Bone Mineral Density Measures in

Female College Endurance Runners

Kristin Casagrand

Introduction

BMD- Measure used to evaluate effects of physical activity on bone mass

Need healthy bones to do daily activities without getting injured

5-8% increase in BMD can increase bone strength 64-87% (Kohrt et al., 2004)

Bone building is stimulated by dynamic, variable mechanical force loading

Introduction (cont’d)

Exercise helps in building bone massPositive effects from high impact and strength –

based activitiesNegative/neutral effects from non-weight bearing

Physical activity prevented or reversed about 1% of bone loss per year in women (Wolff et al., 1999)

Maximizes bone mass during childhood, maintains through adulthood, slows loss during aging, and helps reduce falls/fractures in elderly

Introduction (cont’d)

Over exertion or stenuous activity may lead to negative effect on BMDCan lead to stress fracturesFuture osteoporosis

My study focuses on the effects of endurance running on females’ BMD

Several studies lookes at effects on endurance running on BMD, but not many longitudinal studies to track changes in BMD over timeMy purpose is to observe this in female cross-

country runners over the span of their college career

Hypothesis

A significant decline in BMD will be observed in Ole Miss cross-country

runners from freshmen to senior year, especially in the lower body and spine.

Limitations & DelimitationsLimitations:

Honest self-reporting on questionnairesAssuming intervention participants will engage in

regular intense runningAssuming control participants will not surpass study

exercise limitations

Delimitations: Female college students at Ole Miss Convenient volunteer sample Limited sample size of 40 Only endurance running Excludes males

Literature Review

34 million people in the US have low bone mass20 million have osteoporosis, which causes 1.3

million hip fractures/yr (NOP, 2011)

Many factors influence BMD…

AgePeak BMD reached around early-mid 20sGradual loss of BMD after menopause

Literature Review (cont’d)

EstrogenHypoestrogenism adolescents develop lower peak

BMD (Zeni et al., 20000)Deficiency impedes normal bone building

mechanism (Bemben and Fetters, 2000)

Menstrual Cycle44% of runners had menstrual disturbances (Mudd

et al., 2007)Athletes with amenorrhea had lower overall BMD

than those with eumenorrhea & control subjects (Christo et al, 2008)

Literature Review (cont’d)

CalciumWith exercise, BMD decreased if daily intake was not

1000-1500 mg/d (Bemben and Fetters, 2000)Regular exercise prevents 1% bone loss/yr 1.3%

increase with sufficient calcium (Wolff et al., 1999)Low calcium lowers effectivness of mechanical

loading (Kohrt et al., 2004)

NutritionVitamin K protects against age-related bone loss

(Booth et al., 2003).Vitamin D

Literature Review (cont’d)

ExerciseRegular exercise builds BMD, too-intense exercise

dangerous In marathon runners intense exercise caused

uncoupling of bone cell metabolism (Crespo et al., 1999)

Negative association between BMD and distance run (Burrows et al., 2003).

So, will we see negative BMD effects of intense endurance running in the study?

Methodology

40 female Ole Miss volunteers 20 cross-country runners 20 control subjects (can’t exercise >60 mins, 5

days/wk)

Recruitment Control- mass email to general, non-athlete student

population

Must agree to participate freshmen- senior year

Exclusions Dropout/transfer Family history of osteoporosis Taking meds that influence bone health

Methodology (cont’d)

Pre-studyFill out dietary, medical history, & menstrual health

questionnaires IRB approval and signed consent formBaseline measures- weight, height, initial BMD

StudyYearly BMD measures (total of 5 measurement

periods)Total body, lumbar spine, pelvis, legsDXA

SPSS data analysis will be performed