Mad Physicist.

[jimboalee]

I made a claim within another thread in this category based upon experience gained during cold climate environmental testing of motorcars. Cold climate testing in both refrigeration chambers in the UK and ‘real world’ conditions in Canada.
The claim was ‘Heart rate does not significantly rise when the body is exposed to depressed ambient temperatures’.

In the manner of all ‘Mad scientists’, I conducted an experiment. Using my Polar FS1 and a pair of underpants, I firstly sat in my centrally heated living room for 30 minutes, observing my Resting Heart Rate. Then I moved outside to my garden bench for 30 minutes.


In scientific experimental language, the result was “No discernable difference”.

The things we scientists go through.

According to Paul Siple, an American Geographer on many Antarctic expeditions, the calorific expenditure of the human body has a calculable relationship with ambient air temp, wind speed and area of exposed naked skin.

Who am I to doubt the man who devised the term “Wind chill”?

With this knowledge, I deduce that my calorific expenditure on the garden bench was greater than that in my living room WITHOUT significant, if not NO difference in Resting Heart Rate.


My challenge quiz was to emphasise the non existant correlation between riding a bike and the amount of nutrition the cyclist actually consumes to replace the spent energy.
In my considered opinion, going to the extreme measures of having a HRM that tells kCals expenditure is meaningless in the real world.

 

[Steve Austin]

Has this study been published, and or peer reviewed?

 

[PrettyboyTim]

My challenge quiz was to emphasise the non existant correlation between riding a bike and the amount of nutrition the cyclist actually consumes to replace the spent energy.[/FONT]
In my considered opinion, going to the extreme measures of having a HRM that tells kCals expenditure is meaningless in the real world.

What has your experiment got to do with the calorific expediture of riding a bicycle?

 

[Fab Foodie]

See here...
http://www.cyclechat.co.uk/forums/showthread.php?t=22363


There's quite a few Scientists around these parts, what's you're scientific background jimboalee?

 

[jimboalee]

If you go riding any distance, 1 mile or 100, fully dressed for the weather, and you eat ALL the calories your HRM tells you to, you’ll probably put on weight.

Short rides of up to 1 hour don’t need any extra nutrition. Everyone has enough inside them to last 1 hour.
As the ride lengthens, the proportion of your HRM result increases until about 10 hours riding, you can eat the amount on the HRM screen IN ADDITION TO YOUR BMR.


My scientific qualifications were sufficient enough to get a job at SAGEM SA and for Peugeot Citroen to certify me to drive an emissions test in a cold chamber dynamometer cell at minus 35 Celsius.
For interest, the test is 40 minutes long, and the car warms up during the test. If the driver wears an arctic suit, it not only hinders pedal control, but we sweat buckets when the car is warmed and Citroen didn’t want an Englishman stinking up their expensive suits. So, we wore 'normal' clothes.
In order to get certified ( health and safety ) drivers needed to be aware of Paul Siple’s work, as well as artificial resuscitation and heart massage. It was a surprise to me when I was told that even at minus 35, the heart rate should not be much different from normal.

 

[Fiona N]

But - just to ask the obvious question - why should your resting HR rise in cold conditions?

(I'm a scientist too )

The HR will only rise if the control mechanism detects a shortage of oxygen (primarily) in some muscles or the brain. If we exclude the brain here on the basis that as you were still compos mentis then you probably weren't short of oxygen at the brain. So why should there be a shortage of oxygen in the muscles if you're resting? Keeping your core warm will use a bit more oxygen than under more temperate conditions. Likewise, a bit of shivering might be using a bit more oxygen than usual. But if the normal circulation is already supplying sufficient to avoid a shortfall, then there's no reason why the HR would increase. I suspect that your HR wouldn't rise until your shivering had become pretty violent so that muscle activity would create enough warmth to keep the temperature of the extremities up and reduce the amount of heat lost from the core (due to warm blood being pumped to cooler extremities). And this would start to deplete oxygen in those muscles and thus require greater circulation.

But I still think Siple is correct (although I thought it was Admiral Bryd who invented windchill and did the experiments in his solo sojourn in the Antarctic by recording the time it took for baked bean cans full of water to freeze at different windspeeds) in so far as increased heat loss from the body will require more energy to replace it if the core body temperature is to be maintained - but I have no idea what energy pathway is used for core heating although I assume it is aerobic.

