Introduction

One of the most effective but problematic means of enhancing difficulty in gymnastics performance is to add a twist and/or somersault to an existing skill. In either case, the athlete must be able to remain in the air long enough to add the additional twist and/or somersault, rotate faster, or both. Although triple-twisting back somersaults have been performed in tumbling and floor exercise regularly for more than two decades, a quadruple-twist is very unique and represents a significant increase in skill difficulty and a major “trademark” skill for any gymnast.

At the request of the Men’s Senior National Team Director for USA Gymnastics, Mr. Ron Brant, we were able to record the performance of a triple- and quadruple-twisting back somersault performed by Alex Artemev. Artemev had performed the quadruple-twist on floor exercise in training and was invited to come to the U.S. Olympic Training Center in Colorado Springs to perform both skills for analysis.

Methods and Procedures

Tumbling Performance. The tumbling performance was conducted on a tumbling strip into a loose foam pit at the United States Olympic Training Center Men’s Gymnastics Training Facility. Artemev performed a self-selected warm up and then performed several tumbling passes along the tumbling strip landing in the foam pit. Although Artemev has performed the quadruple-twist successfully on a standard floor exercise surface, a foam pit landing area was selected for this study for safety reasons. Artemev performed several tumbling passes culminating in two triple-twisting somersaults and three quadruple-twisting somersaults. The United States Men’s National Team Director selected the specific trials for analysis.

Analysis Methods. Twisting somersaults must be characterized by three-dimensional motion analysis methods. The tumbling performances were videotaped via two genlocked (synchronized) video cameras and stored in two mini-digital video recorders for later computer analysis. The video was recorded with a sampling frequency of 60 frames per second (60 Hz). The space where the performance occurred was calibrated using standard procedures (PEAK Performance Technologies, Inc. Centennial, CO). Calibration allows the motion to be “mapped” by computer software to accurately describe the athlete’s motion within the calibrated space volume (i.e., where the gymnast performs).

Following the tumbling performances, both videotapes of each performance were digitized manually using computer software (PEAK Performance Technologies, Centennial, CO). Digitizing is the process by which anatomical joint centers and other landmarks are identified from the video images and thus located in the calibrated space volume (X,Y,Z coordinate space). A body segment model is used to represent the human body so that the center of mass of the entire body can be derived from the various segments of the body as shown by the video image records. The anatomical landmarks are used as a model of a body for which one can determine an overall center of mass. A 23-point model of the human body was used to represent the athlete’s body in this investigation. This model is readily visible in the following images that show “dots” where the athlete’s stick figure is represented. These larger “dots” of the stick figure are the points showing where the athlete’s joint centers were located during the movement. The analysis of the tumbling passes began a few frames prior to feet contact of the round off and continued through to the position of a simulated landing. The landing position was identified as the frame when the gymnast’s feet passed the tumbling strip surface during the descent phase of the somersault. This final position of the body was used to identify when/where the athlete would have struck a mat with his feet and thus landed.

Results and Discussion

The results and discussion are organized in the following way: 1) orientation videos, 2) center of mass path comparison, 3) nutation, and 4) twist position comparisons. Videos 1 and 2 show side views of the performances of the triple- and quadruple-twists. These videos serve to orient the reader to the skills and movements involved. Videos 1 and 2 show a topmost view of the captured video as well as a corresponding stick-figure view below. Note that the stick figures portray the movements of the athlete precisely and in synchrony.

Video 1: Triple Twist Video 2: Quad Twist

The paths of the centers of mass in the two skills are shown in Figure 1. The quadruple-twist shows that the athlete begins to travel vertically earlier than the triple-twist, and the overall trajectory of the quadruple-twist is slightly higher. This is achieved by a slightly more acute forward lean of the body during the early foot contact phase of the take-off (not pictured), resulting in a higher vertical component velocity of the center of mass at take-off. In gymnastics terms, this is often referred to as a greater “block.” Moreover, the gymnast may also apply more downward and rearward force to the spring strip during the take-off for the quadruple-twist.

