did you take in?) perspective as well as from a training preparation point of view. When you know that you need to produce 3200 kilojoules in order to complete a given race you can then adjust your training so that you achieve a sufficient overload of greater than or equal to 3200 kilojoules through combinations of long rides or intervals, a demand that replicates or slightly exceeds the demands of the race. The use of power can also greatly influence your pacing strategy knowing that you need to maintain a given power out put in order to hold a certain run pace can really make a difference in struggling on the run and having the run split of you life.

With a power meter a coach can now objectively analyze workouts permitting better feedback on what you can do to get more out of a training session. There’s no hiding from a power file, if you went harder than you should have…they see it, if you did not go as hard as you should have…they see it and you’ll hear about it. Your coach can then guide you to a better workout next time but what they can also do is monitor what the level of fatigue is and adjust your workouts accordingly. For example, you may be able to achieve a power output of 230 watts for a 4 x 8 minute training session on week 2 of a block but on the next week you are struggling to hold 210 watts. Is it because you are fatigued, has the interval length been progressed more than what your body was ready for, were the initial training ranges too high, are external variables taking a toll on you (stress, sleep, diet, etc…)? All of these are questions that you and your coach can consider and if necessary modify your training appropriately.

Power meters also give the athlete and coach a measure by which to terminate a workout or adjust a subsequent workout because the desired overload for the session has been achieved. Take for instance a session of 6 x 3min VO2 intervals that are to be done at a maximal effort. Previously athletes might go out and try to do a workout like this with their heart rate monitors and a predetermined heart rate that they were to try and achieve. After 3 or 4 intervals they are still hitting the heart rate range but they are covering less and less real estate and the intervals are getting harder and harder but they persist on because they set out to do six. The question then becomes are they doing themselves a favor by continuing the workout or are they generating much more fatigue than they need to be only to be rewarded by a greater than necessary need for recovery days (which they may or may not actually take). Keep in mind the heart rate is still plenty high, so the athlete very much feels like they are still getting a benefit out of the effort but as mentioned previously heart rate is not a good indicator of current workload it is only a response to a stress previously placed on it. In this respect the athlete that was initially doing their VO2 work at 415watts has now fatigued to the point that they can only maintain a power output of 310 watts, quite likely a power that is not high enough to stress their VO2 max. At this point all the athlete is doing is digging them self into a hole and increasing the amount of recovery they will need from this workout. There is really no good effect going on here, the level of stress needed to overload this specific energy system has been achieved and the workout should be concluded with a warm down ride back to the stables. With heart rate we have no way of knowing this definitively and in some cases the ability to reach that defined heart rate range will be depressed so the athlete feels like they are not working hard enough in an interval session and in reality they are either working too hard as they try to elevate heart rate or they have fatigued and need to end the effort. Often this can be the greatest asset of having a power meter, it keeps you honest and going hard when you need to but it also offers feedback on when it’s time to back it off and recover. Your coach can then get a better idea of what your strengths and weaknesses as an athlete are as well as monitor your training with more specificity and objectivity. Power meters are an investment into your success as an athlete and as an athlete the ability to utilize your training time and energy to its maximum is invaluable.