3 Chapter 3: Assessing general skeletal muscle function

Melissa Markofski

Background

Assessing general skeletal muscle function

Skeletal muscle strength is of great interest to a wide range of people. It is commonly used by people wishing to improve their fitness, as a goal for athletes, and to assess decline in clinical and aging populations. This is a wide range of applications, and as such there are a wide range of tests that can be performed. This lab will cover three different assessments: skeletal muscle endurance, strength, and static (isometric) strength.

Skeletal muscle strength can be measured by isometric, isokinetic, or isotonic testing. Some populations, such as unfit older adults or other groups at a high risk of injury, are often tested with isometric exercises. Athletic and young, healthy populations are typically tested with isotonic exercises. As with aerobic endurance testing, muscular strength testing can be a maximal effort, or a submaximal test that will estimate maximal strength.  For this lab, we will assess skeletal muscle endurance and strength with isotonic and isometric tests.

 

Health and safety warning: As with all activities in this class, only perform the activities you feel are safe for you to complete. Always follow your medical care provider’s recommendations.

Class activity

Activity 1: Upper body skeletal muscle strength and endurance (push-up test)

Push-up tests are a simple method for testing skeletal muscle strength and endurance in healthy individuals. This test requires little equipment and space, and can be conducted as either a one-on-one test or as a field test. However, it is not well-suited for all age ranges or people with shoulder injuries.

Research spotlight: Researchers followed male firefighters for 10 years. Those who could perform 40 push-ups at the start of the observation period had the lowest risk of cardiovascular disease. Read more: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2724778

Equipment: Workout mat

Participant: Each person (who is cleared for activity and does not have shoulder concerns) will participate in the activity

Additional reading: Your textbook (page 97) has additional instructions and pictures. Use this table to interpret the results: https://canadacollege.edu/fitnesscenter/assess-muscle-endurance.php

Instructions: (abbreviated from your textbook)

Notes: only count complete push-ups in the correct form

  1. Stand in the push-up “down” position. Men: start in the standard push-up position. Women: start on knees, with lower legs on the floor and feet planter flexed and laying on top of the mat
  2. Raise the body by straightening the elbows to just before they lock, then return to the staring “down” position. This is one repetition.
  3. Continue with good technique (back straight, arms fully extended) until the participant is unable to maintain the correct technique for two repetitions. After the first incorrect push-up technique, give a warning to the participant. Although this is not a cadence test, if the participant requires a rest of more than ~3 seconds between repetitions the test can be terminated for excessive rest.
  4. Compare your results with the table in the link above.
Virtual Lab Activity 1:
Perform the push-up test:
1. Using the instructions above (from your textbook), perform the push-up test.
2. Note the maximum number of push-ups you were able to complete.
3. Use this table (https://canadacollege.edu/fitnesscenter/assess-muscle-endurance.php)
to assess your fitness classification (Needs Improvement -> Excellent).

 

Activity 2: Lower body skeletal muscle strength and endurance (Single-Leg Wall Sit)

This test measures lower body skeletal muscle strength and endurance and requires little equipment and space. However, it is not well-suited for all age ranges or people with lower body or knee injuries.

Equipment: Wall space, timer

Participant: Each person (who is cleared for activity and does not have lower body or knee concerns) will participate in the activity

Additional Reading: This website has the scoring and normative data for the single-leg wall sit test: https://www.topendsports.com/testing/tests/wall-sit.htm

Instructions:

  1. Stand with your back against a wall with feet shoulder length apart.
  2. Slowly slide down the wall until your knees and hips are both at 90 degree angles.
  3. Start the timer when one foot is lifted off the ground. Stop the timer when the subject can no longer hold their foot off the ground.
  4. Perform this test with both the right and left leg.
  5. Compare the times for both legs with the table in the link above.
Virtual Lab Activity 2:
1. Perform the single-leg wall sit for both the right and left legs
2. Compare both your results with this table to assess your fitness classification: https://www.topendsports.com/testing/tests/wall-sit.htm

 

Activity 3: Skeletal muscle endurance testing

This test uses the stacked weight machines common in many fitness centers. Participants cleared for strength testing can complete the muscular endurance test. This protocol can be conducted on either the lat pulldown machine or the leg extension.
This test uses a relative weight for the strength assessment.

Equipment: Lat pull down and leg extension machine

Participant: Anyone cleared for weight training can participate. If a participant has a knee concern, the lat pulldown exercise should be used. If a participant has shoulder concerns, the leg extension exercise should be used.

Instructions:

  1. Calculate the weight the participant will use in this exercise. For the lat pulldown, men will use 66% of their body weight, and women will use 50%. For the leg extension, both men and women will use 50% of their body weight. Round to the nearest weight available on the machine.
  2. Set the machine for the participant’s height.
  3. Count how many repetitions can be safely completed.
  4. Compare the results to the table below:

 

Repetitions Fitness category
>13 Excellent
12-13 Very good
10-11 Good
8-9 Fair
6-7 Poor
<6 Very poor
Virtual Lab Activity 3:
Practice Calculations:
1. A female weighing 140 lbs is going to perform the lat pulldown test.
—-1a. What should the weight on the machine be set to?
—-1b. If she performs 14 repetitions, what fitness category is she in?
2. A male weighing 166 lbs is going to perform the leg extension test.
—-2a. What should the weight on the machine be set to?
—-2b. If he performs 10 repetitions, what fitness category is he in?

 

Activity 4: Static leg strength

Equipment: Goniometer, static strength platform

Participant: Anyone cleared for weight training can participate. A second person is needed to check the joint angle prior to the start of the test.

Instructions:

  1. Have the participant stand on the platform in a partial squat while holding the hand bar across their thighs. Using a goniometer, confirm that the participant‘s knees are flexed at an angle between 130-140° and adjust the length of the chain as needed.
  2. After a brief post-setup rest, the participant holds the hand bar with a pronated grip and rests the bar across their thighs.
  3. Using only the legs (not the back), slowly extend the knees and exert as much force as possible.
  4. The participant will do two attempts with a one minute rest in between. Record the highest attempt.
  5. Convert to kg and use the table in the Blackboard folder for this lab to look up strength classification (use the “Leg strength (kg)” column for this test).

Video: Example of a lower body static strength test

 

Virtual Lab Activity 4:
Practice Determining Fitness Classification:
1. Practice determining the fitness classification for the participant below.
(The table used is located in the Blackboard folder for this weeks lab)
*Hint* For this test, remember that the highest score is used, not the average.