Figure 1. Center of Mass Paths. Note that the quadruple-twist center of mass trajectory, as viewed from the side in this figure, shows the gymnast rising earlier and higher than in the triple-twist (shown in blue).

One of the most important aspects of twisting somersaults is that they develop a natural “crookedness” during their execution (1-3). This crookedness is called nutation. The “crookedness” or wobble is often seen in the motions of a gyroscope or an American football pass that results in the tips of the football spinning in a circle about the line of the overall trajectory flight path of the spinning ball. When the somersault is completed from positions of feet contact to feet contact (i.e., a complete somersault), the body tends to return to its normal upright and vertical orientation. However, when the athlete performs fractions of the somersault (and/or fractions of the twist), the body may not land in a vertical standing position on impact with the floor. This “off vertical” landing is one of the common faults seen in multiple twisting somersaults in tumbling, trampoline, diving and so forth. The nutations present in the triple-twist and the quadruple-twist are shown in Videos 3 and 4.

Videos 3 and 4 are rendered by using a computer transformation of the positions of the body so that it orients the movements as if the viewer is now standing in the landing area or suspended over the foam pit. Thus, the gymnast appears to be tumbling toward the viewer. Nutation is visible as the pronounced shift of the feet to the left during most of the somersault while the head is shifted to the right. Note that the gymnast’s body orientation relative to vertical returns to a vertical position at the end of the triple-twist, but doesn’t quite return to a vertical position in the quadruple-twist. The slight tilt that remains during the landing phase of the quadruple-twist may result in the gymnast’s inability to land the skill easily, safely, and without deductions.

Twist position comparisons are shown in Figures 2 through 4. The objective of these figures is to show the athlete’s strategy in converting his triple-twist to a quadruple-twist. Figures 2 through 4 show the gymnast’s positions at the ends of each of the first three twists.

Figure 2. End of the first twist. Note that the gymnast’s positions are nearly identical in both twisting skills

Figure 3. End of the second twist. Note that the gymnast’s positions are nearly identical.

Figure 4. End of the third twist. In this figure, note that during the quadruple-twist (right side), the gymnast ends the third twist in the position shown. This indicates that the gymnast must fit an entire full turn after this position and before the feet strike the landing area.

Figures 2 through 4 indicate that the gymnast’s strategy for performing the quadruple-twist is to simply perform a triple-twist and then add the fourth twist after the existing triple. Figure 4 shows that the gymnast has very little time and height remaining following the end of the triple-twist to add the fourth twist. The gymnast has been counseled to increase the height of the somersault and to attempt to enter the twist sooner in order to gain more time, altitude, and portion of the somersault to complete all the twists.

The second issue arises in the twist performances that can be observed in Videos 3 and 4. When viewed from behind one can note that the right (green) arm tends to shift to a position that is not held tightly to the body during portions of the twist execution. This arm movement increases the gymnasts moment of inertia about his longitudinal axis and thus slows the speed of the twisting motion. The gymnast was also counseled to ensure that his right arm remains tightly next to his body during the twist performance.

Conclusion

The comparison of the triple-twist with the quadruple-twist shows marked similarities between the two with the fourth twist clearly “added” to the end of the triple. To enhance his performance, the athlete may need to address the idea of trying to initiate the twist slightly earlier in the somersault in the hope that he can get a “head start” on the twisting motion and thereby have an easier time completing the four twists. Moreover, by holding his right arm closer to his body he may be able to complete the fourth twist more easily and thus reduce the problems of nutation that are apparent as he performs his landing.

References

1. Frohlich, C. Do springboard divers violate angular momentum conservation? American Journal of Physics 47, 583-592. 79.
   Notes: Reference Id: 5013.
2. Gluck M. Mechanics for gymnastics coaching. ed. Springfield, IL: Charles C. Thomas, 1982.
3. Yeadon, M. R. The biomechanics of human flight. American Journal of Sports Medicine 25(4), 575-580. 97.
   biomechanics.