Thermal Modalities and Blood Flow Restriction

How would you describe BFR to a patient?

BFR is a completely safe modality that restricts blood flow (scientifically arterial blood flow is partially cut off and venous blood flow is completely cut off) while you exercise to allow you to get stronger without lifting heavy weight. It feels like you are getting your blood pressure taken while you exercise and you may experience muscle soreness from this treatment.

Procedure for using BFR - % occlusion, exercise intensity, where to put it, reps, frequency

What are indications of BFR use?

Improve hypertrophy and strength - when can't lift heavy

Improve aerobic capacity

Avoid/delay/minimize atrophy

Recovery

What are contraindications of BFR use?

DVT or PE

Impaired circulation or PVD

Sickle cell anemia

Infection

Distal tumor

Open or unstable fracture

Clotting disorder or on clotting medication (anti-coagulants)

Cancer

Lymphectomies

Severe crushing injuries

Pregnancy

What are precautions of BFR use?

Patients who are obese

Diabetes

Sickle cell trait

General infections

Hypertension

Cardiopulmonary conditions

What is the physiological mechanism of volitional exercise?

Henneman's Size Principle: muscle fibers recruited smallest to largest motor units

Type 1 fibers (slow twitch) are activated first during low-force activities

As force demands increase, Type 2 (fast-twitch) recruited

Type 1 Fiber Characteristics

Use O2

Fatigue slowly

Best for endurance and posture

Type 2 Fiber Characteristics

Produce greater force

Faster to fatigue

Used for strength and power

Type 2 Fiber response to strength and immobilization

Type 2 hypertrophy more with strength exercise

Type 2 atrophy first after injury or immobilization

What is the physiological mechanism of BFR?

Type 1 (slow-twitch) normally rely on O2 for aerobic metabolism

BFR partially limits arterial blood flow, creating a low-O2 (hypoxic) environment for muscle

Because less O2 available, muscle shifts from aerobic metabolism to anaerobic metabolism --> earlier recruitment of Type 2 (fast-twitch) muscle fibers

And we know Type 2 fibers are responsible for greater strength and hypertrophy gains

Resulting in muscle atrophy occurring with low-load exercises (15-30% 1-RM), even though no heavy lifting is involved

How BFR works: metabolite theory - lactate production

BFR creates a low-oxygen (hypoxic) environment, causing the muscle to rely more on anaerobic metabolism.

Lactate, a by-product of anaerobic metabolism, accumulates in the muscle during BFR training.

Because venous blood flow is occluded, lactate and other metabolites cannot be cleared efficiently.

The buildup of metabolites promotes greater recruitment of Type II (fast-twitch) muscle fibers.

This contributes to muscle hypertrophy and strength gains despite using low exercise loads.

The accumulation of lactate may also help explain the muscle soreness/burning sensation experienced during BFR training.

How BFR works: metabolite theory - cellular swelling

BFR causes metabolites to accumulate within the muscle.

This draws water into the muscle cells, causing them to swell.

The swelling signals the muscle cell that it needs to strengthen and grow to maintain its structural integrity.

This response stimulates increased protein synthesis.

Increased protein synthesis contributes to muscle hypertrophy.

How BFR works: growth hormone release

BFR causes lactate and hydrogen ions to accumulate in the muscle.

This buildup signals the brain that the muscles are under significant stress.

In response, the body releases growth hormone (HGH) at levels that may be much higher than with traditional high-intensity strengthening.

Increased HGH promotes collagen synthesis and supports tissue repair.

The hormonal response contributes to muscle hypertrophy and strength gains despite using low exercise loads.

How BFR works: increased protein synthesis

For muscle hypertrophy to occur, protein synthesis must exceed protein breakdown.

With traditional high-load strengthening:

- Muscle damage occurs (protein breakdown).

- Inflammatory markers are released.

- This contributes to delayed onset muscle soreness (DOMS).

- The damage stimulates protein synthesis to repair and rebuild muscle.

With BFR training:

- Protein synthesis is increased.

- Low loads cause minimal muscle damage and protein breakdown.

Therefore, protein synthesis greatly exceeds protein breakdown, promoting muscle growth with less tissue damage.

