# velocity meter

## The Peaks and Troughs of the Swimming Stroke Cycle

###### Obeying the Law

Once we understand how important it is to obey the law of inertia in the water, how do we really know if we are? Each of the four strokes demonstrates peaks and troughs of our body’s speed during the swimming stroke cycle. In freestyle and backstroke, there is a right arm peak and trough speed and a left arm peak and trough speed. Butterfly has a peak for the first down kick, which occurs while the hands are pulling underwater, and a peak for the second down kick, when the hands are recovering over the water. Between each peak is a trough. In breaststroke, there is a kick and pull peak and a trough that follows each.

At The Race Club, through the technology of the velocity meter, we measure a swimmer’s velocity, acceleration and deceleration at all times throughout each swimming stroke cycle. It enables us to identify and quantify all of the peak and trough speeds. When synchronized with video, it also enables us to identify stroke deficiencies, such as poor kicking or pulling motions or head and body position that magnify the differences between peak and trough speeds. The velocity meter enables us to make corrections in technique that we could never identify from the deck nor from an underwater window without also understanding the impact they have on body speed.

###### Desirable Values

After performing many of these studies on great and not-so-great swimmers, we have come to appreciate what the ‘desirable values’ are for the differences between peak and trough speeds in each swimming stroke cycle. Backstroke is the most conforming stroke with a difference between peak and trough speed on each arm of .35 meters per second or less considered to be very good. In freestyle, the difference between peak and trough speeds for each arm should be .5 meters per second or less.

Looking at butterfly, we often see a difference range of 1 to 1.5 meters per second or more between the peak and trough speeds. In breaststroke, since we are starting from nearly a dead stop before beginning each kick and the kick provides the majority of propulsive forces, we want to see a big increase in speed, or a large difference between peak and trough after the kick.  Breaststroke is analogous to doing a standing dunk under the basketball net.

Certainly in freestyle and backstroke, minimizing the difference between peak and trough speeds conforms to the law of inertia and makes us more efficient swimmers. The question is how do we do that?

In both strokes, there are really only three things we can do to conform to inertia. First, sustain a steady six-beat kick. Second, increase the stroke rate, which lessens the ‘down time’ of our pulling propulsion. Third, reduce frontal drag in all aspects possible; better head and body position, proper elbow bend and arm position and a tighter kick.

###### Improve Your Swimming Stroke Cycle

For example, in a study of my freestyle pull (no kick involved), I found that in the three tenths of a second between the peak and trough velocities of each hand, the deep arm pull caused a 40% drop in body speed due to increased frontal drag versus a 25-30% drop in speed with the high elbow pull (less frontal drag). The amount of work required to overcome a 10% difference in body speed on each and every pull is overwhelming. The speed cannot be sustained for long with the deeper pulling motion.

For starts and turns, conforming to the law of inertia generally means not waiting too long to initiate the dolphin kicks off the wall or entry. Or it means keeping the kicks fast and tight and transitioning to flutter kick before the breakout….all designed to help sustain our speed.

In summary, don’t ignore Galileo’s discovery and Newton’s first law of motion. Inertia is vital to our success as swimmers. If we learn to conform to it, we might just win some races.

Yours in swimming,

Gary Sr.

## Trust the Data of Velocity Meter to See How You Can Swim Faster

While the velocity meter is not new technology, at The Race Club, we have spent much of the past year understanding how to better use it in order to understand how you can swim faster. We spend an average of ten hours performing and analyzing each test. We have learned a lot.

First, technique in the sport of swimming is extremely important; more than we had imagined. With water being some 800 times denser than air, the laws of motion that affect our speed in water come into play at much slower speeds than with sports in air. Significant deceleration can occur very quickly, within hundredths of seconds, with very small adverse changes in our body’s position or shape. The result of high deceleration is slower speed and a greater fluctuation of speed, an inefficient way of swimming. Flow dynamics are also very important and affect our propulsion.

Second, we have learned that by measuring acceleration and deceleration, in addition to velocity, we can more precisely identify poor technique. Peak deceleration, for example, measures the mistake(s) in real time, while trough velocity occurs later as a result of the deceleration. Even though the loss of velocity may occur just fractions of a second after the peak deceleration occurs, for example, the poor technique that resulted in that change may already be gone. By identifying the time where maximum deceleration takes place, we can then more easily find the bad technique that caused it. When looking at moments of peak acceleration, we can also better identify the propulsive forces that resulted at that moment in the higher acceleration and resultant increase in velocity.

Another parameter that we have learned to use is the difference between peak and trough velocities (∆PT). To our knowledge, this data had never been analyzed in swimmers before. The level of peak velocity is a fairly close indicator of the amount of propulsion a swimmer can create on a given cycle. Trough velocities correlate more closely with the amount of frontal drag occurring between propulsive efforts for a given stroke rate or cycle time. The ∆PT is a better measure of efficiency, as the greater the change in velocity that occurs with the swimmer, the more energy required for the swimmer to average a certain speed (law of inertia).

