By Nenad Rodic
posted 04/05

It is important to know that training zones or energy systems as some people call them do not differ from sport to sport. They are the function of two things: exercise intensity and the availability of oxygen. Based on these two factors we can divide exercise into two categories: aerobic (that exercise that requires oxygen) and anaerobic (that that does not require oxygen).

Triathlon is an aerobic sport. Basically every race that is longer than one minute requires a development of one’s aerobic capacities. This does not mean that anaerobic training is irrelevant to the sport of triathlon, it is just not as important as aerobic training. Pure anaerobic training yields little if any benefit to a regular triathlete. Those who can benefit form it are, for instance, ITU world cup racers since the tactics of a draft legal race can sometimes demand an all out anaerobic effort. That said it is important to know what training zones are and how to incorporate them into one’s workout regime. Parameters that determine workload zones are blood lactate level, speed and lastly and most inaccurately heart rate. It is unlikely that you will be able to test your blood lactate during training. That leaves us with speed and heart rate as main parameters for determining the training zones. Swimming training is performed in a controlled environment (pools) which makes speed a perfect tool to determine a training zone. Back to top

Workload zones or energy systems are:

1) LSD (long slow distance), low intensity, EN1a (endurance 1a) zone.
This exercise can last as long as your muscles can handle it, during which time your heart rate should be between 65 % and 87 % of its maximum. If your heart rate falls below 65 % of your maximum heart rate, you gain no fitness benefits. The energy used during an EN1a exercise comes from the breakdown of glycogen and fatty acids. If you are trying to loose fat, I recommend doing this type of work first thing in the morning on an empty stomach. This will quickly deplete your glycogen reserves and begin the utilization of fatty acids. For this particular exercise there is no recovery period necessary. In swimming this zone usually includes warm ups, warm downs and extremely long sets that are rarely used in triathlon training. Speed is under 75% of maximum speed for specified distance.

2) Light intensity (intense aerobic), maximum aerobic function (180-age heart rate, approximately), EN1. This exercise is similar to long time trials, those of 25 miles or more. Your heart rate should be at 80 %- 90 % of its maximum. It is an exclusively aerobic state. Your body will use glycogen first and fatty acids later. No recovery period is necessary. Majority of swimming is performed in this zone. Speed is at 75-80% of maximal speed for specified distance.

3) Average intensity, AT (anaerobic or lactate threshold), EN2 (endurance 2).
This is a border line between an aerobic and an anaerobic state, but it is purely an aerobic exercise. A world-class swimmer can sustain this effort for at least 30 min, a runner for about one hour and a cyclist for a little longer than an hour. Depending upon the sport, sets can last for up to one hour with a work to rest ratio of 1:1/2 or less. This is a highly energy demanding workout so you will use glycogen exclusively. Your heart rate should be 90-95 % of its maximum. There is no recovery period necessary. For a triathlete AT swimming sessions are highly specialized training. This training is close to the race speed in an Olympic distance race. Speed is at 78-85% of maximal for shorter distances and up to 98% for longer (1000-1650yd)

4) High intensity (long interval) VO2max, EN3.
Your heart rate should be at its maximum. Your aerobic capacities are employed to their maximum and your anaerobic systems are working as well.
VO2max is measured by increasing the intensity of each repetition until the athlete reaches the plateau after which the up-take and consumption of oxygen starts to drop. Speed can still increase due to employment of the anaerobic system and quick energy derived from the bio-chemical process: Pyruvate=lactate + energy. The result is the accumulation of lactic acid which limits this type of exercise to 10-15 min of sustained effort or a set up to 40 min long with work to rest ratio of 1:1. A period of up to 48 hours is required to fully recover from a good VO2max workout. Dietary supplements, massage, and stretching can help reduce this period to one day. In swimming this training will yield most improvement. Speed is 85-95% of maximal for shorter distances and over 100% for longer. I do not advise doing repeats that are longer than 1 min in this zone since such workout requires great local muscular endurance that can be gained only through real swimming training (15+ hours a week). An elite triathlete with strong swimming background might try longer repetitions.

