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Development Team Member
Posts: 35

Moxy-6x1k.png I've promised myself I would start using Moxy more this season, and have been having some success using it with ramp tests for zone setting. However, I'm curious about a 6x1k (treadmill) running session today - specifically the tHb reaction on the 5th interval.

Laps 1&2 are the warmup
3,5,7,9,11,13 are 1k intervals at a hard pace (slightly increasing from 1-3, 4th and 5th same as 3 but "broke" during the 5th and jogged to the end. 6th hard but much slower than the others)


My interpretation

1st (lap 3) - sudden SmO2 drop - probably not fully warmed up (also, SmO2 still rising during the warmup and doesn't hit its later peaks). Fairly minor tHb reaction but increases nicely during the interval suggesting appropriate cardiac/respiratory response.

2nd (lap 5), 3rd (lap 7) - more "normal" response (properly warmed up now). Smooth SmO2 drop and tHb rise suggesting intervals having their desired effect.

4th (lap 9) - SmO2 graph looks OK, but much deeper tHb drop this time and later recovery. Is this the start of the limitation that killed the next interval? Interestingly HR was only at 95%HRMax by the end of that interval, though I've been working night shifts which never helps! Low tHb suggests a cardiorespiratory limitation coming in

5th (lap 11) - this is the one where I failed. SmO2 curve looks OK but tHb plummets to a much lower value than any previous interval and shows no signs of coming back up until I stop. Again HR was only up to 95%HRMax, but the low tHb suggests cardiorespiratory limitation?

6th (lap 13) - this one was only at ~95% the speed of the others (and effectively after a longer rest), so it's no surprise that the SmO2 doesn't go down so much. However again the tHb drops and stays low for the entire interval.

Low tHb during intervals
This is my main query - is this simply a cardiac/respiratory limitation that needs training (or just resting away from night shifts!). Or are there alternative explanations? On nights my nutrition goes a bit messy so I was wondering if you'd see something similar if I'd burned up too much glucose on the first four intervals.

Alternatively could this just relate to muscle recruitment?

Grateful for any thoughts!


Development Team Member
Posts: 213
Moxy placement location?
I do night shift too and my last meal is about 9pm as it makes me feel better during the 12 hour shift. My training perceived effort is always higher after a night shift, but it could be that I only manage to get about 5.30 hours of sleep during the day.

Development Team Member
Posts: 4
* for better interpretation it is useful to also plot HR 
* I do not see any ventilatory limitation
   - smo2 keeps returning + getting higher that previous value, also higher than basal         
     (starting) smo2, the slower recovery is perhaps caused by motion of measured muscle
     group during recovery
   - to clearly see ventilatory limitation during recovery it is neccessary to avoid any motion
      of measured musle group.
* Lap 11 - in the middle of the bout you achieved arterial muscle occlusion, your cardiac
   output was not high enough to overcome the sum of pressure in the muscle capilaries (the
   venous outflow was not impacted as you do NOT see elevation on HHb )
   - reason for that: harder to guess without HR trend, but either cardiovascular limitation or
      muscle exhaustion leading to recruitment of more motor units (but due to lower
      desaturation not very probable)
* Lap 12, 13 complete loss of ability to sustain or recover homeostasis

Conclusion: cardiovascular limitation, training should had been stopped after lap 9, futher bouts only led to "cardivascular catastrophe" and if applied repeatedly may lead to overtraining.


Development Team Member
Posts: 213
Thb rebound after each load period gets progressively lower. Maybe blood pressure protection. But SmO2 on rest periods is increasing even with a decreasing tHb, blood flow velocity higher or left shift of O2 dissociation curve.

Development Team Member
Posts: 1
I agree with @Hiblbauer but could this be partially due to dehydration? I know I have a tendency to sweat a lot more when I am running on a treadmill, if you are already starting moderately dehydrated, and not rehydrating throughout the workout then blood volume is going to go down, which is indicative by the decreasing THb rebound signal during rest and since you are already maximizing stroke volume, by being at 95%HRmax, this might mean you just aren’t delivering adequate blood to the working muscle. 

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