In freestyle and backstroke, we can identify peak and trough velocities for right arm pulls and left arm pulls. In breaststroke, we find peak and trough velocities for the pull and the kick. In butterfly, we find peak and trough velocities for each of the two down kicks, one of which occurs during the underwater pull and the other during the hand entry. After just a few seconds of swimming, we can measure several peaks and troughs for each stroke. From that data, we derive ∆PT measurements for each stroke.

The analysis involves not only measuring the magnitudes of peaks and troughs, but also comparing symmetry (right arm vs left arm) and consistency (does the peak or trough vary much from stroke to stroke or over time). One of the challenges of this analysis is having a better understanding of what is normal or expected for a given age or ability of a swimmer.

For example, in the ∆PT velocity measurement for freestyle, the majority of better distance swimmers seem to keep under .5 m/sec. With elite swimmers using sprint technique, however, we find the ∆PT goes higher (.75 m/sec or higher) from the increase in propulsion and in frontal drag caused by the deeper, stronger pulling motion. In backstroke, the ∆PT’s are lower, likely due to the changes in flow dynamics of the kick on the back compared to the stomach. We have found in backstroke a ∆PT less than .35 m/sec appears to be desirable. For the same reason, the ∆PT is less in dolphin kick under water on the back than it is on the stomach. In flutter kick, a ∆PT of less than .25 m/sec is desirable.

The higher ∆PT measurements are usually accompanied by higher amounts of deceleration and/or acceleration. While we understand the importance of having a lower ∆PT, particularly on events over 50 meters, we also have found that the highest peak deceleration points are the most important single parameter to help us find poor technique. In nearly every case, we feel confident in being able to identify the cause of the deceleration. Often, there is more than one cause.

When going over our VM data with our Race Club members, it is one thing to show a swimmer video of his dropped elbow, elevated head position, overly bent knee on a kick or a hanging foot in breaststroke or fly, and explain that you think it is bad technique. It is quite another to show a swimmer that as a result of that mistake, the acceleration went from 10 m/sec² (increasing speed) to a deceleration of -10m/sec² (losing speed) in less than .06 seconds. That is not an unusual scenario.

If nothing else, each swimmer doing the VM study has a new respect for the extreme sensitivity of swimming technique. I call swimming a sport of millimeters, tenths of seconds and degrees. Drop the elbow a few millimeters, for example, and the frontal drag goes way up. If a swimmer is a tenth of second late in initiating the push back from the breaststroke kick or in performing the second hard down kick in fly, the swimmer misses the coupling effect of the body motions and loses out on the additional propulsion. For every degree of external rotation of the hip, there may be 5-10 percent more propulsion from the breaststroke kick with the same amount of effort. In swimming, little things matter.

There is no mercy in the water; very little margin of error. In my experience, the Velocity Meter test provides the most important information we have available to help you swim faster. I hope that you will come to Islamorada or to Coronado and allow us to test you.

Yours in swimming,

Gary Sr.

## The Peaks and Troughs of the Swimming Stroke Cycle

Once we understand how important it is to obey the law of inertia in the water, how do we really know if we are? Each of the four strokes demonstrates peaks and troughs of our body’s speed during the swimming stroke cycle. In freestyle and backstroke, there is a right arm peak and trough speed and a left arm peak and trough speed. In fly there is a peak for the first down kick, which occurs while the hands are pulling underwater, and a peak for the second down kick, when the hands are recovering over the water. In between each peak is a trough. In breaststroke, there is a kick and pull peak and a trough that follows each.

At The Race Club, through the technology of the velocity meter, we measure a swimmer’s velocity, acceleration and deceleration at all times throughout several stroke cycles. It enables us to identify and quantify all of the peak and trough speeds. When synchronized with video, it also enables us to identify stroke deficiencies, such as poor kicking or pulling motions or head and body position that magnify the differences between peak and trough speeds. The velocity meter enables us to make corrections in technique that we could never identify from the deck nor from an underwater window without also understanding the impact they have on body speed.

After performing many of these studies on great and not-so-great swimmers, we have come to appreciate what the ‘desirable values’ are for the differences between peak and trough speeds in each of the four strokes. Backstroke is the most conforming stroke with a difference between peak and trough speed on each arm of .35 meters per second or less considered to be very good. In freestyle, the difference between peak and trough speeds for each arm should be .5 meters per second or less. In fly, we often see a difference range of 1 to 1.5 meters per second or more between the peak and trough speeds. In breaststroke, since we are starting from nearly a dead stop before beginning each kick and the kick provides the majority of propulsive forces, we want to see a big increase in speed, or a large difference between peak and trough after the kick.  Breaststroke is analogous to doing a standing dunk under the basketball net.

Certainly in freestyle and backstroke, minimizing the difference between peak and trough speeds conforms to the law of inertia and makes us more efficient swimmers. The question is how do we do that?

In both strokes, there are really only three things we can do to conform to inertia. First, sustain a steady six-beat kick. Second, increase the stroke rate, which lessens the ‘down time’ of our pulling propulsion. Third, reduce frontal drag in all aspects possible; better head and body position, proper elbow bend and arm position and a tighter kick. For example, in a study of my freestyle pull (no kick involved), I found that in the three tenths of a second between the peak and trough velocities of each hand, the deep arm pull caused a 40% drop in body speed due to increased frontal drag versus a 25-30% drop in speed with the high elbow pull (less frontal drag). The amount of work required to overcome a 10% difference in body speed on each and every pull is overwhelming. The speed cannot be sustained for long with the deeper pulling motion.

