labcon presentation - muscle

Experiment 10Experiment 10

Influence of Load on Influence of Load on Muscle ContractionMuscle Contraction

ObjectiveObjective

To measure and compare the influence To measure and compare the influence of different loads on contraction of of different loads on contraction of muscle.muscle.

MethodologyMethodology

Experimental animal: frogExperimental animal: frog Specimen: nerve-muscle preparationSpecimen: nerve-muscle preparation Equipment: Kymograph, lead weightsEquipment: Kymograph, lead weights Procedures:Procedures:

Set up this experiment as in Experiment 9Set up this experiment as in Experiment 9 With the drum remaining stationary, record the With the drum remaining stationary, record the

contraction of the muscle stimulated by break contraction of the muscle stimulated by break shocks capable of producing maximal contractionshocks capable of producing maximal contraction

MethodologyMethodology

Turn the drum 1 cm and repeat the procedure after Turn the drum 1 cm and repeat the procedure after placing 1 gm weight then 5, 10, and 20 gm weights. placing 1 gm weight then 5, 10, and 20 gm weights. Increase the weight progressively until the muscle is Increase the weight progressively until the muscle is unable to lift the loadunable to lift the load

RecordingRecording Label the tracing indicating the load in grams for each Label the tracing indicating the load in grams for each

contractioncontraction Measure the height of the contraction from base to the Measure the height of the contraction from base to the

peak, following a straight line. Do not measure the curve of peak, following a straight line. Do not measure the curve of the contractionthe contraction

Results and DiscussionResults and Discussion


Based on the results of our experiment, Based on the results of our experiment, there is an inverse relationship between there is an inverse relationship between the load and muscle contraction. When the load and muscle contraction. When the muscle is free from load, it is able to the muscle is free from load, it is able to reach maximum contraction, which is reach maximum contraction, which is 14.33 mm. When the 114.33 mm. When the 1stst load weighing 1 load weighing 1 gm was added, it reached 13.5 mm. The gm was added, it reached 13.5 mm. The 22ndnd load weighing 5 gm reached 5 mm. load weighing 5 gm reached 5 mm.


The third load which is 10 gm. reached 3 The third load which is 10 gm. reached 3 mm. The fourth load weighing 20 gm mm. The fourth load weighing 20 gm reached 2 mm.reached 2 mm.

• This experiment was able to show the This experiment was able to show the effects of different loads on muscle effects of different loads on muscle contraction.contraction.


The group chose to perform this The group chose to perform this experiment since it shows the effects of experiment since it shows the effects of adding loads to muscle contraction, adding loads to muscle contraction, which in turn relates with the changing which in turn relates with the changing rates of exercise in response to variation rates of exercise in response to variation of load during exercise.of load during exercise.

Results and DiscussionResults and DiscussionLoad (in gram/s)Load (in gram/s) Height of contraction Height of contraction

(in mm)(in mm)

0 (free from load)0 (free from load) 14.3314.33

1 1 13.513.5

5 5 55

10 10 33

20 20 22

ConclusionConclusion

As the tension or the load increases, the As the tension or the load increases, the amount of muscle contraction decreases.amount of muscle contraction decreases.

Answers to QuestionsAnswers to Questions

What is the afterload of the muscle? What is the afterload of the muscle? What is its importance?What is its importance? A weight attached to a muscle but supported A weight attached to a muscle but supported

so that it is not engaged until the muscle so that it is not engaged until the muscle begins to contract constitutes an afterload.begins to contract constitutes an afterload.

The afterload determines the work that the The afterload determines the work that the muscle must do.muscle must do.

Answers to QuestionsAnswers to Questions

What is the optimum load?What is the optimum load? The optimum load for a muscle is its ability The optimum load for a muscle is its ability

to produce external power. At both lighter or to produce external power. At both lighter or heavier than the optimum load, the output heavier than the optimum load, the output power diminishes.power diminishes.

Answers to QuestionsAnswers to Questions What is isometric contraction?What is isometric contraction?

If the afterload is greater than the muscle If the afterload is greater than the muscle can lift, the muscle develops tension can lift, the muscle develops tension without shortening externally.without shortening externally.

What is the influence of load on muscle What is the influence of load on muscle activity?activity? As the load increases, the rate of As the load increases, the rate of

contraction will decrease.contraction will decrease.