Suunto SHRB2 Firmware 3.2.6.8 Update

[Speed Man]

After the update, I’m having trouble understanding the Flight Time data. The values seem lower, while the Avg GCT:FT Ratio seems higher.

Could anyone help me understand how to interpret these metrics? I’d really appreciate your advice. Thank you!

[snow*]

@Speed-Man was you running slow or uphill ?
imho, they seem like legitimate values.

(329/45)*100 woudl be 731% vs 891%

so why it spikes to 891%? I guess since the flight time is in the denominator, any step with a slightly shorter air time may create a huge ratio spike which pulls up the overall average ratio. ofc take this with a grain of salt

[atoponce]

@Squirrel 6.14.3

[matram]

@Speed-Man
This looks wrong.

With cadence 80 the time for a stride (L+R step) is 750 ms.

Flight time is stride time minus GCT so should be 421 ms.

I have upgraded my belt too. Today is rest day, but I can report back after tomorrow’s run.

[snow*]

@matram said:

@Speed-Man
This looks wrong.

With cadence 80 the time for a stride (L+R step) is 750 ms.

Flight time is stride time minus GCT so should be 421 ms.

I have upgraded my belt too. Today is rest day, but I can report back after tomorrow’s run.

Hi, if I’m not wrong you’re subtracting the GCT of a single step (329 ms) from the total duration of a full stride / 2 steps (750 ms). A full stride includes two ground contact phases (left + right), not just one

Per single step (1 leg):

At 160 spm (80 rpm), each step lasts 375 ms (750 ms / 2) so Step time = GCT (329 ms) + Flight Time (46 ms) = 375 ms.

Per full stride (2 steps):

Stride duration = 750 ms.
Total GCT for both feet = 329 ms × 2 = 658 ms.
Total Flight Time for both steps = 750 ms - 658 ms = 92 ms (which equals ~46 ms of flight time per step).

If Flight Time were actually 421 ms per stride (~210 ms per step), on a 375 ms step duration your GCT would be only ~165 ms—a ground contact time achieved by world-class sprinters, not during a relaxed 80 rpm run

[greenfish29]

@atoponce What does “Optimize the light reminder logic” mean?

[matram]

@snow
I must confess that I find this confusing, but for a recent very slow run Suunto reported …

• Cadence 76
• GCT 447 ms
• FT 325 ms

GCT + FT = 772 ms
60 / cadence = 789 ms

This seems to me to say that both GCT and FT are the sum of both feet in one stride?

I can add that I also have Stryd Duo data for this run. Stryd GCT is 445 ms so basic numbers agree. Footpath data indicates that each foot has ground contact for about 20 cm or slightly more.

With a stride length of 79 cm this would indicate a GCT of around 200 ms for one foot and 400 for both feet in a stride.

[Speed Man]

@matram Let me try again. Thank you.

[snow*]

@matram said:

I can add that I also have Stryd Duo data for this run. Stryd GCT is 445 ms so basic numbers agree. Footpath data indicates that each foot has ground contact for about 20 cm or slightly more.

yep, with a total stride length of 79 cm and ~20cm of ground contact per foot measured by stryd, each foot stays on ground for ~25% (20/79) of the total stride distance 79.
at 76 RPM, a full stride lasts ~789 ms so if a single foot is on the ground for ~25% of the stride, it stays grounded for 25% of the total time which equals ~200 ms of GCT per single foot (25% of 789mS is ~200ms) so gives ~400 ms of total GCT across the entire stride

[atoponce]

@greenfish29 It has to do with the LED behavior. I don’t know how it was optimized, but guessing it’s related to this:

LED Signal	Meaning
No light	The belt is either off or in normal operating mode but saving power by keeping LED off. The power save mode can be turned off to keep the LED on.
Green flash	The belt is active and not in power save mode.
Green double flash	A host has just connected.
Red light	Low battery, change the battery.
Red→Green→Blue cycle	Firmware is being updated or a factory reset is active.

