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Stryd Power: Power Outside vs Indoors (Hill repeats)
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I had a wierd issue today. I made two hill repeat workouts that I hoped would be fairly similar. One outside, one on the treadmill. Each effort was at similar pace and grade for similar time (about a minute). The issue here is, the efforts outside produced almost 100W more despite the inside effort being a fair bit more difficult. The treadmill effort was much harder on the heart than the legs, and vice versa for outside. Temperatures may have played a role, but I don't feel it'd be that significant. Outside was 30F and dry, inside was 70F with moderate humidity. I had two fans on me during the treadmill run. Same shoes.

I should add my goal here was a power workout. 325W is around my threshold pace outside, but was a VO2max effort here with the incline.

Why would the treadmill be the more difficult effort despite 25% reduced power? I have included the data for discussion. I'd like to hear your opinions on this.



Strava
Last edited by: rsjrv99: Jan 28, 21 11:05
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [rsjrv99] [ In reply to ]
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So I am not a Stryd expert but...

a) Stryd doesn't know when you are using the incline on the treadmill and so the power won't adjust.

b) I use the wind Stryd, and it always reads less power indoors for the same effort and speed (and yes, my treadmill is accurate on pace). I suspect it's the lack of wind resistance throwing stuff off (but do not know for sure).
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [darkwave] [ In reply to ]
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I have no idea of how Stryd works but does it have some way to calculate incline? If that is the case then maybe that is the problem on the treadmill?
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [darkwave] [ In reply to ]
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I would assume stryd would not need incline information as it is measuring power from the stride and the power it takes to complete that stride (accelerometer?). Id assume that stryd doesnt have incline info for outside either. Though now that you say that, 325w would be my 9.0mph pace, so that may be the answer but for another reason.

I have the wind stryd as well though i believe it just uses wind to correct measurements, it doesnt need wind to make them

Strava
Last edited by: rsjrv99: Jan 28, 21 12:01
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [rsjrv99] [ In reply to ]
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Stryd's official statement on inclines on treadmills:

Why does my power not go up if I increase the treadmill incline? – Stryd
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [darkwave] [ In reply to ]
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darkwave wrote:
Stryd's official statement on inclines on treadmills:

Why does my power not go up if I increase the treadmill incline? – Stryd

Thank you for this. I must have missed it in my research. Problem solved. Looks like i need to learn how stryd works a bit better

Strava
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [ In reply to ]
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While you're here...........does Stryd give you a kilojoules measure for a workout since it is power? Instead of calories from HR?

I'd be interested in that as it relates to run "ftp" and tracking it in Trainingpeaks versus HR. I feel using HR for it really is off given my bike fitness and run power may help the data make more sense.
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [burnthesheep] [ In reply to ]
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Stryd provides a run ‘’power’’ number not a measure of physiologic power out. What on earth running “power” is a while different topic but luckily for you what you are looking for is super simple to calculate.

You need to know two things to calculate energy consumption from running assuming you start and finish in the same place: how far did you run and how much you way. Heart Rate, speed, time etc are all not relevant. You can look up charts on line for calories per mile for a body weight and then convert calories to kJ. Heart rate can be used as rough proxy for work when distance isn’t representative the exercise but in running always use distance.

The irony here is that because energy is basically just a function of distance (normalized to weight) power in running is just a function of pace (normalized to weight). If you want to be 100% correct you do need to account for elevation changes, wind resistance due to wind and energy transfer difference between different road surface ie it takes more power to run in mud than on road for a set distance. Personally I have yet to see any data that shows Stryd or any other product on the market can makes these corrections in a way that meaningfully improves on pace alone. They certainly try and get fancy with algorithms but it’s still essential pace with level of noise thrown in to keep people off the scent.
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [scott8888] [ In reply to ]
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scott8888 wrote:
Stryd provides a run ‘’power’’ number not a measure of physiologic power out. What on earth running “power” is a while different topic but luckily for you what you are looking for is super simple to calculate.

You need to know two things to calculate energy consumption from running assuming you start and finish in the same place: how far did you run and how much you way. Heart Rate, speed, time etc are all not relevant. You can look up charts on line for calories per mile for a body weight and then convert calories to kJ. Heart rate can be used as rough proxy for work when distance isn’t representative the exercise but in running always use distance.

The irony here is that because energy is basically just a function of distance (normalized to weight) power in running is just a function of pace (normalized to weight). If you want to be 100% correct you do need to account for elevation changes, wind resistance due to wind and energy transfer difference between different road surface ie it takes more power to run in mud than on road for a set distance. Personally I have yet to see any data that shows Stryd or any other product on the market can makes these corrections in a way that meaningfully improves on pace alone. They certainly try and get fancy with algorithms but it’s still essential pace with level of noise thrown in to keep people off the scent.

You ignored two things: elevation change and running efficiency. It takes more energy to run a hilly mile than it does to run a flat mile. As far as running efficiency, pace can certainly have an impact on how much energy is required to cover 1 mile. With each stride there is some energy going towards forward propulsion and some going to vertical motion. The energy going into vertical motion is needed to allow you to run, but does not directly contribute to covering any distance. Stryd does seem to do a decent job of distinguishing between the two and therfore providing a better measure of effort than pace alone. This is especially true when attempting to maintain a relatively constant effort as grade changes.
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Re: Stryd Power: Power Outside vs Indoors (Hill repeats) [rsjrv99] [ In reply to ]
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A couple tips from a near 100% treadmill runner...

Always let your phone/app connect to you Stryd pod first, then turn your watch on and let it connect... If you’re watch connects before the app, you’ll play hell getting the app to ever connect.

Adjust the incline before you hit start... just move it to .5%. I’ve been extremely frustrated that the power number never changed after I made incline adjustments. Doing this seemed to fix the problem.

Hope I saved you some frustration
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