View Full Version : Heart rate during weight training--smaller muscles=>faster rate
09-12-2010, 10:01 AM
I have a heart rate monitor that I have used when doing aerobic exercise. A couple of days ago, I tried it while I was doing my weight training. I do a whole-body routine, and start my routine with legs and work my way through descending muscle size. I noticed that my heart rate was lower for the heavier weights and bigger muscles, and got higher through my routine. For example, immediately after a leg extension it was around 102 and after biceps curls was over 120.
I am trying to figure out why my heart rate would be lower when lifting heavier weights with larger muscles. Is this because the heart rate is getting higher just come continued exercise, regardless of the weight, or is there something more interesting going on?
09-12-2010, 10:11 AM
Are you sure your heart rate isn't just going up over time as you gradually build up exertion? Try doing your routine backwards and see what happens.
09-12-2010, 11:19 AM
The bigger the muscle the more oxygen you use. This is why the thigh muscle can quickly leave you breathless.
Where is your heart rate monitor? Is it a wrist monitor? Or does it go around your chest? The wrist monitors are much less accurate.
My guess is with bicep curls your lifting too light a weight in proportion to your leg extension. That way you're going faster rising your heart rate.
If you are curling 10 pounds quickly your heart rate should be greater than if you're lifting 100 pounds with your legs slowly.
09-12-2010, 11:32 AM
For the particular examples I gave, I was using a LifeFitness leg extension (http://www.lifefitness.com/commercial/lfstrength/SignatureSeriesSingleStations/lowerbody/legextension.html) at 145 lbs, hitting about 11 reps, and for the biceps curls I was doing a seated curl with two dumbbells, 32.5 pounds each (both at the same time, not alternating), at 8-9 reps.
The heart rate monitor uses a chest strap to pick up the heart rate, and a wristwatch to display it. I have checked it out vs. taking my pulse manually and it seems very accurate.
09-12-2010, 01:50 PM
I expect you will find that with so few reps that much of your leg exercise was anaerobic, and your capacity for anaerobic exercise using your legs is much greater than for anaerobic exercise with your arms - due to muscle bulk and the ability of muscles to store glycogen.
The smaller the muscles, the sooner you would need to go into aerobic operation, and the sooner that this will show up on breathing and pulse rate.
As soon as you start aerobic movement with the large muscle groups you'll find your pulse rate rises very rapidly, and you will also find a rapid rise in temperature - and so this will give rise to sweating.
How about increasing your reps and reducing the weight, and working for longer period? I bet your pulse will rise much more on the heavier muscle groups - instead of being repetition bound training, try do go for number of reps within a given period of time, try out maybe 5 minutes of repeats - in other words you are going for rate rather than repetitions.
This type of circuit training is very useful developing power rather than strength. The idea is to set a time, find the number of repeats you can do with a certain weight, and then train to improve that number.
For example, half squats - do it with 30 pounds for 5 minutes - see what you can achieve, rest, rinse and repeat until your performance drops below 80% of that number.I expect a reasonably fit person to be able to handle 150 to 200 repeats of such an exercise.
Once you can keep to within 80% across 3 circuits, add another 10 pounds.
You can do this across other muscle groups, adjusting weights and times according to the particular muscle group.
I have seen this done using recovery times instead of numbers of repetitions, in this case you work out you maximum aerobic pulse rate, and exercise to around 90% of that. You then rest until you recover to around 50% of maximum and go at it again, and you stop when it takes more than 5 minutes to recover to 50%.
There are many variations of this, such as increasing weight whilst decreasing the number of repetitions, to reaching a point where you go up to being only able to do 10 repeats, and then you work your way back down again in weight, and up again in repetitions.
Rowers and cyclists have equipment available - though very expensive - that can directly measure power output, which is a much more objective measure of performance, other sportspersons have the means to make such calculations - such as swimmers but its very much more complex.
This sort of training lends itself very well to charts and measurement, you can schedule your performance much better, work out how to break up the training better so you concentrate on differant muscle groups on differant days - but you will not end up with the huge bodybuilder type physique - its much more suited to athletes
09-13-2010, 02:40 PM
I checked with a swimming coach on my facts, turns out I was pretty close, I got my substances wrong, glycogen should have been replaced with ATP.
For a brief outline, try this
Anaerobic exercise depends upon the amount of stored glucose, the larger the muscle group, the more is stored and so the greater the work capacity under anaerobic conditions.
You arms will quickly resort to aerobic activity and you will feel this in breathing and pulse rate, but your body is capable of supporting this for a long time.
Your legs will last a little longer on anaerobic activity, but once the aerobic activity kicks in, you will need far more oxygen as the larger muscle groups demand more support.
What it boils down to is this, if you want to improve cardiovascular fitness, you need to move the large muscles for longer periods of time.
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