Anatomy & Physiology
The biological and mechanical systems behind climbing performance: muscles, tendons, energy systems, joint function, and adaptation.
Overview
Why PIP & DIP Joint Angles Matter (Joint Mechanics for Climbers)
PIP and DIP joints control the shape of the finger and therefore the path of force. Angle instability, not load, is the main cause of pulley stress and tendon overload in climbing.
How Load Travels Through the Finger (Force Lines Explained for Climbers)
The force line is the path load takes from muscle to bone. Joint angles, hold size, and pulley direction determine how force is distributed. Sharp angles overload structures; smooth angles protect them.
Finger Structure for Climbers: Bones, Tendons & Pulleys (Simple Overview)
Finger strength relies on two flexor tendons and a series of pulleys that guide them. The PIP and DIP joints determine force distribution, and understanding this structure is essential for safe, effective finger training.
Structures
Ligaments, Capsules & Passive Structures: What Supports Your Fingers When Technique Fails
Ligaments, joint capsules, and other passive structures stabilize the finger and limit motion under load. They become overloaded when technique collapses, angles drift, or sessions are chaotic. Stable joint angles, slow progression, and predictable training protect passive tissues and reduce irritation.
The Forearm Flexor System: The Muscles That Drive Finger Strength
The forearm flexor system powers climbing finger strength. FDP creates deep pulling force, FDS stabilizes the PIP joint, and key wrist flexors ensure efficient tension transfer. Forearm mechanics explain grip strength, fatigue, and load safety better than finger isolation alone.
FDP vs FDS: What Each Tendon Really Does in Climbing
FDP and FDS are the two flexor tendons that power your fingers in climbing. FDP is the main engine that pulls through the fingertip, while FDS stabilizes the PIP joint and supports crimping. Different grips shift load between them, and understanding their roles explains why certain positions feel strong, weak, sharp...
The A3 & A4 Pulleys: Small Structures, Big Influence
The A3 and A4 pulleys are small but essential stabilizers in the finger. A3 controls tendon alignment at the PIP joint, and A4 stabilizes the fingertip joint. They rarely rupture but strongly influence force distribution, grip stability, and how “smooth” or “sharp” a hold feels. Protecting them requires stable joint...
The A2 Pulley: Function, Stress Points & Why Climbers Injure It Most
The A2 pulley keeps your flexor tendons close to the bone. It takes the highest stress in crimping, is sensitive to angle drift, and fails when load increases exceed structural adaptation. Stable angles and slow progression protect it.
Mechanics
Force, Time & Tissue Stress: The Biomechanics of Injury Risk
Force, time, and stress distribution determine injury risk in climbing. High force, long duration, or unstable mechanics each increase load on pulleys and tendons—and when two or more combine, injury risk spikes sharply. Structured progression works because it controls these variables.
How Hold Size Changes Tendon Load (15mm vs 10mm vs 6mm)
Hold size changes tendon path, joint angles, and pulley stress. Larger edges keep forces smooth and stable, 10 mm edges increase sensitivity, and 6 mm edges create sharp angles that multiply load and instability. You don’t get strong from small edges—you get strong toward them.
Crimp vs Open Hand vs Drag: The Mechanical Differences Explained
Crimp, open hand, and drag grips change tendon path, joint angles, pulley stress, and load distribution. Open hand is smooth and safe, half crimp balances strength and stability, and full crimp creates the highest mechanical stress due to sharp tendon angles.
Bowstringing: What It Is and Why It Matters to Climbers
Bowstringing happens when the flexor tendon lifts away from the bone, increasing pulley tension and destabilizing the finger. It’s the core mechanical failure behind most pulley injuries and is triggered by PIP collapse, DIP unrolling, small edges, dynamic catches, and fatigue-driven angle drift.