Secrets of Speed and Quickness Training A collection of articles
by Dr. Larry Van Such  Vol. 17  Part 3
Part 1  Resistance Band Training For Athletes
Part 2  Resistance Band Training vs Weights  Do The Math
Part 3  Resistance Band Training with Isometrics
Part 4  Becoming An AllStar Athlete
When it Comes To Using Resistance Bands, It's Best To Use Them With An Isometric Training Strategy.
Part 3 of 4
When most people first start to exercise with the resistance band, what tends to happen is that the same types of routines they normally do with weights tends to carry over with the resistance band used in their place.
What this means is that most weightlifting exercises are usually done while performing repetitions with the weights, where the muscles are exercised through their full range of motion.
The biceps curl with a dumbbell is one example; while holding the dumbbell down by the side, the forearm is flexed at the elbow until the weight held in the hand ends up in front, up near the chest, and then lowered back down again. This process is typically repeated 812 times.
Through habit more than anything else, this same strategy is carried over with the exercise bands. The most likely first attempt at an exercise when one is handed a band therefore is to do the same thing with them as they would normally do with a weight. Whether its performing biceps curls, triceps push downs, or seated rows etc, the band is typically used as a resistance aid, in place of the weight, to exercise a muscle through its full range of motion.
There is nothing wrong with this strategy but there are a few things to be aware of. First of all, with regards to training with resistance bands, whenever you train with them, you should be aware that when you start an exercise, you are typically at your weakest. This is because your joints are typically fully extended where you cannot get much leverage (think arm bars in jiu jitsu) and there is no momentum from the exercise that you can initially take advantage of such as is common with body weight exercises. Combine this with the resistance band having not yet been stretched to a point where its resistance has any impact on the exercise, and you can see where the beginning of any exercise using an unstretched band will have little or no effect on your conditioning.
As you proceed with the exercise, the range of motion of the joint being exercised starts to increase, and as that is happening, the band is starting to stretch, increasing in resistance. You end up at a point in the exercise where your leverage over it is very high and therefore you have maximum control of it and the resistance of the stretched band is also at its highest.
So, by using the resistance band with a repetitious strategy similar to weight training, the only real affect they have on the muscle is the latter part of the exercise.
But let’s take a closer look at the mechanics involved in using the resistance band this way. Let’s look at what happens to the amount of force it delivers as it goes through various stages of the common biceps curl.
We are going to start the analysis of forces exerted on the elbow joint by a resistance band with the elbow already flexed to 90º. This is because we are going to eventually compare each stage of the biceps curl with a resistance band with those of the previous article in which a 25 lbs weight was used.
In that article, we learned that a 25 lbs. weight had its maximum moment of force of 25 lbs. feet when the elbow was at 90º. This is shown again here in Figure 1.
Figure 1. Elbow is flexed to 90º.
(This is also Figure 4 in Part II) 
So this will be our reference point to match the resistance band with 90º of elbow flexion. We already know that the dumbbell has its maximum moment of force at this angle and now we are going to purposely set up the resistance band to deliver the same moment of force at this 90º angle as well. After that, we will also see how the force of the resistance band begins to differentiate itself from the force of the dumbbell at different degrees of elbow flexion.
Now, in Figure 2 below, the athlete is holding a resistance band in his hand with the elbow flexed to 90º, similar to when he was holding the 25 lbs. dumbbell in this position. Here we need to make sure this position will also deliver a 25 lbs. feet moment of force back to the elbow with the resistance band used in its place. To do that, we first have to be aware of a unique difference between the force of the band and the dumbbell weight.
The force of the resistance band, F_{1}, always points back to where the band is attached, and not straight down as is always the case with a weight. You can compare directions of F_{1} in both Figure 1 above and Figure 2 below to see this difference.
In Figure 2, the force of the resistance band is not perpendicular as in Figure 1, but rather at an angle, A_{1}, calculated to be about 18º to perpendicular. (You can see how this angle was calculated in Figure 5 below.) Therefore, unlike this position of the weight at 90º of elbow flexion where there was no need to convert it to a perpendicular force equivalent since it was already there, this conversion needs to be done here.
