# 6 Chapter 6: Skeletal muscle strength and power

Melissa Markofski

# Background

## Skeletal muscle Strength and power testing

Skeletal muscle strength and power testing is of interest for a wide range of individuals. It can be used to evaluate the effectiveness of a training plan, or the potential next season performance of an athlete. For example, several of the tests in the NFL combine are evaluations of skeletal muscle strength and power.

The vertical leap is a test of skeletal muscle power. The gold standard method of measuring skeletal muscle power from a vertical leap is to use a motion analyses system and measure the distance the participant’s center of gravity travels from standing to the highest point of the jump. However, motion analyses systems are costly and require specialized training to use and analyze the results. Simple analog systems (like the Vertec) that can measure distance jumped have decent reliability when compared to motion capture systems and are frequently used instead. However, in this class we will use an electronic system called “Just Jump”. Just Jump will measure the time off the ground to calculate the jump height. The Just Jump system has a higher correlation coefficient than the Vertec system, and although it costs more than a Vertex system it is still much less than a motion analyses system. Unlike a Vertec system, there are no bars to reset and therefore Just Jump is a very quick measurement and set-up.

There are several methods to evaluate skeletal muscle strength and power. The tests are specific to the muscle groups being tested and the specific protocol. For example, a test of upper body skeletal muscle strength at a low velocity will not indicate the same performance of the lower body to at a high velocity.

In this lab, we will use a variety of methods to measure or estimate skeletal muscle strength and power. Some of these measurements, like 1RM, are useful for evaluating resistance training program effectiveness and for setting training loads. Other tests, such as the vertical jump, are used to measure skeletal muscle power.

# Class activity

## Activity 1: One repetition maximum (1RM) and 8RM testing

Equipment: bench, barbell, weight plates

Participant: one person from your group (ideally someone who knows approximately how much weight they can bench press)

Instructions:

1. Warm up. When conducting a 1RM test, a proper warm up is important for reducing injury and for obtaining a good effort on the test.
2. Begin with a weight of approximately 50% of 1RM, and have the participant perform 8 repetitions.
3. Move to a heavier weight and have the participant perform 5 repetitions.
4. As we are also doing an 8RM test, at this point ask the participant how many more repetitions they think they could have performed at that weight.
5. Adjust the weight as needed.
6. Have the participant attempt their 8RM.

a. If the participant cannot perform eight repetitions, lower the weight and try again,

b. If they do eight repetitions and state they are able to do more, increase the weight and try again.

7. After the 8RM test, use the 1RM estimation equation (below) to estimate 1RM. Calculate a weight ~10% lower as a starting weight for the 1RM test.

8. Adjust the weight as needed until the participant can only lift the weight one time. The participant should have 2-3 minutes rest between each attempt.

To estimate 1RM from 8RM:

There are several different equations that can be used to estimate 1RM, and each one will result in a slight variation of 1RM prediction. For the purpose of this lab, we are using the Epley 1985 equation. This equation assumes the participant could lift 3% more weight for every repetition that was completed.

((Weight lifted for 8RM) * 0.03 * 8)+weight lifted for 8RM = estimated 1RM

## Activity 2: Barbell velocity

Equipment: bench, barbell, plate weights, stopwatch, Open Barbell barbell velocity measuring device

Participant: One person from your group (the same person who volunteered for 1RM testing) will perform the test, and other members of the group will collect measurements and set up the weights.

Instructions:

1. Perform 3 single repetitions with 40% of 1RM. Use the Open Barbell device to measure (and record!) barbell velocity.
2. Perform 3 single repetitions with 60% of 1RM. Use the Open Barbell device to measure (and record!) barbell velocity.
3. Use the average of the average velocities for each intensity (40% and 60%) calculate power. (below)

P= Fv (Power= Force * velocity)

F=MA (Force = Mass * Acceleration)

A=v/t (Acceleration = velocity / time)

Notes:

The Mass of the barbell is given (convert pounds to kilograms).

Velocity is measured by the Open Barbell.

Time is the measured time of each squat’s concentric portion.

Short promo video of the Open Barbell unit we will use in the class (optional watching)

## Activity 3: vertical leap

Equipment: Just Jump system

Participant: Everyone (without exercise limitations) participates

Instructions:

1. Select mode of operation by pressing push-button switch while the appropriate mode is flashed on the display.
2. From a standing feet together position, leap into the air as high as possible. Do not move off the mat until the numbers are read.
3. The unit will display two numbers: your air time and your vertical jump (in inches).
4. Three attempts, with one minute rest between attempts. Use your best attempt to determine your power percentile (see table in Blackboard folder) and peak power (in Watts) using the Sayers 1999 equation (below).

Peak power (W) = (60.7 * jump height) + (45.3 * body mass) – 2055

Units: jump height (cm) and body mass (kg)

Note: there are several equations to calculate peak power from the vertical jump

Video on how to use the Just Jump system and positioning for an effective countermovement jump.

## Activity 4: Standing long jump

Equipment: Long jump mat

Participant: Everyone (without exercise limitations) participates

Instructions:

1. Start with the toes just behind the starting line (not in the feet!)
2. Perform a countermovement and jump as far forward as possible
3. Measure from the back of the heel. If the person falls down, the trial is repeated
4. Record three trials to the closest 0.5 inch