I have been using a Kickr for indoor training. Mainly adaptive, though I have completed some plans and also just ride what I feel like. My AI FTP is 217.
I am doing more outdoor riding, so I just bought some Garmin pedals. These are NOT installed on the bike I use for indoor training, so I can’t use power matching.
One of my goals for these new pedals is to be able to pace myself appropriately outside, regardless of wind, hills, and other conditions. I want to be able to stay in zone 2. I also envision pushing some longer endurance workouts, e.g. Boarstone -1 to the Garmin head unit.
My question is how consistent are the pedal power to the trainer power? In other words, is my 217 FTP good for estimating zones outside on a different power meter?
I put my outdoor bike on the trainer and readings seem different and challenging to interpret.
Should my main metric outside be 3 sec power, or 10 sec or something else?
Other suggestions?
I am not too concerned with high intensity intervals outside, I’ll do those inside. But I am really curious about the effort on my 2 hour rides outside.
You need to put your outdoor bike on the trainer then compare the wattage from the trainer on whatever you use for TR to that from the pedal displayed on your bike computer. There will be a difference. Even if the hardware was perfect, the pedals measure power before drivetrain losses. Additionally, most people find they can produce more power outdoors.
If your goal is to learn to pace, I recommend that you use an unfiltered power value. Yes, it fluctuates a lot, but you must have immediate feedback to make the correct adjustments. With practice you can expect to be within±10W or better, for extended time if the road is flat.
Regarding power difference between trainer and outdoors I wouldn’t be to concerned if Z2 is your main focus. Z2 can be paced by heart rate so just be mindful about power to heart rate indoor vs outdoor and make appropriate power adjustments and you will be fine.
I did Boarstone -1 today. Let TR control the trainer, and recorded Garmin workout. Here are
the results:
Metric
TR
Garmin
% diff
Avg Power
125
132
5.6%
Max Avg 20 Min Power
136
146
7.4%
Normalized Power
126
134
6.3%
TSS
53
61
15%
Calories
713
879
23%
Not crazy different (except for calories, which I’m very interested in), but significant.
When I ride outside, without TR, I can just deflate reported numbers as appropriate I suppose. I could also adjust the value I entered into Garmin for FTP, i.e. change from 217 (TR) to 229. Should I do this? Which percentage would you use?
When pushing a TR workout to Garmin, will this mean I am just riding a bit easier than TR wants me to?
Nevertheless, I wouldn’t worry about it if we’re focused on zone two riding outside. Set your Garmin for three second power readings and follow the prescribed outdoor workouts.
If you’re new to this, you’ll quickly realize that it’s very difficult to hold an accurate power level with hills and stoplights
These numbers are pretty good. Drive train friction explains at least most of the disparity between the numbers. It would be useful for you to know if the delta between the trainer and the pedals is constant or increases with increasing power. The only numbers of interest are the power numbers. TSS, NP are going to change proportionally to the difference in power. As a point of reference, my Neo2 is about 10% below my Vector pedals at 250W while my Neo3M is only about 3% lower. I verified the pedals values by hanging a known weight from them.
While we tend to “geek out” about training zones and want precision, it is important to accept that a “zone’ is by definition a range not an exact number or point. The power you can produce for any duration is likely different every day and throughout the day.
One note on calories. Garmin Connect shows the sum of resting (basal) and active calories for an activity. Most all other apps that I’m aware of only use the active calories, which makes sense as that’s what you’ve expended by doing the activity. One one of my recent rides Garmin showed 1043 total calories, 207 resting calories, and 836 active calories. 836 corresponds to what other apps would show.
Did another ride indoors today - James (basically 85 minutes at 72% FTP). Here are the results:
Measure
TR
Garmin
% Diff
Avg Power
155
164
5.8%
Max 20 min Power
161
171
6.2%
Calories
885
938
6.0%
Also interesting, this was the first ride I have done in a very long time with a HR monitor. I was quite surprised to see these time in zone results:
Zone
TR Power
Garmin Power
Heart Rate
Zone 2
86%
32%
Zone 3
5%
51%
12%
Zone 4
0%
5%
85%
Based on power differences, I should increase the FTP entered into Garmin by 6% to get consistent zone reporting with TR. However, I wonder why HR was so high (avg 88%) for this supposed Zone 2 workout (it felt pretty hard). I use AI FTP detection to get my FTP from TR.