Converting the force, F_{1}, to a perpendicular equivalent force, F_{P}, will mean that F_{1} is going to have to be a value greater than 25 lbs. in this position to end up at an F_{P} of 25 lbs.
Let’s calculate the amount of force, F_{1}, needed by the resistance band in Figure 2 before going any further.
Figure 2. Elbow flexed to 90º. 
A force, F_{1}, of 26.28 lbs. will be needed by the band in this position to end up with a perpendicular force, F_{P}, of 25 lbs. This will match up with the 25 lbs. weight, thereby both producing a moment of force of 25. lbs. feet when the elbow joint is 90º.
This is obviously a different amount of force that needs to be supplied by the band to end up with an equivalent moment of force of 25 lbs. feet at the elbow. This difference is primarily due to the fact that the force of the resistance band does not act perpendicular to the ground as the weight does, but rather, it always acts in a direction back toward its attachment. This force, F_{1}, will continuously change throughout the range of motion for the biceps curl using a dynamic resistance band. It will not change when using a static dumbbell.
Spring Constant, “k”, of the Resistance Band
The next thing we need to know about this setup is we need to know the spring constant or stretch constant, k, of the band. The spring constant ‘k’ is defined as how many lbs./inch the force of the band can supply when stretched a certain distance. In mathematical terms, this equation is written as: k = force/distance.This equation is more commonly written in the form of:
F = kx
This equation is referred to as Hooke’s law where ‘F’ is the restoring force exerted by the resistance band; ‘x’ is the displacement or distance the band stretches; and ‘k’ is the spring constant. This equation has a negative sign in it because the restoring force always acts in the opposite direction of the displacement. For example, when the band is stretched upward, it pulls back downward.
Since the comparison is being made between performing a biceps curl with weights and one with the resistance band, this information is required. The spring constant for the band being used in Figure 2 above is 0.75 lbs./inch. However, the band used in our example is actually tied in a loop and therefore consists of ‘two’ bands of resistance. The spring constant for this exercise is then: 2 x 0.75 = 1.5 lbs./inch.
How far does the band stretch when the elbow starts out at 0º of flexion and ends up at 90º of flexion?
The biceps curl exercise typically starts with the elbow extended down by the side at 0º as shown in Figure 3. In this sample exercise, it will end up when the elbow is flexed to 90º as shown in Figure 4. Naturally the band will have to stretch to get there, so along with knowing the spring constant of the band, we will also need to know the distance, ‘x’, it will be stretched.
Figure 3. 0º elbow flexion.Figure 4. 90º elbow flexion. 
Let’s first calculate how far the band stretches from its position in Figure 3 to Figure 4. We know that the moment arm (length of forearm), L_{A}, doesn’t change and it is estimated at 1 foot long. We also know the angle of the elbow joint will be 90º. Therefore, we get the following in Figure 5:
Figure 5. 
Line AB represents the length of the forearm (moment arm, L_{A}) in the starting position and is 1’ long. Line AD also represents the length of the forearm, L_{A}, but in the ending position. Again, its length is 1’.
Line BC represents the distance from the hand holding the band in Figure 3, to the ground. This distance was estimated at 2’. Line BC therefore also represents the starting length of the resistance band at the beginning of the exercise.
Line CD represents the ending length of the resistance band when the elbow is flexed to 90º. Its length was determined to be 3.16’ based on Pythagoreans Theorem for right triangles.
It was calculated as follows: C = hypotenuse of triangle, or line CD.
A = length of one side (line AC); B = length of other side (line AD).
Determining the amount of prestretch force needed in the band at the beginning of this exercise
Now, since all bands are made differently and therefore have different spring constants, we will need to determine how much prestretch resistance there needs to already be in the band in Figure 3. In other words, the band held in the hand in this position will need to have a certain amount of stretched tension in it even before starting the exercise so that the target force of 26.28 lbs. can be met and matched up with the 25 lbs. weight in this same position.
If the band is stretched a total of 13.92 inches when going from the first position in Figure 3 to the second position in Figure 4, then the amount of force is increased by:
