High Exercising HR Varies During Spinning

[Samantha_cass]

I have recently started getting back in shape again, spinning the last 5.5 weeks around 5-6 days a week, for a total of about 3-5 hours per week. I am 133 lbs, 38 year old female. I have noticed sometimes although my body doesn't seem to reflect it, my spin bike's watch (Bowflex comes with their own hr watch to wear during rides) my hr can go as high as 160. It has only happened twice, the first time my fitbit was calculating 20 beats lower, and today they were within a beat or two. It had me at 163. 

My question is why after almost 6 weeks of riding and having done the same class 10x would my hr get so high so easily? Shouldn't I have to work to where I feel extremely out of breath for that? I did feel like I was able to add more resistance this time which is the only thing that was different, but it wasn't beyond hard, instead of burning 8 calories per minute it said 10. Once I saw I was creeping into the 160's I eased off, this was 13 minutes into the ride. I usually ride around 145-150 bmp. I had a rest day yesterday with no exercise. 

[t.parker]

@Samantha_cass I'm curious why are you assuming 160bpm is high? When you see 160bpm how does it feel? Easy, moderate, can you breathe normal (or almost normal)? What kind of effort is it when you see 160bpm? Working out when you feel extremely out of breath (all-out), with maximum effort is a normal element of training. You have workouts when you go easy/moderate, developing an aerobic base but also you have interval workouts when you're supposed to go all out and work at anaerobic/neuromuscular capacity. Don't focus too much on HR but rather learn what HR is relative to different levels of effort. You should go for all ranges of effort in your workouts.

On the bike, you'll have easy aerobic effort (long rides), tempo effort (racing), aerobic/neuromuscular (short bursts of effort for example uphills etc.). The effort during indoor rides can be controlled by factors like resistance and cadence. Increasing cadence will increase your HR more significantly than increasing the resistance and keeping cadence low (like a tough uphill ride). The stance (standing/sitting) will affect HR, too. A different combination of all those elements will trigger a slightly different response of your body. I know how it works for me, for you it may differ - this is something you have to learn empirically. If your bike comes with a power meter (I think ie. Bowflex C6 has a power meter) then find your FTP and train with power rather than HR. 

My HR could be considered high, too if I thought 160bpm is high 🙂 If I limited myself, I'd probably never progressed. My last week 5K Parkrun race (all-out effort) ended with an average HR of 178bpm and max HR 189bpm. If limited my HR to 160bpm I would need to slow down my pace by almost 2 minutes per km. The respiratory rate went up to 41brpm which means that I couldn't probably recite a poem but still was able to deliver enough oxygen to keep it going. My Monday run on the other hand was a tempo/threshold run for which average HR was 167bpm (current threshold at 173bpm). Not all out, more like racing effort for half-marathon+ distances. I can run easy (base aerobic) and my HR still will get to 150-155bpm. I don't consider it high but I know where's my limit (max and min HR). And limits are not fixed 😉

[Samantha_cass]

My 90-100% max for my age is 164-182 and I was one away.  With having POTS I have had to pay special attention to my heart rate, for example a shower will prompt my hr going from 80 to 135. This usually doesn't affect exercise as the blood is circulating but as a habit pay very close attention. I also lost a family member (not blood related) to a heart attack at 59 with no warning so I am very cautious to not exceed my body's maximum. I know it's good to work out and get to a point of rapid breathing etc as spin and exercise I am very familiar with, but what I was trying to say was I wasn't at that max heavy exertion level and I had reached 160+. I'm confused why sometimes my heart rate can be so high when I have not worked out to the point of max exertion, and others my hr is the usual 145-150 but no change in activity level. I hope that makes sense!

[t.parker]

@Samantha_cass you haven't mentioned POTS so I assumed you're rather healthy. Mind that your max HR doesn't depend on age that much. The formula 220-age is outdated. My max HR should be 180 and yet it is 189.

"I was trying to say was I wasn't at that max heavy exertion level and I had reached 160+" - this probably means that it's nowhere near your max HR (and possibly 182 isn't your max) but since you have a condition I won't place my bet on it. That's something to ask of a cardiologist not people on forum 🙂

[Samantha_cass]

I was explaining why I watch my heart rate so closely. I was not hoping for a diagnosis but rather someone else's experience on whether this happens to them or not. I was looking to learn. I guess maybe I can't do that on a forum. 🙂 

[t.parker]

@Samantha_cass so my experience is that it happens to me and it's normal (I'm 40, fit, RHR: 39bpm, MaxHR: 189bpm, LT: 173bpm). It's normal for me and for many other healthy individuals, too. It's mostly driven by two things: a) genetics, b) training. People who have a high lactate threshold (this is a kind of "border" HR between aerobic and anaerobic effort) often see such a pattern in heart behaviour. A high lactate threshold usually means that the maximum HR is also quite high (again, forget about 220-age). Using myself as an example, my HR goes up to higher values quite quickly. My base aerobic effort (very easy runs, very easy cycling) it's up to 152bpm. A comfortable effort is slightly above 160bpm (tempo) and this is what I usually get during "untargeted" workouts. As "untargeted" I mean that I don't look at any metrics but judge my effort by how it feels. As I said, I'm healthy, with no heart condition, all thoroughly checked. However, for a person with a heart-related condition, it may go either way.

[charleskn]

@Samantha_cass, there is a lot of good information here from @t.parker.

Given you have POTS, of which I am unfamiliar with the details, I do have a suggestion. When I started experiencing AFIB during my workouts, I became much more interested in what my heart rate was doing during my workouts. 

First, keep in mind that optical heart rate monitors (HRMs) have limitations, and especially when worn on the wrist, over bone. Other factors, such as tattoos and skin tone can affect basic optical HRMs. I like my Fitbit as it has some other nice benefits and features, but it is certainly not a medical device, and I find the heart rate monitoring to be hit or miss. It's good enough for most folks to give a general idea.

A chest strap HRM uses electrodes to very accurately measure your heart rate. For myself, I didn't want chest strap, and went with an optical monitor that I wear on my upper arm, or forearm. This has proven to be quite accurate and reliable, and I am often surprised how different the Fitbit HR readings are. Especially for certain exercises. There are a number of options available. The Quantified Scientist (YouTube) does excellent reviews of fitness devices.

I use a Polar optical armband, which allows me to monitor my HR live on my mobile device while I am doing my cardio routines. I believe there is even a way to receive audio cues about your HR, from some apps.

Also, I have a Kardia 6L which can detect Afib, and will record a 30 second 6 lead EKG, which I can email to my doctor.

Below are the HR plots from my Fibit and my second monitor for the same rowing session.

Good luck 🙂

[emili]

Unless you are wearing a chest strap, the HR function isn't 100%, especially during aerobic activities. I also generally go by how I feel over the number. There are days when 130 HR has me tired and sweaty and others where 190 is a pleasant burn. I am 51, 135 pounds and when I ran my HR was anywhere between 170-192. Occasionally it would spike over 200 and I chalked it up to booze/salt the night before or an inaccurate reading. Cheers to your continued heath adventures!