Heart Rate Monitor ~ chest strap v.s. wrist sensor??

What heart rate monitor is good for hiking?

Chest-strap heart rate sensor

Embedded wrist heart rate sensor

There are a lot of devices which have heart rate sensors!!

Running devices, activity tracker, Apple watch and so on!

A several years ago, most of heart rate sensor for running was chest strap type.

Now, it is getting popular to use embedded heart rate sensor in a device.

I had a comparison about the accuracy!

Offset of measured heart rate between a chest-strap sensor and embedded wrist sensor

Offset of measured heart rate

I collected heart rate data based on my regular running exercise for a month.  I was wearing the both type of heart rate sensors, a chest-strap type and an embedded wrist sensor when I ran.

The chart above is the offset of the both measurements.  More than 90% of samples are within 4 (bpm).    This shows the embedded sensor is probably accurate enough for running and hiking.

Here is an example which has larger offset:

An example of larger offset 

The orange color is a data captured by a chest-strap sensor (with Garmin Forerunner 910XT).
In the middle of chart, there are some portion where the offset is bigger.  However the reading is more than 180 (bpm) which is probably way bigger for mild jog.  Therefore, I assume this data captured by a chest-strap sensor might be something wrong.

Another example is the the following:

Another bad example with larger offset

The blue color is captured by an embedded writ sensor (Garmin Vivosmart HR).  The early part, there are some spikes.  This data captured by an exercise using StarMaster in a gym.  It is hard to believe there is such spike during the exercise since the type of exercise won't introduce such narrow heart rate spikes.  Therefore, I assume this would be wrong reading by the embedded sensors.

Conclusion:The both sensors might have some wrong reading!

The both example shows there might be some wrong reading for the both sensors.  It is hard to identify the reason why the reading gets some offset.  Overall reading is matched well.   I think as long as contact between the sensor and body is good, the reading can be accurate.
My best guess is that if the contact is getting loose or dislocate a proper position to the body, the reading might be offsetting.

When people using a chest-strap sensor, it is probably easy to dislocate position due to a backpack.  I think that would be one of issue when I use the chest-strap type sensor during hiking.
Therefore, I would recommend embedded wrist sensor for hiking!

 

This device is with GPS function and it can track where you hike.

 

This device has pulse oximeter function, but no GPS.
It might be good to see your oxygen saturation which might be a good index for your body reaction of elevation!

Are you ready camping in a rain?? ~ Gore Tex Sleeping bag cover!

Camping in Rain? No problem!

In case you need to camp in rain,  it is better to be prepared!

I usually use Gore-Tex Sleeping cover to minimize wetting my sleeping bag.

Memorial day weekend!

This weekend is Memorial Day weekend in the United States.  Our family usually go camping in Memorial day weekend.  Unfortunately, weather forcast says it will be raining.

We are discussing if we need to cancel the camping or not.  It is probably canceled.....

However, it is different story if raining is during hiking / backpacking.  You are not much choice.

Once your sleeping bag gets wet, it is not very comfortable the rest of nights.
To minimize the impact of raining, it is better to prepare in advance!

I am not sure why I cannot see sleeping bag cover in the United States.
In Japan, sleeping bag cover is very popular and it is very useful to protect from rain.

There are some sleeping bag with Gore Tex shell, it is probably one of better sleeping bags.
However, majority of sleeping bags do not have Gore Tex shell and it is easy to get wet if people are camping in a rain.

A solution is using Gore Tex sleeping bag cover, then it will be much better!!

Tea / Coffee in Outdoor!! ~ Gas stove / cooker for picnic

Tea / Coffee in Outdoor?

How often do you go out and enjoy Outdoor activities?

Don't you think that it is a great idea to have some tea / coffee in outdoor?

Camping Gas Stove / Cooker would be a good gear to carry for hiking / picnick!!

Summer is coming!

This weekend is a long weekend, Memorial Day weekend!
Although it is still raining some time even in late May, summer is comming.  It is a good time of a year for outdoor activities!!