This number represents the change in the amount of force of the resistance band when the elbow was at 0º, down by the side, to one where the elbow is at 90º. What this means is this number will need to be subtracted from the final force, F_{1}, to determine the amount of prestretch force needed in the band to start the exercise:
Therefore, when the band is being held down by your side to start the exercise as shown in Figure 3, it will need to already be pulling 5.4 lbs of force. In other words, the band simply cannot be hanging down in this position with out any tension in it; it has to be prestretched from the ground up to the hand with a 5.4 lbs force.
While this 5.4 lbs starting force may seem a little odd, you have to remember that the 25 lbs. dumbbell weight held down by the side in this same position also has a force; that being the static 25 lbs. It just doesn’t have a moment of force at the elbow and neither does the resistance band in this same position.
These two positions with the resistance band, when compared to identical positions with a weight, show just how different the forces in each are when an exercise as simple as the biceps curl is being performed with them.
Let’s now take a look at three more positions of the biceps curl using the resistance band and compare them to similar positions when a dumbbell is used.
Calculating the Moment of Force on the elbow, M_{Elbow},
at 30º of elbow flexion.
Figure 6. Elbow flexed to 30º.Figure 7. 
Step 1. Calculating how far the band stretches from its position in Figure 3, the starting position, to Figure 6, the new ending position.
We know that the moment arm (length of forearm), L_{A}, doesn’t change and it is estimated at 1 foot long. We also know the angle of the elbow joint will now be 30º. This information is drawn out in Figure 7 above.
The line CD represents the new length of the resistance band after it has been stretched from its original position to one where the elbow is now at 30º. Its value was calculated using the Law of Cosines as follows:
A = The distance of line AC, which is: 1 + 2 = 3
B = The distance of line AD, which is 1
C = Line CD, which is the new stretched distance. Its value is unknown and is what we are going to calculate.
gamma = Angle DAB which is 30º
C_{2} = A^{2} + B^{2} – 2AB (Cosine (gamma))
C^{2} = 3^{2} + 1^{2} – 2(3)(1) cosine (30º)
C^{2}= 9 + 1 – 5.19 = 4.80
C = 2.19 feet.
Therefore, to calculate how far the band stretches, we simply subtract the beginning length from the ending length and get:
Band stretch = 2.19’ – 2’ = 0.19’ or (0.19’) x’s (12 inches/foot) = 2.28 inches.
Step 2. Determining the force in the resistance band, F1.
If the band is stretched a total of 2.28 inches when going from the first position in Figure 3 to the second position in Figure 6, then the amount of force is increased by:
2.28 inches x (1.5 lbs./inch) = 3.42 lbs.,
where 1.5 lbs./inch represents the spring constant.
This number represents the change in the amount of force of the resistance band when the elbow was at 0º, down by the side, to one where the elbow is at 30º.
If the resistance band already had a prestretch tension in it of 5.4 lbs., then the new force, F1, of the resistance band with the elbow flexed to 30º is:
F_{1} = 5.4 lbs. + 3.42 lbs. = 8.82 lbs.
Step 3. Determining the angle of this force, F1, to the moment arm (forearm) and then determining the angle needed to bring this force perpendicular to it.
First, we need to determine the angle ADC in Figure 7. This is the largest of the three angles however it is also easily solved by the law of cosines:
3^{2} = 1^{2} + 2.192 – 2(1)(2.19) cosine (ADC)
9 = 1 + 4.79 – 4.38 cosine (ADC)
3.20 = 4.38 cosine (ADC)
0.7315 = cosine (ADC)
ADC = 137.01º
ADC = 137.01º = Angle of F1 in relation to the moment arm.
Therefore, the angle needed to bring F1 perpendicular, A0 in Figure 6, is:
A0 = 137.13 – 90 = 47.13º
Step 4. Calculating the perpendicular force, FP.
FP = F1 cosine (47.13)
FP = 8.82 x (.6803) = 6.00 lbs.
Step 5. Calculating the Moment of Force, Melbow, at the elbow.
M_{elbow} = F_{P} x L_{A}
M_{elbow} = 6.00 lbs. x 1 foot = 6.00 lbs. feet.
Calculating the Moment of Force on the elbow, M_{Elbow}
, at 45º of elbow flexion.
Figure 8. Elbow flexed to 45º.Figure 9. 
Step 1. Calculating how far the band stretches from its position in Figure 3, the starting position, to Figure 8, the new ending position.
Again, we know that the moment arm (length of forearm), L_{A}, doesn’t change and it is estimated at 1 foot long. We also know the angle of the elbow joint will now be 45º. This information is drawn out in Figure 9 above.
The line CD represents the new length of the resistance band after it has been stretched from its original position to one where the elbow is now at 45º. It’s value was calculated using the Law of Cosines as follows:
A = The distance of line AC, which is: 1 + 2 = 3
B = The distance of line AD, which is 1
C = Line CD, which is the new stretched distance. Its value is unknown and is what we are going to calculate.
