On Dec 1st 2007 Seattle University's Sports Performance Laboratory (SPL) performed a sequence of tests on an elite level Ultimate Disc player. The tests included a Resting Metabolic Rate (RMR) analysis, a VO2 Max test, and a series of motion capture/EMG recording actives. The object of the testing was to gain an understanding of the required athleticism of the subject and the muscle coordination involved in the throwing of a 175g disc.

The Disclaimer
This report is a quick look into the data and as such does not by any means constitute a clinical study. The metabolic information garnered is accurate only for the equipment used for the tests. The test results may or may not directly compare to the results from other equipment and that must be taken into consideration. In addition, the testing for comparison sources may be done in a different posture (treadmill, ergometer, recumbent, rowing...) or at a different effort buildup rate. The comparison data listed in this study is unconfirmed and lacks the due diligence and references required for a clinical study. For the motion capture portion of this study, too few throws were captured to produce a statistically meaningful analysis.

That being said, the study is still quite interesting and offers insights into the throwing of a 175g sport disc and the general athleticism demonstrated by the sport's participants.

Test Participants and Venue
The subject, Ray Illian, is a member of the 2007 UPA National Champion Club Open Team, Seattle Sockeye. The tests were conducted at Seattle University's Sports Performance Center facility located within the Cardiowellness Center of Swedish Hospital (Cherry Hill Campus).

The principle investigator was the subject's father, Paul R, Illian, a Sports Engineer with Seattle University and the Biomechanics Lab manager. McLean Reiter and Sean Machak, two exercise physiologists, also with Seattle University, assisted Illian in the tests.

Also present, as observers and support were four of the subject's Seattle Sockeye teammates; Michael Caldwell, Ben Wiggins, Michael Jaeger, and Sam Chatterton-Kirchmeier.

Resting Metabolic Rate (RMR) evaluation.
The RMR measures the minimum amount of energy (kcal) the body requires for living (think couch potato). Normal is in the range 1600 – 2400. It does not include the energies required to digest food or to carry on normal activities. The subject was requested to fast for the 8 hours leading up to the test, since any digestive activity would contaminate the results. The subject was instrumented with a facemask connected to a monitoring device, placed in a quiet environment and asked to lay still. The instrumentation monitored the subject and calculated RMR from the test data. The subject's RMR was 2065 kcal/day. The subject tested to very much in the middle of the normal range.

Maximal Oxygen Uptake Evualuation (VO2 Max , or aerobic capacity)
This test was conducted last in the testing sequence, but is listed 2nd here for the purposes of grouping with the above RMR evaluation. The VO2 Max test measures how efficient the body is in bringing oxygen into the body for use by the subject's muscles. Once the subject's VO2 Max is exceeded, the metabolism shifts from aerobic to include anaerobic processes and energy is drawn from energy stores within the muscle. With fluid replenishment the aerobic metabolism can be maintained for long periods of time, while the anaerobic metabolism (sprinting) cannot. VO2 Max values for a typical young untrained male are 45 ml/kg/min. A young untrained female would be about 38 ml/kg/min. These values can and will increase with training and weight loss.

A male club (professional) athlete will typically have a VO2 Max of around 70 ml/kg/min. I do not have documented numbers for the female athelete, but I would swag them at 65 ml/kg/min.

For the world class athlete, a male's VO2 Max level is typically over 80 ml/kg/min and a female's is over 70 ml/kg/min. These levels generally represent the maximum capability of the subject and are to a large degree genetic. Training can only nudge the max level, but losing weight can significantly increase the calculated values.

A table of typical VO2 Max values can be found here.

Again, keep in mind that these numbers do not reflect the equipment used or testing protocol.

In this test, the subject was fitted with a mask covering both the mouth and nose. The mask was connected to equipment which measured the air chemistry as the subject inhaled and exhaled during the test.

The subject was asked to step onto a treadmill. Initially, the treadmill surface was level and the speed set to 1 mph. After the subject became accustomed to the process, the grade and speed were incrementally increased until a final incline of 18 degrees and a speed of 6 mph were reached. In this test, the subject continues running on the treadmill as long as possible. A typical test will last 15-16 minutes until the subject is physically exhausted and steps/falls off the back of the machine.

The subject then has a 10-minute cool down period (with mask on).

The data is then post-processed and the subject's performance levels ascertained from the recorded data.

In this test, the subject lasted 17 minutes and produced a VO2 max of 4.887 l/min. At the tested body weight of 169.9 lbm, the subject's VO2 Max is 63.39 Adjusted for the subject's playing weight of 165.0 lbm, the VO2 Max is 65.27 ml/kg/min. Maximum achieved heart rate was 194 bpm. View 12 minutes of behind-the-scenes footage of the mo-cap and V02-Max testing

Motion Capture

Motion capture testing was performed using Vicon MX equipment, with measurements taken 100 times a second. This is the same equipment used in Hollywood studios and by video game producers. Six high contrast MX cameras were used to record the reflective markers. Four cameras were mounted high on the wall and two were mounted low to floor to capture the lower side of the disc. A high speed Basslar camera was synced with the MX cameras to visually record the testing. Additionally, a hand held video camera recorded the testing.