[VoiGAS]

My Runnin Form improvements are turning out to be garbage
Before the Update:

After the update:

Same Route, little bit slower. But the Flytime (Flugzeit)? Whats going on here? At least GCT seems consistent

What’s also interesting: I have more steps at the second run, but my cadence is lower. Same distance. Hm…

[snow*]

@VoiGAS imho I would say that there’s something odd the firts time ( flight time of 403 ms at 166 spm sounds odd) and the second one (i.e. after the update) is ok at first glance i.e. values make sense

[VoiGAS]

@snow given the description in the App both Values seem unrealistic. I don’t care, as the GCT and their Balance is the metric I am interested in.

[Inge Nallsson]

I tested the LED behaviour in relation to connections with both the Suunto App and the Race S. First with Firmware 3.2.6.2, and after upgrade with the 3.2.6.8 version. It was not easy since the two choices we are offered didn’t really seem to stick until I had revisited the App page again after a change. Also, the use of different colours and number of flashes and number of sequences just made my head hurt, as well as question what I just had written down. Take the below with a pinch of salt, and perhaps do tests of your own.

The explaining text in the Suunto App [upper left hand corner HR icon] --> “Battery mode” is strange and only correct in parts and in a general sense:

“Power saving” [Default mode]
“The blue indicator light does not flash to show the number of connected hosts in this mode”

“Normal”
“When enabled, the indicator light will stay on continuously”

The “Power saving” behavior with 3.2.6.2 was:

Strap on chest: LED Off.

Connection to App or watch running activity: LED Single green flash.

While connected: LED Off.

The “Normal” behaviour was:

Strap on chest: LED Off.

Connection to App or watch running activity: LED Single green flash.

While connected: LED Double green flashes every 5 seconds.

These double flashes continued as long as the strap was on the chest, also after the running activity, and only quit 5 to 6 minutes after the strap (or pod) was removed.

The “Power saving” behavior with 3.2.6.8 is:

Strap on chest: LED Off. (Or the same as in “Normal” mode… It seems to vary… Or not stick)

Connection to App or watch running activity: LED Single (or double?) green (or blue?) flash. With the watch there then was a 4 times sequence of double green flashes.

While connected: LED Off.

The “Normal” mode has a lot of LED flashes:

Strap on chest: LED Single green flash every second until removed, plus 3 minutes. The flashes can start just by touching one of the electrode studs, or when snapped on, touching a plastic strap electrode. If not on chest the flashes stop after 3 minutes.

Connection to App or watch running activity: LED Single (or double?) green (or blue?) flash. With the watch there then was a 4 times sequence of double green flashes.

While connected: LED Off.

Yikes… Not clear at all! Sorry.

[atoponce]

I was hoping the update would address this, but I guess not.

However, I think the flight time is per step, rather than per stride. IE, you’re in flight until a foot hits the ground, then you’re not. You’re in flight again until the opposite foot hits the ground. So your flight time is between left/right steps.

The math checks out for me:

• Cadence = 170 spm
  • Time per step = 1/170 spm
  • => (1 min / 170 steps) * (60,000 ms / 1 min)
  • => 60,000 ms / 170 steps
  • => 352.9 ms/step
• Flight time = time per step - ground contact time
  • => 352.9 ms - 295 ms
  • => 57.9 ms
• GCT:FT ratio
  • Ratio = GCT/FT
  • => 295 ms / 56 ms
  • => 5.27 or 527%
• Share of each step on the ground
  • 295ms / 352.9 ms = 0.84 or 84%

[Inge Nallsson]

@atoponce said:

I was hoping the update would address this, but I guess not.

Thanks for posting that so I didn’t have to try it. Instead I could test a new length of protective rubber tubing. Yesterday, while using the old short version, I discovered that the twisting of the torso made the tube migrate, slide a bit to the side, and expose ca 1/3 of the SHRM2 pod. This led to HRV noise in the latter part of the run. Anomalies was still 0.0% but the Artifacts stood at 2.0% according to Runalyze. Today I used a 70 mm length of the old bicycle inner rubber tube (round diametre ca 30 mm, flattened the height is ca 46 mm). It stayed in place beautifully and the Anomalies were back to 0.1% with Artifacts at 0.2%.

