Running in heat and high humidity

[SunsetRunner]

Do any runners out there have any feel for the increase in the level of exertion when running on wet sand in the tropics? I am a new runner, but very comfortable with 5k distances. When on holiday in Mexico it was a delight running barefoot on the packed sand, but I struggled to get past what I estimated was 2.5 miles without slacking. I wasn't getting overheated, was adequately hydrated, and wearing just very light swimwear - not dork shorts.

What sort of "offset" do those conditions create for running?

Thanks!

[wilcoxunlimited]

Yep, It is even harder than in simple rough terrain. Without being a scientist, i observed the following when running on the beach:

1. Depending on wind coming from the land or fron the sea, the differences were more than 30 seconds every 5 minutes.

2. Temperatures over 34 deg C and an air pressure over 1032Hpa just slowed me down.

[Heybales]

Depending on your running style, a huge amount of your forward energy is spent pushing and moving the sand, rather than moving forward.

The smaller the concentrated force, the worse the effect. So learning to take off and get max forward movement with almost whole foot on sand is better than the normal raising and push off on the small little forefoot area.

[Algenon]

From what I understand your heart rate increases but not the amount of calories.  You actually burn more calories in cold temperatures because your body shivers(This is why people who go to arctic have to eat more).   In the humid weather, the air moisture makes it harder for sweat to evaporate from our bodies. This is why you feel like you need a shower on a humid day because the sweat does not  evaporate. It doesn't mean we burned more calories.  You should always look at hard you are working out.  I would also use a heart rate monitor as well as a calorie counter to help figure this out.  If it is humid, you should drink a lot to replace the fluids your body as lost.  

[Heybales]

Running in heat would indeed cause elevated HR not related to the workload.

So normally a HR of say 150 for running 7 mph, becomes 160 doing the same speed.

Increased blood flow to help with cooling.

Go 1 hr without drinking in that heat, it now becomes 170, because blood is thicker and harder to pump the required level of oxygen around. Biggest reason for cardiac drift for sustained efforts.

HRM in those conditions is going to give inflated readings for calorie burn for the 160 and 170.

It's the one downfall to using HR zone training on longer endurance efforts, because you'll be slowing down to keep HR low, but not because you really need to. Though if that hot, usually pretty useful.

But I recall the energy wasted pushing in to the sand was enormous compared to the heat, but heat and trying to keep pace just made it worse.

[wilcoxunlimited]

After a beach run @ 6am. I could not blame the heat (only 30 deg C), or humidity 65%, so the next morning run i removed my shoes.  Guess what? it went simply a bit faster, a bit less draining my energy levels on the same distance. the only thing i have not measured is different windspeed, but that is usually very low in the morning.