Understanding Bones

A fracture often raises questions about healing, bone strength, and a return to normal activities. Fractures can occur at any age, but their frequency and location change over the course of a person’s life. A large British study confirmed these differences based on age and sex, though it did not allow for predicting an individual’s risk based on these factors alone.¹

Bones are living tissues that regenerate and can heal a fracture. Bone union—that is, the healing process that brings the bone fragments together—depends, among other things, on the bone involved, the stability of the fracture, and the treatment. The healthcare team monitors this healing process through physical examinations and, if necessary, X-rays.

Four things to remember about bones:

• Bones are constantly being renewed: Your skeleton is renewed through bone remodeling, which replaces old bone with new bone throughout your life.²
• Exercise can improve bone density: Bone density measures the amount of minerals in a specific area of bone. A review of 162 randomized controlled trials reports small to moderate gains in several areas of the skeleton, but not in all. Results vary depending on the type of exercise and the study population. This review does not identify a single ideal program that works for everyone.³
• Healing is an active process: A fracture can heal with a visible callus—that is, a repair tissue that forms around the fracture line and hardens over time—or directly under rigid fixation, when a plate or screws hold the fragments tightly in place without allowing them to move. The final shape and strength vary depending on the fracture, its alignment, its stability, the treatment, and the individual.^{4, 5}
• Physical therapy supports recovery: A review of 26 studies involving adults with an average age of 50 or older who had sustained a fragility fracture following a minor impact reported improvements in daily functioning and pain relief with exercise. The results regarding strength and balance were less consistent. Programs are tailored to the specific fracture and any medical limitations.⁶

To learn about the treatments available after a bone injury, check out our comprehensive guide to physical therapy.

What are Bones?

Bones are living organs that support the body, protect internal organs, and house bone marrow. They contain cells, blood vessels, and a solid substance called the matrix. This matrix combines collagen, a fibrous protein, with calcium- and phosphate-rich crystals called hydroxyapatite.⁷

The human skeleton typically consists of 206 bones in adulthood and about 270 at birth. Many bones fuse together during growth; certain anatomical variations also affect this number.⁸

Collagen fibers allow bone to deform slightly and absorb energy before failing. Minerals contribute to its rigidity and strength. The water present in the tissue also influences these properties. The arrangement of these components allows bone to withstand stress while maintaining a certain degree of flexibility.⁹

Bone remodeling involves three types of specialized cells in particular:

• Osteoblasts: Cells that produce the matrix of new bone and then contribute to its mineralization—the accumulation of minerals that hardens it¹⁰
  
• Osteoclasts: Cells that resorb (break down) old bone tissue—that is, they break it down piece by piece, first dissolving the mineral component and then digesting the collagen matrix¹⁰
  
• Osteocytes: cells embedded in bone that detect forces applied to the tissue and transmit signals to other bone cells¹⁰

Remodeling replaces small areas of old or damaged bone. This renewal maintains the tissue and helps it adapt to stress. However, a long-term imbalance between the amount of bone removed and the amount reconstructed can weaken the bones. The remodeling cycle depends on the coordination of several cells¹¹.

How are bones structured?

Bones consist of a dense outer layer, called cortical bone, and an internal network of small bone units, called trabecular bone. The spaces between these units and the bone cavities contain bone marrow. The distribution of these two structures varies depending on the bone.¹²

Layered Structure

Cortical bone: Cortical bone, also known as compact bone, forms the solid outer layer of the bone.

Trabecular bone: Trabecular bone, also known as spongy bone, forms a network of fine bony structures. It is particularly abundant in the vertebrae, the bones of the spine, and at the ends of long bones.

The spaces in the trabecular network make this structure more porous than cortical bone. The amount of each type of bone varies depending on the region being examined. The chapter on bone tissue structure describes these differences¹³.

Bone Marrow

Bone marrow: This soft tissue fills the cavities of many bones. It consists of red and yellow regions.

• Red bone marrow: It produces red blood cells, white blood cells, and platelets. This process is called hematopoiesis.¹⁴
• Yellow bone marrow: bone marrow composed primarily of fat cells, found mainly in the cavities of many long bones in adults.¹⁵

The Periosteum

The periosteum is a membrane that covers the outside of bones, with the exception of the surfaces that meet at the joints. It contains blood vessels, nerves, and cells capable of contributing to bone formation. The periosteum plays a role in bone growth and repair following a fracture.¹⁶

This complex, multi-layered structure allows bones to fulfill their many functions while continuously adapting to the body's needs.