Our family is not only go camping / hiking, but also we go to a beach to enjoy nice Sun shine during summer time!   For those outdoor activities, one of good gear I always carry is a Gas stove for backpacking.  It is really small and light.  But it helps to have tea/coffee in outdoor.

For me, a two  burner camping stove might be too big to carry everywhere other than family camping next to our car.  However, this small stove only occupy very small space in a small backpack.

To carry this stove, a cooker from MSR would be very nice fit.  It can be used for boiling water as well as a container to carry the stove, liter, cap and etc.

I think they will help you to have a great day in outdoor!!

Power Solution in Outdoor / Hiking!

Power Solution in Outdoor / Hiking

There are many electoric devices which do not accespt a regular battery.

Smart Phones, GPS devices and etc.

Do you have any power solution to chage those devices in Outdoor?

Here is the Power solution in outdoor / hiking!  

"Solar Panel"

Smart phone consumes a lot of power!

You may charge your smart phone almost every day.  Even a middle of a day, you might run out the battery and you eventually chage battery.  I think many people have such experience 

Do you have any power solution in outdooer / hiking?

You may have not only smart pohne, but also digital camera, action cam recorder, GPS devices, InReach and etc.  Many devices might not accept a regular AAA / AA battery.

A good solution would be "Solar Panel" and "Power Bank (External Battery)"

Solar Panel is not enough!

Just having solar panel is probably not enough to cover to chage your smart phone, digital camera duing daytime.  Since you may want to use them when you are in the trail.  

It is probably better to chage an External Battery Pack (Power Bank) when you walk in daytime.

The best solution is Combination of Solar Panel & Power Bank!

There are so many external battery.  My recommendation is something around 20,000mAH capacity.

It is probably good enough to chage a typical smart phone around 5 times if it is full.

You can chage it in a campsite during night.  Also, even if it is not clear day to get enough Sun shine, it is probably enough to cover a few days.  As long as you can keep chaging day time in some days.  It can cover your entire overnight hiking!

Avalanche Safety Gear ~ Avalance beacon and snow shovel and probe

Avalanche beacons

Avalanche safety....

There might be higher risk for avalanche when people ski in back country, outside of ski resorts.  I saw many people ware avalanche beacon in Europe even if in a ski resorts.

This is an equipment to identify a location in snow when people meet an avalanche.  It is better to ware avalanche beacon when we go skiing in back country.

Also, we need snow shovel and snow probe as well!

Although an avalanche beacon is useful, it is not good enough to rescue people in snow in a short time.   

Snow probe and Snow shovel

Once we identify a rough location where a person in snow, we need to have a probe to identify exact location / depth where he/she is.  Then we need to dig him/her out.  Without a snow shovel, it is very hard to do in a short time.   Therefore, snow probe / snow shovel are really necessary to rescue people as well.  Basically all member need to carry them.

Snow saw 

Snow saw is probably nice to have.  I think most of cases, we probable do not need snow saw to rescue from avalanche accident.   Since the snow might not be very hard in most of cases.   However it is very useful to make a snow cave especially some emergency case in a snow.

Snow cave would be a good shelter to unexpected camp in a snow without a tent.

Water Treatment - UV light

Water Treatment - UV light

   One of outdoor equipment I got before is a water treatment with UV (Ultra Violet) light.  The idea of this is to kill almost all bacteria, viruses and protozoa.  The advertisement says 99.9%.   They have some data to show it works.  Typically, I am using a filter type purifier when I hike.   Actually, I did not have a chance to use this even if I own it.

   There are a couple reason I did not use:

1. If I camp on a trail, the amount of water I need is not small amount.  It only takes care of 1 litter of water at one time.   Therefore, if I need a few litters and water for the next days.   It will be a several litters of water.   To process such amount of water with this is not really efficient.  The filter type is probably much convenient.
2. I have never seen people who use this type of water purifier on a trail.   I guess the experiment data the vendor shows is probably true.  However, some of my friends had some questions if it really works or not.  Another words, people could not completely believe this product.

