Download File

Ruth Spitsbergen
Kines 326
Isokinetic Dynamometry and Resistance Assessment
Abstract
Background: Muscle strength is the greatest amount of force produced by a given
muscle group. Muscle endurance is the ability for a muscle group to sustain that
force over a longer period of time. AIM: The purpose of this study was to introduce
the isokinetic dynamometry machine to students to evaluate muscle force (torque in
ft-lbs) and exertion at the knee for angles of extension and angles of flexion at
various degrees. The assessment also compared maximum strength fatigue with
endurance fatigue. Method: 5 subjects, three females and two males, (mean age±22
SD ±.63) warm-up on a stationary cycling ergometer for approximately five minutes.
Subjects’ questionnaire consisted of height (inches), weight (lbs), and age (years).
This information was imputed into the Biodex software program where individual
data would be generated. Trial one had three subjects one male and two females
participate in 5 sets of maximal force exertion of the dominant leg at contraction
and relaxation rates ranging from 30- 300 degrees/second. Trial 2 consisted of one
male and one female with the same questionnaire and warm up. This test consisted
of flexing and extending the quadriceps for 80b repetitions at an angle of 180
degrees/sec. This test is to maintain force throughout the entire 80 repetitions as
consistently as possible. The strength test measured peak torque for extension and
flexion at 30 degrees. Results: During trial 1, subjects exerted an average of 177.6 ftlbs±67.29 at 30 degrees/sec and 51.66ft-lbs±24.22 at 360 degrees/sec. During trial
2, subjects averaged a fatigue of work output of 77.2%±4.10 over 80 repetitions. As
velocity increased force output of the knee extension and knee flexion decreased.
Conclusion:
At an increased rate of contraction, force output contraction decreased. For the
endurance test as repetitions increased the force output decreased.
Questions:
Table 1: Individual and Mean Values for Peak Torque at 30 deg/sec
Extension
(ft-lbs)
Flexion (ftlbs)
Rachel
106.1
Sam
219.8
Chris
213.0
Total
538.9
Mean(±SD)
179.63(±63.77)
65.8
98.2
108.6
272.6
90.87(±)22.32
2. The results indicate that they have greater extension torque than flexion torque
because all subjects have greater torque capabilities in their extensors opposed to
flexors. The weaker the hamstrings are compared to the quadriceps, the more
susceptible an ACL injury is to occur.
3. Table 2 Isokinetic Knee Extension vs. Contraction Velocity
250
Extension Torque (ft-lbs)
200
Isokinetic knee Extension vs. Contraction
Velocity
150
Subject 1
Subject 2
100
Subject 3
50
0
0
100
200
300
Contraction Velocity (degrees/second)
400
As the contraction velocity increases on the graph you see a decrease of torque
produced over degrees/time (speed).
4. Warming up will increase the length of muscles but excessive stretching and
shortening will impair the ability to produce optimal force during contractions. Not
warming at all can exert the muscles too quickly without allowing enough blood
supply, actin and myosin interaction and ATP binding to occur therefore creating a
potential injury to the muscles.
5. Table 3 Total Work 180 degrees/sec
David
Jamie
Total work
4160.9
3677.2
Work 1st and
3rd
Work last 3rd
% Fatigue
2701.4
1991.9
Mean±SD
3919.05±
342.02
2346.6±501.69
536.7
80.1
720.3
74.3
658.5±87.39
77.2±4.01
Data showed a significant decrease in torque as repetitions prolonged to eighty.
Fatigue is responsible for a decrease in force and power output during prolonged
exercise and the metabolic role reasoning for the depletion of energy substrates
such as ATP and other fuel sources which assist the production of ATP (Hargreaves,
2005) ATP production is essential to maintain force and power production during
exercise therefore depletion and other biproducts can be the reason for fatigue.
(Hargreaves, 2005) Also in exercises that are a new stimulus to the subjects that are
not conditioned for this specific test are more likely to fatigue faster than a trained
individual.
6. Muscle meets are force demands by recruiting other muscles groups and by
metabolic fuel sources. As an action continues and force demands are increasing,
type ll a (fast twitch) and llb (fast twitch) will be stimulated and excited. (Astorino,
2012) For Trail one muscle force was at its peak for contraction at the slowest
velocity first set of 5 reps. As the speed of contraction and velocity sped up more
fibers were recruited and excited thus fast twitch lla and llb were firing. Trial 2
showed a lot more of type 1 fibers working but also type ll working with type one to
maintain contractions for prolonged amount of reps. Over time type ll will fatigue
and produce more byproduct due to lack of enough fuel supply and rest therefore
slowing down contraction and force output. Type 1 will continue to fire, generating
less force but will endure till the end of the trial.