What Do Bones Do in the Human Body?

Bones support the body, protect organs, enable movement in conjunction with muscles, house blood cell production, and serve as a storehouse for minerals. The exchange of substances between bones and blood also helps maintain calcium levels.⁸

1. Structural Support

The skeleton forms the rigid framework upon which all the body's soft tissues rest. Without this bone structure, the human body could not stand upright or maintain its shape. The long bones of the legs, for example, support the entire body weight during walking and running.

2. Protection of Vital Organs

Several bones form protective structures around the most vulnerable organs:

• The skull protects the brain from impacts
  
• The rib cage (ribs and sternum, the bone in the middle of the chest) protects the heart and lungs
  
• The vertebrae—the bones of the spine—protect the spinal cord, the bundle of nerves that connects the brain to the rest of the body
  
• The pelvis protects the reproductive organs and part of the digestive system

3. Facilitating Movement

Muscles pull on bones through tendons, the bands of tissue that connect them. Joints, where bones meet, allow for the movements produced by this pulling action.

4. Blood Cell Production (Hematopoiesis)

Red bone marrow produces all types of blood cells:

• Red blood cells (erythrocytes): transport oxygen
  
• White blood cells (leukocytes): defend against infections
  
• Platelets (thrombocytes): help form clots that stop bleeding

Red bone marrow provides an environment where blood cells are formed and mature before entering the bloodstream. The structure of the bone cavities provides a home for this tissue¹³.

5. Mineral Storage

Bones store calcium and phosphorus. These minerals can be released into the bloodstream when the body needs them. Calcium plays a key role in muscle contractions, nerve signals, and blood clot formation. Its level in the blood also depends on absorption by the intestines and excretion by the kidneys.¹⁷

6. Regulation of calcium exchange

Hormones—messengers carried in the blood—regulate these processes. Parathyroid hormone helps raise blood calcium levels when they drop. Calcitriol, the active form of vitamin D, promotes its absorption in the intestine.¹⁷

How Do Bones Renew Themselves?

Bones are renewed through remodeling: osteoclasts remove old bone tissue, and osteoblasts build new bone tissue. These processes take place in many small areas throughout the skeleton.

During growth, bone formation exceeds bone resorption—that is, the amount of bone removed. As a result, the skeleton gains mass.¹⁸ Later in life, aging can disrupt this balance and lead to bone loss. Declining levels of sex hormones, particularly after menopause, contribute to this. The review on bone aging also describes other mechanisms¹⁹.

The Remodeling Cycle

Bone remodeling is described as a series of overlapping phases² :

Phase 1: Activation. Signals related to mechanical stress or hormones trigger the renewal of a small area. Cells that are still capable of changing their function then transform into osteoclasts.

Phase 2: Resorption. Osteoclasts attach themselves to the bone surface. They dissolve minerals and break down proteins, creating a small cavity.

Phase 3: Transition. Resorption slows down, and signals promote the arrival and maturation of the cells that will form the new bone. This coordination links the removal of old tissue to its reconstruction.

Phase 4: Formation. Osteoblasts deposit a collagen-rich matrix, and minerals then accumulate within it. Some of these cells become osteocytes that are integrated into the tissue. The cycle then ends with a period of rest for this surface, until it is activated again.

Regulation of Remodeling

Bone remodeling is regulated by several factors²⁰ :

• Mechanical stresses: The forces transmitted by body weight and muscles contribute to bone adaptation. Conversely, periods of weightlessness often lead to bone loss in areas that are normally weight-bearing, especially the lower limbs. The extent of this loss depends, in particular, on the location and duration.²¹
• Hormones: Estrogens, in particular, help prevent excessive bone resorption. Parathyroid hormone and active vitamin D also play a role in calcium metabolism and bone remodeling.
• Vitamin D and calcium: Calcium forms crystals that strengthen bones. Vitamin D helps the intestines absorb this calcium.
• Growth factors: These proteins act as local signals. They influence the proliferation and maturation of cells that resorb or form bone.

Bone remodeling maintains bone health during everyday life and also reorganizes the tissue formed after certain fractures. However, fracture healing involves additional steps, which are described below.

