Aerobic & Glycolytic Power (VLamax)
The maximum aerobic power is commonly measured as VO2max – the maximum oxygen uptake capacity. Why is VO2max important? For each milliliter of oxygen processed in the aerobic metabolism, energy is produced.
In the glycolytic metabolism (glycolysis) lactate (or pyruvate) is produced out of glucose. This anaerobic process (no oxygen is involved) also produces energy. The amount of energy produced per piece of glucose is much less compared to the aerobic metabolism. However, this type of energy is produced at a much faster rate. Therefore, glycolysis is much more important for shorter, high intensity efforts. For such short efforts, a high energy production in a short time is needed. As the amount of energy produced is proportional to the amount of lactate or pyruvate produced, VLamax is a feasible way to measure glycolytic performance. VLamax stands for max production of lactate.
Glycolysis is not only important for sprinters but has a tremendous effect on endurance performance. Glycolysis is the only way to utilize carbohydrates as a fuel during exercise. High glycolytic rates enable high rates of utilizations of carbohydrates as a fuel. On the other hand, a high utilization of carbohydrates as fuel, reduces the need for fatty acids as a fuel- thus lowering fat metabolism. Furthermore, the maximum glycolytic power – or VLamax – influences the glycolytic rate at endurance exercises.
High VLamax will trigger high lactate production during endurance exercises. This high lactate production lowers power at anaerobic threshold and the ability to recover from lactate accumulation.
Note these two athletes. These athletes share identical body weight and body composition (muscle mass, fat mass, etc.), identical efficiency (energy needed to produce one Watt of power), identical buffering capacity, identical aerobic capacity (VO2max), but with two different VLamax. The high VLamax triggers higher lactate production rates at all sub maximum intensities. The athlete with the higher VLamax possesses a higher lactate production rate, for any given power output, when compared to the athlete with the low VLamax.
For the athlete with a higher VLamax, this higher lactate production results in a lower intensity at which lactate production equals lactate clearance. This is the mechanism of how a high VLamax lowers anaerobic threshold- as shown below in Figure 1.
Fig 1: Muscle Metabolism in steady state conditions are shown here. The influence of a high vs. a low VLamax on the lactate production, and anaerobic threshold is noted: all dotted lines = high VLamax, all solid lines= low VLamax. Blue line shows the maximum possible lactate clearance rate by aerobic metabolism. The red line shows the lactate production. The yellow line shows the corresponding lactate concentration for steady state conditions.
Higher lactate production rates come with the cost of higher carbohydrate utilization – therefore reducing fatty acid combustion
Muscles produce lactate when fueled by carbohydrates. Therefore, a high lactate production rate consequently results in higher carbohydrate utilization rates.
With a higher amount of energy coming from carbohydrates, fat combustion rate decreases. Figure 2 shows an example of two athletes with different glycolytic capacities. Note the difference in output in the Fatmax zone as a result of VLamax.
Fig 2: Carbohydrate combustion (red) and fat combustion (green) for a high VLamax (dotted lines) and a low VLamax (solid line)
At Endurance Performance Training Center, we provide a detailed metabolic profile for athletes using both clinical-grade respiratory gas exchange measurement and blood lactate analysis. The result is optimal training and nutrition recommendations for better endurance performance.
Article Courtesy of Sebastian Weber