Should I sit or should I bend?

March 25, 2005 10:04 AM

I have a mountain bike on a resistance roller that I use to workout, and I also use a heart rate monitor to keep my heart rate at 145. If I workout in a cycling position with my hands on the handlebars, it takes much more effort to maintain 145 than if I sit upright with my hands by my side. Why is this, and does this mean my upright workout is less effective than my bent over one, even though I'm maintaining the same heart rate?
posted by forallmankind to health & fitness (13 comments total)

You're probably able to take deeper breaths when sitting upright than when your torso is crunched into the cycling position.
posted by skwm at 10:17 AM on March 25, 2005

what do you mean by "less effective" and "more effort"? do you have some measure of the speed/resistance, or does it just "feel" harder? do you want to get better at cycling, or just burn calories?
posted by andrew cooke at 10:22 AM on March 25, 2005

It just feels harder - increased breathing rate and sweat production.
I guess from the literature I'd read, I'd formulated the assumption that working out at 145 was I good way to just maintain fitness. But now I have the option of harder 145 bent over or easier 145 sitting upright, I'm rather considering myself a lazy sod for taking the path of least resistance....
posted by forallmankind at 10:45 AM on March 25, 2005

If you're riding at a 145 bpm, do you find you are sustaining a lower speed in the crouch? (If you don't have a speedometer hooked up, you can count cadence.)

It wouldn't surprise me too much if this were true, although A) when actually moving, aerodynamics would more than negate the breathing advantage; B) sitting with all your weight on your butt would probably get to be a problem pretty quickly. Even if you could steer and brake.
posted by adamrice at 11:05 AM on March 25, 2005

my guess would be that your position on the bike is messed up. you should take the bike down to your local shop and have someone who knows fit you to the bike. any good shop should be able to do this for you. the shop where you bought your bike should do it for free if they didnt provide such a fitting at the time of purchase. others will likely have a minimal change for the service. but an improperly sized, fitted bike is a pain, and less efficient, for anyone to ride.
posted by RockyChrysler at 11:50 AM on March 25, 2005

You are getting your heart rate to your target regardless of position. You are getting more air when you are sitting upright., and it sounds like the bike doesn't fit all that well. You might be a little too stretched out when you are reaching for the bars, not the most efficient position.
posted by fixedgear at 12:10 PM on March 25, 2005

if you're aiming to burn calories then your best simple way to measure that is probably the speed of the roller (assuming you keep resistance fixed). most of your energy is going into that, and energy is calories.

in other words, it doesn't matter how you feel, what matters is how fast your feet are moving. if they're going round at the same rate in both positions (when at 145 bpm) then it "just" feels worse with your hands on the handlebars.

alternatively, if the speed of the rollers drops when you go down onto the handlebars (even though you stay at 145bpm) then your heart rate is going up for reasons unrelated to the amount of energy you're burning. most likely you're not breathing enough and your heart is ramping up in an attempt to compensate. in which case using bpm as a guide to burning calories is not reliable.
posted by andrew cooke at 12:28 PM on March 25, 2005

hmmm. if i have that right, then bending over will either burn the same calories or less. so either way, you are doing nothing wrong by sitting upright (from a burning calories point of view).
posted by andrew cooke at 12:30 PM on March 25, 2005

From my experience it feels easier when you are sitting straight up because of 2 reasons.

a) Like was said above; you are able to breath better because you are not compressing your chest.

b) The angle between you body and your legs is "better". Try sitting in your chair and bringing your knees up to your chest, a lot of effort, which is essentially what you are doing when you lean on the handlebars of your bike.
posted by Sonic_Molson at 12:31 PM on March 25, 2005

Here's something else to consider. The filling pressure of the heart is only about 7 mm Hg. That is the pressure in the veins at the point where the vena cava meets the heart. In an upright heart, the filling is from the top, so that the heart expands under the weight of the filling blood. (Remember, the heart is basically surrounded by lungs, which have the density of shaving cream.

If you are keeping your torso horizontal, then the filling is not nearly so efficient, meaning that each stroke sends less volume. The whole system is less efficient. Since this "starves" the muscles of O2 and less effectively clears CO2, the muscles feel like they must do a lot more work for a given energy output.
posted by RMALCOLM at 1:32 PM on March 25, 2005

I think the physiology is that, for a given energy production by your leg muscles, your heart has to send a certain amount of oxygenated blood to power your leg muscles. Your body can increase its blood output in two ways:

a) it can increase the heart rate (beats per minute)

or

b) it can increase the stroke volume (amount of blood pumped with each beat)

The heart rate is controlled (to a first approximation) by adrenaline production.

The stroke volume is controlled by how much blood fills your heart while it is relaxed between beats. The amount of blood that fills the heart is increased by muscular activity of your legs that helps to pump blood out of the muscles into the circulation, by contraction of the big veins in your legs, abdomen and chest, by the decrease in intrathoracic pressure associated with deep breathing and, importantly in this case, by your position.

Imagine you're standing upright: your blood would tend to be pulled by gravity down into your legs. Imagine you're lying flat on the ground: your blood would tend to be evenly distributed through out your body.

So, when you are cycling with your hands on the bars more blood is filling the heart than when you are sitting upright, so your heart can pump the same amount of blood at a slower rate. The flip side of this is that if you keep your heart rate constant when you change position you will pump out less blood sitting upright, and you will be doing less work with your legs.

So the answer is that your upright workout is less effective.
posted by v-tach at 6:16 PM on March 25, 2005

You have discovered something that most riders know, that sitting upright is less efficient, not just for air resistance, than leaning over. When you lean over your bpm goes down because you are more efficient.

You should balance yourself on the tripod of your hands, feet and seat, each with about equal weight. As you pedal harder your feet take more weight and you need to lean forward more to transfer weight to your hands. A pretty good forward crouch is efficient for your legs, but less so for your lungs. On the road the air resistance says stay in the crouch, but on the trainer a little more upright position is most efficient, although that position is still probably more forward than your average coffee shop rider would ever assume.
posted by caddis at 7:31 PM on March 25, 2005

Perhaps you need more effort when leaning forward because you are using more body muscles to maintain the position - arms shoulders upperback.

This in turn requires more overall oxygen which you supply by increased breathing = more effort. If your breathing stayed the same no doubt your HR would increase.

I'd guess that sitting forward and maintaining the 145 is better for you physiologically speaking because you are working out more muscles (comparatively) and this in turn would lead to an increased metabolic rate and greater weight loss (should that be the goal).
posted by peacay at 11:29 PM on March 25, 2005