How to determine your 'critical speed'

If you want to race to your full potential, it is helpful to determine your critical speed. On paper, the athlete with the fastest overall critical speed in three events will most likely be the victor.

Critical speed (CS) represents your race pace for any endurance event lasting between 30 and 60 minutes. It applies perfectly for those triathletes competing in the Olympic distance triathlon. However, long-course athletes can benefit as well.

CS becomes an important tool in determining fitness level and different training intensities and in predicting performance in all triathlon distances, as well as single race events. It can also provide realistic targets during the racing season and become a tool with which to evaluate your performance after each race.

Determining your CS is much easier than pinpointing your anaerobic or lactate threshold. No expensive laboratory testing or analyzers are required. We look to mathematics and good old-fashioned time trials to determine CS. You must complete two time trials (TT) each in the disciplines of swimming, biking and running.

The TT distances should be chosen carefully, as they must represent the duration of approximately three minutes (plus or minus 30 seconds) and 17 minutes (plus or minus two minutes). These are maximal efforts, so proper warm-up and preparation is necessary. The six TTs should be done within a four- to five-day period.

Time trials

I recommend the following time-trial distances and methodology for most triathletes. I have given sample results for later comparisons and applications. In my research and example, the bike time trials were done on a wind trainer, where the resistance was slightly more difficult than on the actual road, and the run time trials were done on a 453.5-meter indoor track.

4K run
Example result: 13:12

A.M.: 10K bike
Example result: 15:30
P.M.: 200m swim
Example result: 2:56

A.M.: 1K swim
Example result: 15:23
P.M.: 1K run
Example result: 2:56

2.5K bike
Example result: 3:15

Optional or recovery

Conducting the time trials

All time trials are at maximal effort or best-effort pace. The swim time trials are very straight-forward with minimal environmental variances. A pool setting is best, but make sure to swim at the same pool and same setup (25 meters vs. 50 meters). If you test without a wetsuit, your CS will apply to that condition. If you want to predict your wetsuit race performance, make sure to do the time trials in a wetsuit.

The easiest method of determining your bike CS is by using a trainer. The CompuTrainer works best, followed by fan, fluid or magnetic resistance. Rollers dont work in this exercise because they do not allow for maximal efforts (at least not without injury).

Determining your CS on these trainers will allow you to control your indoor or stationary bike training session, but may not be applicable to the road. Consistent bike set-up is critical to get accurate TTs and CS. Your bike computer must be mounted on the rear wheel for data collection. If the display unit cable will not reach the handlebars, mount it temporarily on your seat post.

If you prefer to determine your road CS, pick a flat section of road and a day with little wind. Your TT distances may have to be extended to 4 to 5K and 15 to 17K.

The run TTs should be done on a track in a climate that is normal for your area. You can also measure the distances on a flat stretch of road with markers at the quarter, halfway, three-quarter and finish points.

These trials should be done with a partner so that lap or interval times can be recorded to rule out a possible blow-up or poor pacing result. Make sure your testing procedures and environment are consistent from one test to the next.

After the TTs are completed, CS can be calculated by using basic mathematics. (If math was not your best subject and you would like the calculations done for you, visit Graph paper will assist in the calculations and conceptual understanding.

For each discipline, draw a vertical axis and label it "distance" (meters). Draw the horizontal axis and label it "time" (seconds). Label the axis scales appropriately to accommodate the results of the TTs. Therefore, CS will be in units of meters per second (mps) and later converted to more appropriate units.

Plot the TT points on the graph. A point represents the time it took to complete the distance of the TT. For example: the 1K swim TT took 15 minutes and 23 seconds, or a total of 923 seconds. The 200m swim took 2 minutes 40 seconds, or 160 seconds. Once these points are graphed, connect the dots by drawing a straight line.

Doing the math

The slope of the line joining the two data points is the CS. The formula RISE (distance) divided by RUN (time) will determine the slope. Using our TTs, the RISE was calculated by subtracting 200 meters from 1,000 meters. The RUN was the difference of 923 seconds minus 180 seconds.

Now you have 800 meters divided by 743 seconds. The CS is 1.08 meters per second. However, the most common units of expressing critical speed for the swim is a pace per 100 meters.

Use this formula to calculate your CS per 100 meters:

1.08 meters per second times 60 seconds = 64.8 meters per minute.
100 meters divided by 64.8 meters per minute = 1.54 minutes per 100m.
1.54 minutes represents 1 minute and 32 seconds (0.54 X 60 sec)
The swim CS is 1 minute, 32 seconds per 100m.

To determine your bike CS, do the calculations using your TT data.