   On the other hand, here is the reason I got this product:

1. I thought it would be convenient to get some water other than a camp site.  Just getting some water on the way to a destination.  It won't be a lot of amount and this might be convenient other than using the filter type (pump type) in that situation.
2. The filter type won't be able to cover everything.  Especially viruses might be too small to filter them out.  So it is probably safer to use this type of product if I need to drink without boiling.

   In a reality, I typically have enough water of a day and I do not have to take extra water on the way.  Also, I have been using the filter type water treatment a several years and I did not have much problem in the past.  So I did not really think I really need such extra treatment.  I think people in the United States is safer side and the water treatment is much more popular than Japan.  On the other hand, at least when I was in Japan, the water treatment was not really popular and I had never used it on a trail.  Even though, I had never had any major issue without any water treatment.   I guess it is probably all right most of cases, but people recommend to use it just in case.  It is probably better to avoid any risk on a trail.

   As my conclusion, I probably won't use it proactively in the future anyway.   However I am curious if there is any way to check this is useful or working all right.   Currently I do not have much idea how I can verify this function.   But I just wonder if there is some good way to verify this.

   Does anybody have any idea about this?  

   I started thinking about this because I found it when I clean my outdoor equipment box this weekend.   I found it and I know I have never used.  I might try something in the future.

Trekking Pole

Trekking Pole and Pole for skiing

   It is September now.  I have been busy this summer for many unexpected things.  New school year started for our kids in mid August and it is back to normal now and finally I have some spare time to write an article.

   Today's topic is "Trekking Poles" that many hikers are using nowadays at least in the US.   I did not use them when I was young.  But I started using them a few years ago since I am getting old and I'd probably better to get some support using them.   I was using one for skiing, but it was broken and I bought a pair of trekking poles last year.

Trekking Poles

What I bought was one from Black Diamond, you can find it in Amazon.  There are many different types, this is a folding type  Another type is an adjustable type, which is easy to adjust the length.  Most of folding type is fixed length, but one I bought was there is a part to adjust the length on the top part.

Adjustable part

   This is a model for women, I think the main difference is strength and weight.  I think it is good enough for my weight.  I am relatively smaller than typical men.
　
   A difference between trekking poles and ski poles are the tip portion.
　

Tip portion for a skiing pole

   Tip portion for skiing is designed easy to stick surface of snow with metal tip.  It is also having larger ring not sinking into the snow.

Tip for a trekking pole

   On the other hand, trekking pole is using rubber material to get more friction on rocks.  The ling is smaller or nothing.  This model can replace the tip to a metal part to use on the snow.

Metal tip for replacement

   Some models, it is also possible to replace the ring to use for skiing.  However, I have different poles for each purpose.  The model i have, it is ok to use on a snow course in summer time.  But for skiing the ling is too small and sinking into the snow when I use them for skiing.  Also, the length on the tip portion is too short to use for skiing as well.
　The tip has many different shapes.  Some of them are bigger tip to get more friction and stable on rocks.

   As I mentioned, I was using poles for skiing in my previous hiking.  However, the stress to the big ring is big on summer trail.  Also, the friction might be smaller and not very stable.   However, the friction is not a big deal, just need to have some experience to adjust how we use it.

Advantage to use trekking poles

   Talking about advantage using trekking poles, the major advantage is helping to keep the balance.  Using poles, the chance to loose the balance is probably getting less, it is also easy to recover when people loose their balance with the poles.  In general, many people select boots to protect their ankles.  However if people using poles they may choose lighter pair and the selection is more flexible.  Especially having heavy backpack, people tend to pick really heavy boots for a better protection.   With the poles, they may pick liter boots.  Also, if they do not have heavy backpack, they may pick shoes instead of boots.  It is really depending on strength of legs, experience and skill to pick shoes / boots.  I would say with combination with trekking poles, the selection will be more flexible and easier for many people.

