Forces in Rehabilitation

Original Editor - Alicia Fernandes Top Contributors - Alicia Fernandes, Olajumoke Ogunleye and Vidya Acharya

Introduction

• A force is a push or pull acting upon an object as a result of its interaction with another object.
• it plays a crucial role in rehabilitation by influencing movement patterns, tissue adaptation, and functional outcomes. Understanding how forces are applied and managed during rehabilitation interventions is essential for optimizing treatment strategies and promoting recovery.
• Whether it's the forces exerted on muscles and joints during exercise, the biomechanical stresses encountered during functional tasks, or the impact of external forces on postural control and balance, a comprehensive understanding of force dynamics is fundamental in guiding rehabilitation protocols.
• By harnessing the principles of biomechanics and applying them effectively, healthcare professionals can tailor rehabilitation programs to address specific force-related challenges and facilitate optimal outcomes for patients recovering from injury, surgery, or neurological conditions.

Types of Force

1. Internal Force: This type of force originates from actions occurring within the object itself. Examples include the contraction and relaxation of muscles, such as those involved in walking, and the pulling of muscles at their attachments to the human body.
2. External Force:External force is exerted on an object by an external agent. Examples include kicking a football, throwing a javelin, or pushing a rug. External force can be further classified into two categories:

• Contact Forces: These forces involve direct contact with the object and are required to change its position. Examples include pushing, pulling, tension, compression, hitting a tennis ball, or trapping a soccer ball.
• Non-contact Forces: Non-contact forces do not require physical contact with the object. Examples include magnetic forces, which attract metallic materials to a magnet, and gravitational forces, which attract objects to the Earth's surface or to each other. These forces, also known as force fields or attraction forces, influence human movement.

It's important to note that not all forces induce or alter motion. For a change in position to occur, the applied force must exceed both the weight of the object and any frictional forces acting upon it.

Types of forces on the body

Compression Force

• Forces are moving primarily in an approximating direction
• Compression stimulates bone, cartilage, discogenic tissue, and often neurological tissue.
• When these tissues are overloaded, this leads to fractures, in some cases disc damage, or even nerve compression.
• Examples: stress fracture of vertebrae, disc herniation, cervical radiculopathy, and compartment syndrome. Insufficient loading may lead to osteoporosis for example.

Shear Force

• Forces are NOT moving in opposite or approximating directions exclusively. This is a COMBINATION of tension and compression.
• When shear is the primary motion occuring, the body often lacks sufficient ways to attenuate this stress and may  lead to degenerative changes over time or perhaps even acute tissue rupture.
• EXAMPLES: This is seen in ACL ruptures and spondylolisthesis.

Tension Force

• Forces are oriented primarily in opposite directions
• Tension stimulates muscle, tendon, ligament and in some cases neurological tissue.
• Overload with “tension” leads to sprains, strains and in some cases peripheral nerve injury.
• Examples: hamstring tear, patellar tendonopathy, brachial plexopathy, MCL tear. Insufficient loading leads to muscle atrophy, and weak ligaments and tendons for example.

Gravitational force

• Gravitational forces exerted on the human body influence biomechanical responses during various activities, such as standing, walking, and jumping
• it play a significant role in postural control, as the body continuously adjusts its orientation and center of mass to maintain stability against the pull of gravity
• it affect gait patterns by influencing the distribution of forces and moments across joints during locomotion, impacting walking efficiency and stability
• also contributes to musculoskeletal loading during weight-bearing activities, influencing bone density, muscle activation patterns, and joint loading
• Understanding gravitational forces is essential for designing interventions to prevent falls in older adults and individuals with balance impairments, as minimizing the effects of gravity on postural stability can reduce fall risk

Bending force

• Bending forces play a crucial role in bone remodeling by stimulating osteoblasts and osteoclasts, leading to the adaptation of bone structure and density .
• During fracture healing, controlled application of bending forces through functional rehabilitation exercises can promote callus formation and remodeling, facilitating the restoration of bone strength and function .
• In orthopedic interventions such as fracture fixation or joint arthroplasty, consideration of bending forces is essential for selecting appropriate implants and optimizing surgical techniques to ensure stability and longevity of the repair .
• Rehabilitation protocols for conditions such as osteoporosis or stress fractures may include exercises specifically designed to apply controlled bending forces to bones, aiming to enhance bone density and strength .

Forces in Human Movement Analysis

How forces are analyzed and measured during human movement assessments in rehabilitation, including techniques such as

Motion Capture

• Motion capture systems utilize multiple cameras to track the movement of reflective markers placed on the body, allowing for real-time assessment of kinematics during rehabilitation exercises
• Motion capture technology enables precise measurement of joint angles and trajectories, providing valuable insights into movement patterns and deviations in patients undergoing rehabilitation
• By combining motion capture data with musculoskeletal modeling techniques, researchers can perform biomechanical analyses to evaluate muscle activations, joint forces, and moments during functional tasks
• Motion capture systems can provide visual feedback to patients and clinicians in real-time, facilitating movement correction and optimization during rehabilitation sessions

Force Plates

• Force plates are used to quantify the forces exerted on the ground during various activities, such as walking, running, and jumping, providing essential information about gait dynamics and loading patterns
• Force plates can assess postural stability by measuring the distribution of forces and moments exerted by the body's center of pressure, aiding in the evaluation of balance impairments and fall risk .
• Force plate data can be integrated with motion capture information to analyze functional tasks, such as sit-to-stand movements or stair climbing, allowing for a comprehensive evaluation of biomechanical performance during rehabilitation .
• Force plates can be incorporated into biofeedback training programs to provide real-time feedback on force production and weight distribution, assisting patients in improving movement quality and motor control .

Applications of Forces in Therapeutic Interventions

how forces are utilized in different rehabilitation therapies and interventions, such as

• resistance training,
• manual therapy, and
• therapeutic exercises.

Impact of Forces on Tissue Healing and Injury Prevention

Wound healing is a complex biological process crucial for tissue repair and regeneration. However, excessive scarring poses a significant clinical challenge, impacting both patient outcomes and healthcare costs. Recent advancements in our understanding of mechanical forces in the wound environment have illuminated the intricate interplay between biomechanics and tissue healing. This article delves into the pivotal role of mechanical forces in cutaneous wound healing and explores emerging therapeutic strategies aimed at minimizing scar formation.

Understanding the Impact of Mechanical Forces:

Studies comparing fetal and adult wound healing reveal profound differences in the response to mechanical forces. Fetal wounds, characterized by lower resting stress levels, exhibit scarless healing, whereas adult wounds are prone to excessive scarring due to increased mechanical stresses in the wound environment. Mechanotransduction pathways play a central role in this process, with mechanical stimulation activating signaling cascades that promote fibrosis and scar formation.

Targeting Mechanical Forces to Minimize Scarring:

Therapeutic interventions focusing on modulating mechanical forces offer promising avenues for scar minimization. By reducing mechanical stresses in the wound environment, these strategies aim to mitigate the activation of mechanotransduction pathways associated with hypertrophic and keloid scar formation. Novel mechanotherapies, such as mechanical offloading and mechanomodulation, have emerged as potential interventions to achieve scar reduction and promote more favorable wound healing outcomes.