5) Sub maximum effort (short interval), anaerobic efforts, lactate tolerance, SP1-SP2 (speed endurance 1,2).
These are purely anaerobic efforts. Your heart rate is irrelevant. The work to rest ratio is 1:(2-4). The benefits of this type of exercise to triathletes are marginal. The time of full recovery is up to 72 hours. The output of power is very high. In swimming this zone accounts for less than 10% of overall volume even at the Olympic swimming level. I don’t think it should be present in triathlon training at all. Speed is at over 92% for specified distance and in case of broken swims (4*50 for example) over 100% for the whole distance (200 in this case)

6) Maximum effort (sprints), alactate speed, SP3.
Even though this type of exercise is not aerobic, it is not truly anaerobic either since it does not cause an accumulation of lactic acid. During an exercise of maximum effort, Creatin phosphate stored within the muscles is used for the immediate delivery of energy to the muscle cells. Your heart rate is irrelevant, the work to rest ratio is 1:6 or more, the duration of repeats is up to 15 seconds, and your power output is maximal. Obviously the aerobic benefits of an exercise such as this are marginal. However, neuro-muscular benefits of this type of exercise are immense and often underrated. Speed of swimming is directly proportional to the technique a swimmer has. I look at this zone as the best tool to judge your swimming efficiency. Simply put, a swimmer who swims 25 yd in 10 seconds is much more efficient than the one who swims the same distance in 12 seconds. It often happens that a swimmer with poor aerobic capacities beats the one with superior aerobic capacities just because of his/her superior speed. Shaving off a half a second off your 25 yd time might improve your mile time by a whole minute, granted that you did all your other zones correctly. Back to top

Workout key:
10”=10 seconds
10’=10 minutes
*=times (for instance 4*100=4 times 100)


4*100 descend 30” 3*(8*50 rest 10” +100 easy between sets) 4*50 easy 15” rest 50'/2100
MEDIUM ADVANCED 400 free 300 (25 nbk/50 drill) 200 choice 500/ 2*250/ 4*125/ 5*100/10*50 swim or
Pull @ 1’30” per 100 base or 10” rest per
300 easy 60’/ 3700
ADVANCED 1000 choice 5*1000 pull or swim @13’ or 1’20” per 100 base 200 easy 85’/ 6200
PRO/ ELITE 1000 choice Pull or swim 800 @10’ + 8*100 @1’15”
700 @8’45”+ 7*100 @1’15”/1’10”
600 @7’30” + 6*100 @1’10”
500 @6’15”+ 5*100 @1’10”/1’05”
400 @5’ + 4*100 @1’05”
300 @3’45” + 3*100 @1’05”/1’
200 @2’30” + 2*100 @ 1
300 easy 100’/ 8300

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10*50 @1’ or 20” rest descend by 2 10*100 @2’ 0r 20” rest fastest avg 200 easy 40’/ 1700
MEDIUM-ADVANCED 4*200 swim-kick-drill-swim by 50 20”rest 10*150 @2’30” or 30” rest fastest avg. 3*100 easy @2’ 50’/ 2600
ADVANCED 3*300 free-choice by 50 descend 1-3 10*200 @3’ fastest avg. 4*100 easy @1’45” 55’/ 3300
PRO/ELITE 3*400 mixed strokes 10*400 @5’ fastest avg. 400 easy 75’/ 5600
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400 build+Warm up set 8*50 descend @1’ 16*50 @1’15” or 40” rest fastest avg. 200-150-100-50 30” rest ascend 50’/ 2100
Warm up set 6*100 descend @1’45”
3*(10 *50 @1’ fastest avg. + 100 easy
between sets)
8*50 @55” ascend 70’/ 3400
ADVANCED 600 build +
Warm up set 12*75 Descend 1-4 @1’20”/ 5-8 @1’15”
9-12 @1’10” 15’/ 900
16*100 @2’ fastest avg. 6*100 1-3 strong/ 4-6 easy @1’30”  
PRO/ELITE 600 build +
Warm up set 12*100 @1’45” 25nbk/25drill/25dps/
25build to sprint
5*500 @7’30” fastest avg. 10 *100 @1’30” 1-6 strong/ 7-10 easy 90’/ 5300
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The work to rest ratio can determine what zone the set is in however, it is not the main factor. Effort mostly determines what zone the work is in. The work to rest ratio is just a tool so that swimmers don’t need to think about what zone they’re in, they just swim as fast as they can. It is the easiest way to accomplish the desired results.
Note that swimming training methodology is far more advanced than that of any other sport. Due to a superior cooling system (water) and the lack of any hard impact to the body, swimmers are capable of extreme training (up to 180 km a week or up to 12 lactate tolerance workouts a week). That being said advanced swimming training is not relevant for an active triathlete regardless of his/her level. A top pro level swim for a triathlete is a seventeen-minute mile, a time which could be achieved with two workouts a week, assuming one has an extensive swimming background like in my case. SP1/SP2 workouts are not necessary for a triathlete, so if you’re swimming with a swim team and the coach gives you a set of 12*50 @2’ all-out, try to avoid it. Back to top

By Nenad Rodic, founder of