CHANGING A REPUTATION
Only exercise physiologists use the term OBLA. Coaches and runners say ‘lactate threshold pace’, ‘threshold pace’ or simply ‘tempo runs’.
Breaking through the confusion begins with understanding the role of lactate in muscle metabolism. Lactate is a chemical with a bad reputation, associated with running too long at anaerobic paces. It has been blamed for everything from sore muscles to the dead-legs feeling you get at the end of fast-paced intervals. But none of this is true. Lactate is simply a by-product of glucose metabolism and is produced any time you move a muscle. At low exercise levels, you use lactate nearly as quickly as it’s formed, and the amount that leaks from the muscles into the blood is minuscule. At higher levels – eg moderate-paced running – you produce it more quickly but also use it more quickly. More gets into the blood, but not much.
Around marathon pace, things change. By this point, the lactate level in the blood has edged up to about two millimoles per litre (mmol). That’s still low, but if you continue to speed up, it rises more rapidly. By the time you’ve reached Daniels’ one-hour race pace, it’s doubled to four mmol, the classic threshold level. Above that, it skyrockets.
Mounting lactate levels sound like a bad thing, but research says they aren’t. George Brooks, an exercise physiologist at the University of California, US, discovered what is now known as the ‘lactate shuttle’. He found that when lactate climbs, the body uses the blood to
ship some of it away from the hard-working muscles where it is produced to places where it can be used more effectively. One of these is the heart, another is the brain. But it also goes to the liver, which can use other energy sources such as fat to turn it back into glucose. Even some less-involved muscles, such as the arms, pull lactate out of the blood for fuel, in lieu of glucose.
This shuttling makes it possible for you to run faster, because glucose is the body’s high-octane fuel. We can generate energy much more rapidly with glucose than through lactate. So rather than being a sign that our leg muscles are drowning in performance-impeding lactate, the rise of lactate means the body is moving it to places where the power demands are lower, keeping the glucose for the running muscles. ‘The organs that most need it get priority and others rely on lactate,’ says Halliwill.
That said, rising lactate and increasing fatigue go hand in hand, which means that even if lactate is no longer the evil we once thought it was, finding ways to train the body to use it more effectively – in essence, postponing the point at which blood lactate starts to rise – will also postpone the point of fatigue, with the hope of running further, faster. This, in fact, is what threshold training, in all of its confusing forms, is designed to do.