Training programs typically focus on highly intensive efforts, and rightfully so. Cellular change is impossible without adequate stress, but speed and power athletes cannot ignore aerobic fitness either. It is unfortunate that low to moderately intensive conditioning has been eschewed by some in the strength and conditioning community exclusively for more fashionable HIIT programs. Intensive interval programs are more glycolytic than they are aerobic, and optimal cardiovascular adaptations are lessened the further training intensity reaches beyond the aerobic threshold.
A well-developed aerobic system is an important aid for recovery, resilience, and overall health. But, because a modestly elevated and sustained heart rate yields different cardiovascular adaptations than repeated spikes with periods of recovery, it must be trained somewhat separately from speed and power. Longer training intervals at lower intensity leads to an increase in the size of the heart’s chambers known as eccentric hypertrophy. This adaptation is the result of cardiac tissue repeatedly stretching due to the complete or near complete filling of blood with the heart. The benefits are better stroke volume, cardiac efficiency, and improved oxygen delivery throughout the body. In short, it’s a cardio-protective adaptation that does a lot of good things for athletes. Faster heart rates associated with intensive training is less likely to produce eccentric hypertrophy. Rapid heartbeats don’t allow the heart to completely fill or achieve a tissue stretch large enough to generate this favorable adaptation. Instead, an uncommon but potentially deleterious adaptation known as concentric hypertrophy may occur over time.
Concentric hypertrophy occurs when the walls of the heart have thickened but the heart itself remains relatively the same size. When this happens, the chambers themselves become smaller and a stiffer cardiac muscle, less efficient of blood flow, and even a possible cardiac muscle degradation may result. When it is progressed far enough, cardiac failure and heart attack is plausible in a seemingly healthy and active individual. There have been some studies that have actually shown a 4 to 8-fold increased risk of atrial fibrillation in athletes, indicating possible evidence of this phenomena. This being said, it is very important to remember that correlation doesn’t equal causation and cases of cardiac failure are very low in athletes.
The biggest takeaway from this information should not be what to omit in your training, but what to include. Despite its dip in popularity there is a place in an athlete’s program for training at a longer and at a less intensive pace. It even has a place in-season within a well-developed program. Aerobic training doesn’t have to be limited to staples like jogging, swimming, or biking. The only requirement is a moderately sustained heart rate over a longer period. An athlete can very train within aerobic parameters through things like drills or extensive tempo runs. The means to how aerobic fitness is achieved is up to the athlete or coach and of little importance to this article. What is important is that athletes and coaches understand cardiovascular health is important for sport and everyday life alike, and the only way to maximize it is through aerobic training methods. Current trends in training sometimes forget lessons we’ve already learned.
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