Health & fitness

Package: HEALTH_PACKAGE. Registered by createEngine(); for a slimmer engine, register it explicitly (see choosing packages).

A few everyday health and fitness sums. They are written as functions, with the numbers in the units the labels state, or with units of your own, which are converted (see measurements with units).

Body mass index

bmi(weight, height) is the body mass index, weight in kilograms over height in metres squared, the standard rough measure of build.

bmi(70, 1.75) // 22.86

Pace and speed

For a run or a ride, pace and speed are the two ways of reading the same effort: pace is the time to cover one kilometre (minutes and seconds), and speed is the distance covered in an hour. Both take the distance in kilometres and the time in minutes.

pace(10, 50) // 5:00 /km
speed(10, 50) // 12.00 km/h
pace(21.1, 100) // 4:44 /km

The last line is a half marathon (21.1 km) in one hour forty, a pace of four minutes and forty-four seconds per kilometre.

Measurements with units

Each function can also be given its measurements with their units, in whatever units you have them: a weight in pounds or stones, a height in centimetres or in feet and inches, a distance in miles, a time in hours. Each one is converted into the unit the function works in before the sum is done, so the answer is the same as for the plain numbers in kilograms, metres, kilometres and minutes.

bmi(70 kg, 175 cm) // 22.86
bmi(154 lb, 5 ft 9 in) // 22.74
speed(10 km, 1 h) // 10.00 km/h
speed(26.2 mi, 3.5 h) // 12.05 km/h
pace(10 mi, 80 min) // 4:58 /km

A pace is still given per kilometre when the distance is in miles; pace(10 mi, 80 min) is ten miles at four minutes fifty-eight a kilometre. A measurement of the wrong kind, a height given in kilograms or a time in metres, is refused rather than read as a number, and so is a negative weight, height, distance or time.

bmi(175 cm, 70 kg) // bmi: the weight is a mass, not a length. Give it with a unit (70 kg or 154 lb) or as a plain number of kilograms.
bmi(70 kg, -175 cm) // bmi: the height cannot be negative.

A plain number keeps the unit the function states, so speed(10, 1) is ten kilometres in one minute, 600.00 km/h.

Writing a pace directly

A pace can also be written the way it appears on a watch, as minutes and seconds over a distance. It is an ordinary quantity once written, so it converts and it multiplies out.

4:30/km // 4:30 /km
4:30/km in min/mi // 7:15 /mi
10 km at 4:30/km as laptime // 00:45:00
42.2 km at 4:30/km as laptime // 03:09:54

The last line is a marathon at four and a half minutes a kilometre, three hours nine minutes and fifty-four seconds.

as laptime writes any length of time the way a stopwatch does, hours, minutes and seconds with colons, and as lap is the shorter spelling:

10 km at 4:30/km as lap // 00:45:00
90 minutes as lap // 01:30:00

The minute unit may be written too, as it is in a converted pace, and per reads as the slash does:

5:30 min/km // 5:30 /km
5:30 min per km // 5:30 /km
10 km at 5:30 min/km // 3,300 seconds

Only a minute unit is read this way, since minutes and seconds are what the two parts of a pace are. 5:30 h/km is not a pace, and neither is a clock time with any other unit after it: it names a moment, so it is refused.

4m30s/km says the same thing and always did; the two are the same quantity and display alike. An hour or more per unit shows the hours:

1:30:00/km // 1:30:00 /km

What makes it a pace

The distance does. A pace is a time over a length, so the unit after the slash is what decides, and that is what keeps every other reading of a clock literal intact: 4:30 on its own is still half past four in the morning, 8:15 + 7:45 is still a duration (sixteen hours, shown as 960 minutes), and 90 km/h is a speed rather than a pace because it is a distance over a time.

The boundary is a pace faster than a minute per unit. A clock shows whole seconds, and rounding one that fast would change the number, so it keeps its digits: a swim written 1:30/100m reads as 0.90 seconds/m, because the denominator reduces to a single metre.