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Go to Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status and plug in your numbers. (HT: Dr. Michael Eades.) You’d want to multiply the time by 5 to get 5,000 IU instead of merely 1,000 IU.

The creator of the calculator says:

Method outline (see the journal article above for details)

FastRT was used to compute erythema [MacKinley and Diffey, 1987] and vitamin D effective [MacLaughlin et al., 1982] UV doses. The former were expressed in standard erythemal units (SED = 100 Jm-2 erythemally effective UV, which for skin type I = half Minimal Erythemal Dose, MED). The latter were computed using the action spectrum for conversion of 7-DHC to previtamin D in human skin [MacLaughlin et al., 1982] with an exponential decay extrapolation. We then defined a Standard Vitamin D Dose (SDD) corresponding to the UV equivalent of an oral dose of 1000 IU vitamin D [Holick 2004c] i.e. the dose recommended to gain all the possible health benefits of vitamin D [Holick, 2004a]. Since radiation is incident on the skin, and the response to either irradiation or oral dosing is measured in the blood, the SDD must be qualified by the conditions of skin exposure. Following the formula of Holick [2004a] that recommends exposure to a quarter of a personal MED on a quarter of the skin area (hands, face and arms), we calculated the equivalent D effective UV. We calculated UV doses for a mid-latitude midday in spring (Boston, 21 March, 42.2 degrees N, ozone = 350DU) when it is known that vitamin D can be synthesised in the skin. This latter assumption is based on the work of Webb et al. (1988) who showed that from November to February there was insufficient solar UVB to synthesise vitamin D in Boston, but by March previtamin D was formed from 7-DHC in both solution and the skin. From this we calculated the time to acquire a quarter MED (= half SED for a fair skinned person). Using the same solar exposure we then calculated the vitamin D effective dose acquired over the same time interval. This is then the SDD based on exposure of a quarter body surface area, and is equivalent to 37.2 Jm-2 vitamin D effective UV for the cloudless conditions above, corresponding to about 16 minutes of exposure at solar noon. A fair skinned person exposing hands, face and arms (ca. 25% of the body) would now make sufficient vitamin D with 1 SDD, and will suffer a minimal erythema after 1 MED (2 SED), which by definition is 4 times the SDD exposure in these reference conditions (i.e. Boston, 21 March, 42.2 degrees N, ozone = 350 DU). Darker skinned people will require both multiple SDDs and a greater number of SEDs to achieve the same effects.

Copyright © 2006 Ola Engelsen

The author also says:

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How’s your heart rate? I checked mine today after exercising. I got this:
1. Heart rate at 4:30 PM, right after exercising for 45 minutes: 152 bpm.
2. At 4:45 PM, after also doing 150 sit-ups and showering: 92 bpm.
3. At 5:40 PM, after reading while standing up: 68 bpm.
4. At 9:15 PM, after finally finishing eating (a process than can go on for an hour or two): 58 bpm.

My exercise routine today was (with 100 = go 50 yds, make it around a bench/tree, go back):
1. Jog 100, walk 50, jog 100, walk 50, sprint 100, walk 100, sprint 100, walk 100.
2. 10 sets of walking up and down a flight of about 15 steps, straight-arming a 35 lb kettlebell; did some single steps, double steps, single arm, both arms.
3. Did 2 or 3 sets hopping up a step or two at a time while straight-arming the kettlebell (both arms).
4. Played with a kettlebell: swings, clean and jerks, this-and-that.

All done in a Houston summer. Weather records say at 4 PM it was 92 deg F, 46% rel humidity, 29.96 mm Hg. My eyes say it was overcast. This is pretty good as far as Houston goes!

My heart rate after dinner probably would have been higher if I had eaten flour and sugar products — which I assiduously avoid.

Update (8-27-09, 8:00 AM):  My heart rate was 50 bpm just a minute ago (after being up for an hour).