Iron, Vitamin D, Bone Density and Running Performance (2)

More than 700,000 high school boys and girls participated in..

high school XC in US in 2016-17, making XC the 4th and 6th most popular sports

The seasonal incidence of injury in high school girls and boys competing in XC is?

Girls: 34-47% (16.7 to 19.6/1000 athletic exposures)

Boys: 26-48% (10.9-15/1000 athletic exposures)

Most common injury sites for XC runners of both sexes are..

Shin, followed by knee then ankle

*many initially are minor but may progress to season ending if not treated

Risk factors associated with running related injuries (RRIs) are divided among...

Personal factors

-age, weight, height, diet

Training factors

-running volume, frequency, intensity, mechanics

Health factors

-meds, previous injury

Many injuries are a result of interaction among several risk factors

Distance running athletes have high requirements for..

If these needs are not met, they may experience..

Nutrition/calorie intake

Low energy availability (LEA)

LEA can be a result of a variety of factors including ...

-Disordered eating (DE)

-Inadvertent lack of apetite

-Poor nutritional knowledge

-Intentionally trying to achieve a physique to optimize performance

LEA may result in...

Adverse health outcomes

-no menstrual cycle

-low iron (anemia)

Increased risk of MSK injuries

Impaired performance

When providing diet logs/records, it is well-documented that..

some individual will under-report their food intake

*can result in potentially false positive diagnosis of LEA

High prevalence of .... indicated that athletes fail to balance energy expenditure with adequate energy intake

Eating disorders, DE and physiological symptoms of LEA such as oligomenorrhea/amenorrea in women and low testosterone in men

In XC and track there is a high prevalence of LEA and ED/DE that are more common in..

Females than males athletes

Much evidence suggests that LEA-related issues may..

Start in the youth

**Females and males diet or skip meals to lose weight thinking that being thinner leads to running faster

Optimal bone health is a factor of..

Adequate levels of circulating vitamin D and iron

Vitamin D contributes to..

Vitamin D also plays a crucial role in muscle including..

Bone health by maintaining calcium homeostasis

Strength, power, endurance

Iron is intricately involved in..

collagen synthesis and conversion of vitamin D to active form

A decrease in intracellular iron can lead to....

Impaired function and activity of osteoblasts (cells that form bone tissue) and osteoclasts (cells that break down old or damaged bone to make room for new bone growth)

Impairment of osteoblasts and osteoclasts may result in..

Imbalance in bone homeostasis and ultimately bone loss

Iron is crucial in..

Oxygen transport to working muscles

*potential for energy/ATP production

Vitamin D deficiency in athletes may be as high as ___.

Iron deficiency in female high school athletes may be as high as ___.

56%

52%

Mechanisms that influence vitamin D deficiency include...

Low bioavailability from sunlight

Inadequate dietary intake

Mechanisms influencing iron deficiency include..

GI bleeding

Hemolysis (repetitive ground impact)

Lack of dietary iron

Iron loss via sweat

__ is a key mediator of iron homeostasis.

It is involved with..

Hepcidin

-iron absorption

-iron release

-iron storage

-iron transport

-preventing iron overload

Hepcidin regulates iron balance by..

binding to the iron export protein (ferroportin), which inhibits iron efflux from enterocytes, hepatocytes and macrophages

Hepcidin is upregulated by..

Increase iron stores and inflammation that occurs as a result of training-and in particular intense training

___ stimulate hepcidin production

Pro-inflammatory cytokines such as Interleukin-6

*strenuous exercise causes inflammation

___ hours following a single, prolonged bout of intense exercise, hepcidin levels peak.

3-6 hours post exercise

In a study looking at iron deficiency and hepcidin levels...

Higher intensity training created a greater iron deficiency and higher hepcidin levels

**Iron supplements did not impact hepcidin, therefore hepcidin levels were elevated DESPITE adequate daily iron intake

Training related factors that influence RRIs..

1. Running the same mileage each day >25% of the time

2. Alternating low and high mileage on different days <25% of the time

3. Training <8 weeks prior to start of competitive season

4. Running on predominately flat or irregular surfaces, including hilly terrain >33% (particularly in females)

College runners who increase their weekly mileage during a season more than 11 miles per week (11-29 miles/week) reported...

More RRIs compared to those who increased their weekly mileage <10 miles per week throughout the season

Specialization has been defined as...

training and/or participating in a particular sport >8 months of the year

-Boys: 36 miles/week

-Girls: 29 miles/week

Lower step rates have been associated with...

Increased risk of shin injury in high school runners

**<166 steps/min=6x greater likelihood of shin injury

Decreased step rate often leads to..

longer stride length and a longer stride length often leads to over-striding as well as vertical oscillation ex: bounce from mid-stance to toe off

Sagittal plane instability relates to...

This can suggest RRIs such as...

Anterior/posterior pelvic tilt

Weak abs & hamstrings

Tight hip flexors & low back

Frontal place instability relates to...

This can suggest RRIs such as...

Lateral pelvic drop

Weak gmax & gmed

Increased Q-angle often accompanied by...

IR of tibia and increased pronation of the foot

A Q-angle of >20 degrees or a Q-angle asymmetry of >4 degrees between L and R sides has been associated with...

Greater risk of RRI during a competitive season

In females with a history of lower extremity stress fracture..

Greater (relative) peak vGRF and loading rates are associated with RRIs

*ex: greater peak vGRF/body mass

Serrum iron is the...

Ferritin is..

Amount of iron circulating freely in the body

Measure of stored iron

*You can have normal serum iron levels with low ferritin

Unsaturated iron binding...

Measures amount of transferrin in blood not yet bound to iron

Total iron binding capacity..

how well your blood binds to the protein transferrin

% iron saturation...

Amount of iron in blood bound to transferrin

(aka transferrin saturation)

Hemoglobin is...

Protein in red blood cells that is involved with carrying O2 throughout the body

**low hemoglobin leads to anemia

Hematocrit is...

Provides a measure of the percentage of RBCs in the blood

Hepcidin is...

Hormone that regulates body's iron levels; essential for iron homeostasis

*involved in iron absorption, release, storage, transport, and preventing overload

Dual energy x-ray absorptiometry=DXA which is a scan..

Considered the gold standard for assessing bone density and osteoporosis

**most accurate tool for assessing body composition

BMC=

Bone mineral content

-measurement of bone mineral found in specific area (g)

BMD=

Bone mineral density

-amount of bone mineral in bone tissue

Bones containing more minerals are..

More dense

Z-scores compare..

A person's bone density to the average bone density of people of the same age, sex, and ethnicity

T-scores compare..

A person's bone density to that of a healthy young adult

**compare participant's results to 2 SDs

Greater than -1.0.....

-1.0 to -2.5 may indicate...

Greater than -2.5...

Normal

Osteopenia

Suggests osteoporosis

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Waist

Hips

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