Keeping an eye on cycling and running Efficiency Factor (EF) can help you unlock better aerobic fitness on the bike and run. Here’s how…
While it might not get the same limelight as FTP or some other data types in training discussions, Efficiency Factor is a figure that shouldn’t be overlooked when it comes to tracking fitness gains. What’s more, you can use it on the bike with a power meter and on the run using pace.
EF is a way of measuring your efficiency during a workout by establishing the relationship between performance and what that performance costs you. An increase in EF over time shows improving aerobic fitness and helps indicate when you’re ready to take training to the next level.
Cycling Efficiency Factor
On the bike, Efficiency Factor is calculated by dividing your Normalized Power – an average that takes into account variance in power over different terrain – by average heart rate. So, as with all power meter training where you’re looking for maximum data, it’s essential to wear an accurate heart rate monitor.
Looking at your post-ride data, EF is effectively telling you how many watts you can produce per heartbeat. If you can increase the watts for each beat, you’re improving efficiency.
It’s not just aerobic fitness that can improve EF though – technique also comes into play. On the bike, you’ll see many pro triathletes who look completely at one with their steeds. In comparison, some age groupers with poor bike fits look like they’re fighting with their machines – sacrificing efficiency in the process.
It’s therefore important to get a great bike fit and work on bike form by utilising drills such as single-leg focus, pedalling in circles, high-cadence reps and sprints to wake up different muscle types.
Running Efficiency Factor
Efficiency Factor for running is calculated by dividing your Normalized Graded Pace – speed automatically adjusted for hills – by average heart rate. Post workout, this essentially tells you the speed you produced per heartbeat.
As fitness and efficiency increase, you’ll be able to hold higher speeds for the same heart rate and your EF figure will be higher.
On the run, technique plays a more important role here than while cycling. If you compare the running mechanics of a pro marathon runner to their mid-pack age-group counterpart, the superior efficiency of the pro’s movement is clear to see.
Everything from their cadence to posture and arm movement is optimised with virtually no wasted energy. On the other hand, you’ll often see Ironman age-groupers shuffling, bent at the waist or heel striking.
Working hard to improve your running technique will improve your efficiency – and you’ll see that reflected in your EF figures too.
Monitoring Efficiency Factor Increases
To get the best quality data to track EF improvements it’s best to compare like-for-like sessions undertaken at the same heart rate effort.
As we’re looking for aerobic improvements, these should be steady Zone 2 workouts. This should be around 55 to 74% of FTP on the bike or 73 to 80% of max heart rate on the run.
The courses you use should be as alike as possible, ideally under similar weather, time and fuelling conditions. The more data you gather, the more easily you’ll be able to spot outlying results and discount these – whether due to equipment failure, vastly different temperatures or simply because you’re fatigued from too much training and need a rest.
Over time, you can track your improving aerobic fitness by charting your increases in EF. Ideally the EF should increase over the weeks, but don’t worry if you have the odd dip occasionally – we’re looking for a steady upwards trajectory on the whole.
Whether improving EF purely through advances in aerobic fitness or with a little technique improvement too, increases will usually plateau after a while. This usually indicates you’re ready for the next phase of training – adding harder workouts to make more gains.