   In my case, my leg strength is getting weaker than when I was young.  It is really helpful to distribute weight with pole to reduce weight to legs.   That is the primary reason I started using poles.
   I think many people using a pair of pole on the both hand.  I guess it might be better to keep balance during hiking.   However, I personally do not like to occupy the both hands, therefore, I just using a single pole to help the balance.

Low cost models?

   By the way, when I am looking into listing on Amazon, there are many low cost models.   Most of time, I usually go to outdoor stores to see one I want to buy.  Therefore, I do not see many low cost model in the stores.  However, some of friends mentioned that there are many low cost models and I realize there are so many low cost models.
   For example, this model  is USD $36.99.  I have never used them and I cannot tell what they look.  Just based on the specification, its pair of weight is 1.1(lb).  One the other hand one I bought is 1.6(lb).  It is about a 0.25(lb) difference.   It is probably some difference for the material and strength.  I do not have any experience to use them, so this is just my speculation.   I guess it is not a big problem in most of cases.  Probably, it might be easy to broken or deform when they get unexpected force during hiking.  So this is really up to how people think and use them.

  Personally trekking poles are probably one of good equipment for middle age to older age hikers to minimize injury during the hiking.

Foot care ~ for Planter Fasciitis

Nano Foot Roller Massager

   I was very busy last week and I could not upload any posts last week.  Now, I have been training for full marathon to run a race again.   However, I have planter fasciitis on my right foot.  It is not really serious, but I still have a little pain especially in the morning.  I have been doing massage the foot after the training.   It was not getting worth, but the pain has not been going away.
   I got a new item to help the massage and I have been trying it.
　
   It is "Trigger Point Performance NANO Foot Roller Massager".  Putting a foot on it and roll it.  It seems that it helps.   Now I am using the stick I introduced in the previous post.   I think massage foot is probably most useful way to release the pain.   If you have some pain due to Planter Fasciities, I think it is worth to try it.

Garmin Vivosmart HR ~ Broadcast mode report

Heart rate plot for a long run on October 1 with broadcast mode

I just wrapped up ......
   In the previous posting, I wrapped up my test report.  However, I have an update about the broadcast mode today.   Actually, I tried to capture the comparison data yesterday.  I did wear the chest strap sensor with Forerunner 910XT and Vivosmart HR and started my training.  But the chest strap sensor did not work.  The root cause was "dead-battery".  I have been using for more than 3 years.   This is the first time to have dead-battery.  The battery life for the sensor is pretty good!!

What does the data look like?

   Regarding the data, I do not see anything new.  The data pattern is similar as other data I already captured.   The red circled portions might not be a correct reading based on the past experience.  So nothing special I can report in this post.

Broadcast mode report

   I have a few things to report about the broadcast mode.  First of all, when we set as HR broadcast mode, the display will be only heart rate.  We won't  be able to change any other display.  This means we won't log any activity and check even if it is just a time.  When I tried to change the display to swipe the touch screen, it just asks if I want to stop the broadcasting or not.  If I stop it, then we can change the display, but the broadcast should be stopped.  Basically Vivosmart HR just becomes a heart rate sensor.   In the background the daily tracking such as steps and heart rate is still keep tracking.  Therefore, after synchronize the data to Garmin Connect, I can see the daily heart rate graph even if it is in broadcast mode.  But no activity tracking, such as running, walking, cardio and etc.   This is a big disappointment for me and it is inconvenient.

   I am expecting to improve this near feature.  For example, if I hike and tracking the hiking activity with broadcast mode, then I won't be able to check time during it.  I guess I can accept no activity tracking but I really expect to switch the display data during broadcasting.

   The other thing I want to highlight is that there are some heart rate data missed during the training.  The heart rate data missed in a few samples sometimes.  It is very rarely happening with the chest based heart rate sensor.  It is not a big deal, but I can recognize it happens during the training at least a several times when I see the display on Forerunner 910XT.

