Friday, November 17, 2017

IF and TSS

There's a couple metrics worth looking at after a ride and they are Intensity Factor (IF) and Training Stress Score (TSS).  I'll define each:


IF (Intensity Factor)= NP/ FTP


where: NP= Normalized Power (watts)
           FTP= Functional Threshold Power (watts)

Normalized Power (NP) is an estimate of the power that you could have maintained for the same physiological "cost" if your power had been perfectly constant, such as on an ergometer, instead of variable power output.

Functional Threshold Power (FTP) is your "hour power".  That is, the maximum sustained average power for 1 hour.  This can be estimated by performing a 20 min TT and multiplying the max sustained average power for 20 min. by 95%.

Example:

I rode for 1.5 hrs. and my Normalized Power for the ride was 230w.  My FTP is 220w.  Therefore, IF= 230/220= 1.05   BTW, that's a pretty intense ride/workout.  Normally, tough workouts are around the 0.75-0.85 mark.  When I see an IF over 1.0 I'm suspect of the NP or FTP, or both.  I think in this example, the NP was too high since I know my FTP is definitely 220w.




TSS (Training Stress Score)= can be manually calculated or determined by an algorithm inside your bike computer or software that looks at the power zones you ride and time you ride in those zones.

Example:

My ride consisted of 30 minutes in L2 Zone, 1.5 hr. in L3 Zone and 1 hr. in L4 Zone.  
By definition, an TSS of 100 is equal to riding at your FTP for one hour.  

L2 (1.3 weight factor) x 30 min= 40 points
L3 (1.5 weight factor) x 90 min= 135 points
L4 (1.7 weight factor) x 60 min= 100 points

Training Stress Score (TSS)= 275 points  BTW, that's a pretty hard ride/workout for 3 hrs.  And, that's NOT the exact weighting factor that's used to compute TSS but you get the idea.

Power ON!  Coach Rob

Monday, November 13, 2017

Rolling resistance- revisited

I made a post a year or two ago on rolling resistance and how different mountain bike tires have different coefficients of friction based on tread pattern.  But, what I didn't mention is how tire pressure affects rolling resistance (generally the higher the pressure the lower the coefficient of friction between the tire and the road due to less tire contact with the road) not to mention the road surface. i.e. how rough it is.

After analyzing one of my post rides the other day, I was wondering why I was putting out more watts (power) on my mountain bike but my average speeds haven't been increasing.  That's because it's been very wet/cold recently and the ground has softened up on the tow path upon which I ride.  The tow path is comprised of dirt, gravel, leaves (lot of them lately), chunk rock, etc.  When it gets wet, the dirt turns to mud and the gravel mixes in with the mud and the leaves.  Thus, a softer surface to ride on.  I'm not sure what the difference is in watts between a soft tow path surface and a hard surface but I'll guess and say it's close to 10% or 20 watts at 200+ watt output.  Here's a table (below) with road surface coefficient of frictions and you can see that concrete has twice as less friction than asphalt does.  And, a rough paved road (I'm assuming something like chip seal) has 4x the friction that a smooth concrete road has.  So, you can imagine what the difference is between hard dirt and soft mud.



So, what does all this mean?  A higher coefficient of friction between the tire surface and the road surface means less speed for a given power output.  How much depends on a lot of things: road surface, bike tire rubber composition, bike tire width, bike tire tread pattern, bike tire sidewall stiffness, tire pressure, road surface temperature, etc.

Power ON!  Coach Rob

Sunday, November 12, 2017

W prime (W')

Since I'm using Golden Cheetah software more often these days, I came across a metric called W prime, written W'.  I think it's a really neat/cool metric that wasn't and probably still isn't available in Training Peaks Software WKO+ 4.  It's new to me, that's for sure.  Before I tell you what W' is all about, you first must understand what CP (Critical Power) and what FTP (Functional Threshold Power) are.  Let's start with the latter.  FTP is your "hour power".  That is, it's your maximum sustained average power output in 1 hour in watts.  It's your average sustained power during a 40k TT.  Another way of determining your FTP is to do a 20 minute TT and find your maximum sustained average power.  Then, take 95% of that value and that's your FTP.  Critical Power (CP) is synonymous with FTP.  To find your CP do a 3 minute, 5 minute and 10 minute Time Trial with a Power Meter.  Or, do a 3 minute, 8 minute and 14 minute Time Trial which I heard is a little better for plotting.  Plot the power (3 pts.) versus duration (time).  Your CP, in watts, is where the line levels off.  You'll need a curve fitting software program to properly plot the graph and find your CP.  i.e. hyperbolic curve fit.  Want an easier way to compute your CP?  Download Golden Cheetah software and use their CP and W' Estimator.  See graph below:


Now, the amount of work that you can do above your CP, shown by the red hatched lines above, is your W'.  It's a fixed amount.  If you're a math geek, and you want to calculate the actual W' value, all you have to do is find the equation of the CP line and integrate (using calculus).  How quickly that fixed amount lasts is dependent on how hard you go above your CP and if you get any rest or breaks.  Go hard above your CP and you're not going to last long.  Go easy above your CP (say 250w in the graph above) and you'll last longer than if you went hard (say 300w in the graph above).  If you get a chance to recover during your ride, or take a break, it will replenish the W'.  How much it replenishes depends on many things such as the amount of time you recover, the power you recover to, etc.  Sooner or later though, whether you go hard or easy above your CP you're going to bonk/crash/run out of gas.  The value of W' where you start to crash and burn is around zero (0).  The units for W', or sometimes labeled W'bal, (balance) is in kiloJoules (kJ).   How long you can keep up the power at W' varies.  How negative a value you can have for W' varies too.

Here's a stress graph (from Golden Cheetah) showing W' for my latest ride today:


Not sure why Golden Cheetah gave me a W'bal of 20 kJ to start with.  I suppose it's based on my FTP of 220 that I entered into Golden Cheetah.  The segment of my ride highlighted in red is a 3 mile Time Trial on my Mountain Bike on the Tow Path.  You can see I started out a little hot, close to 300w, and backed it down to about 250w.  I should have done this TT fresh, if I wanted a personal best time, but I had just ridden 8 miles prior.  Nonetheless, you can see my W'bal plummet because 250w is definitely above my FTP or CP of 220w.  In fact, W'bal went negative at the end of my TT.  Was I exhausted at W'bal=0, hell yeah, but you could see I still had about 1.5 miles to go.  So, at 250w (30w above my FTP) it only took about 5-6 minutes before I was near 0 W'bal.  It doesn't take long.  Lessons learned, if you want to do a TT do it fresh and don't start out too hot (rookie mistake).  You can also see that my W'bal didn't start to recover until I walked over the bridge from Bulls Island, NJ to the PA side.  The PowerCal HR monitor/meter showed 100w when in reality I wasn't even on the bike.  I was walking my bike across the bridge because of the heavy pedestrian traffic.  Anyway, that's W'bal and I think it's a neat/cool metric for post-ride analysis.  Probably even better for post-race analysis.

Power ON!  Coach Rob

Saturday, November 11, 2017

Cold Flu Season is Here

Just saw this chart/graph today from Training Peaks showing that moderate intensity exercise is better than no exercise (sendentary) for staving off the cold, flu, sore throat, etc. during the Winter season.  But, that with intense exercise you're more at risk of infection.  To me, this is obvious.  It's all about a healthy immune system.  If you're healthy and your immune system is working as it should, you'll most likely be able to stave off most colds, flus, etc.  But, if you exercise at a high intensity level you're more susceptible.  That's because you start to run your immune system down at high intensity levels.  Even if you don't train intensely, it's still probably not a bad idea to get a flu shot.  Flu shots are not a guarantee you won't get the flu, because when they develop the vaccine, they pretty much guess at what strain will be the most prevalent in your area when flu season rolls around- which is right about now.  They manufacture this vaccine in late Summer, months before the flu season, so they have enough to go around and can get it to market on time.  So, if they make strain A of the flu vaccine (and disseminate it and you get the flu vaccine shot), and they discover that strain B is the actual flu bug going around it will help but you're still susceptible to getting the flu.


Other than exercising at moderate intensity what else can we do to lower your risk of infection during the flu season?  Here's a list:
1.  Wash your hands often- with soap.
2.  Get plenty of sleep.
3.  Eat well.
4.  Stay away from sick people.
5.  Avoid sharing cups/utensils/water bottles/etc.
6.  Avoid crowds, public venues, planes, trains, etc. if you can.
7.  Avoid binge drinking or excessive alcohol consumption.
8.  Wash your pillow case and bed sheets at least once per week.
9.  Use two towels in the bathroom: 1 for your body and 1 for your face.
10.  Use a humidifier if your house is too dry.
11.  Hydrate often.

Power ON!  Coach Rob

Strava Ride Segment


I created a ride segment the other day on Strava.  The ride segment is from S. Washington St. in Frenchtown, NJ to Kingwood Stn Rd 3 miles down the towpath from Frenchtown.  What's pretty cool is that Strava will give you all of the metrics for your ride segment.  Does anyone know how that works?  Is it being done real-time?  I'm not even sure my phone was on.  I know Strava wasn't running on my phone.  Does Strava do it all post ride when I download my ride from my Garmin Edge into Strava?  That is, Strava looks at my ride and says, "hey I've got a segment along that ride in my database so lets capture the metrics for that segment for you".  The average Power is a little high but that's because I was wearing my PowerCal HR monitor/power meter instead of my hub based power meter on my road bike.  I'd say it was 5-10% high...closer to 10%.