Nice experiment though - I'm glad to see that I'm not the only HRM nerd about

 

[jimboalee]

My first HRM was back in the early - mid eighties. The wrist mounted unit was the size of a cigarette packet and the chestband transmitter clipped onto the chestband pads with press-studs.
It wasn't water resistant.

It was basic. It showed HR and had an upper and lower limit to set-up a zone.

I used it for street running and it bleeped when it hit the upper limit.
I strapped it onto my handlebars on a short length of Water pipe insulation.
I used it for about two months and then decided "My MAX heart rate is whatever the cycling conditions dictate".

I could slowly wind my way up a 13% and not have a Myocardial infarction, so what do I need this stupid HRM for?

I never use them now.


I have another queerie. I remember jumping off the side of a boat into the English channel ( water skiing ). I remember my heart pounded, increased its stroke volume, but cannot remember it racing.


For interest... The Chinese literal translation of 'Engine speed' is "Racing heart". Good old Beijing Jeep.

 

[Fab Foodie]

OK
This is interesting stuff.
Heat generation IIRC is either non-shivering by burning of fat in Brown adipose tissue (I've got the fat burning chemistry bit in an old dusty tome upstairs somewhere) or by shivering, rapid contraction of muscle pairs generating heat by friction. In both cases Oxygen is required to convert food fuel to heat. I think we agree on this bit.

Am I right in thinking the question then becomes whether in cold conditions, the amount of increased Oxygen required to keep warm is sufficient to cause a detectable rise in HR over resting at ambient conditions. If so I'm thinking that one of the issues here is that the body does other adaptive things to protect the core in cold conditions which somewhat complicates the issue (reduced blood flow to extremities, changes in blood pressure etc).

It's an interesting question... and now I want to know the answer.

 

[mickle]

Capillary dilation comes into it I expect. And if you have a hairy back.

 

[alp1950]

But - just to ask the obvious question - why should your resting HR rise in cold conditions?

You guys ask some difficult questions. In general, the heart rate tends to fall in response to cold temperatures, however various factors can influence the response and in fact studies show that it may also rise, or stay the same.

In extreme cold the heart rate slows to a very slow rate, and may stop altogether in hypothermia or when the heart is cooled for cardiac surgery. In less extreme conditions, one of the first responses to cold is that the superficial blood vessels constrict, forcing blood away from the skin into the central vessels. The increase in blood pressure that results is sensed by the baroreceptors which in turn activates reflexes that slow the heart. However shivering causes a major increase in muscle metabolism (and metabolic rate) and this inevitably will increase the heart rate in order to increase oxygen delivery to the tissues.

It will get even more complicated when you consider the effects of adrenaline, noradrenaline, the HR response in athletes versus untrained, the HR response to exercise at different ambient temperatures, the diving reflex, longterm adaptive responses to cold.... and that's even before we've started to consider the effect of ambient temperature on metabolic rate which if I remember correctly is where this thread all started..

 

[jimboalee]

Cheers alp1950.

I've read the basics. How to expect a trauma victim to behave in reduced ambient temperature.

"Is there a Doctor in the house?"

I can only report my own findings on research using some fool as a study volunteer. Now where did that fool go......? Ah, he's on CycleChat again.

 

[Dave5N]

1 - why here?

2- I felt bloody cold reading this stuff, partly because I couldn't see the point.

 

[jimboalee]

If you'd care to knock both your brain cells together, you might realise this is the 'Health and Fitness' category, where we discuss nutrition, anatomy and physiology.

In future, if you haven't got anything constructive to say, STFU.

 

[Dave5N]

Mornin'!

STFU - not sure if that's polite?

 

[jimboalee]

I have taken a few minutes before work this morning to analyse the Garmin Edge history from yeaterday's 25 miler.

1hr 30. 16.6 mph average.
9 deg C. Gentle breeze.
HRM in use. Didn't notice any untoward excursions.

Didn't wear my long trousers and Efficiency worked out to 21%. 1030 kCals.
Enter in my calcs 'Longs?' YES, efficiency would have been 29%. 730 kCals.


Whice only goes to prove :-

1/ For fat loss, wear less.
2/ For endurance, wear sensible clothes to cover up nakedness.
3/ HRM doesn't appear to correlate.
4/ Put HRM on e-bay.