   The setup is really easy and it is the same operation when I pair the regular chest based heart rate sensor.  This time it is unexpected event.  Even though I did setup within a several minutes in the beginning of the training.

   Except those two things, it is very good feature.   I hope the display function is improved with a firmware update in the near future.

Garmin Vivosmart HR (9) ~ Wrap up

 Vivosmart HR

Wrapping up Vivosmart HR

   I have been using Garmin Vivosmart HR about a half month.  Overall, this is a good one to keep tracking daily activity including heart rate 24/7.   The embedded wrist based heart rate sensor gives very similar reading as a chest strap heart rate sensor I have been using for a while.  The detail review is still on-going, however, overall it is reasonable to monitor the heart rate based on the past data I got with my usage, such as running, walking, hiking and cardio in a gym.  I probably keep using the chest strap sensor for running.  But it is probably good enough for hiking based on the result last 2 weeks.  Here is summary what I feel about this product. 

Battery life

   With my current usage, which is wearing the device almost all day with 30 minutes to 90 minutes workout with heart rate monitoring, the battery life with a single full charging is about 3 ~ 4 days.  So I probably need to charge the device twice a week.   I have not tried to use this device with activity tracking mode for very long time like all day yet.  However just check the heart rate, we do not have to use activity tracking mode.  Therefore, we will be able to use at least 3 ~ 4 days without charging again.  The heart rate sampling in non-activity tracking mode would not be so often.  However it is probably all right for managing the pace during a hiking I have been talked in this blog.

Sleep tracking

   This feature exists in the previous model “Vivosmart”, however, the auto-sleep detection feature is much better in Vivosmart HR.  For most of automated detection, I do not have to adjust it.  This is a big improvement from the previous model.

Display

   It is also improved from the previous model.  It is better even if under sun light.  Also, I think the operation is improved as well.  In the previous model, to enable the display, I need to tap the display.  Also to get a menu, I also need to hold the display.  In the new model, the basic display is always on and there is a dedicated button to get the menu.    The touch screen operation is also getting much better.  In my opinion, it is much better to use this device than the previous “Vivosmart” during hiking.  Although the heart rate trend graph is small, it is a good information to see the heart rate trend during hiking.

Activity tracking

   The menu is changed, there are categories, running, walking, cardio and others.  I do not know what is actually different between them.  At least running and walking, they are using different a step length to calculate the distance.  Also, there is no distance / pace information for cardio, only heart rate information shows up in the result.

   The big difference from the previous model is Vivosmart HR has embedded wrist based heart rate sensor.  Therefore, I do not have to wear the chest band based heart rate sensor to monitor during a training.  The detail evaluation is still on-going, but so far I am getting very good result for my usage, such as running, walking and hiking.   As I mention earlier, I would probably use the chest strap sensor for some training for running, but it is good enough for hiking and some “casual training”.   Especially some indoor activity which cannot be tracked with GPS, this is a good device for such purpose.

Floor climbing

   In the Garmin web site, a feature table shows there is “barometric altimeter”, however, it is not really “altimeter”.  The feature probably just using to find out “stair climbing”.   It shows some, however, it is not very useful for me.   So I disable this display.

24/7 Heart Rate Monitor

   This is a new feature.  For most of healthy people, they might not be interested in so much.  However, I am interested in this feature to see if there is any difference between the daily heart rate and high altitude environment, especially during sleep.  Actually, that is one of motivation I am evaluating the embedded wrist based heart rate sensor.  This would be an interesting data after the actual walking to see if there is any new finding and some sign for the altitude acclimatization.  Overall, the embedded heart rate sensor could be close enough to check this type of data.  So I will plan to capture some data in my next Mt. Whitney trip.

  Also, it is very easy to figure out the resting heart rate for the heart rate zone definition.  There are a few different method to define the heart rate zone for the heart rate based training.  One is using just the maximum heart rate with a percentage of the maximum heart rate.  The other is using reserved range which is defined by the resting heart rate and the maximum heart rate.  The second option would be a better way to define the heart rate zone in my opinion.  The Garmin device has another setup based on a lactate threshold.  However it is not easy to find out a person’s lactate threshold.  There are some devices which can estimate the lactate threshold value.  That would be another item I want to evaluate in the future with the other device. 