Anyway, I think it's pretty cool that it gives the metrics for the segment- see chart/graph above.

Power ON!  Coach Rob

PowerCal Ride Segment

Here's a ride segment from my ride the other night wearing my PowerCal HR Monitor/Power Meter estimator.  I was pretty happy with the results.  I'd say the power numbers were a tad high, maybe 5% high, but that's not a problem since I can adjust the power output (across the entire ride) using Golden Cheetah software (open source).  Just go into the main menu, choose Edit then choose Adjust Power Values and Enter "-5" (in my case) and it will adjust the power profile 5% lower for the entire ride.

Here's my ride profile:

Power ON!  Coach Rob

Friday, November 10, 2017

Bright Lights- revisited!

5000 Lumen 2x CREE XML U2 LED Cycling Bicycle Bike Light Lamp HeadLight Headlamp


I had purchased the 5000 Lumen 2x Cree XML U2 LED bike light via Amazon this week for $22.  I used it last night for the first time.  My impression?  Fair at best.  You get what you pay for.  The light has 3 brightness settings: High, Med & Low.  It puts out a good flood light with a width of about 30-40 ft.  The length of light (ahead of the bike) is about 20 yds.  It definitely doesn't put out 5000 lumens.  I'm not even sure it puts out 2000 lumens.   If I had to guess, I'd say it's more like 500 lumens..so they had a typo in their advertised output. 

I fully charged the battery pack (4 x 18650 Lithium-ion batteries) before I connected it to the light.  I have no idea what the capacity of the 4 batteries are.  There was no paperwork.  If I had to guess, I'd say each battery had only an 1100 mAh capacity.  And, I'd say two of the batteries were connected in series and two in parallel from looking at the case.  Since Li-ion batteries have a terminal voltage of 3.7v that makes for a 7.4v on-load voltage for the battery pack (2 batteries in series).  The charging voltage of the battery pack is 8.4v and is advertised as such.  Therefore, the battery pack is an 8.4v 2200 mAh battery pack.  Why do I think the capacity was only 2200mAh?  Because 3/4 of the way through my 1.5 hr. bike ride, the light shut down completely.  It just shut off.  And, that was on Med power.  I knew there was no way the battery pack would last the entire 1.5 hr. bike ride on high power. 

Anyway, I'm in search for a new battery pack for my new light.  I'll probably end up paying more for the battery and charger then I did for the entire kit...but that's ok.  I knew a 5000 lumen bike light for $22 was unrealistic.  When I get a new battery hooked-up, I'll give yet another report/update.

Until then, Power ON!  Coach Rob

PowerCal First Ride

I had my first ride last night with the PowerCal HR/Power Monitor.  The PowerCal HR/Power Monitor is made by PowerTap- one of the leaders in bicycle Power Meters.  www.powertap.com   They make quality products.  I own two hub-based power meters from Power Tap and they've given me reliable performance/service for over 10 yrs.

So, what was my initial impression of the PowerCal HR/Power Monitor?  I like it.  It does exactly what it was advertised to do and that is use it's internal algorithm to give an estimate/approximation of the power output of your ride based on your HRmax.  Check out one of my earlier blogs/posts on the PowerCal.   Watch the short video given by Dr. Allen Lim (a world recognized expert in power meters). 

Last nights ride was not your typical ride.  It was cold (45F), rainy, muddy & wet- not to mention "dark".  I rode on my Mountain Bike and I had a waterproof jacket, winter riding pants, gloves, hat, etc.  I was pretty much all bundled up.  Not really the best attire for producing maximum watts on the bike.  Besides, I wasn't really fresh or in "form".  I was still feeling the effects of an earlier workout in the week.  I'm still trying to get back in cycling shape.  I've only been riding since July of 2017 after a couple year layoff.

I included the graph above to show the Garmin Edge output from the PowerCal.  It says my HRavg for the ride was 146 bpm, Avg Speed of 12.5 mph and Avg Power of 190w.  You can see why the average speed is only 12.5 mph when it looks like the majority of my ride was above the 15 mph line.  That's because there are a lot of times where I had to slow down to say 5-8 mph during road crossings, bridge crossings, deer crossing, etc.  Those times/speeds are used in the average calculation.  If I had to guess, I'd say my "real" average power output riding at 16 mph was about 190-200 watts.  PowerCal reported over 200watts, more like 220watts.  That's not too far off.  What I'll do this weekend (or next week) is use the PowerCal HR monitor on my Computrainer and compare the outputs during a steady state ride.  That will truly tell me what the delta is between the two.  I'll use my Garmin Edge to capture the PowerCal HR and  estimated power and I'll use my Computrainer to capture the "true/actual" power.

Until then, Power ON! Coach Rob