Define Physical Agents

broad group of procedures using various forms of energy that are applied to tissues in systematic manner

Purpose of Physical Agents

Increase tissue extensibility

Increase healing rate of wounds or soft tissue

Modulate pain

Reduce swelling

Remodel scar tissue

Treat skin conditions

What is the 1st Law of Thermodynamics?

energy can neither be created nor destroyed, but is transferred from one form to another; during process some energy released as heat

What is the 2nd Law of Thermodynamics?

heat transfer always occurs from higher to lower temperatures until state of equilibrium achieved

What are the types of heat transfer?

radiation

conduction

convection

conversion

What is radiation? Examples?

transmission of energy through space

Ex. infrared heat lamp, UV light

What is conduction? Examples?

heat transferred by successive molecular collisions when two objects of different temperatures touch

Ex. hot pack (158-168 degrees F), cold pack, paraffin

What is convection? Examples?

heat transfer dependent upon movement of the heating medium (usually gas or liquid) and the target tissue. As the gas or liquid flows around body part, energy transferred

Ex. whirlpool, fluidotherapy

What is conversion? Examples?

non-thermal energy (mechanical or electrical) is converted to heat energy as it passes through substance

Ex. ultrasound

How to subjectively measure heat transfer?

ask the patient (light, moderate, or intense heat or cold)

How to objectively measure heat transfer?

hot/cold discrimination testing (assess pt's perception of various intensities of heat/cold)

What patients may need hot/cold discrimination testing?

Peripheral neuropathies: Polyneuropathy - diabetes and Mononeuropathy - peripheral nerve injuries

SCI: Complete cord resection, Brown-Sequard Syndrome - partial resection with loss of temp sensation contralateral to lesion

Stroke

Benefits of heat

Vasodilation and increased blood flow

Increased metabolic rate

Relaxation of muscle spasm

Pain relief

Increased elasticity of connective tissue

What is the proposed physiologic effect of heat?

Vasodilation → increased blood flow → soft tissue healing

Increased thermoreceptor activity → counter irritation effect → decreased pain

Decrease joint viscosity → warming of intrarticular fluid → reduce joint stiffness → increase joint ROM

Safety/Contraindications for heat use

Do not use over areas of impaired temperature sensation found with testing methods

Do not use over areas of malignancy

Do not use over hemorrhagic or thrombophlebotic areas

Do not use over areas of acute inflammation

Do not use on confused patients

Do not use over abdomen of pregnant women

Must use adequate layers to prevent burns (4-6 layers depending on hot pack)

Paraffin Baths: who uses them, how are they used, contraindications

patients with RA

Dip and wrap to conserve heat (124-130 degrees) over area being heated

contraindcations: same as hot packs but also do not use over broken skin

Benefits of cold modalities

Vasoconstriction and decreased blood flow → reduces edema

Decreased metabolic rate

Pain relief through counterirritation and decreased nociceptor sensitivity

Reduced spasticity → decreases muscle spindle and Golgi tendon organ activity

Safety and contraindications of cold modalities

Do not use over anesthetic skin

Do not use over areas of cold hypersensitivity

Do not use with Raynaud's disease

Do not use over open wounds or areas of PVD because of decreased blood flow

What is ultrasound? How effective is it?

Deep heating modality that travels well through tissue and can heat deep tissues → little evidence that this is effective though for conventional (strong for LIPUS and MIST for corresponding functions)

Types of ultrasound and what they are used for

Conventional for soft tissue pathology

Low-intensity pulsed (LIPUS) for bone healing

MIST for debridement of wounds

Effects of types of ultrasound

Conventional: thermal and mechanical

LIPUS: mechanical

MIST: mechanical

What causes thermal effects of ultrasound?

microcellular vibration

Two types of mechanical effects of ultrasound and how they work

Stable cavitation: formation of microbubbles in the tissues which expand and contract in the tissues

Microstreaming: minute flow of fluid in the vicinity of the pulsating bubbles

How does frequency of ultrasound relate to depth of penetration?

Depth of penetration inversely related to frequency of ultrasonic energy

1 MHz → deeper penetration

3 MHz → more superficial penetration (absorbed more readily)

What factors affect dosing of ultrasound?

Frequency

Delivery Mode

Transducer ERA (Effective Radiating Area)

Duration

Treatment Frequency - 8 minutes to bill for it typically

Types of ultrasound delivery modes

Continuous vs. Pulsed

- Continuous: for thermal

- Pulsed: for non-thermal

Contact vs. non-contact

- Gel needed but can use gel pads or water for non-contact

Define attenuation

total decrease of sound energy as it travels through tissue

What factors affect attenuation of ultrasound?

absorption

reflection

refraction

What tissues absorb sound energy?

blood and other fluids (low), bone (high)

What is reflection in regards to ultrasound?

sound waves reflected when move into areas of different impedance

What is refraction in regards to ultrasound?

sound waves bent as they pass from one medium to another in relation to the impedance of each tissue

What is intensity in regards to ultrasound?

amount of acoustic power needed to deliver energy to tissues

What are some safety considerations before using ultrasound?

Inspect skin

Do not use over insensate skin

Always use coupling medium (gel)

Keep sound head moving (conventional and MIST)

Treatment area no larger than 3x area of sound head

Use caution (low dose) over epiphyseal plates in children

What are contraindications for ultrasound use?

Do not use:

- Over impaired sensation areas

- Areas of malignancy

- Hemorrhagic or thrombophlebotic areas

- Acute inflammation

- On confused patients

- Abdomen of pregnant women

- Gonads, eyes

- Plastic or electronic implants