Wrist based heart rate sensor

   To measure heart rate during a workout, I used to use chest strap heart rate sensor during a workout.  I compare the measurement data between the two sensors how much gap we can see.  Based on my experiment, overall reading is close enough for typical running, walking, hiking and cardio in a gym.  The both sensors might have incorrect reading sometime.  I am not really sure why the incorrect reading happens.  I usually wear them almost the same way and the incorrect part is not the entire workout, it is usually just a part of workout only.  Once one of sensor reading becomes incorrect the offset between the sensors is getting bigger.  Based on the past data, the chest strap type sensor tends to be inaccurate in the beginning.  However, I saw sometime in the middle of a workout.  The wrist based sensor sometimes gets incorrect reading anytime or random, but usually the duration of incorrect reading is short, most of them are spike.   Overall, the chest based sensor gives us more stable reading comparing with the wrist based sensor.  It seems the chest strap sensor could be more accurate than the wrist based sensor in general and I probably continue to use the chest strap sensor for some point training for running.  But for a casual running, jogging, walking and hiking, I would use the wrist based sensor.  It is much easier for me not to wear the chest strap sensor for those activities.  Especially during hiking, without wearing the chest strap based sensor, I guess I would be much more comfortable in many cases.

   One item I have not done my testing is broadcasting the heart rate reading through ANT+.  Basically for the other device such as handy GPS device with map, a legacy GPS watch which requires an external heart rate sensors like my Forerunner 910, they can pair this Vivosmart HR and we can get the heart rate number instead of the chest strap sensor.  This feature is probably useful if people using a handy GPS device with map to log a hiking data.  This is one of good option to track heart rate and the location information during hiking.  I will plan to do some testing in the future. 

My conclusion

   Vivosmart HR is a good device to track daily activities.  It could be a good option to use for the heart rate based pacing I have been talking in my posting.  This device can broadcast the heart rate data to the other device through ANT+.  Therefore, we can track the locations and heart rate with those device.  It is a good option for hiking.  The battery life with some active tracking mode is something around 3~ 4 days.  So most of hiking can be covered.  The handy GPS device is usually using standard size of battery and it is easy to replace.  Thus, people do not have to worry about the battery life so much.   The high end running GPS device with longer battery life is usually very expensive just for hiking.  Unless people also do some serious running, it might be too much.  I am basically stick to Garmin due to the past data in Garmin Connect website, based on the recent product line, running GPS devices battery life is something around 12 hours for most of product.  They are probably not enough for most of people for a day trip to Mt. Whitney.  The round trip probably takes more than 12 hours for most of people.  So for those people, they probably need Forerunner 735 / Fenix 3 with the embedded wrist based heart rate monitor to cover a day trip hiking to Mt. Whitney.  People just need up to 10 hours a day, then they have more choice to pick low end models which is starting from around USD $200, such as Forerunner 35, 235, Vivoacitve HR and etc.  If people look for a low cost solution, Vivosmart HR could be a good option

Garmin Vivosmart HR (8) ~ Statistics for the offset

Statistics for offset between the chest based sensor and the wrist based sensor

Statistics for the offset

   Today, I show a statistics for the offset between the chest based heart rate sensor and the wrist based heart rate sensor.  This is based on the past half month data.  Since the number of samples for each data is different, using the percentage of the total samples for each data to compare them.   As you can see, more than 90
% samples are within less than 4.

   Then, I can look into the worst a few data.  The worst one is a data on September 14.

The worst data on September 14

  The orange is a data for Forerunner 910XT with the chest based heart rate sensor.  In the middle section, the chest bases sensor reading shows much higher value.   However, those reading is probably incorrect reading.   The heart rate should not be around 180 bpm in that section.  So I would assume the data read by Vivosmart HR could be close to the real value.   This means, the offset is due to wrong reading by Forerunner 910XT in this case.