gamma = Angle DAB which is now 45º
C^{2} = A^{2} + B^{2} – 2AB (Cosine (gamma))
C^{2} = 3^{2} + 1^{2} – 2(3)(1) cosine (45º)
C^{2=} 9 + 1 – 4.24 = 5.75
C = 2.399 or 2.40 feet.
Therefore, to calculate how far the band stretches, we simply subtract the beginning length from the ending length and get:
Band stretch = 2.40’ – 2’ = 0.40’ or (0.40’) x’s (12 inches/foot) = 4.80 inches.
Step 2. Determining the force in the resistance band, F_{1}.
If the band is stretched a total of 4.80 inches when going from the first position in Figure 3 to the second position in Figure 8, then the amount of force is increased by:
4.80 inches x (1.5 lbs./inch) = 7.20 lbs.,
where 1.5 lbs./inch represents the spring constant.
This number represents the change in the amount of force of the resistance band when the elbow was at 0º, down by the side, to one where the elbow is at 45º.
If the resistance band already had a prestretch tension in it of 5.4 lbs., then the new force, F_{1}, of the resistance band with the elbow flexed to 45º is:
F_{1} = 5.4 lbs. + 7.2 lbs. = 12.60 lbs.
Step 3. Determining the angle of this force, F_{1}, to the moment arm (forearm) and then determining the angle needed to bring this force perpendicular to it.
First, we need to determine the angle ADC in Figure 11. This is the largest of the three angles however it is also easily solved by the law of cosines:
3^{2} = 1^{2} + 2.42 – 2(1)(2.4) cosine (ADC)
9 = 1 + 5.76 – 4.8 cosine (ADC)
2.24 = 4.8 cosine (ADC)
0.4667 = cosine (ADC)
ADC = 117.82º
ADC = 117.82º = Angle of F_{1} in relation to the moment arm.
Therefore, the angle needed to bring F_{1} perpendicular, A_{0} in Figure 9, is:
117.82 – 90 = 27.82º
Step 4. Calculating the perpendicular force, F_{P}.
F_{P} = F_{1} cosine (27.82)
F_{P} = 12.6 x’s (.8844) = 11.14 lbs.
Step 5. Calculating the Moment of Force, Melbow, at the elbow.
M_{elbow} = F_{P} x L_{A}
M_{elbow} = 11.14 lbs. x 1 foot = 11.14 lbs. feet.
Calculating the Moment of Force on the elbow, M_{Elbow}
, at 120º of elbow flexion.
Figure 10. Elbow flexed to 120º.Figure 11. 
Step 1. Calculating how far the band stretches from its position in Figure 3, the starting position, to Figure 10 , the new ending position.
Again, we know that the moment arm (length of forearm), L_{A}, doesn’t change and it is estimated at 1 foot long. We also know the angle of the elbow joint will now be 120º. This information is drawn out in Figure 11 above.
The line CD represents the new length of the resistance band after it has been stretched from its original position to one where the elbow is now at 120º. Its value was calculated using the Law of Cosines as follows:
A = The distance of line AC, which is: 1 + 2 = 3
B = The distance of line AD, which is 1
C = Line CD, which is the new stretched distance.
Its value is unknown and is what we are going to calculate.
gamma = Angle DAB which is now 120º
C^{2} = A^{2} + B^{2} – 2AB (Cosine (gamma))
C^{2} = 3^{2} + 1^{2} – 2(3)(1) cosine (120º)
C^{2}= 9 + 1 – 6(0.5) = 13.00
C = 3.60 feet.
Therefore, to calculate how far the band stretches, we simply subtract the beginning length from the ending length and get:
Band stretch = 3.6’ – 2’ = 1.6’ or (1.6’) x (12 inches/foot) = 19.2 inches.
Step 2. Determining the force in the resistance band, F_{1}.
If the band is stretched a total of 19.2 inches when going from the first position in Figure 3 to the second position in Figure 10, then the amount of force is increased by:
19.2 inches x (1.5 lbs./inch) = 28.80 lbs.,
where 1.5 lbs./inch represents the spring constant.
This number represents the change in the amount of force of the resistance band when the elbow was at 0º, down by the side, to one where the elbow is at 120º.
If the resistance band already had a prestretch tension in it of 5.4 lbs., then the new force, F_{1}, of the resistance band with the elbow flexed to 120º is:
F_{1} = 5.4 lbs. + 28.8 lbs. = 34.2 lbs.
Step 3. Determining the angle of this force, F_{1}, to the moment arm (forearm) and then determining the angle needed to bring this force perpendicular to it.
Now we have to determine the angle of F_{1} is to the moment arm and then the angle needed to bring this force perpendicular to it.
To do this we need to determine the angle ADC in Figure 11. This is the largest of the three angles however it is also easily solved by the law of cosines:
3^{2} = 1^{2} + 3.62 – 2(1)(3.6) cosine (ADC)
9 = 1 + 12.96 – 7.2 cosine (ADC)
4.96 = 7.2 cosine (ADC)
0.6889 = cosine (ADC)
ADC = 46º
ADC = 46º = Angle of F_{1} in relation to the moment arm.
Therefore, the angle needed to bring F_{1} perpendicular to A0 in Figure 11 is:
90  46 = 44º
Step 4. Calculating the perpendicular force, FP.
F_{P} = F_{1} cosine (44)
F_{P} = 34.2 x (.7193) = 24.6 lbs.
Step 5. Calculating the Moment of Force, Melbow, at the elbow.
Melbow = F_{P} x’s L_{A}
M_{elbow} = 24.6 lbs. x 1 foot = 24.60 lbs. feet.
Comparing the starting Force, F1, between the resistance band and the 25 lbs. dumbbell at the same positions
Elbow Joint Position

