CH 19 & 21 - Factors Affecting Human Performance

Exercise Physiology: Factors Affecting Human Performance

Introduction

Course Code: EXSC 4400

Instructor: Emily Post, PhD, CSCS

This course focuses on the various factors that affect human performance in the context of exercise physiology. This document outlines the major themes and detailed points covered in chapters 19 and 21 from the course syllabus.

Chapter 19 - Factors Affecting Human Performance

Performance Factors Overview

  • Diet:

    • Carbohydrate: Essential for energy production during exercise.

    • Water Intake: Critical for maintaining hydration levels which affect performance.

  • Environment:

    • Altitude: Can influence oxygen availability, affecting performance.

    • Heat: High temperatures can lead to performance decrements due to overheating.

    • Humidity: Affects sweat evaporation and, therefore, cooling efficiency.

  • Strength/Skill:

    • Practice: Repetition leads to improved performance through skill acquisition.

    • Body Type: Physical characteristics can influence athletic performance.

    • Muscle Fiber Type: Different muscle fibers (fast-twitch vs slow-twitch) contribute differently to performance.

  • CNS Function:

    • Arousal: The state of being physiologically alert, which can enhance performance.

    • Motivation: A mental driving force that influences performance levels.

  • Energy Production:

    • Anaerobic Sources:

    • Phosphocreatine (PC): Key for short bursts of high-intensity performance.

    • Glycolysis: Provides energy in the absence of oxygen for moderate-intensity activities.

    • Aerobic Sources:

    • Maximal Oxygen Consumption (V˙O2max): The maximum rate of oxygen uptake, indicative of aerobic fitness.

    • Cardiac Output: Amount of blood pumped by the heart, influencing oxygen delivery.

    • Oxygen Delivery [Hb] PO2: Factors such as hemoglobin concentration and partial pressure of oxygen impact oxygen transport.

    • Oxygen Extraction: Efficiency with which muscles extract oxygen from the blood.

    • Mitochondria: Organelles where aerobic production of ATP occurs.

Fatigue and Performance

Brief Overview of Muscle Fiber Type Recruitment

  • Order of Recruitment: Starting from type I muscle fibers transitioning to type IIa and IIx based on exercise intensity (% V˙O2 max).

  • Performance Metrics: For instance, during exercise at 60% MVC (60 rpm), fibers recruited consist of approximately 40% type I and the remainder split between IIA and IIx.

Factors Affecting Fatigue in Various Performance Durations

Ultra Short-Term Events (<10 seconds)

  • Key Factors Influencing Performance:

    • Practice and technique

    • Muscular power

    • Fiber type distribution

    • Motivation and arousal

    • Anaerobic energy sources (PC and glycolysis)

Short-Term Events (10–180 seconds)

  • Influence of Fatigue:

    • Muscle and Blood pH: Increased hydrogen ions (H+) during glycolytic processes.

    • Energy Sources: ATP production primarily from glycolysis, PC contributing a significant portion (40–90%).

    • Fiber Type Distribution: Type II fibers dominate in performance intensity.

Aerobic Performance Factors (3–20 minutes)

  • Factors Limiting Aerobic Performance:

    • Maximal cardiac output (CaO2–Cv–O2)(CaO2–Cv–O2).

    • Influences on VO2 max and FIO2.

    • Genetics and training adaptation, including mitochondrial density and oxygen saturation in hemoglobin [Hb].

Aerobic Performance Factors (21–60 minutes)

  • Factors Limiting Aerobic Performance:

    • Maximal cardiac output (CaO2–Cv–O2)(CaO2–Cv–O2).

    • Influences on VO2 max and FIO2.

    • Genetics and training adaptation, including mitochondrial density and oxygen saturation in hemoglobin [Hb].

Ultra-Endurance Events

  • Examples of Events:

    • 166 km mountain run, Triple Iron Triathlon, 24-hour run.

  • Key Performance Variables:

    • V˙O2 max and %V˙O2 max sustainability.