   The second worst data is September 23.

The second worst data on September 23

   The blue is a data for Vivosmart HR with the wrist based heart rate sensor.  In the beginning, there are a several spikes on the reading by the Vivosmart HR.    For this data, I do not believe the reading value by Vivosmart is correct reading and the offset is due to this wrong reading.

The both sensors might have incorrect reading

   This data shows the both sensors have a chance to get incorrect reading.   However, I have no idea why it happens and where it happens.   For the both examples, they show a part of period gets larger offset and the other parts are matched well.   The offset is not due to a problem of the wrist based sensor.   As long as the both sensors read reasonable value, the trend would be close enough.   I am not sure if this offset due to how I wear the sensors or not.  But the bottom line is the both sensors might have incorrect reading.  So as long as, people recognize this, it should not be a big problem for general usage.  The data shows majority of samples are reasonably close each other.
   Please note, this data is collected for running / walking and cardio exercise.   For those type case, the wrist based sensor could be all right to use.   Actually, it is a benefit not wear the chest based sensor.

   I will continue to collect the both heart rate reading data during my training for a while.  To see this result is consistent or not.   Overall, the incorrect reading happens in different type of exercise.  It also happens in random.

Garmin Vivosmart HR (7) ~ Quantify the offset Part 2

Data on September 20, 2016

An example with a similar trend

   In the previous post, I showed a data with big offsets during some period.  This post shows a good data which has smaller offset.  The plot above shows the trend is almost the same between the chest band based heart rate sensor and the embedded wrist based heart rate sensor.  I applied the same method to calculate the offset and plot.  The following is the plot for the offset distribution.

 The offset distribution

   This plot shows majority of samples are in a group that the offset is within 2.   It is hard to tell if there is any difference on the first plat.   However, there is a portion the offset is bigger in the beginning where the heart rate value has a big transition.  The reason is not very clear with the data I have.  But it may be the following reasons:

• In many cases, the reading in the beginning of the training is not very accurate
• It is probably the offset is bigger when it has a big transition

   We might need more data to tell the clear reason.  I plan to correct more data and analyze them.
   It is clear that even if the heart rate trend looks a similar, but there are some big offsets.   It is hard to tell where the offset is coming from.   I guess it is worse to analyze the data more.

Actual amount of offset?

   Now, to check how much offset we need to consider to use data, here is another plot that indicates the amount of offset and total number of samples for each offset group.

 Distribution of samples for each offset amount

   The data shows more than 92% samples are less than 2 offset.  The other observation is that a section which has a big offset is only beginning, the rest of parts are really stable and matched.  Based on those indications, it is worth to evaluate to analyze the offsets to quantify the offset.
    Based on the data I posted last week, it seems that data for outdoor running has some bigger offset than the indoor training in a gym, such as elliptical, stair master and so on.

Other finding

   When I analyzed the data, I found out the sampling is not synchronized between the two devices.  Especially the data sampling rate between the two devices is not the same.   Even the same device in the different training log has some variation.  The overall sampling rate is something around 3 ~ 7 seconds.  But I have no idea how a device defines the rate.
   As an example, Vivosmart HR data on September 21 has every 4.1 seconds as an average, the minimum is 1 second and the maximum is  25 seconds.  On the other hand, Forerunner 910XT has every evey 4.2 seconds as an average, the minimum is 1 second, and the maximum is 10 seconds.  The entire training data is for 1 hour.  The total number of sampls for Vivosmart HR is 910 and 898 for Forerunner 910XT.

  In addition, the heart rate data for Vivosmart HR is 143 [bpm]  per minutes as an average, 76 [bpm] for minimum and 169 [bpm] for the maximum.  Forerunner 910XT, it shows the average heart rate is 146 [bpm] , the minimum is 80 [bpm] and the maximum is 168 [bpm].  I think they are close enough