ExerciseExercise

Monica V. TrevathanEducation Specialist

Human Health and PerformanceJohnson Space Center - NASA

June 2, 2005

William E. Amonette, M.A., CSCSAstronaut Strength, Conditioning, and

Rehabilitation TeamJohnson Space Center - NASA

Web Seminar Objectives

1. Review physiology of bone remodeling

2. Discuss changes that occur in micro-gravity

3. Discuss Astronaut exercise programs

4. Discuss the importance of exercise

Human Body as an Automobile

• Brain is the computer of the system

• Motor and drive train are the muscles

• Bone is the chassis (frame)

Definitions

• Bone Mass – The total amount of bone.

• Bone Mineral Density (BMD) - The amount of bone in a given area of space.

• Bone Strength – The breaking strength of a bone. Factors in density, mass, and the structural make-up of the bone.

Definitions

• Osteoblasts – cuboidal cells that synthesize components of bone matrix and are also responsible for the production of new bone.

• Osteoclasts – multinucleated (50 + nuclei) bone cells that dissolve bone matrix.

Types of Bone

Cortical bone (compact) / Trabecular bone (spongy)

Wolf’s Law:

“As bones are subjected to stress demands in weight bearing posture, they will model or alter their shape

accordingly.”

Journal of Subluxation Research

Bone Remodeling

• Ongoing process that happens throughout life.

 • Osteoclasts remove bone, and osteoblasts come

in behind the osteoclasts and lay down new bone.

 • The bone quantity of the adult skeleton may be

replaced in 5 years.

• Process is not uniform throughout the skeleton.

Factors Affecting Bone Remodeling

• Activity Level

• Age

• Force on bone

– Compression (impact)

– Torsion (twisting)

– Strain (pulling)

– Shear

• Rate of Force Development

• Volume of Impacts

• Diet (calcium & Vitamin D)

• Etc.

Bone and Astronauts During Spaceflight

• Bone begins to remodel in as little as 3 days of microgravity.

• Over-time the changes in bone resorption result in losses of bone mineral density (BMD) and strength.

Bone and Astronauts During Spaceflight (cont.)

• The magnitude of changes are not uniform, and seem to occur faster in trabecular (spongy) bone than coritcol (compact) bone.

• The changes occur faster in load-bearing bones.

Bone and Astronauts During Spaceflight (cont.)

• Changes are specific to load bearing sites of the skeleton, most dramatically in the

– Calcaneous (heel bone), – Femoral neck, – Lumbar spine, and

– Pelvis.

Bone and Astronauts During Spaceflight (cont.)

• About 1% of total bone mass is lost per month. 12x faster than with osteoporosis.

Astronaut Strength and Conditioning

• Exercise is the most promising countermeasure for microgravity related bone loss.

• Astronauts perform exercise:– Pre-spaceflight– During-spaceflight– Post spaceflight

Astronaut Strength and Conditioning

• Exercise programs are designed to develop or maintain:

– bone mineral density,

– aerobic and anaerobic capacity, – strength, – power, and

– local muscle endurance.

Strength & Conditioning

• Structured program begins 6-months prior to shuttle flights and 1-year prior to ISS flights.

• Two-hours per day 2-3 times per week is scheduled for exercise preflight, but adjusted if there are other training requirements.

Strength & Conditioning (cont.)

• Space Shuttle astronauts

• ISS crew members

Exercise on ISS Resistive Exercise (IRED)

Exercise on ISS

Treadmill (TVIS)

Exercise on ISS

Cycle Ergometer (CEVIS)

Post-Flight Reconditioning

• After long duration flight, astronauts go through a 45-day reconditioning program.

• The program is progressive and it involves a number of variables.

Post-Flight Reconditioning (cont.)

• Purpose – to safely return to activities of daily living as soon as possible.

• Within the 45 days strength, power, flexibility, and aerobic and anaerobic capacity are usually restored.

• Loses in bone mineral density may take more than 2 years to restore.

How do we prevent bone loss?

• The number one preventative measure is to achieve high levels of peak bone mass early in life.

• Peak bone mass is achieved between the ages of 25-30.

• After the ages of 25-30, we can only flatten out the rate of decline of bone mass.

25-30

Bone loss can be thought of as

saving for retirement.

Kids and Training

* Forces measured during weightlifting can be 40x body

weight.*

• Junior Olympic weightlifters (ages 15-17) have much greater BMD than age matched controls.

Kids and Training (cont.)• They have greater BMD in the

spine and femoral neck than adults between the ages of 25-30.

• Greater bone BMD is likely due to the high force and rate of force production from weightlifting.

* Forces measured during weightlifting can

be 40x body weight.*

Kids and Training (cont.)• Junior gymnasts (7-8

yrs. old) have greater BMD in load bearing sites of the sport.

• The magnitude of changes appear to be related to volume of training.

* Forces during landing from a jump in gymnastics are up to 16 times body weight.*

What does this mean for our Kids?

• BMD is affected by activities that involve impact loading.

• Any sport or other physical activity involve impact loading.

• BMD can be enhanced in children as young as 7 and they should remain active throughout life to prevent low bone mass later in life.

How can you help NASA?

• Presidential initiative states that we will go to the planet Mars bythe year 2030.

• Astronauts with low bone mass will likely be disqualified for a Mars mission.

How can you help NASA? (cont.)

• Potential astronauts for a Mars mission are likely in grades 5-8 right now.

• If your desire is to be a long duration astronaut, you must be attaining high levels of bone mass now.

Conclusion

• Bone remodeling is a process that continues throughout life and is affected by daily activities and exercise.

• Astronauts who go to space lose BMD at a rate 12x faster than osteoporotic humans on Earth.

• NASA implements exercise pre-, during-, and post-spaceflight to minimize loss of bone.

Conclusion (cont.)

• Number one preventative measure for diseased levels of bone mass is exercise early in life.

• BMD can be enhanced in children as young as 7 and they should remain active throughout life to prevent low bone mass later in life.

Related NASA Education Material

• National Space and Biomedical ResearchInstitute

• Activities Guides for Teachers5-8 grade

http://www.nsbri.org/Education/index.html

Related NASA Education Material• NASA CONNECT™

• Good Stress – Building Better Muscle and Bone

• Better Health from Space to Earth

• Grades 5-8

http://connect.larc.nasa.gov

Related NASA Explores Articles

• “Flying Fit”• “Muscle-bound Research”• “Use It Or Lose It!” • Articles and lessons for:

K-4, 5-8, 9-12 grades

http://www.nasaexplores.com

Monica V. TrevathanEducation Specialist

Johnson Space Center - NASA

William E. Amonette, M.A., CSCSAstronaut Strength, Conditioning, and

Rehabilitation Team

Thank You!