In a motion capture system there are special cameras (MX). These cameras are actually CCD sensors and a microcomputer connected to the command station using a dedicated intranet. Each MX flashes an intense IR strobe light. The CCD camera creates a high contrast image, which is converted to dot positions. The reflections from special markers are so bright that the computer can easily distinguish them from anything else in the testing environment. The dot positions are extracted then sent over the intranet to the command station to be processed.

The command station compares the dot patterns as seen from each MX camera and creates a 3-D location for each dot.

The subject was affixed with 39 reflective markers. The markers were placed in accordance with something called the "Conventional Gait Model," a de facto industry standard. Use of this model allowed the lab to infer the subject's skeletal structure, muscle and body mass characteristics.

In addition, eight surface muscle groups were identified for EMG transducer recording and assigned unique channels.

Channel 1 - Deltoideus p. scapularis
Channel 2 - Infraspineus
Channel 3 - Triceps brachii
Channel 4 - Smaller forearm
Channel 5 - Pectoralis major
Channel 6 - Rectus abdominis
Channel 7 - Brachioradialis
Channel 8 - Obliquus extremus abdominis

Surface muscles were chosen, as they did not require any invasive procedures (hole poking).

A 175g Discraft was chosen for the testing, as it is the disc of choice for most ultimate players. The disc was fitted with 4 reflective markers.

The subject was asked to make eight throws; four backhand and four forehand. Each throw was recorded by the motion capture system as its own trial. Owing to the camera setup limitations, no hammer throws were possible.

Following the completion of testing, each recorded trial was assessed for completeness of camera coverage and general ease of post processing. The best forehand and backhand trial was selected for further processing and analysis. See motion capture of Ray's throws here.

The motion capture data are cleaned up using a spline fitting algorithm to fill gaps due to occluded markers and camera coverage limitations. The cleaned up data was then stored into a file using the industry standard .C3D format.

The 3D points were then processed using some dynamic gait analysis software which created a skeleton and a muscle configuration.

Post-Processing

The trial data was exported into a .CSV file and imported into Microsoft Excel. Within Excel, the joint centers were evaluated for speed and the bone segments were evaluated for rotation rates.

Joint speeds were determined by change in position of the joint from the current frame to the joint position in the previous frame and dividing by the framing rate. The magnitude of the resultant vector was plotted.

Bone segment rotations were determined by taking the dot product of the bone segment vector in the current frame and the vector of the previous frame. The dot product calculates the angle between two lines and does not by itself contain any information on rotation relative to the throwing motion. This accounts for the spikiness of some of the plots. See motion capture with side-by-side video and muscle EMG readouts.

Analysis

As tested, the subject tests as being a superior athlete with an excellent level of fitness. Further testing and research would be required to gain a more accurate assessment.

Backhand throw

The backhand throw behaves as would be expected. Looking at the plots, it can be seen that there is a smooth and continual build up of disc speed up to the release. Notice though, that the disc speed is less then the finger speed at disc release. This difference is due to the fingers changing direction to impart spin to the disc.

Spin is imparted to the disc in a smooth and continuous manner. There appears to be a slight dip in the disc rotation rate just prior to the release. This is not the case; it is merely a mathematical artifact indicative that the thrower has finished raising (rotating) the disc, from edge down to horizontal, just prior to release.

The displayed disc angle is measured from the horizontal. It combines the lift angle and the side angle.

Including the windup, the throw takes 0.4 seconds. In this particular throw, the disc speed at release is 72 fps (50 mph). The disc spin at release is 900 rpm (15 revolutions per second).

Forehand throw

The forehand is an interesting throw. Looking at the plots, several things are apparent. As expected, the forehand is a quick throw. From the time the thrower commits to the throw to release is 0.2 seconds, half that of the backhand. 90% of the disc's rotational energy is applied in less then 4/100's of a second just before release (the flick).

Including the windup, the throw takes 0.2 seconds. In this particular throw, the disc speed at release is 61 fps (40 mph). The disc spin at release is 720 rpm (12 revolutions per second).

Comparing the two throws

As expected, the backhand is a more powerful throw with the potential for greater distance. But... surprisingly, it is not as big an advantage as one would expect from the speed and rotation data recorded. I would speculate that the backhand throw wobbles more on release and disc momentum is lost while the disc stabilizes. This wobble is probably due to the poor gripping options during the throwing motion. This wobble can be seen in the disc angle plots. There is also the possibility that the disc is warping during the throwing motion. With the limited data available, it is difficult tell for sure. A more statistically accurate assessment would require 30 different throwers doing 30 throws of both the forehand and backhand, as well as recording more of the disc's flight path.

Paul Illian Sr.
Sports Engineer, Seattle University
Dec 26th 2007