strength

mechanical advantages of pulley systems & how it means your whole life has been a lie.

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Hey there! Finally put the finishing touches on a report for my strength & conditioning program design class. Last week, we had more of a hands-on lab inside my university’s fitness center. We inspected the pulley systems used in a few different types of isolating machines. What we discovered was jaw-dropping (at least for those who frequently use these machines).

Systems of pulleys can decrease the force required to lift a certain amount of weight.

For example, if I want to lift a 100 lb weight, and I have a pulley system with 3 pulleys, that gives me a mechanical advantage of 2. If I use this pulley system, I only have to exert 50 lbs of force to lift the 100 lb weight. (100/2 = 50). Does that make sense?

Now apply this to the strength training machines you see in weight rooms. Most of these machines have a complex system of pulleys. Meaning that you are never actually lifting the amount of weight you think you are.

MIND BLOWN.

Pulley LAB # 1/ 2-14-12

Measurement ofApplied Resistance From Selected

Strength-Training Apparatus

Koleana Kai McGuire

Discussion

The pulley lab definitely challenged the way we look at strength training machines by critically examining a variety of exercise equipment. Looking at its overall apparatus set up and design, and specifically each of its pulley systems and its impact on the “perceived” load. It made me realize that some manufactures didn’t take into consideration the effects of pulley systems on weight lifting. This is important as a user of these types of machines, because now I have a more accurate understanding of the weight that’s being lifted. As well as a future professional when training clients, I will know what recommendations to make, and how best to design strength training programs based upon the equipment available.

Apparatus # 1: Pulldown

Brand Name: Equalizer

Description of: 3 lines of pull attached to load, 1 line as free end pulling down

Apparatus Commonly used for tricep extensions

# pulleys 1 movable pulley

M.A. 2

Trial  (lbs) 70 lbs

Notes Measured 32.5 lbs on spring scale, which is pretty close to the predicted weight by our formula

P = ½ x (70 lbs) = 35 lbs

This is assuming that the pull is smooth and has no friction.

However, there must be some friction and with P measured at 35 lbs,

Conclusion: The plates actually weigh less than we are lead to believe.

Apparatus # 2 Pulldown

Brand Name Magnum

Description of 2 pulleys

Apparatus Commonly used for bicep curls

# pulleys 2 movable pulley

M.A. 2

Trial  (lbs) 50 lbs

Notes Measured 30 lbs on spring scale, which is greater than the force of pull as predicted by our formula

P = ½ x (50 lbs) = 25 lbs

This is assuming that the pull is smooth and has no friction.

However, there must be some friction making more force required to pull the weight.

Conclusion: The plates may actually weigh less than we are lead to believe.

Apparatus # 3: Pull ups

Brand Name: Life Fitness

Description of: 3 lines of pull attached to load, 1 line as free end pulling down

Apparatus: Can be used for bicep pull ups

# pulleys: 2 pulleys

M.A.: 1

Trial  (lbs): 50 lbs

Notes: Measured 52 lbs on spring scale, which is almost the same force of pull indicated by the weights.

This is assuming that the pull is smooth and has no friction.

Conclusion: The manufacturers of this apparatus designed the machine to accurately measure the force exerted. Meaning that the user is actually lifting (almost exactly) the amount of weight selected with the pins.

Apparatus # 4: Wheelchair accessible

Brand Name: Uppertone

Description of: lever systems

Apparatus: Can be used for upper body workouts, like the chest and arms, for people in wheel chairs

# pulleys: N/A

M.A.: N/A

Trial  (lbs): 30 lbs. The weight could vary depending on how the lever was oriented.

Notes: When the axis of rotation changes, the required force to move the weight changes.

Conclusion: The manufacturers of this apparatus designed it differently from traditional weight machines. The user can increase or decrease the required force by changing the axis for the levers, whereas most other machines will do so by changing the weight plates. By increasing the force arm, we decreased the force required to lift the weight- from 22 lbs to 5 lbs.

Resistance Band work outs

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I had to turn in a report on resistance bands for my Strength & Conditioning Program Design class (as mentioned in a prior post). For any fitness enthusiasts out there, or just anyone curious about this piece of equipment, here is my summation. It’s basically a product description, talks about some mechanical advantages and disadvantages, and my personal opinion on the bands’ effectiveness. Again, this was written for a class, so I apologize if it’s tough to interpret the biomechanical nomenclature, I’m sure you’ll be just fine =) Here ya go!

Machine Description

Manufacturer’s description: 

“Bodylastics Resistance bands / Exercise bands are no longer just for aerobics classes. The cutting edge resistance band systems by Bodylastics stand toe to toe with the biggest and best home gyms, and even fully equipped health clubs. Do over 140 of the best muscle working exercises, on your own terms…anywhere…anytime. I am Blake Kassel, the inventor of the Bodylastics Resistance bands home gym. Are you skeptical that elastic resistance bands could work all of your muscles as well as the HUGE weight machines? Well you should be. But I am here to tell you that you will love this product, and will end up loving our company, because you are going to get in amazing shape and save a ton of cash at the same time. You will absolutely be able to work your muscles to the max. All of the best exercises for the chest, arms, legs, back, shoulders and abs can be performed with this compact workout system. Bodylastics offers resistance band gym systems that can stand toe to toe with the large bulky home gym machines.