What are the general steps followed after a bone fracture?

The healing of a fracture generally involves an initial inflammatory phase, followed by callus formation and remodeling. The callus is the repair tissue that gradually connects the bone fragments. Some well-aligned fractures that are rigidly stabilized can heal directly, without significant external callus formation.⁴

Phase 1: Initial Inflammatory Response

The rupture of small blood vessels causes bleeding around the fracture. This blood forms a hematoma, an accumulation of blood that forms a clot. Immune cells, particularly macrophages, help clear away damaged tissue and release repair signals.²²

Local signals attract cells capable of forming cartilage, bone, and blood vessels. Their origin may vary depending on the injury; the periosteum and surrounding tissues contribute to this process. The inflammatory response begins early and overlaps with the initial stages of reconstruction. The biology of bone repair describes these processes⁴.

Phase 2: Bone formation and mineralization, depending on the type of fracture and its stability

This phase is divided into two stages:

Soft callus formation: Cartilage and other reparative tissues develop between the fragments. This initial bridge helps connect them. It does not yet have the strength of reconstructed bone.²³

Bone Callus Formation: The cartilage mineralizes, then is gradually resorbed and replaced by bone tissue. New blood vessels form as part of this process. Stability increases, but the medical team determines when and how to resume weight-bearing.

A callus may be visible on an X-ray during certain types of indirect healing. Its appearance and progression depend on the type of fracture, its stability, and the treatment.

Phase 3: Remodeling over a variable period of time

Osteoclasts and osteoblasts then reorganize the bone callus. The original tissue is replaced by bone with better-organized layers, and the cavity containing the marrow can reform.

The bone defect gradually decreases, and the bone can return to its original shape. This remodeling can continue for years after the fragments have fused. It often occurs more rapidly in children. The final shape and strength also depend on alignment, stability, and blood supply.²⁴ Marsell and Einhorn⁴ distinguish this long-term reorganization from the early stages of union.

Factors influencing healing

Several factors affect the speed and quality of healing:

• Age: Healing and remodeling often occur more quickly in children, largely due to the periosteum. However, age alone is not sufficient to determine a timeframe.⁴
• Type and location of the fracture: The healing time varies depending on the bone, the region, the stability of the fracture, blood supply, and treatment. An open fracture, in which the wound communicates with the bone, or significant tissue loss can complicate healing.²⁵
• Blood Flow: Blood delivers the oxygen, nutrients, and cells needed for repair. Insufficient circulation can hinder this process.
• Immobilization: The degree of stability and permitted movement depends on the type of fracture and the chosen treatment.
• Nutrition: Requirements for calcium, vitamin D, and protein vary; a deficiency or nutritional risk warrants an appropriate assessment.
• Smoking: A review of studies found that smokers experience approximately twice as many delays or failures in bone healing. This includes fractures and various bone surgeries; this average risk does not predict your specific recovery time.²⁶
• Certain medical conditions —such as diabetes, osteoporosis (a disease that weakens the bones), and their treatments—are among the factors considered in the overall assessment.

Decisions regarding treatment and the timing of exercises depend on the fracture, its stability, the treatment plan, and medical instructions.

Delayed union means that healing is progressing more slowly than expected. Nonunion means that the bone fragments are not fusing together. Persistent pain or a course of healing deemed insufficient by the medical team requires follow-up; the diagnosis is based on a combination of physical examination and imaging.^{27, 25}

How Does Physiotherapy Help After a Bone Injury?

Physical therapy helps restore mobility, strength, and the ability to perform daily activities after a bone injury. The physical therapist selects the exercises and determines how to progress through them based on the stability of the fracture, any medical restrictions, and your goals.

Timing of Physical Therapy Intervention

The physiotherapist's role evolves according to the healing phases:

During the protection period: Some fractures require immobilization; others allow for early movement. The physical therapist follows medical restrictions and maintains the permitted range of motion, particularly in adjacent joints. He or she may recommend isometric contractions—in which the muscle works without moving the joint—when the fracture allows it.

After immobilization: Movement is gradually resumed according to the healthcare team’s instructions. A review of 40 studies confirms that immobilizing a limb reduces muscle strength and size, to varying degrees depending on the duration and the body region.²⁸ Stiffness can also persist after a cast is removed, as explained in the guide on arm and wrist fractures²⁹. Physical therapy can help restore these functions.

