EXAMINING THE EFFECTS OF SPACE FLIGHT ON THE MUSCLES

CASE STUDY 4 THE EFFECT OF SPACE FLIGHT ON THE MUSCULAR SYSTEM
Principal Investigator: Kenneth M. Baldwin, Ph.D. University of California at Irvine Irvine, California

INTRODUCTION

Pump iron for a month and, presto, your muscles get stronger. Take to your La-Z-Boy chair for a month and your muscles go soft (Figure 1). Everyone knows this happens, but why does it happen? Why should you have to work to keep your muscles in shape? Why can't you relax and take a pill that duplicates two hours at the gym? Or wouldn't it be nice to be able to just swallow a can full of spinach and physically transform ourselves, as Popeye the sailor man is able to do? Unfortunately, we all know it's not that easy. In this chapter we are going to examine how our muscles work and this will lead us to understand what we must do to "feed" our muscles so that they do not atrophy, or get soft and waste away. We will start with a description of the structure and mechanical action of muscles. We will then look at the chemical activities that take place in the muscles to assure that they receive the appropriate levels of energy to keep us moving. Finally, we will learn about an important space study that was carried out to see how and why the muscles of astronauts can change their very character as they adapt to the new environment of space where the natural gravitational pull is absent. Let's first examine how the muscles behave on Earth.

Figure 1. Use of the television remote control may build muscles in the index finger, but the rest of your body requires movement and exercise.