[My re-post from AquaVolo.com]
What things should you consider when shopping for new power training gear? Which equipment will be the most beneficial for you or your team? Making the right decision while trying to weed out marketing hype from essential data can be challenging, but, you can simplify the task by evaluating each training device against three essential properties: effectiveness, convenience and price. In this article I will walk through an example of such an evaluation and discuss the merits and disadvantages of a power tower, a parachute, old running shoes, and DragSox. Hopefully, by the time you are done reading, you will have a clear idea of what questions to ask when shopping for new training equipment.
Effectiveness is a crucial property of training gear. I use the following definition for effectiveness: A training device is considered effective if it brings about the intended results while not introducing any drawbacks. The second aspect of this definition is as important as the first because introduced drawbacks may negate any benefits gained and diminish intended results. Bearing this definition in mind, we are now ready to evaluate the effectiveness of power tower, parachute, running shoes, and DragSox.
Swimmers have been using power towers to develop strength and power for a long time. One of the earlier mentions of a power tower as a training device for swimmers was made in the 1973 patent application for “Swimmer Training Device”:
“Apparatus having variable weights which may be attached to a line connected to a belt worn about the waist of a swimmer for applying weight to provide a restraining force against a swimmer attempting to swim away from the device which helps build, condition and tone the various muscles of the human body employed in swimming.“ 
This is an accurate description of the benefits that a power tower claims to provide. And indeed, true to its claim, power tower does help swimmers develop stronger and more powerful muscles thus fulfilling the first factor of effectiveness. While doing that, however, it introduces one drawback: it alters the swimmers body position so that it is no longer streamlined. The following image illustrates this point:
The line that connects the swimmer to the tower, together with the surface of the water (marked in blue) form an angle (marked A). As the athlete swims away from the tower, the restraining force of the power tower starts to pull her back and up along the connecting line (indicated by the black arrow) effectively compromising the swimmer’s streamlined body position. Because of this drawback, power tower fails the second aspect of effectiveness.
Conceptually, a parachute and a power tower are similar: both connect a swimmer to a resistance-generating component with the means of a line. The methods by which they generate resistance are, however, different. Power tower uses variable weights to generate restraining force, whereas a parachute uses actual water to generate resisting drag. The objective of training with a parachute is to help swimmers develop stronger and more powerful muscles. Similarly to the power tower, parachute does meet the first factor of effectiveness: it helps swimmers get stronger. But, it introduces two drawbacks. First, a parachute, like a power tower, negatively affects swimmer’s streamlined body position. Again, let’s use an image to clarify this point:
You, no doubt, noticed the similarities between this image and the image used during the power tower evaluation earlier. Both images show how the connecting line and the surface of the water (marked by a blue line) form an angle (marked A), but, there is a difference in the position of connecting lines. Power tower’s connecting line extends above the surface of the water, while the parachute’s line extends below. Therefore, unlike the power tower that pulls a swimmer back and up, the parachute pulls the swimmer back and down, along the connecting line. This “pull down” hinders swimmers streamlined body position and leads to a deteriorating technique. The second drawback that a parachute introduces is, again, related to the position of the connecting line. Because it is extended underwater, along the swimmer’s legs, the line can’t help but be in the way of a swimmer’s kick. As a result, swimmer’s feet get snared in the line as she tries to kick. This incessant entanglement of swimmer’s feet in the line hampers swimmer’s technique. Thus, because of these drawbacks, parachute fails the second factor of effectiveness.
The purpose of swimming in running shoes is to develop strong legs and a powerful kick. Because wet shoes are heavy, kicking with the extra weight is like training with weights at the gym. Like the power tower and the parachute, running shoes do fulfill the first portion of effectiveness: swimming in old running shoes does make swimmer’s legs stronger. But, running shoes introduce several drawbacks. First, because of their weight, running shoes tend to pull swimmer’s legs down therefore encumber streamlined body position and balance. Second, running shoes restrict ankle movement and minimize the range of motion of swimmer’s feet resulting in a less efficient kick. And finally, swimmers training with running shoes loose the “feel” of the water with their feet. This drawback is more psychological than physical, nevertheless it is very important. Without the “feel” of water, it’s hard to swim with a good rhythm and learn how to be more efficient. Because of their weight, restriction of movement and impediment to sensory input, running shoes fail the second aspect of efficiency.
Finally, let’s evaluate the effectiveness of DragSox. DragSox – a relatively new power training device – were specifically designed to obviate the limitations and drawbacks described above.
