Lactate threshold testing in Santa Monica

Lactate is constantly
produced by the body

Lactate is constantly produced by the body. At its simplest, energy in the form of ATP is essential for muscle contraction and can be produced via aerobic or anaerobic pathways. At rest and in light aerobic exercise, the level of lactate produced is small enough that it is used as fuel, or buffered. As intensity increases, lactate production increases and reaches levels that are reflective of a loss of aerobic efficiency.

In general, low levels of lactate are the sign of an efficient aerobic, fat-burning system. High lactate levels at easy workloads are a sign of an underdeveloped aerobic system. High lactate levels at maximal workloads are a sign of a well-developed anaerobic system. For each athlete and sport there is an optimal balance of aerobic and anaerobic qualities. Testing unveils that balance.

Over time, with correct aerobic training, lactate levels at a given workload will decrease — showing an improvement in aerobic conditioning. That is a metabolic gain: less lactate at the same power or pace, or the same lactate at a higher power or pace. Guessing from how a session felt cannot tell you which one you got.

One of the main advantages of lactate testing is that it is robust: more stable, and less open to big swings in levels from day to day. That is why it is the number-one test of choice here, and why it is used to set your optimal training zones — heart-rate, plus power or pace if you have access to measuring those too. Tests are available for cycling, running, swimming and rowing. You test in your own discipline — a bicycle ergometer on your own bike for cyclists, a treadmill for runners, and for triathletes both of those and sometimes a pool-based swimming test. The data is only useful if it comes from the movement you actually train.

Two thresholds that
set the rest

A heart-rate zone calculated from your age is a guess about a stranger. These two marks are measured from your own blood, on the equipment you actually train on. They are where your training zones actually begin and end.

The aerobic threshold — AeT, or lactate threshold 1 (LT1) — is the first shift away from a baseline of lactate production. It is a moderate effort for most athletes, usually somewhere between 1.5 and 2.2 mmol of lactate. Knowing this is very helpful for long-distance performance — think Ironman, marathon, ultra — and for the development of Zone 2. Often a high percentage of fat is being used for energy here, and this can often correlate to Fat-Max. On a typical curve the top of Zone 2 sits at 2 mmol. Those millimole figures describe a staged response. They are not your personal numbers.

Steady-state threshold — SST, or lactate threshold 2 (LT2), also called maximum lactate steady state (MLSS) or onset of blood lactate (OBLA) — has many names that try to lead to the same place. This is the last intensity where lactate concentrations will stay the same as time progresses, hence “steady-state”. For many athletes it is around 3.5 to 4.5 mmol of lactate, though that can vary widely. Often there is a spike in lactate production soon after this intensity, which helps identify it. This is the number that sets realistic race pace. On a typical curve Zone 4 is the narrow band just below and just above 4 mmol.