by Isabelle Breier
Hopkins School, Woodbridge , CT
First place
Tanya’s warm-up was nearly complete– her sweatshirt was saturated with perspiration- her flexibility and strength were finely honed. One last stretch for her beautifully sculpted calf muscles before facing the intense competition. Tanya grabbed her gear- pointe shoes skillfully enhanced with engineering through hundreds of years. These shoes would protect her from injury and propel her to a winning medal…
Ballet began as pure art, growing out of Italian court productions. It was further developed in France in Louis XIV’s court.1 In 1832, Marie Taglioni was the first to dance on pointe in Paris during the premiere of La Sylphide.2 Pointe was likely an attempt to make dancers appear ethereal and embody Romantic values of femininity and otherworldliness.3 Since then, and especially over the past fifty years, the physical requirements needed to achieve ballet’s ever-growing demands have increased logarithmically.
Ballet is now viewed as a supremely competitive activity calling for strong, carefully tuned musculature and top physical conditioning. A 1975 study by Dr. James Nicholas highlighted the demanding athleticism of professional ballet. The study evaluated 61 sports based on the degree of difficulty with respect to physical, mental, and environmental factors. Adding these categories together, ballet scored a 55, second only to football, which earned the highest score, 56.4 A 2009 study examined ballet as a sport. After assessing aerobic capacity, muscular power/endurance, muscular strength, anthropometry, flexibility, and agility, the study found that ballet is similar to other high-intensity interval training.5 Influenced by conventional opinion that ballet has become a sport, Under Armour, a brand known for outfitting football players, launched an advertising campaign in 2014 starring an American Ballet Theatre soloist. In the ads, she performs feats with the aplomb of an accomplished athlete and ballerina.6 Also, pre-professional ballerinas participate in international competitions where they win scholarships and company contracts.7
The pointe shoe is essential gear and highly specialized equipment for any ballerina. As ballet has transitioned from art to sport, pointe shoes have had to keep pace. When the pointe shoe was first employed, this technology was very primitive. It was merely a simple slipper heavily reinforced with darning around the toes. Dancers relied solely on their own strength and could not stay on pointe for long. Later in the nineteenth century, the shoes were modified and the tip was called the box. The box was satin on the outside, covering layers of burlap held together by glue; it supported the sides of the foot and provided a wide base for standing on one’s toes, called the platform. The satin was pleated on the underside of the shoe where it met the shank. The shank, or sole, was made of leather. It supported the arch. Ribbons held the shoe on at the ankle, and elastic was added later. The pointe shoe must be strong enough to support the feet, but flexible enough to allow complex movements. In the twentieth and twenty-first centuries, engineers have made the shoes more ergonomic and efficient, taking advantage of new technologies.2,8,9,10 More specifically, as the physical demands of ballet have increased, biomechanical and materials engineers have refined pointe shoes to allow for better alignment, shock absorption, and durability. This has created less injury and more savings.
To comprehend the significance of engineering advances in ballet, one must understand the biomechanics of dancing on pointe, or on the tips of the toes. The loading force created is particularly important. When a ballerina rises to the on pointe position, the bones in her foot and leg, as well as the upward tension of her Achilles tendon, lock and stabilize her ankle.2,10 Her body weight is supported by the tips of her toes, which align with her foot’s longitudinal axis.2 Walking in pointe shoes places twice the peak pressure on the foot as walking barefoot (41 N/cm2 vs. 86 N/cm2).2 Moving from a flat-footed position to on pointe will increase the peak pressure to 115 N/cm.2 With active dancing, forces may increase to ten times a ballerina’s weight.11 The average pressure on the box of the shoe while on pointe is 220 psi or 1.5 MPa.2 However, a 60-kg ballerina landing on pointe from a height of one meter generates an impact force of approximately 4950 N or 700 psi, 650 N more than the compressive strength of five pointe shoe brands studied.12 The difference between the force generated and the shoe’s ability to absorb force is a source of potential injuries. The more load the shoe can absorb, the safer the ballerina.
Another important concept is alignment. When on pointe, a dancer must maintain her center of gravity directly over her toe, which requires precise alignment. As a dancer moves, her center of gravity continually shifts and she must adjust her alignment to avoid injury. In a 1990 study, 80% of professional dancers surveyed suffered an ankle injury in their careers.11 A biomechanical engineer and former dancer stated, “Straight ankle alignment is stressed as a part of proper ballet technique. This is a biomechanically smart element of technique because misalignment transmits these high forces to the medial/lateral ankle structures.”11 In addition to dancers’ continual, subtle adjustments, pointe shoes may also be designed to improve this issue.
One notable technological advance by materials and biomechanical engineers working in the world of pointe shoes is the introduction of elastomers into the shoes’ boxes and shanks.13,14 Elastomers are polymers possessing both viscous and elastic properties when undergoing deformation. They return to their former shape because their monomers rotate freely, the forces between the polymer’s chains are weak, and the elastomer’s chains are cross-linked to a common point in the elastomer.15 Two elastomers that have been used are urethane foam and D30, which have also been integrated into sports and work clothing for impact protection. These elastomers act as shock absorbers that reduce trauma from dancing. Another addition that absorbs impact is Poron 4000 (cellular urethane foam), used as lining.13 It is also used in orthoses and running shoes.16,17 In a study, podiatrists reported a statistically significant (18%) reduction in plantar pressure in the feet of dancers wearing shoes with elastomers and Poron 4000 compared to dancers wearing shoes without these innovations.18 This could lead to a reduction of overuse injuries from plantar pressure during jumps.