DragSox are simple, small and light. They are worn around the swimmer’s ankles, feel natural and allow swimmers to maintain their natural body position and balance with complete freedom of movement. DragSox generate resistance by utilizing available natural resources: water and air. In order for a swimmer to move forward, she needs to expend energy to “pull the water apart against its own cohesive forces to make room … to pass through. The energy expended varies with the shape of the object moving through the fluid. If the fluid is pulled a part in such a way as to force it into eddies and other unevennesses of motion (turbulence) the energy expended is multiplied …”  This description precisely explains how DragSox work. DragSox, due to their special design and material, pull water apart by forcing it into “eddies and other unevennesses of motion” and in doing so, they generate a lot of drag. To overcome this drag, a swimmer has to expend a lot more energy, eventually becoming stronger and more powerful.
In contrast to a power tower and a parachute, DragSox require neither a belt nor a connecting line. The absence of a connecting line makes DragSox immune to the drawbacks of a power tower and a parachute, or any other device that requires a connecting line for that matter. Moreover, because DragSox are soft and light, they don’t have the drawbacks introduced by running shoes: DragSox do not pull swimmer’s legs down or restrict the ankle’s range of motion. Thus, DragSox have none of the drawbacks that other power training devices carry. Adam Cremieux, the head coach at Westmont Swim Club, put it this way: “we’ve tried everything we could think of to increase our power of our kick from, fins, zoomers, power towers, parachutes and med balls and nothing matches the DragSox. Everything we’ve tried always had a set back from loss of technique or wasn’t efficient enough for a large group.“  DragSox are effective because they make swimmers stronger and more powerful while not introducing any drawbacks.
Before we begin evaluating convenience of a training device, let me define convenience as a combination of size, weight, storage, maintenance, portability and usefulness in crowded pools. There might be other factors that each swimmer or team needs to consider based on their own unique training environment. The given definition, however, is a good starting point for the purpose of this evaluation.
Power tower is one of the least convenient training devices available for swimmers. It is bulky, heavy, consists of many parts, and requires special tools to assemble and extra space for storage. It is essentially a static training device: once it is installed at your pool, you cannot easily take it with you to another pool. Furthermore, only two people per lane at the most can use a power tower at the same time. This is a serious limitation, especially for those who train in crowded pools.
Unlike a power tower, parachute is small, light, dries quickly, doesn’t require extra space for storage and is easily portable. On the other hand, because it has a relatively long connecting line extended behind a swimmer, parachute is not convenient for swimmers training in crowded pools. Swimmers in crowded lanes have to stay closer behind each other when they swim, thus, the parachute gets in the way of the person swimming behind. Overall, parachute is a convenient training tool as long as you don’t train in a crowded pool.
Compared to a parachute, running shoes are bigger, heavier and require a significantly longer time to dry. In fact, running shoes might not even get completely dry between workouts. Perpetually wet shoes become pungent and start to disintegrate. In addition, running shoes are not portable. Swimmers might be able to use them at their own pools, but it is unlikely that other swimming pools will allow people to swim in shoes. On the plus side, running shoes work well in crowded pools. On the whole, though, running shoes are not convenient.
Like a parachute, DragSox are small, light, easy to dry, require no extra space for storage and are highly portable. In contrast to parachute, because of their small size, DragSox can be used in crowded pools. As Chris Plumb, the head coach at Carmel Swim Club, said: [DragSox] are simple to put on and take off, are easy to store, and have been a terrific tool for the Carmel Swim Club to use.”  What’s more, DragSox can be used in any size pool and during meet warm-ups. By and large, DragSox are considerably more convenient than the other items evaluated here.
The only training gear property that we haven’t considered yet is price, which also happens to be the easiest to evaluate. All you need to do is to look at the prices and decide whether the price reflects your perceived value of the device and whether it is within your budget.
Power Tower: $2,000+
Running shoes: $50-$100
Rarely are potential drawbacks of training equipment outlined online or elsewhere. However, any swimmer or coach can evaluate gear against the three essential properties – effectiveness, convenience and price – described in this article. We have looked at four popular power training devices for swimmers – Power Tower, Parachute, Running Shows, DragSox – and evaluated these properties. Hopefully, having read this article, you are now armed with the right questions and will be able to pick the best training gear for you or your team. Good luck!
 Hopper, R. T. (1973). Patent No. 3861675. US.
 Cremieux, A. (2012, 12 14). AquaVolo Testimonials. Retrieved 04 20, 2013, from AquaVolo: http://aquavolo.com/community
 Asimov, I. (1993). Understanding Physics. New York: Barnes & Noble, Inc.
 Plumb, C. (2011, 06 26). AquaVolo Testimonials. Retrieved 04 13, 2013, from AquaVolo: http://aquavolo.com/community