1
Laboratory 2: The Measurement of Strength and Factors Associated with Expression of Strength
Strength is the maximal amount of tension that can be generated in one maximal effort. Muscle
contractions are categorized as dynamic (moving through a range of motion (ROM)) or static (no
movement through ROM). Strength is measured by means of three different types of muscular
contractions that are defined by the method of assessment (i.e., equipment used).
Strength assessment/training equipment are of two major types: (a) isometric (“static”) with no
movement and (b) dynamic with movement through the ROM. Dynamic equipment include constant
resistance (“Isotonic”), (c) variable resistance, and (d) isokinetic equipment (constant velocity). Of
all the types of testing/training equipment, isokinetic contractions require the most specialized and
costly strength testing equipment and is considered to be the most accurate method for assessing
muscular strength.
It is important to recognize that the maximal force developed when strength is measured is affected
by behavioral (i.e., neurally-mediated) factors such as motivation or emotional state, as well as
physiological factors such as structural components of muscles and neuromuscular components.
We often speak of a strong person or a weak person implying that strength is a general quality (i.e.,
that all of an individual's muscles are strong or weak to the same extent). The relationship of
strength among the various muscles favoring one person is not perfect, yet a high degree of
association generally exists. Also, a person’s strength can be expressed either as an absolute or
relative value.
Purpose
The purpose of this laboratory experience is to investigate some of the factors associated with the
measurement and expression of strength. Specifically, the following topics will be addressed: (a)
relationship between muscle size and body size to muscular strength, (b) absolute versus relative
muscle strength measures, (c) relationship between the strength of different muscle groups, and (d)
behavioral influences on strength.
Equipment
Skinfold calipers
Measuring tape
Grip dynamometer
Procedures
1.
Relationship of muscle size to muscle strength.
1.1
Determine the right and the left maximum grip strength (lbs).
Trial 1
Trial 2
Best
Right Grip
_____
_____
_____
Left Grip
_____
_____
_____
2
1.2
Estimate muscle diameter by determining the arm diameter corrected by skinfold fat
of both the left and right forearm using the following procedure:
a.
Measure the forearm circumference of each arm with the arms hanging freely
(area of greatest girth).
Right_______ mm
b.
Left______ mm
Correct for fat by measuring skinfold thickness over the dorsal (S1) and
ventral (S2) sides of each arm.
Right: S1_____ mm S2_____ mm
Left: S1_____ mm S2_____ mm
c.
C = circumference = π x diameter
 diameter = C / π
Right forearm diameter (cm):
C / π - [S1 / 2 + S2 / 2] = _____ - _____
= _____ mm = _____ cm
Left forearm diameter (cm):
C / π - [S1 / 2 + S2 / 2] = _____ - _____
= _____ mm = _____ cm
1.3 Determine the strength to diameter (lbs/cm) ratio of the best right and left grip strength
results and their respective forearm diameters.
2.
Best Grip (lbs)
Diameter (cm)
Strength/Dia(lbs/cm)
Right Forearm
_____
_____
_____
Left Forearm
_____
_____
_____
Behavioral influences on strength.
2.1
Using your dominant hand, make two maximal efforts with a loud SHOUT and
compare value to the results obtained under non-verbal conditions.
Normal Max
(Best from 1.1)
With SHOUT
Trial 1
Trail 2
Best
_____
_____
_____
_____
_____
_____
3
3.
A comparison of absolute versus relative body strength.
3.1
3.2
Using a weight machine or free weights, determine the subject's upper arm and chest
strength (bench press and tricep extension), hip and leg strength (leg press). Take
care to avoid undue fatigue by means of numerous single repetitions to determine
your "true max."
Maximum Bench Press =
_____ lbs
Maximum Leg Press =
_____ lbs
Max Bicep Curl =
_____ lbs
Compute your "Total Strength Index" (TSI) using data from previous determinations.
The TSI value is an index of your absolute body strength.
Grip
(no shout)
3.3
+
Bicep
Curl
+
Bench
Press
+
Leg
Press
=
Total
(TSI:lbs.)
Compute a measure of relative body strength by correcting your TSI by your body
weight using the following equation:
Relative Body Strength
=
TSI (lbs) / body weight (lbs)
=
_______ lbs strength / lb body weight
4
Graph 2.1
1)
a.)
b.)
2)
3)
5
Graph 2.2
1)
a.)
b.)
2)
3)