What Influences Fat Metabolism During Cycling?
During endurance training, carbohydrates and fats are used to provide energy to fuel metabolism. We have limited carbohydrate energy in our muscles and liver, known as glycogen, which can be depleted at low levels during endurance exercises such as an Ironman triathlon. Our fat energy reserves, while metabolized more slowly, are virtually limitless when it comes to exercise. As a result, you may want to understand the factors that affect your fat metabolism during your rides. These factors include your lactate threshold, your cardiovascular peak, and your cadence.
VO2 peak
The VO2 peak is the maximum oxygen uptake during intense physical activity. Several factors influence the VO2 peak, including age, gender, body weight and training status. Generally, male athletes tend to have higher VO2 values than females.
An individual’s VO2 max is estimated by dividing their heart rate at rest by their heart rate at maximum exercise. Generally, the higher the VO2 max, the better the aerobic capacity.
In addition, higher VO2 can lead to increased free fatty acid (FA) metabolism. This might result in a higher oxygen requirement. However, it is unclear how increased FA uptake leads to a higher VO2 or whether the increase is the result of increased metabolism.
Athletes with high VO2 can work at a high work rate for prolonged periods. This allows them to increase their endurance and improve their cardiovascular fitness. Typically, a good amateur cyclist has a VO2 max of around the mid-60s to low-80s.
Several studies have suggested that athletes with higher VO2 max have improved performance in aerobic sports. Some of the reasons for this may include the recruitment of lower efficiency type two fibres, increased oxygen intake and synthesis of key proteins such as creatine phosphate.
Studies have also shown that VO2 max is a predictive indicator of endurance sport performance. Elite endurance athletes have been reported to have higher VO2 max values than trained individuals.
It is, therefore, important to understand the factors that affect VO2 max. Besides genetics, the following are known to influence VO2: sex, age, gender, training, body type, and intensity of exercise.
Although VO2 max is not the only measure of a person’s aerobic ability, it is considered the gold standard for assessing cardiovascular fitness.
Lactate threshold
In endurance cycling, a lactate threshold (LT) is an estimated maximum power output when the body’s lactate clearance and production mechanisms are in balance. This power is important for successful cycling performances.
Athletes who train above their lactate threshold experience more rapid fatigue. Therefore, if athletes are to succeed in their sport, they need to improve their aerobic capacity. For this reason, the lactate threshold is an important performance indicator for a wide range of sports.
Several studies have investigated the effects of training above the lactate threshold on aerobic and anaerobic efficiencies. Some have reported a positive correlation between lactate threshold and fat oxidation. However, cardiorespiratory fitness may be a factor in this weak correlation.
In the context of a resistance training workout, the lactate threshold is an alternative to using a VO2 max. Although the lactate threshold may not have a direct influence on sports performance, it is still a valuable indicator of the power of exercise.
The lactate threshold is often expressed in terms of a % of a person’s maximum VO2 max. It can be measured by the ModDmax method, which calculates an AT based on the first time a person’s blood lactate concentration increases above 0.4 mmol/l. Using this fixed value does not take into account the individual kinetics of LA.
Lactate production is a complex process that is influenced by several factors. Some of these include the individual’s ability to clear lactate during high-intensity or prolonged activity. Training that boosts the ability to clear lactate can be an effective strategy to improve endurance.
Some studies have suggested that training to increase the efficiency of the lactate transport system is the most effective way to improve threshold power. However, training for lactate clearance is more complex than just increasing VO2 max. By designing workouts to improve lactate clearance, athletes can reap the rewards of increased speed and strength.
Exercise intensity
The intensity of a cycle exercise has been shown to affect the oxidation of fat in the body. Exercises that are longer and more intense, like long-distance cycling, produce a higher caloric expenditure. Several physiological mechanisms contribute to the increase in metabolism. These include increased blood circulation and ventilation, lactate removal, and replenishment of oxygen stores.
Fat oxidation kinetics is the speed at which a molecule of fat is oxidized. This can be expressed as a relative value, a relative percentage, or an absolute value. During high-intensity exercise, muscle deoxygenation is slower than during lower-intensity exercise; thus, prolonged fat oxidation can occur.
Cyclists exhibit significantly higher fat oxidation kinetics compared to active individuals. They have a higher MAP (maximum air velocity) and RCP (respiratory cyclic power), as well as lower FM. They also have a shallower slope in their a1 values.
For the study, a cyclist performed three 20-minute exercise bouts at varying intensities. In each bout, they were provided with muscle samples before oxidative phosphorylation and after glycolysis. Muscle samples were obtained before the first 30 s of an all-out cycling exercise and after the second and third submaximal incremental exercise bouts.
Compared with the active group, the cyclist group had a higher a1 value and lower a1 value, which means that the cyclists had a higher MAP and a lower FM. They were also able to achieve a greater proportion of fat oxidation during the exercise.
These findings suggest that cycling is an effective training tool for fat oxidation. Nevertheless, the differences between the active and cyclist groups may be due to hemodynamic considerations, muscle mass, and environmental conditions.