When it comes to Running Form I now have numbers from both Firmware versions. The only parts that I can put a firm handle on is Pace and Cadence, and using 180 bpm cadence music* allowed me to focus on the pacing, where I with success managed the intended ca 6:30/km.

Let me just get this out of the way and say that the “Flight time” and “Avg GCT:FT Ratio” in this last Firmware are crazy numbers! I can’t wrap my head around the numbers from the old version either, but at least they were worthy of questioning and computation. I’ll write all the numbers that can be squeezed from the App below, as well as the wrist-based equivalent from the Garmin Forerunner 955 control watch.

Both runs had “Avg. ground contact balance” of 50.0% - 50.0% which also is a bit strange since all of my running shoe soles have a wear pattern speaking of an imbalance.

FW 3.2.6.2 6.00 km, 00:38:50.5, 6947 steps:
Avg Pace: 6:28/km
Avg Ste. Cad: 180 spm
Avg Ste. Len: 86 cm
Avg GCT: 343 ms
Avg VO: 5.3 cm
Avg FT: 324 ms
Avg GCT:FT Ratio: 106.0%

FW 3.2.6.8 6.01 km, 00:38:53.4, 6920 steps:
Avg Pace: 6:28/km
Avg Ste. Cad: 180 spm
Avg Ste. Len: 86 cm
Avg GCT: 342 ms
Avg VO: 5.3 cm
Avg FT: 1 ms
Avg GCT:FT Ratio: 11320.4%

FR955 6.03 km, 00:38:55:
Avg Pace: 6:27/km
Avg Run Cad: 179 spm
Avg Stride Len: 0.86 m
Avg GCT: 266 ms
Avg VO: 7.4 cm
Avg Vertical Ratio: 8.6%

Here are kilometre by kilometre numbers for the interested mathematician:

FW 3.2.6.2 Avg Pace, Cad, GCT, VO, FT, GCT:FT
6:30, 90, 341, 5.6, 323, 105.1%
6:27, 90, 343, 5.3, 324, 105.9
6:28, 90, 345, 5.2, 322, 107.2
6:26, 90, 344, 5.2, 325, 106.2
6:25, 90, 343, 5.2, 323, 106.2
6:30, 90, 342, 5.2, 324, 105.6

FW 3.2.6.8 Avg Pace, Cad, GCT, VO, FT, GCT:FT
6:31, 90, 337, 5.6, 2, 9639.4%
6:29, 90, 344, 5.3, 0, 12104.8
6:27, 90, 344, 5.2, 1, 15041.3
6:27, 90, 344, 5.2, 1, 12659.3
6:26, 90, 343, 5.2, 1, 11125.8
6:28, 90, 343, 5.2, 0, 13166.7

[I thought division by zero was forbidden… And observe how same GCT with same FT produce wildly different GCT:FT percentages]

FR955 Avg Pace, Cad, GCT, VO, Vert. Ratio
6:30, 177, 266, 7.3, 8.6%
6:28, 180, 266, 7.4, 8.6
6:27, 180, 266, 7.4, 8.6
6:26, 180, 267, 7.4, 8.6
6:24, 180, 266, 7.4, 8.6
6:27, 175, 266, 7.3, 8.4

All the numbers are correctly transcribed from the Suunto App and Garmin Connect.

* Cadence mp3 from Steve Boyett at https://www.podrunner.com/about.html

[isazi]

Forwarded this discussion to the product manager at Suunto

[snow*]

tried this morning the new fw (don’t pay attention to the noisy part—I was fiddling with my running vest)

thanks @łukasz-szmigiel for this handy tool

that said I keep trying with ESD tape/bags (not used in the above run)…

[atoponce]

@snow I’m about to test the same. I chopped up an ESD bag hard drives come in, wrapped it around the module, and taped it to the back careful to not short the snaps. About to head out on a run with it now and see how it performed.

[ggrego]

Hello little have returned to the previous version that version is meh the flight times no longer work 45 ms the previous outputs were at 290 ms thank you