- In ERG mode the trainer adjusts its resistance to hold your power target as your cadence changes.
- In resistance mode you set the resistance, and your power follows how hard and how fast you pedal.
- ERG suits intervals and steady blocks. Resistance mode suits sprints and riding by feel.
Two ways to ride a trainer
A smart trainer can work in two ways. In ERG mode the trainer is in charge of the resistance. In resistance mode you are.
ERG mode
In ERG mode you get a power target, say 225 W. The trainer watches your power and changes its resistance to hold that target. Pedal faster and it eases off. Pedal slower and it adds some. Either way you ride the number, until your cadence gets so low that the trainer runs out of resistance.
That makes it a good fit for intervals. You do not have to find the right gear or watch a power meter. The target is set from the first second of the step, and the trainer reaches it within about three seconds. Your job is to keep pedalling.
ERG has one catch. If you stop pedalling or slow right down, a trainer that keeps adding resistance can leave you stuck, with a target you can no longer turn. Good apps let go when that happens.
If you do get stuck, stop pedalling. With some trainers you then need to backpedal or coast for a few seconds until the resistance loosens. Check your trainer’s manual for how yours behaves.
Hammy releases ERG when your cadence drops below 20 rpm for 3 seconds, or stays below 55 rpm for about 5 seconds on a target above 85% of your FTP. Without a cadence reading it judges from your power instead. The trainer then eases to a light resistance and the ride screen says ERG released. Pedal above 60 W and ERG comes back on its own, with a short ramp up to the target. If ERG is released twice within 30 seconds, it stays off until you have pedalled steadily for 10 seconds. If a target feels too hard on the day, the Intensity control scales the targets down or up for the rest of the ride, in 1% steps between 50% and 150%.
Resistance mode
In resistance mode the trainer keeps a fixed resistance. You change it with your bike’s gears or the trainer’s own setting. Your power depends on your effort and your cadence.
It is the right choice for sprints, warm-ups, free rides and anything you want to ride by feel. Very short efforts also ask a lot of ERG, because the trainer has to change resistance in a moment and trainers differ in how fast they respond.
Which to use
- Use ERG for intervals, steady blocks and any workout where the target matters.
- Use resistance mode for sprints, easy spinning, and efforts you want to pace yourself.
- Check your trainer. Hammy controls trainers that support Bluetooth target power. With other trainers it shows the target and you shift to match it.
The 20-minute FTP test mixes both. On a trainer that can leave ERG, Hammy holds ERG for the warm-up, lets go of the resistance for the 20-minute effort so you can pace it yourself, and holds ERG again for the cool-down.
Show sources (1)Hide sources
- Martin JC, Milliken DL, Cobb JE, et al. (1998). Validation of a Mathematical Model for Road Cycling Power. Journal of Applied Biomechanics, 14(3), 276–291. doi:10.1123/jab.14.3.276
