Interval training, particularly very “intense”, short interval protocols like Tabata are still very much en vogue in rugby conditioning circles these days. Coaches and players alike still seem labour under the misapprehension that steady state cardio makes you slow, fat and weak. Far from it. Steady state aerobic training is a vital component of any successful rugby conditioning programme. And here’s why…
Today’s post is a straight copy of a paper by Russian sport scientist Victor Seluyanov PhD, who was a mentor to both Val Nasedkin and Natalia Verkhoshansky (start reading if you don’t know who these people are!), which is kind of a big deal. In the paper Victor talks about why steady state training is so important to rugby, and why interval training might actually be potentially lethal.
What is happening to the heart during training? It is important to understand that the heart is not a mechanical machine and it is relatively easy to damage it by training incorrectly. The main effect of training on the heart is the increase in minute volume, the amount of blood the heart is able to pump in a minute.
The heart gets larger, or develops hypertrophy with training. There are two types of cardiac hypertrophy: L-type, when the heart muscle stretches, its muscle fibers get longer and the volume of the heart increases; and D-type, when the thickness of the heart wall increases, therefore increasing the strength of contraction.
In order to increase the volume of the heart they use training at heart rates corresponding to the maximal stroke volume. Just as the reminder, stroke volume is the volume of blood expelled by the heart during one contraction. Usually stroke volume sharply increases at HR of 100/min, at 120 increases more and in some individuals still increases until HR of 150.
Prolonged training at maximal stroke volume is, figuratively speaking, “stretching exercise” for the heart. Muscles pump the blood, and the heart get stretched by the increased flow. As the consequence the heart dilates. It is possible to double its size, and 30-40% is almost a guarantee. That’s what is meant by coaches when they say “building the base”; it is, in fact, stretching of the heart.
D-type hypertrophy is stimulated by the work at heart rates close to maximal – 180.min and higher. Again, a little reminder of physiology. The heart is the muscle and therefore needs the blood in order to contract. The blood is delivered to it mostly during diastole, or relaxation phase. When working at maximal heart rate, the heart does not fully relax, and the blood supply is impaired to some degree.
What follows is the accumulation of acidic substances leading to acidosis which, in turn, stimulates growth of the heart muscle. This is typical interval training, the rave of the fitness crowd in recent years. The problem starts when this kind of training is done too often. If the heart does not relax, its blood supply is impaired, the delivery of oxygen becomes inadequate and anaerobic glycolysis starts.
As the resulting lactic acid is produced and leads to the acidosis inside the cell. If it lasts long enough, some cellular structures die. And if it lasts some more, the whole myocardiocytes – heart muscle cells – can die. This is microinfarction. If the training of this intensity is repeated again and again, more cells die and are replaced with the connective tissue which, in turn, is poorly distensible and does not properly conduct electric impulses necessary for adequate cardiac contraction. Apparently this has been confirmed by autopsies of athletes who suddenly died during physical activity.
That is why it is important to first build the base – dilate the heart – and only then increase intensity. Working at heart rates close to maximal must be introduced gradually and done infrequently, especially at the early stages of training.
This also brings us to the topic of recovery and frequency of training. If your muscles are sore after a workout, you take a day or two off and allow them to recover, to heal. Why should the heart be different? Adaptation takes days and the heart muscle needs rest in order for these processes to take place.
This is not just a theory. Every year you hear of a few athletes dying as the result of sports activity, both professional and amateur. This year a 27 year old man died during City to Surf race in Sydney, the run only 14 km long. Did he have some undiagnosed cardiac condition? It is possible. But it is also possible that his heart was damaged by overzealous training.
This is certainly food for thought in the rugby community. Might be actually be harming rather than helping our performance- and more importantly our health- by shying away from steady state aerobic training, and incessantly flogging ourselves day after day. My guess is yes, and that is why all my athletes perform steady state training in all of their energy system development programmes.
I’d recommend you implement this in your programme too for this forthcoming pre-season. When you do, here are Victor’s recommendations for cardiac development. The volumes with no doubt raise an eyebrow, but Dr Keir prescribes you deal with it and take your medicine. Greatness takes time!
- Approximate 20% increase in stroke volume, at least 3-4 times a week for 2 hours (120-130 beats per minute, at which the maximum stroke volume is achieved).
- For 50-60% increase, train 2 times a day for 2 hours, at least 3-4 days a week.
- To double eccentric cardiac hypertrophy, the heart has to do 2 times more, which requires very large volumes. It’s every day for 4 to 5 hours.
Obviously the second and third examples are only possible if you are a full time endurance athlete. But the first is eminently doable in pre-season, and the take home message is this: optimal rugby conditioning cannot be achieved solely with a few minutes of hectic interval training per week.