F_{1} Resistance Band

F_{1} 25 lbs Dumbbell

0º

5.40 lbs.

25 lbs.

30º

8.82 lbs.

25 lbs.

45º

12.60 lbs.

25 lbs.

90º

26.26 lbs.

25 lbs.

120º

34.20 lbs.

25 lbs.

Comparing the force F_{1}, of the resistance band with the dumbbell shows what you probably already expected and that is the force of the resistance band varies throughout the range of motion. What is interesting here is that the force F_{1} not only starts out lower than the 25 lbs dumbbell, but that it also goes higher than it as well. Because of the changing values in force supplied by the resistance band, it is probably not best to use them in an exercise that involves gross movement in the joints, as in this example. Instead, using them with an isometric training strategy will have a much larger impact on the tendons and muscles.
Comparing the Moment of Force, M_{elbow}, between the resistance band and the 25 lbs. dumbbell at the same positions
Elbow Joint Position

M_{elbow} Resistance Band

M_{elbow} 25 lbs Dumbbell

0º

0.00 lbs.

0.00 lbs.

30º

6.00 lbs.

12.50 lbs.

45º

11.14 lbs.

17.67 lbs.

90º

25.00 lbs.

25.00 lbs.

120º

24.60 lbs.

21.65 lbs.

Comparing the moment of force at the elbow also shows just how different using the resistance band and dumbbell is. At first glance, it looks as though the peak moment of force occurs at 90º of elbow flexion for both and that the moment of force of the dumbbell drops off faster after that, which is true. However, the moment of force supplied by the resistance band actually peaks higher than the dumbbell. Its value peaks at 26.07 lbs. feet when the elbow is flexed to 105º. So, whereas the moment of force turns around at 90º of elbow flexion using the dumbbell, it doesn’t turn around until the elbow is at 105º when the resistance band is used.
How sensitive are your muscles to these changes?
What he have shown here in this example of the biceps curl are some of the obvious and outward differences between the amount of force supplied by the resistance band and that supplied by the 25 lbs. dumbbell at different degrees of elbow flexion.
These types of changes will always be present whenever you exercise your muscles.
Your awareness to these changes in resistance level and joint position is known as proprioception. Proprioception means a sense of self. It is an awareness of where your arms and legs are in space. For example, if you were to close your eyes and place your right hand behind your back, you would know that your right hand is behind your back, even without having to see it.
Your awareness to your arm’s position is supplied to your brain by specialized receptors called proprioceptors which are located in your muscles, joints and tendons. They provide information about the angle of the joint, length of the muscle and tension in the tendons. All of this information is integrated to give your brain the awareness of the position of your arm.
The two most common proprioceptors are the muscle spindle and golgi tendon organ. Muscle spindles provide information about the changes in muscle length. They are located in parallel and within the muscle belly themselves. Golgi tendon organs provides information about the changes in muscle tension and are located in series with the muscle tendon.
Both of these proprioceptors are highly sensitive to even the slightest amount of change in position and tension. You don’t have to move your arm several inches for the muscle spindle to signal that a change in position has occurred. You can sense a change of the order of millimeters. As an example, try moving the tip of your index finger ever so slightly. Your muscle spindles signal this change immediately.
You also don’t need to increase the resistance by a few pounds for the tension in the golgi tendon organ to signal that an increase has occurred. Try interlocking your fingers together and then slowly begin to pull apart. You can sense the increase instantly.
While your sensitivity to changes in muscle tension and position is high to begin with, it becomes even more pronounced when the effort required by the muscle increases.
We will discuss the significance of this for your athletic training in the next article and also show you why using the resistance band with an isometric training strategy is such a great training strategy when your goal is to build strength and speed within the muscle.
“We’ll bring you up to speed!”^{®}
Part 1  Resistance Band Training For Athletes
Part 2  Resistance Band Training vs Weights  Do The Math
Part 3  Resistance Band Training with Isometrics
Part 4  Becoming An AllStar Athlete
Always glad to help!
Dr. Larry Van Such
