physical activity markers

Reconstructions of physical activity from the skeleton

• long-bone cross-section morphology

• muscle attachment site (enthesis) morphology

• Osteoarthritis and other traumatic lesions

physical activity

It can be recorded in one’s teeth and bones

What types of activities can leave marks on the skeleton?

Exercise, repetitive movements, and trauma (acute or chronic).

What are the main limitations of activity markers?

What is preserved in bone/teeth and how accurately we can interpret it.

Why do researchers study skeletal activity markers?

To reconstruct past activity patterns, link past and present, and aid in identification.

Long-bone cross-section morphology

One of the first researched areas for activity reconstruction; analyzes bone shape and structure to infer mechanical stress and activity

Ruff et al. (1984)

Structural changes in the femur with the transition to agriculture on the Georgia Coast

What did Ruff et al. study?

The differences in femur structure between pre-agricultural and agricultural populations.

What change was observed in agricultural populations?

A significant reduction in second moments of area

How did bone shape differ in agriculturalists?

The bone diaphysis was more circular, as opposed to ovoid, cross-sectional shape

What conclusion did Ruff et al. draw about agriculturalists?

They had lower mobility and reduced physical activity compared to foragers.

Wolff’s Law or Bone functional adaptation

Bone adapts to altere physical stimuli

What involves the Wolff’s Law?

Physical loading or strain (tension and compression) stimulates bone deposition, and thus creates an increase in thickness/density at stress points

What types of forces influence bone remodeling?

tension and compression

optimum customary strain level

It varies depending on the bone and individual, and is subject to variables like anatomical location, diet, genetics, disease, age, sex, etc.

cross-sectional geometry of long bones

It models the diaphysis as a cylinder, especially as a hollow beam

What influences the size and shape of a bone’s diaphysis?

Is influenced by strain experienced over a long period of time (years to decades)

loading forces that act on the bone

tension, compression, bending, torsion, shear

bone strength

The ability to resist fracture

bone rigidity

The ability to resist deformation before breaking

cross-sectional cortical area (CA)

determines strength and rigidity under pure tension and compression

types of loading most important in bones

bending and torsion

bending and torsional strength

estimated using cross-sectional properties known as section moduli (Z)

bending and torsional rigidity

Estimated using multiple cross-sectional properties known as second moments of area (I)

What measures torsional rigidity?

Polar moment of area (J)

Muscle Attachment Site Morphology

Refers to where the tendons attach to the bones → an enthesis

Entheseal change (EC)

the current preferred term for changes at muscle attachment sites

At what levels can entheseal changes be analyzed?

individual, population, and for different muscles

How are entheseal changes evaluated?

By scoring each enthesis according to features such as robusticity, osteophytes, and osteolytic lesions.

robusticity

size and roughness of the area

osteophyte

A bony outgrowth → bone extending beyond the normal surface

osteolytic

bone loss such as cavitation and pitting

Palmer et al. (2016) study

The focus was on reconstructing physical activity using osteoarthritis (OA) and entheseal changes (ECs) of Post-Medieval Dutch Rural Villagers from their upper limb

What types of activities characterized this population?

Dairy farming and manual labor with a gendered division of labor

What was a key research question of the study?

Whether activity differences between males and females could be detected

Enthesial changes observed

Slight left side dominance; clear differences between males and females in activity patterns

How was left-side dominance interpreted?

The left side provided force; the right side guided movement.

What activities are associated with the biceps brachii?

Lifting heavy objects

What male activities matched with biceps use?

Consistent with historical records that males herded cattle, dug ditches, worked the field, carried and travelled with heavy objects

What activities are associated with the triceps brachii?

Arm extension, pushing, and pulling.

What female activities matched with triceps use?

Consistent with historical records indicating females milked cows, churned butter, made cheese, and washed laundry with a scrubbing board

limitations affecting ECs interpretations

There’s a strong positive correlation between ECs and age.

• As one gets older, our ECs become more pronounced

• Age effects may be stronger than activity effects.

• We should only compare similar age groups

What did Godde and Taylor (2011) investigate?

The relationship between musculoskeletal stress markers (MSMs), activity level, and BMI.

Argued that obesity increases mechanical loading stress on the skeleton

individuals were categorized as normal, active, or obese

They looked at the upper limb only

Vilotte and Knusel (2012) criticism

The authors didn’t control for age-at-death, and this omission could undermine all the results because age has a stronger effect on EC than any other factor

Why should forensic anthropologists be cautious using ECs?

ECs cannot reliably indicate activity or body mass on their own.

osteoarthritis (OA)

A mechanical joint disorder involving degradation of synovial joints.

Cartilage breaks down, and bone becomes damaged

one of the most common conditions in the skeleton

Joints that don’t move don’t develop OA

OA characteristics

• formation of marginal osteophytes → new bone around the joint margin

• pitting of the joint surface, some of which may communicate with subchondral cysts

• changes in the normal joint contour, often a widening of the end and flattening of the contour

• eburnation production → highly polished area that can be grooved in the direction of the joint movement

major risk factors for OA

genetics (50%), age, sex (more common in females), anatomy, obesity, trauma, and activity

how does age affect OA?

It worsens with increasing age

primary OA

OA with no prior joint condition; the bone was healthy before OA happened

secondary OA

OA with a preceding condition, such as trauma, and other joint diseases

Is osteoarthritis reversible?

No, it’s irreversible and progressive

Where is OA most commonly found?

knee, hips, hands, and spine; less common in ankle and elbow

Palmer et al results

no significant asymmetry between the right and left hands

The shoulder had the highest OA frequency (44.9%)

The elbow had the lowest OA frequency (8.7%)

The right clavicle showed more OA in the shoulder

Most cases were mild, increasing with age

No significant differences in sex

Do OA and EC results always align?

No, studies have found poor correlations between OA, EC, and long bone shape

What types of activity differences might affect markers?

• Low vs. high strain

• Monotonous vs. varied activity

• Long-term vs. short bursts

What do all activity markers (OA, EC, bone shape) have in common?

They’re all multifactorial

Osteochondritis dissecans (OD)

Refers to bone ‘chips’ on the joint surface

Associated with repetitive physical stress and microtrauma

usually found in the knee, elbow, and ankle

high prevalence in athletes and workers with physically strenuous or repetitive jobs

Rare to be encountered in archaeological populations → <1%

Middenbeemster cemetery

Has a high prevalence and distinctive pattern of OD

Vikatou et al. (2017)

They examined OD in the foot bones of a 19th-century rural Dutch population.

12.9% of the population had OD

Adults were mostly affected by OD, with only one teen

found to be more common in males, but still present in females

No difference between left and right side

Where were all OD lesions found in this population?

In the feet because of rigorous physical activity, plus wearing wooden clogs

What are klompen?

Traditional wooden clogs worn in parts of Europe.

How did clogs contribute to OD?

They transmitted impact forces to foot bones, increasing stress and injury