In-Depth Notes on Exercise Science and Adaptations

Graph of Adaptation

  • Researcher: William Kramer
    • Known for studies related to steroids and exercise adaptation.

Key Lines in the Graph

  • Overall Strength: Combination of neural adaptation and hypertrophy.
  • Neural Adaptation: First response during the initial phases of training.
  • Hypertrophy: Develops after a significant time; at least 6 weeks required for noticeable effects.

Time vs Strength Gains

  • Y-Axis: Strength levels.
  • X-Axis: Time.
  • Early Training: Neural adaptations dominate strength improvement regardless of training program (e.g. 2 sets of 15 vs 4 sets of 4).
    • Faster adaptations since they don't require immediate protein synthesis.

Hypertrophy Timing

  • Noticeable hypertrophic effects typically start after approximately 6 weeks of consistent training.
    • Initial strength gains from neural adaptations can feel overwhelming but will plateau over time.

Limitations of Study Data

  • Kramer notes a lack of long-term studies (beyond 6-8 months) affecting understanding and predictions of adaptations after prolonged training.

General Resistance Training Adaptations

  • Individuals Starting Training: Experience increases in:
    • Muscle Strength
    • Muscle Power
    • Muscle Endurance

Muscle Enzyme Concentrations

  • Phosphagen Enzyme (Creatine Kinase): Important for ATP production.
  • Concentration vs. Total amount:
    • Total muscle enzyme concentration increases due to overall muscle size increase; concentration may remain stable.

Lactate Dynamics

  • Lactate Increase During Exercise: Generally decreases due to improved buffering systems.
    • Muscle Buffering Systems:
    • Bicarbonate: Blood buffering.
    • Carnosine: Muscle buffering, improved through training.

Muscle Fiber Adaptations

  • Type 1 vs Type 2 Fiber Changes:
    • Type 2 fibers (fast-twitch) increase more than Type 1 fibers.
    • Limited research shows fiber type shifting; mainly hybrid fibers shift phenotype.
    • Aging leads to a shift from Type 2 to Type 1 fibers, reducing muscle power/size with age.

Cross-Sectional Area (CSA)

  • CSA Significance:
    • Cross-sectional area of muscles increases with training.
    • Type 2 Fibers: Greater capacity for hypertrophy compared to Type 1.

Factors Influencing Muscle Strength

  • Muscle Activation and Neural Function: Only factors that can be significantly altered through training include:
    • Neural Activation
    • Muscle Size
    • Other factors like muscle length and architecture remain largely unchanged.

Benefits of Resistance Training

  • Fat Loss: Decreases fat percentage while increasing fat-free mass.
  • Metabolic Rate Increase: Muscle mass increases metabolic rate; muscle at rest is 6 times more active than fat.
  • Reduction in Injury Risk: Resistance training strengthens connective tissues, reducing the chance of injury.

Bone Density Considerations

  • Increased Bone Density: Requires high intensity and volume in training; simply doing high rep doesn’t suffice.
  • Necessary to load bones to stimulate osteoblast activity for safety against osteoporosis.

Neural Adaptations

  1. Rate Coding: Improved action potential firing rates lead to enhanced force production and contraction speed.
  2. Co-contraction: The ratio of agonist to antagonist muscle activation improves with training, leading to stronger agonist contractions.
  3. Synaptic Efficiency: Increased efficiency in acetylcholine processing and release occurs across various training types.

Metabolic Goals and Hypertrophy

  • Hypertrophy Pathways: Activated through mTOR and phosphatidic acid pathways.
  • Acute Response: Protein synthesis increases dramatically in untrained individuals post-session compared to trained.
  • Energy Availability: Protein synthesis is hindered in energy deficit situations, stunting muscle growth despite effective training protocols.