purpose: improving energy system efficiency goal: Muscle retention + conditioning #### Focus - high-effort, compound movements (using multiple muscle groups simultaneously) e.g., push-ups, pull-ups, squats - little to no rest - Elevates heart rate and challenges muscles - Improves how efficiently your body burns fuel (fat, glycogen, ATP) #### How Energy Systems Work in Strength-Based MetCon | Energy System | Used For | How It Works in Strength-Based MetCon | Example in Your Circuit | | ------------------- | ------------------------------ | ---------------------------------------------- | --------------------------------------------------- | | ATP-PC (Phosphagen) | Short bursts (0-10 sec) | High-power, short-duration strength efforts | First few reps of pull-ups (explosive strength) | | Glycolytic | Medium bursts (10 sec - 2 min) | Sustains muscular endurance, burns glycogen | Push-ups, squats in succession (higher-rep efforts) | | Oxidative (Aerobic) | Sustained effort (2+ min) | Keeps you moving efficiently with less fatigue | Walking + circuit pacing | #### Time Under Tension (TUT) - tool to make light resistance feel harder by keeping muscles working longer during each rep - Muscles fatigue more, recruiting deeper muscle fibers Example: - Fast push-up: 1 sec down, 1 sec up = 2 sec/rep × 10 reps = 20 sec work - Slow push-up: 3 sec down, 1 sec hold, 2 sec up = 6 sec/rep × 10 = 60 sec work #### Muscle Fiber Recruitment - The body recruits muscle fibers in a specific order based on the effort needed. This follows the Size Principle. - (Henneman's) size principle: motor units are recruited in order of increasing size, from smallest to largest, as the intensity of muscle contraction increases ##### Types of Muscle Fibers | Muscle Fiber Type | Activation Order | Force Output | Fatigue Resistance | Function | Example | Motor Unit Type | | -------------------------------------- | -------------------------------- | ------------ | --------------------- | -------------------------------------- | ---------------------------- | --------------- | | Type I (Slow-Twitch) | First (Low-intensity activities) | Low | High (Endurance) | Endurance, fatigue-resistant | Walking, light activity | Small | | Type IIa (Fast-Twitch, Moderate Power) | Second (Moderate-intensity work) | Moderate | Moderate | Strength + endurance balance | Push-ups, pull-ups | Medium | | Type IIx (Fast-Twitch, High Power) | Last (Only when needed) | High | Low (Fatigue quickly) | Explosive, high force, fatigue quickly | Max effort pull-ups, sprints | Large | ##### Types of Motor Units | Feature | Small Motor Unit (slow-twitch) | Large Motor Unit (fast-twitch) | | ---------------------------------- | ------------------------------ | ------------------------------ | | Motor Neuron Size | Small | Large | | Number of Muscle Fibers Controlled | Few (10–100) | Many (up to 1000+) | | Type of Muscle Fibers | Type I (slow-twitch) | Type II (fast-twitch) | | Force Output | Low | High | | Speed of Contraction | Slow | Fast | | Fatigue Resistance | High | Low | | Activation Order | First | Last (only when needed) |