RISE = 7,500m (10,000m - 2,500m)
RUN = 728 sec. (15.30 minutes or 930 sec. - 3.15 minutes or 195 sec.)
Critical Speed = 7,500m divided by 735 sec. = 10.2 mps.

To convert to kph:
10.2 m/sec. x 60 sec. x 60 min divided by 1,000m = 36.7 kph

To convert to mph:
10.2 mps x 60 sec. x 60 min. divided by 1,600m = 23.0 mi/hr

To determine the critical speed for the run:


RISE = 3,000m (4000m - 1000m)
RUN = 616 sec. (13.12 or 792 sec. - 2.56 or 176 sec.)
Critical Speed = 3,000m divided by 616 sec. = 4.9 mps

To convert to minutes per kilometer:

4.9 mps x 60 sec. divided by 1,000m = 0.29 km/min.
0.29 km/min. or 1 divided by 0.29 km/min. = 3.45
3.45 = 3.27 min./km (0.45 times 60 sec. = 0.27 sec.)
Critical speed is 3.27 min./km

To convert to min./mile

4.9 mps times 60 sec. divided by 1,600m = 0.18 miles/min.
0.18 miles/min. or 1 divided by 0.18 miles per min. = 5.56
5.56 = 5:34 per mile (0.56 x 60 = 34 sec.)
Critical speed is 5:34 min/mile

Keep in mind that these calculated critical speeds are applicable to the environment and equipment used during the time trials. For example, the run CS was determined on an indoor track with no hills and no wind.

The bike only applies to the same trainer used and is not applicable to the road (unless your trainer can simulate the road accordingly).The swim CS was done in a pool with no wetsuit.

Predicting an indoor triathlon or individual time trial performance would be accurate in these controlled settings. Typically these settings are more applicable to training rather than racing.

This sample athlete has now determined his CS using indoor facilities and equipment for all three disciplines. To identify the race pace for these events and distances, do the following calculations:

Predicting single event performances

1,500m swim: 103 percent of your CS
(92 sec. times 0.97 = 89.24 sec./100m x 15 divided by 60 = 22.31 or 22:18)
3,800m swim: 100 percent of your CS
(92 sec. x 38 divided by 60 = 58.27 or 58:16)

40K bike on trainer: 100 percent of your CS
40K divided by 36.7 kph = 1.09 or 1:06
180K bike on trainer: 85 percent of your CS
36.7 kph x .85 = 31.2 kph
180K divided by 31.2 kph = 5.77 or 5:46

10K run: 100 percent of your CS
4.9 mps x 60 divided by 1,000 = 0.294
1.0 divided by 0.294 x 10 = 34.01 or 34:00
42.2K run: 90 percent of your CS 4.9 meters/sec. x 0.90 x 60 divided by 1,000 = 0.265
1.0 divided by 0.265 x 42.2 divided by 60 = 2.65 or 2:39

Predicting triathlon performances

Olympic distance
Swim: 103 percent of your CS (same as single event)
Bike: 98 percent of your CS
36.7 kph x 0.98 = 36.0 kph
40K divided by 36.0 kph = 1.11 or 1:07
Run: 95 percent of your CS (most will run at 90 - 95% of their CS)
4.9 meters/sec. x 0.95 = 4.8 x 60 divided by 1,000 = 0.28
1.0 divided by 0.28 x 10 = 35.71 or 35:42

Ironman distance
Swim: 100 percent of your CS (same as single event)
Bike: 80 percent of your CS
36.7 kph times 0.80 = 29.4 kph
180K divided by 29.4 kph = 6.12 or 6:07
Run: best case is 80 percent of your CS; a good run is 70-80; most run at 60-70 percent
4.9 mps x 0.80 = 3.84 times 60 divided by 1,000 = 0.23
1.0 divided by 0.23 x 42.2 divided by 60 = 3.06 or 3:04

To determine the six training intensities, a percentage of critical speed can be used. As your race nears, your CS should be faster. Make sure to test your CS every three months or training season. In preseason, your CS may represent an intensity level close to anaerobic threshold. In competitive season, your CS could be as much as eight percent greater than a speed at anaerobic threshold.

Training speeds

Lactate tolerance: equal to or greater than 120 percent of CS
Aerobic power: 110 percent of CS
Olympic course race pace: 100 percent of CS
Endurance tempo: 90 percent of CS
Aerobic capacity/Ironman: 80 percent of CS
Recovery: equal to or less than 70 percent of CS

Now that you are able to calculate your CS, you have eliminated the guesswork involved in training intensities. You can also predict performances and foresee your true triathlon potential. Now theres only one thing left to do: Go out and race at your critical speed!

Calvin Zaryski holds a masters degree in kinesiology, has15 years of triathlon racing experience and coaches athletes worldwide. He can be reached for online coaching at

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