In the same shoe brand with added elastomers, engineers also increased the shoe’s usable platform area (in part, by removing the pleats) and therefore improved dancers’ alignment. Podiatrists showed that with 38% more usable platform area, dancers demonstrated more stability on pointe and, consequently, better alignment.18 A second study, performed in 1997 in the Biomechanics Section of the Exercise Science Department at the University of Massachusetts, demonstrated that dancers in the redesigned shoe with greater platform area stood straighter and had reduced ankle adduction, or “sickling.”11 For example, a dancer straightening her alignment by 12° in the experimental shoe removed about 24 pounds of laterally placed force when she went on pointe.11
One other advantage in addition to the positive effects on injury via impact and misalignment is the durability of the new synthetic materials. A study from an Orthopedics Biomechanics Laboratory showed that shoes made of elastomers exhibited a fatigue range approximately ten times higher than the traditional shoes.12 They also demonstrated the highest vertical strength.12 This translates to longer-lasting pointe shoes. A professional ballerina may use one pair of pointe shoes per performance. It is estimated that shoes made of elastomers would last five times longer- a significant financial advantage for dancers.12
There are many possible future directions for the further pointe shoe refinements. Materials engineers could experiment with fabrics and other platform modifications to address the coefficients of friction and frictional rotation, which would facilitate turning, critical to dancing. Even more elastic materials could be tested to improve jumps. These, in turn, might further decrease risk of injury.
Biomechanical and materials engineers face the constraints of a required look and general shape of the pointe shoe. This clearly would limit choice of materials, as the shoe itself is thin and materials must be able to fit in less than ���������-inch. Also, part of the ballet world is devoted to tradition. They worry that innovations will “help” dancers too much. Another argument is that pain from pointe is a “rite of passage,” and to some, the art form’s value is reduced when the pain is alleviated. This hampers progress due to less support for innovation.14
Engineering, through sophisticated elastomers and biomechanical innovations, has advanced the pointe shoe, the gear of the ballerina. This has minimized injury and maximized durability. One can imagine that dancers’ careers will be significantly lengthened with less impact on their feet and ankles, as well as fewer injuries from misalignment. Ballet companies, often in need of funding, could function more successfully by spending less on pointe shoes. Most importantly, Tanya, our aspiring professional, will fulfill her heart’s desire– as she leaps and turns effortlessly- beautifully- brilliantly- supported not only by her Cavalier but also by the amazing world of engineering.
Citations
"Dancing Online, History of Ballet." Web.
Shah, Selina. "Pointe Shoes Complicate Biomechanics of Ballet." Lower Extremity Review Magazine. Web.
Johnson, Greg. "A Pointe in Time: Graduate Student Whitney Laemmli Discusses the Evolution of Pointe Shoes." SAS Frontiers. Penn Arts and Sciences, 29 Mar. 2012. Web.
Nicholas, James A., MD. "Risk Factors, Sports Medicine and the Orthopedic System: An Overview." Journal of Sports Medicine 3.5 (1976): 243-59. Ovid. Web.
Jenkins, Becca Borawski. "Classical Ballet: An Art or a Sport?" Breaking Muscle. Web.
I Will What I Want. Perf. Misty Copeland. Under Armour. Web.
Youth America Grand Prix. Web. http://yagp.org/, and Prix De Lausanne. Web.
"History of the Pointe Shoe." 13 Things. JIAAW Workplace. Web.
Missaghi, Mariam. "The Physics of Toe Shoes." Web.
D'Alessandro, Donna M., MD. "What Are Considerations for a Dancer to Begin Pointe Training?" PediatricEducation.org. 19 Jan. 2015. Web.
Worthen, L., et al. "Biomechanical Issues in Ballet: Alignment at the Ankle in Pointe Shoes." Performing Artists Medicine Association, Proceedings of Annual Meeting. 1997. Web.
Cunningham, Bryan W. "A Comparative Mechanical Analysis of the Pointe Shoe Box: An In Vitro Study." The American Journal of Sports Medicine 26.4 (1998): 555-61. Print.
"10 Ergonomic Secrets." Gaynor Minden Pointe Shoes. Web.
"Eliza Gaynor Minden." Ballet Connections. Web.
MacDonald, Amy. "Ballet Shoes and Elastomers: Have I Made My Pointe?" CurioCity. 26 June 2013. Web.
Caselli, M. A., S. J. Levitz, N. Clark, S. Lazarus, Z. Velez, and L. Venegas. "Comparison of Viscoped and PORON for Painful Submetatarsal Hyperkeratotic Lesions." Journal of the American Podiatric Medical Association 87.1 (1997): 6-10. Web.
Levitz, Steven J. "PORON Medical ® Urethane Plays Supportive Role in Orthoses Lab." Poron Prescription. Rogers Corporation, 2008. Web.
Anderson, Ann C., Gregory Ng, Jennifer A. Benwood, and John H. Walter, Jr. "F-Scan Evaluation of a New Pointe Shoe Design." Temple University School of Podiatric Medicine 14th Annual Scientific Seminar. 1999. Web.