# 1. A closer look - Muscles and their role in health and energy needs of athletes...

###### Question:

1. A closer look - Muscles and their role in health and energy needs of athletes

Skeletal muscles, which move bones, consist of cells fused into long fibers. These muscle fibers can increase in size when contracted, which is what happens as a result of some exercise. This animation shows the structure of vertebrate skeletal muscles. It starts at a large scale, showing the muscles of a human upper arm, and then gradually zooms in to smaller and smaller levels, labeling each structure along the way. Watch the animation and then answer the question that follows.

Many bundles of skeletal muscle fibers grouped together form a     .

a.myofibril

b.sarcomere

c.skeletal muscle

The increase in volume of the muscle fibers due to the enlargement of its components is referred to as     .

a.hypertrophy

b.atrophy

c.hyperplasia

Kevin and Dmitri are friends who both enjoy exercise. They are a similar height and weight and both are in good shape, but they have different workout activities. One does primarily aerobic exercise, and the other does primarily anaerobic exercise. They both enroll in a study that measures the concentration of lactate in their blood over the course of their normal workouts.

The following charts present the results of the study and show the percent of lactate concentration in each man's blood over the course of their workouts, measured at two-minute intervals.

On the following graph, use the points indicated in the charts to graph the results of the study for each man. Click and drag the points on the right-hand side of the graph onto the grid of the graph; line segments will automatically connect the points. Remember to plot from left to right. There are 6 points for each man, so when you are done, there should be 12 total points on the graph. Look at the pattern the points make, and then answer the question that follows.

Kevin's Lactate Concentration in the Blood (Blue points, circle symbol)

Duration of exercise (Minutes) 0 2 4 6 8 10
Lactate concentration in the blood (Percent) 0 15 25 35 45 50

Dmitri's Lactate Concentration in the Blood (Orange points, square symbol)

Duration of exercise (Minutes) 0 2 4 6 8 10
Lactate concentration in the blood (Percent) 0 5 10 10 15 20

KevinDmitri024681050403020100Lactate concentration in the blood (Percent)Duration of exercise (Minutes)10, 20

Which man is doing a workout that primarily involves anaerobic exercise?

Kevin

Dmitri

In the previous question, you identified the individual who was completing aerobic exercise. This aerobic exercise helps to increase

a.musculoskeletal fitness

b. flexibility

c.cardio respiratory fitness

, or the ability to perform moderate-to-high-intensity activity involving large muscle groups for long periods of time.

Identify the activities that would most likely improve an individual’s cardiorespiratory fitness.  Check all that apply.

Bench pressing

Stretching

Triathlon

Running

The excitation, contraction, and relaxation of skeletal muscle require the use of ATP. Because only limited stores of ATP are immediately available in muscle tissue, ATP must be continually supplied if contractile activity is to continue.

Depending on the type of movement or exercise, one or more pathways can be used to provide the most efficient way of supplying the ATP.

For example, a friend of yours goes to the gym and takes a 30-minute, cardio interval training class. While switching between doing high-intensity push-ups, jumping jacks, and weight training, she notices that there is a burning sensation in her muscles.

The burning is due to the buildup of

a.creatine phosphate

b.lactate

c.alcohol

in the muscle tissue, a result of her muscles supplying ATP   .

a.anaerobically

b. aerobically

a.This pathway typically utilizes creatine phosphate supplies to provide short bursts of high-intensity contractile effort.

b.Known as glycolysis, this pathway is ideal for endurance-type exercises, where glycogen stores are slowly and steadily depleted to provide a consistent rate of ATP production.

c.This pathway is typically used when oxygen delivery or oxidative phosphorylation capacity is exceeded.

d.Compared to oxidative phosphorylation, this pathway can generate ATP more rapidly but also depletes glycogen stores more rapidly.

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