Advanced rehabilitation phase: The physical therapist can guide a gradual return to activities, work, or sports based on the patient's limitations and goals.

Main interventions

Joint Mobility: These exercises move the joints within their permissible range of motion. You can perform them on your own, with the help of another person, or with a physical therapist. The range of motion increases depending on any restrictions and symptoms.

Muscle strengthening: Exercises can begin with appropriate contractions and then incorporate resistance bands or weights once weight-bearing and exertion are permitted. The physical therapist adjusts the difficulty, the number of repetitions, and the rest periods to build strength and the ability to sustain repeated effort.

Gradual weight-bearing: After a leg fracture, the physical therapist will teach you how to bear the permitted amount of weight on the affected limb. They can guide you on how to use crutches, shift your weight, and walk. Weight-bearing should follow medical guidelines; it should not be determined solely by pain.

Balance exercises: Appropriate exercises help develop body control while standing or moving. Following a fragility fracture, research findings on balance remain mixed. In older adults, balance and daily activity programs can reduce falls.

Managing Swelling: After the fracture has been treated, recommendations may include permitted movements, elevating the limb, or applying appropriate compression. Manual drainage uses gentle techniques to help move accumulated fluid. A review of eight trials involving fractures of the radius near the wrist reported less swelling when drainage was added to standard care³⁰. Another trial comparing two methods of swelling management found no difference in volume reduction at six and nine weeks but reported fewer treatment sessions with the modified method³¹. These results do not automatically apply to all fractures. Increasing swelling, a numb limb, or fingers that change color require medical reevaluation.

Returning to Activities: The exercises gradually replicate useful movements, such as getting up from a chair, climbing stairs, picking up an object, or carrying a load. The goals depend on which limb is affected and the activities you wish to resume.

Possible effects depending on the intervention and the population

A review of 26 studies reports improvements in functional ability and pain with exercise programs following a fragility fracture. Participants had a mean age of at least 50 years; therefore, these results do not reflect all fractures or all age groups. This 2026 review also shows less consistent results for strength and balance⁶.
Depending on the situation, physical therapy may:

• Tailoring mobility solutions to an individual’s limitations, restrictions, and needs
  
• Tailor your workout based on your limitations and the activities you want to resume
  
• Take into account pain and its impact on daily activities
  
• Preparing for a Gradual Return to Daily Activities and Work
  
• Developing the physical abilities that are relevant to the individual

To learn more about bone, muscle, and joint care, check out our comprehensive guide to physical therapy.

How to maintain healthy bones?

Physical activity, a diet that meets your nutritional needs, and quitting smoking all contribute to bone health. Screening for and treating osteoporosis—a disease that weakens bones—complements these measures when your risk warrants it.

Exercise: The Foundation of Bone Health

Exercises that work the muscles against resistance and those that place stress on the skeleton can improve bone density. The gains are generally modest and vary depending on the area being measured. Balance is another important goal, as it helps prevent falls.

Recommended activities:

• Weight-bearing exercises: Walking, dancing, and climbing stairs place the body’s weight on the skeleton. Running and jumping add impact. The choice of exercise depends on your experience and your risk of fracture; impact activities may need to be adjusted if you have osteoporosis.

• Resistance training: Muscles work against weights, resistance bands, or body weight. The difficulty increases gradually. The 2023 Canadian guidelines recommend this type of exercise at least twice a week for postmenopausal women and men aged 50 and older. The Canadian guidelines also recommend balance exercises and activities of daily living³².

• Balance exercises: Standing on one foot near a support, shifting your weight, or practicing adapted tai chi can help improve balance. The difficulty level should remain safe. The Canadian guidelines recommend these exercises and daily activities at least twice a week for this population. Check out our fall prevention exercises.

Swimming and cycling remain beneficial for physical fitness and heart health. However, a review found no clear benefit of these activities on bone mass; several studies of elite cyclists even observed lower bone density.³³ To support bone health, you can combine these activities with appropriate resistance and weight-bearing exercises. Yoga can also complement your routine to improve mobility and well-being, with modified movements if your bones are fragile.

