High resting heart rate? It may not just reflect your fitness level, it’s a red flag for insulin resistance. This connects to metabolic issues, not laziness.
Insulin resistance revealed by your heart rate
High resting heart rate? It may not just reflect your fitness level, it’s a red flag for insulin resistance. This connects to metabolic issues, not laziness.
What is your resting heart rate ?
Heart rate is a number often associated with fitness, the idea being that the lower it is, the fitter you are. But is it really just about fitness?
Counting fitness
I would describe myself as being pretty fit. Fit enough to do a 50 minute STEP class without too much trouble. Don’t get me wrong, it’s not a walk in the park, but I hold my own.
My resting heart rate should be on the low side of normal.
For the record the normal range for an adult is 60-100 beats per minute. The exact number depends on your age, gender and “fitness”.
Athletes can go as lower than the 60 beat mark.
So where am I on this scale ?
Nowhere near 60 beats. Or 70 beats : my fit bit says I average 81 bpm. Yup ! That puts me at “Below Average” despite my gym activities. Ouch !
And it has been on the high side of normal, since I first actually noted it, which was in a first year university practical session.
A painful memory
Now if you’re going, OMG, you remembered this…..
Well yes, it caused me a great deal of anxiety and upset at the time, when I realized that my heart rate was significantly higher than my peers. At the time, I didn’t think I was any less fit than most of them, but this was not how the number was interpreted.
High heart rates belong to the UNFIT AND LAZY !
The heart rate myth
NO………….I just came across research that puts a completely different spin on the high heart rate story.
A high heart rate is a marker for insulin resistance, long before the rubber hits the road….
In search of clues
The study comes out of Sweden, motivated by the desire to PINPOINT insulin resistant individuals EARLY enough to intervene and course correct, the researchers enrolled 73 healthy young adults into their study. The only real exclusion factor was obesity and a close family member with diabetes. The individuals were normal young adults, a couple smoked, they all claimed to be active but none of them were especially sporty.
One morning, the participants arrived at the lab and got a metabolic work over which included snatching a tiny piece of thigh muscle. Ouch !
Below is the summary of their health markers, confirming that they were indeed HEALTHY. They weren’t fat, sugar and insulin levels were excellent and blood pressure was normal.
The muscle biopsy was teased apart and the muscle composition determined for each individual.
Muscle composition – what’s this ?
Muscles are composed of countless tiny fibers bundled together, much like threads in a rope. These fibers are like the building blocks of muscles, and different types of fibers have different abilities. Type I fibers are slower and red in color, designed for sustained effort, while type II fibers are faster and paler, built for explosive power.
Most muscles, contain a combination of both types, allowing them to handle a variety of activities.
The muscle behind insulin sensitivity
The team quantified the level of type I muscle fibers in their participants thigh muscle samples and then plotted this against their metabolic parameters, and this is where things got interesting.
Correlations relating to whole body insulin sensitivity (SIgalvin), muscle fiber composition and heart rate. © 2024 Blackwood et al
The level of type I muscle fiber tracked overall whole body insulin sensitivity, this is reflected by the r number. Now the slope of the line is not perfect, that r number suggests that 49% of the variability in insulin sensitivity is accounted for by the amount of type 1 muscle fibers in the thigh. 51 % of the variability is caused by other things…..
BUT type 1 muscle fiber type is definitely telling a lot more of the story than BMI.
When BMI is plotted against insulin sensitivity, it only accounts for 11 % of the variability…
Correlations relating to whole body insulin sensitivity (SIgalvin), muscle fiber composition and BMI. © 2024 Blackwood et al
Surprised ? I’m not surprised. About a third of people who are insulin resistant are not actually obese. And on the flip side, about a third of people who are obese are actually insulin sensitive. Learn more here.
So what does this have to do with heart rate ?
The heart rate insulin resistance connection
Well since figuring out whether someone’s muscle composition is not for the faint hearted, the team was interested in looking for more accessible markers.
So they used the results of the muscle biopsy to create two groupings.
- Group 1 was loaded up with people who had > 50 % type 1 muscle fibers.
- Group 2 was loaded up with people who were type 1 muscle fiber challenged i.e. their count came in below 40 %.
The people in between were BENCHED. They found heart rate was the swing factor. A high resting heart rate is a red flag for metabolic trouble.
Cut offs for heart rate
Which brings us back to what does your heart rate look like ?
Which side of the line are you ?
NOTE : Those numbers are all within the NORMAL range, but running on the “high” side of normal is not good spot to be in.
Can high heart rate be fixed ?
The standard advice would be GET MOVING. Will this “fix” the problem ? I don’t think it’s as easy as we’ve been led to believe.
Officially resting heart rate is determined by genetic influences and training status. This research adds to a body of work that suggests it is also influenced by insulin resistance.
Genes are not a leverage point
There is not a whole lot you can do about your genes, so this is not a lever you can pull.
Exercising will help……
A little, but it is NOT a magic bullet and the odds are stacked against you.
Muscle fiber numbers and types are set early on. Plus, if you have lower type I muscle fibers you’re probably going to have a hard time exercising, especially in the traditional sense of the word. Running marathons is NOT something you will be inherently good at and/or motivated to do.
Having said that YOU SHOULD EXERCISE !
Engaging in resistance exercise will be more do-able. The good news is, there is evidence exercise can nudge the fiber type in the RIGHT direction. You probably won’t get type 1 fibers per se, but you will get hybrid fibers.
Unfortunately, on the flip side, just simply being metabolically challenges puts type 1 muscle fibers AT RISK. Eish !
Type 1 muscle fiber magic
The research team did explore the molecular basis of the red fiber BENEFIT. It turns out red fibers produce more nitric oxide. Nitric oxide is a potent vasodilator so more nitric oxide helps with DELIVERIES of insulin, sugar and EVERYTHING ELSE.
Plan B
Fortunately, type 1 muscle fibers are not the only way to generate nitric oxide, this is biology, there are always more ways to skin a cat………..
Click here to discover 9 strategies that will help you if you are fibre 1 deprived.
NOTE : None of them involve exercise.
And if you need more personal support – I’ve got you. Sign up for a one-on-one health conversation or enroll in the BETTER BODY CHEMISTRY ACCELERATOR.
Further reading
Tots watching too much TV end up being muscle flops
And muscle flops ……. are on the road to a lifetime of weight troubles, because they hate to move.
Metabolic syndrome is not a fat thing, it’s a muscle thing
Teens with metabolic syndrome, that are not obese are slightly muscle deficient. Obese teens also have low muscle mass – suggesting metabolic syndrome is a muscle thing
Go on a diet even if you think you have nothing to lose
Not all type 2 diabetics are fat, for skinny diabetics this frequently constrains their options since advising them to lose weight seems impertinent, it’s NOT