KIN 3382: Anaerobic Metabolism in Children

• Pediatric Exercise Science( KIN 3382) covers the the topic of Anaerobic Metabolism in Children.
• Guest Lectures are ongoing for the next two Thursdays (Feb 6th&13th).
• Quiz #2 is on February 11th.
• The Midterm is on February 27th.

Basic Exercise Concepts

• ATP-PC system is the a basic exercise concept.
• ATP hydrolysis converts ATP molecule to ADP molecule + energy is used in muscle contraction.
• ATP resynthesis converts creatine phosphate and ADP molecule to create creatine and ATP molecule.

Glycolysis System

• Glycolytic pathway can resynthesize ATP rapidly.
• ATP produced by this system has limits.
• Glycogen-phosphorylase converts glycogen to glucose-6-phosphate.
• Phosphofructokinase converts fructose-6-phosphate to fructose-1,6-diphosphate.

Aerobic vs. Anaerobic

• During a 15 second burst of maximal exercise: 88% of the energy comes from anaerobic and 12% is aerobic.
• During a 4 minute burst of exercise: 80% of the energy comes from aerobic and 20% is anaerobic.
• During a Wingate test, 19-44% of energy comes from aerobic sources.
• During the Wingate test, the aerobic contribution is 26% in children.
• In children (ages 9-12) aerobic input to a Wingate test was 34% compared to 23% input in men (ages 19-23).

Terminology

• Peak power is described as the highest mechanical power generated during a ≤10-second task.
• Mean power is described as the average mechanical power generated during a Wingate test task.
• When external power is plotted against time, it generates a hyperbolic curve.
• Hyperbolic curve changes ability to sustain exercise over time.

Anaerobic Performance: Children vs. Adults

• Anaerobic performance is lower in children in comparison to adolescents, and is lowest in adults.
• 8-year-old's power output range of 70-80% when normalizing to body weight compared to young adults who are higher.

Absolute Peak Anaerobic Power: Boys vs. Girls

• There are similar age and gender-related changes during anaerobic power.
• Power increases linearly until the age of 14.
• Girls continue to increase linearly.
• Boys increase significantly faster and higher than girls.

Relative Peak Anaerobic Power: Boys vs. Girls

• Similar trends in age and gender-related changes when scaling to body weight.
• Increases linearly over time.
• Sex difference is more important after age 14 when power is compared to body weight.

Why Children Have Lower Anaerobic Performance

• The reason why anaerobic performance in children is unclear despite growing research.
• These factors may play a role: smaller muscle mass/unit body mass, lower glycolytic capability, and neuromuscular deficiency.
• Ability to generate force depends on muscle mass.
• Children have lower cross-sectional area (CSA).
• Children have lower CSA fibers type II, and higher CSA fibers type I.
• There is smaller absolute and relative muscle mass in children.
• Absolute and relative muscle mass is smaller in children than in adults.
• There is a gradual increase of muscle mass with age through childhood and adolescence.
• Children's lower ability to muscle mass contributes to their lower ability to generate force.
• As muscle mass increases with age, so does power.
• The main age-related difference is lower glycolytic capacity.
• Muscle concentration of ATP, there is no change.
• Muscle concentration CP, it decreases in children.
• Muscle concentration of Glycogen, it decreases in children.
• The muscle glycogen difference reported is 50-60% in children.
• Produced: 6.0 mg/kg/min, uptake by CNS is 4.0 mg/kg/min, 67% made.
• Produced: 1.7 mg/kg/min, uptake by CNS is 0.86 mg/kg/min, 50% made.
• Maximal blood lactate surrogate measure declines 35% in men compared to boys.
• It is unethical to measure a surrogate when children have a lower maximal blood lactate than adults.
• Reducing Phosphofructokinase (PFK) will also reduce glycolytic activity.
• Reducing Lactate dehydrogenase (LDH) will also reduce glycolytic activity.
• Reduce Baseline/resting glycogen
• Glycolytic activity and blood PH can also affect Anaerobic performance
• Maximal anaerobic capacity is defined by the accumulation of hydrogen ions (H+).
• During exercise, pH falls from 7.0 to 6.3 which leads to complete inhibition of Phosphofructokinase and Glycogen-Phosphorylase.
• Deficient neuromuscular coordination requires muscle coordination during anaerobic tasks.
• Task success depends on reaction time + movement time.
• Motor neuron conductivity velocity in infants ~1/3 that of mature individuals by 6 years values.

Heredity Factors Impacting Anaerobic Performance

• Anaerobic performance contributes 50%.
• Fat-Free Mass contributes 30%.
• Fiber type distribution contributes 45%.
• Glycolytic-to-oxidative enzyme activity contributes 50%.

Children's Anaerobic Trainability

• Anaerobic trainability occurs in just a few weeks.
• There are performance improvements irrespective of test.
• Such tests include force/velocity test, Wingate test, Treadmill sprint/sprint velocity, and Muscular endurance (# of push ups/pull ups).

Neural Adaptations and Biochemical Adaptations to Training

• Neural adaptations enhance activation of motor unit and reduce in muscle co- contraction, improves inter muscular contraction.
• Biochemical adaptations increase anaerobic enzymes and glycogen, and increase in glycogen flux.