Smoothest Resistance – When we were first developing the Bodylastics System, we searched for the smoothest source of resistance on the planet. Well, we found it – elastic resistance tubing (bands). Not only is resistance tubing super smooth when you stretch it, but it is incredibly light and flexible. That means it is easy to store – no extra room needed!”

  1. Cost: One band- $9.95-$17.95 US dollars depending on if the buyer wants a different amount of resistance.Locations where equipment is most likely to be used: Physical Therapy offices, Rehab facilities, Athletic Training facilities, etc:
    • The resistance band is a great tool for rehabilitating specific body parts, so it is found in almost every physical therapy setting. Because the bands can come in variations is resistance, they are often seen in athletic training settings, too.
  2. Governing mechanism for providing resistance?
    • Resistance bands are rubber tubes with handles on both ends that provide resistance as you row, curl, and otherwise extend them. The handles and the clipping mechanisms at the end of each band can be detached. The bands can be combined on the handles to generate a heavy load. Resistance bands hold their own when one is resistance training.  They are good for giving the muscles something a little different to control; the weight actually increases as you extend them. The handles are cushioned and comfortable and the clipping mechanisms are usually found in plastic, not metal, so they click on easy and don’t abrade the body when exercising.
  3. Affected Joint(s):
    • Resistance bands can work many joints of the body, depending on what a person wants to focus on training or rehabilitating. Bands can often be used to target the sacroiliac joint with a seated row movement. Bent over rows and chest presses can work the glenerohumeral joints and the elbow joints. Band squats can work the knee and ankle joints.
  4. Prime Movers :
    • Again, because the resistance bands are so versatile, there are many prime movers that one can choose to target. I will cover popular examples of muscles people choose to target such as the muscles of the upper arms (biceps brachii, triceps brachii, supraspinatus, deltoids).

    Stabilizing muscles, including muscles controlling the axial skeleton.

    • While choosing to target muscles of the upper arms, one would start by placing the band under one foot and stepping back with the other foot. Muscles of the lower leg stabilizing the band would be the Gastrocnemius, Hamstrings and Quadriceps. Keeping the core stable and tight throughout the movement would engage the Rectus abdominis, Transverse abdominis and Internal/External obliques.
    • Primary Movement(s):
        • Initial Body Position: The initial body position is standing upright on the ground, both legs kept straight and locked, feet staggered, back straight and arms placed in front of the body with each hand holding either handle of the band.

      Max/Min. R.O.M. : The resistance band is designed to simulate many movements dependent upon what the user is trying to mimic. The band is not designed to create a resistance level high enough to reach a 1-RM max, but rather to use resistance to quantify a multiple RM level. Nor are bands designed to improve range of motion. Those who use the bands for rehabilitation, possibly those just recovering from surgery, may only be able to initially complete 1 repetition, and can build strength from there.

      Affected Joint(s): 

      Resistance bands can work many joints of the body, depending on what a person wants to focus on training or rehabilitating. Bands can often be used to target the sacroiliac joint with a seated row movement. Bent over rows and chest presses can work the glenohumeral joints and the elbow joints. Band squats can work the knee and ankle joints.

      Using all the above information, determine if the advertising claims of the manufacturer are valid:

      If the claims have merit, identify those areas that are credible.

      If any portion of the advertising is misleading, make a case for refuting the claims using sound principles of the exercise sciences.

      Resistance bands offer many benefits over conventional weights and dumbbells. For one, they’re lighter and more convenient to pack while on vacation. Moreover, resistance bands offer constant tension on your muscles during the entire concentric and eccentric portions of the movement. That’s something you won’t get with free weights wherein resistance is dependent on gravity. And resistance bands can be used to many muscles in the body; they’re very versatile. Their versatility makes them a very attractive style of training.

      An effective resistance band routine will yield results. I’d recommend keeping rest periods short; as one moves quickly from exercise to exercise, one will be able to get some great fat-burning cardiovascular benefits as well.

      Although resistance bands allow portability and the freedom of movement, these two benefits can also be potential stumbling blocks. Certain exercises and motions require only that one stands on the band, but for other motions one may need to attach the band to a strong, stable surface at a certain height. It may be difficult to find a suitable stabilizing point, depending on the location. Also, the ability to provide resistance to almost any motion can be tantalizing; however, the risk performing the movement incorrectly is fairly high if one has not been taught proper form. My main concern with band usage lies within the knowledge of the user on proper body mechanics prior to use. Misalignment of the body during exercise can damage muscles, ligaments and tendons, and may cause serious pain. Talk to a certified trainer or exercise physiologist about the use of a resistance band first.

      With proper coaching on the usage of resistance bands, I believe they can be a very effective apparatus for training and rehabilitation. I have personally used them when rehabilitating a knee injury, and have found them to be adequate tools in a physical therapy setting.

STRENGTH & CONDITIONING PROGRAM DESIGN CLASS

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I have to do a report on a piece of training equipment. I can choose any type of fitness equipment or apparatus I want, as long as it is relevant in the fitness industry. Hmmm…I think I want to write about the resistance band. That’s a pretty versatile device. Any thoughts?

-Koleana K. M.