Nutrition for Strong Bones

Calcium: The Essential Bone Mineral

Calcium and phosphate salts contribute to bone hardness.³⁴ The recommended intake of calcium is 1,000 milligrams (mg) per day for adults aged 19 to 50 and men aged 51 to 70. It increases to 1,200 mg for women aged 51 or older and all adults over 70. These amounts include both dietary intake and supplements, according to Health Canada’s reference values³⁵.

Many foods provide calcium. The amounts vary depending on the product and serving size; you can compare them using the nutrition label. Health Canada³⁶ lists several sources, and the table of calcium-rich foods³⁷ provides additional examples:

• Dairy products: milk, yogurt, and cheese
• Fish with edible bones: canned sardines or salmon
• Green vegetables: pak choi or curly kale
• Nuts and seeds: Almonds and chia seeds can supplement other sources; check their nutritional content per serving
• Fortified plant-based beverages: Choose a product whose label lists added calcium
• Tofu: Some products are high in calcium, depending on how they're made

A calcium supplement can make up for insufficient intake. If your diet already meets the recommended requirements, taking a supplement generally does not provide any additional protection against fractures. A healthcare professional can assess your intake, your medications, and whether a supplement is necessary.

Vitamin D and Calcium Absorption

Vitamin D helps the intestines absorb calcium and supports bone health.³⁸ It occurs naturally in few foods; fortified products are also a source.

• Fatty fish: salmon and trout, for example
• Eggs: especially the yolk
• Fortified products: milk, plant-based beverages, and certain juices; check the label for vitamin D

The skin also produces vitamin D when exposed to the sun. The season, age, skin color, and clothing all affect this production. Therefore, spending a set amount of time in the sun does not guarantee an adequate intake.

After age 50, Health Canada recommends a daily supplement of 400 international units (IU) of vitamin D in addition to foods that contain it. This supplement contributes to the total recommended intake: 600 IU per day for ages 51 to 70 and 800 IU for those over 70. Specific needs may require a professional adjustment. Health Canada’s guidelines explain dietary sources and supplements³⁹.

Proteins: Building Blocks for Bones and Muscles

Protein provides the building blocks needed to produce collagen and maintain muscle mass. The Bonjour review describes benefits for bone health and certain improvements in recovery associated with increased protein intake following a hip fracture.⁴⁰ This finding does not mean that a supplement is beneficial for everyone. A varied diet that meets your nutritional needs remains the foundation; specific needs should be discussed if you are not eating enough to meet your requirements or if a medical condition alters them.

Lifestyle Factors

Avoiding Smoking: Smoking is associated with an increased risk of fractures, only part of which can be explained by bone density.⁴¹ It is also associated with poorer healing following certain fractures. Support can make it easier to quit smoking.

Limiting Alcohol: Heavy alcohol consumption is a factor to consider in the overall assessment of bone health.⁴²

Avoid being underweight: Being underweight is associated with an increased risk of fractures, particularly hip fractures. It may warrant an assessment of dietary intake and overall health, but is not sufficient on its own to diagnose osteoporosis.⁴³

Osteoporosis Screening

Who should have a bone density test? Osteoporosis Canada’s 2023 recommendations suggest this test for postmenopausal women and men:

• 70 years of age or older, even without other risk factors
• aged 65 to 69, with at least one clinical risk factor for fracture
• ages 50 to 64, following a fracture related to osteoporosis or with at least two clinical risk factors

These thresholds serve as a guide for discussion with your doctor. Screening recommendations vary among Canadian organizations, particularly for men; your medical history and personal preferences also play a role. The Osteoporosis Canada guide provides more details on these guidelines³².

Bone mineral density testing is a test that measures the amount of minerals in the bones. The results help estimate how fragile the bones are, but the risk of fracture also depends on age, previous fractures, and other factors.⁴⁴ Our guide on osteoporosis and osteopenia explains these changes in bone density.

Bone health can be maintained at any age. During growth, physical activity and diet help build the skeleton. Later in life, exercise helps maintain physical function, and certain medications reduce the risk of fractures when osteoporosis warrants it. The review on postmenopausal osteoporosis describes possible treatments⁴⁵.

A 2017 review cites a global estimate that approximately one in three women and one in five men over the age of 50 will suffer an osteoporosis-related fracture during their lifetime. These proportions provide a general idea of the scale of the problem; they are not a substitute for an assessment of your individual risk.⁴⁶

When to consult a healthcare professional for your bones?