For starts and turns, conforming to the law of inertia generally means not waiting too long to initiate the dolphin kicks off the wall or entry. Or it means keeping the kicks fast and tight and transitioning to flutter kick before the breakout….all designed to help sustain our speed.

In summary, don’t ignore Galileo’s discovery and Newton’s first law of motion. Inertia is vital to our success as swimmers. If we learn to conform to it, we might just win some races.

Yours in swimming,

Gary Sr.

Swimming fast is a skill that demands great strength and stamina. Yet swimming is neither baseball nor boxing. One cannot hit the water like a ball crushed over the center field wall or knock it out in the first round. One cannot simply power through the water. To swim fast, one also needs great timing and swimming finesse.

What does finesse mean with respect to swimming fast? In water, where frontal drag forces are so compelling, swimming finesse means learning to swim with the lowest possible drag forces. It means pulling with an arm motion that may seem totally inept or awkward, yet works better. Finesse means timing the powerful, but rarely appreciated coupling motions of body rotation and arm recovery to augment the pulling and kicking forces. Finesse means using a surge kick, a strong down kick that occurs shortly after the opposite hand entry, in order to increase the body’s speed when its drag coefficient is low, another timing issue. It also means dipping the head slightly underwater after the breath, at the same crucial time of maximum body speed. Finesse means avoiding the temptation to dig your arm deep into the water and muscle yourself across the pool. In swimming, finesse means using your brain, not your brawn.

The nuances of swimming fast are not easy to learn. Some require extraordinary flexibility, such as in the ankles and shoulders, in order to implement. All require great strength in the legs, core and upper back in order to sustain well. Yet, if we do not learn to finesse our freestyle, we will all succumb to the drag forces, much sooner than we would like.

While swimming is not very forgiving with respect to technique, there is some margin for error. It’s just not much. I call the permissible angle or bend of a swimmer’s body or limb motion the ‘threshold’ for frontal drag force. Bend your knee 35 degrees for a kick and you may be ok. Bend it 60 degrees or more and you come to a screeching halt. Drop your elbow on the pull by more than a few inches and the frontal drag forces go up a lot. Bending the knee more or dropping the elbow more results in more powerful propulsion. Unfortunately, getting to those positions causes so much frontal drag that the additional propulsive forces can’t overcome it. Don’t forget the law of inertia. Each time we slow down more, it takes a lot more force (and energy) to get us going again. The key to finessing your freestyle is to know what the thresholds are and to learn to swim within them.

One of the best tools I have found for learning more precisely where these thresholds are is the velocity meter technology. With the velocity meter, we measure your body speed (and acceleration/deceleration) at all points through your swimming cycle and synchronize them with video. By doing so we can measure your peak and trough velocities for both right and left arm strokes repeatedly. You would be amazed at how very small deviations in technique lead to significant changes in speed in a very short period of time, tenths of seconds. With this technology we can identify exactly where the mistakes in swimming technique are being made and often repeated over and over again and how big a price is being paid for them in terms of loss of speed.

In my swimming career, which has spanned some 55 years and included 3 Olympic Games, most of my best swims were not the most exhausting. In fact, those feelings belonged to some of my worst swims. It wasn’t the exhilaration of setting a PR or even a World Record that made me feel as if the race was easier. I may have been physiologically or mentally more prepared on those great days, but I can also assure you that I swam with more finesse. I swam smarter races.

At The Race Club, we teach swimmers how to finesse the freestyle, how to swim smarter and faster. No matter what your age or experience level, you can still learn how to finesse your freestyle, to swim faster with less effort, and to feel really good after your race. Are you ready for that?

Yours in swimming,

Gary Sr.

## A Lesson Learned

Many people feel that the introduction of the high-tech, full-body suits did more harm than good to the sport of swimming. At the very least, they devalued the World Record and perhaps worse, they erased some records that might have stood a long while otherwise. If there is one thing we should all have learned from this experience, it is the relative importance of fluid mechanics in swimming.

Think about it. 180 or so World Records did not fall in 1 ½ years due to some miraculous breakthrough in training, nor in nutrition (even banned performance-enhancers would be hard pressed to match that). Nor is it conceivable that so many swimmers got faster in such a short period of time for any other reason but one. The new suits reduce drag….significantly.

There is no doubt about that. Research has shown that the suits reduce both friction and pressure drag, just by changing the material and compressing the body inside it. I don’t think anyone would have predicted the dramatic effect these suits would have on times when they first appeared. What we now have learned, if we didn’t appreciate it before, is that for the human body in water, little changes can make huge differences in drag….and speed. The lesson to be learned is to not focus on a better suit to make the human body more streamlined, but how to reduce drag on the human body without using the high-tech suits. In other words, we need to focus much more on improving stroke technique to reduce drag, not just on improving aerobic fitness and power. Read more