    • Metabolic adaptations post-event, including increased fat oxidation and decreased muscle glycogen availability.

    • Risks such as hyponatremia due to prolonged exertion.

Ethical and Philosophical Implications in Sports Performance

  • The consideration of athletes as machines highlights the potential risks and ethical concerns surrounding performance enhancement and training. Institutional Review Boards (IRB) should critically evaluate training methods to avoid exposing athletes to unnecessary risks.

Chapter 21 - Training for Performance

Types of Performance and Energy Systems

  • The course covers different types of performance based on activity duration:

    • Strength-Power Activities: Rely primarily on ATP-PC and glycolytic pathways.

    • Endurance Activities: Involve aerobic oxidative systems, particularly for activities such as running longer than a mile.

  • Energy Contributions in Sports: Refer to Table 21.1 detailing ATP contributions based on various sports activities, illustrating how different sports utilize distinct energy pathways.

Energy Pathways

  • The foundation of training programs must be a thorough understanding of energy pathways. Different activities necessitate distinct energy systems:

    • Creatine Phosphate System: High-intensity bursts (e.g., throwing, jumping).

    • Glycolytic System: Sustains energy for moderate-intensity activities.

    • Mitochondrial Respiration: Essential for longer-duration aerobic efforts, highlighting the separate physiological demands for endurance training.

Influence of Gender and Initial Fitness Level on Training Response

  • Both male and female participants display similar responses to training, but improvements are often greater for those with lower initial fitness levels. Notably, sedentary individuals can experience up to a 50% increase in VO2VO2 max with training, whereas trained athletes may only see modest improvements (3–5%).

Influence of Genetics on Training Response

  • Genetics plays a critical role in the adaptability and efficiency of individuals concerning training regimens. For instance, anaerobic performance enhancement is less pronounced compared to aerobic due to its dependence on fast-twitch fibers. Individuals typically fall into responder and non-responder categories based on their genetic make-up.

Components of a Training Session

  1. Warm-Up: Increases muscle blood flow and metabolic rates, while reducing the risk of injury.

  2. Workout/Exercise Phase: The core of the training designed to develop fitness levels.

  3. Cool-Down: Aids in recovery by promoting venous return and lowering heart rate gradually.

Specific Training Modalities

  • Interval Training: High-intensity bouts interspersed with rest, proven to improve VO2 max and running economy. The effectiveness of interval training can be monitored through specific ratios of work to rest intervals.

  • Long Slow Distance (LSD) Training: Focused on maintaining lower intensities for extended periods to build endurance.

  • High-Intensity Continuous Exercise: Functions to markedly increase VO2 max and lactate threshold by sustaining exercise intensities at or near the lactate threshold (80-100% VO2max).

Injuries and Conditioning

  • Emphasis is placed on preventing overtraining and injuries through gradual increases in training loads, while also considering potential risk factors related to biomechanics, nutrition, illness, and terrain.

Muscle Soreness and Mechanisms

  • Delayed Onset Muscle Soreness (DOMS) resulted from eccentric exercises, presenting structural damages in muscles as well as inflammation responses accompanied by pain.

  • Strategies to minimize DOMS include gradual progression and limiting eccentric contractions initially. Treatment methods focus on rest and rehabilitation through methods like ice and elevation.

  • Sequence of events:

    • High tension in muscle → structural damage to muscle, cell membrane

    • Membrane damage disturbs Ca2+ homeostasis in injured fiber

    • After a few hours, circulation neutrophils rise

    • Products of macrophages activity, intracellular contents accumulate

    • Fluid and electrolytes shift into the area, creating edema

Summary

These chapters provide comprehensive insights into the multifaceted aspects of exercise physiology, notably how physiological, environmental, and genetic factors collectively shape human performance. Understanding these elements is crucial for effective training and optimizing athletic output while mitigating risks associated with physical activity.

Check In Questions:

  • What are the main factors impacting performance?

  • Review each of the summary figure slides

  • What is DOMS?

  • What are the main steps of DOMS?