A suspected fracture, persistent bone pain, or signs of fragility warrant a medical evaluation. Certain signs, such as a deformed or numb limb following an injury, require emergency care. Physical therapy is then provided based on the diagnosis and the available treatment options.

Signs requiring prompt consultation

The time frame for seeking medical attention depends on the following signs. Do not try to reset a bone on your own.

After an injury: A possible fracture must be evaluated promptly. See a doctor the same day if you notice any of the following signs:

• severe pain that worsens or prevents the use of the arm
• pain when putting weight on the leg or an inability to bear weight
• great difficulty moving or marked stiffness
• significant swelling or bruising, or swelling or bruising that is getting worse
• very localized pain on the bone after the impact

Go to the emergency room if the injured limb is misshapen, if a bone is protruding through the skin, if a wound is bleeding heavily, or if the arm, hand, leg, or foot becomes numb, very pale, or blue. A tingling sensation after an arm or wrist injury also requires urgent evaluation. Call 911 in case of a serious injury accompanied by difficulty breathing, severe discomfort, or signs of shock. Guides on arm and wrist fractures²⁹ and leg fractures⁴⁷ provide more details on these signs.

No obvious injuries:

• Persistent bone pain, especially at night, requires a doctor's appointment.
• Any new pain in a patient with a history of cancer should be reported to the doctor.
• Bone pain accompanied by a fever or a worsening general condition requires prompt medical attention. A painful, red, warm, and swollen area of bone should also be evaluated promptly, even without a fever.
• A fracture following a minor impact—or one that occurred without any apparent impact—requires medical attention and an evaluation for bone fragility.

These signs alone are not sufficient to establish a diagnosis. Information on bone infection⁴⁸ and on bone-related symptoms that should be evaluated⁴⁹ explain when to seek medical attention.

Risk factors to discuss during the checkup

Osteoporosis may not cause any symptoms until a fracture occurs. Therefore, an evaluation may be helpful even in the absence of pain, depending on the risk factors and screening guidelines described above.

Risk factors to discuss:

• menopause, especially when it occurs early
• a parental history of hip fracture or a family history of osteoporosis
• low weight for height, as measured, in particular, by body mass index
• long-term use of corticosteroids, such as prednisone, which are medications that reduce inflammation
• hyperthyroidism, which is excessive activity of the thyroid, a gland in the neck; celiac disease, a condition in which gluten—a group of proteins found in certain grains—damages the intestines; or inflammatory bowel disease
• previous fragility fracture or repeated falls

Possible signs of a spinal fracture:

• a noticeable loss in size, especially if it has occurred since the last measurement
• a back that becomes more hunched, known as kyphosis
• persistent or new back pain

These symptoms can have several causes. They warrant a medical evaluation; a vertebral fracture cannot be confirmed based on posture alone.

The Role of Physiotherapy

Physiotherapists play an important role in several aspects of bone health:

After a fracture: If a rehabilitation program is recommended, the timing and content of the program depend on the fracture, the treatment, medical instructions, the patient’s abilities, and their goals:

• Restoring the range of motion
  
• Progressive muscle strengthening
  
• Exercises for balance and limb position awareness
  
• A gradual return to daily activities, work, or sports

Osteoporosis Prevention: A physical therapist can:

• Choosing resistance and weight-bearing exercises that promote bone health
  
• Practicing balance to reduce the risk of falls
  
• Build strength based on individual abilities and specific activities
  
• Adapt daily activities based on medical history, abilities, and the assessed risk

After a diagnosis of osteoporosis: The program takes into account previous fractures, physical abilities, and personal preferences. Certain movements that involve bending or twisting the back require modification when they are performed quickly, repeatedly, held for a long time, performed while bearing weight, or carried out through the full range of motion. Advice from a trained professional is particularly helpful after a recent fracture or when the risk is high.

Persistent bone pain: A physical therapy evaluation can help:

• Assess symptoms, movements, and limited activities
  
• Determine if a medical consultation is necessary
  
• Develop a pain management plan if appropriate

When to Act?

A recent fracture or new symptoms should not be put off until a preventive screening. If your concerns are more about bone fragility without any urgent symptoms, make an appointment to discuss screening and appropriate measures.

At Physioactif, the physical therapist assesses your abilities following a bone injury and works with you to plan your return to permitted activities.

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