Title

Determining muscle-tendon characteristics and function of stretch-shortening cycle performance in dancers

Author Identifiers

Paige Rice
ORCID: https://orcid.org/0000-0002-8899-5385

Date of Award

2021

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Medical and Health Sciences

First Advisor

Professor Sophia Nimphius

Second Advisor

Kiisa Nishikawa

Third Advisor

Kevin Zwetsloot

Abstract

Dancers are aesthetic athletes with extraordinary skillsets defined by muscle-tendon unit (MTU) properties and stretch-shortening cycle (SSC) proficiency. Early on in athletic development, dancers are instructed to maintain aesthetic posture, wherein the hips are directly beneath the shoulders, during most jumps and leaps. Different from a countermovement jump, leaps such as the saut de chat (split leap) have been shown to cause distal shifts in torque from the hips to the ankle, likely due to postural maintenance. Thus, the role of the ankle in dance is potentially twofold as the primary joint: to both generate torque during dance-specific SSC’s and to achieve stylistic “pointing” of the toes – hyper-plantarflexion. Little research has delineated the MTU properties surrounding the ankle-joint of dancers and how they might influence dance-specific SSC performance, like saut de chat leaping. Furthermore, ankle-specific strength and conditioning tactics to simultaneously improve maximal strength capacity, MTU properties, and saut de chat leaping performance have yet to be investigated in dancers. Therefore, this thesis was founded in the following purposes: 1) to elucidate whether isolated ankle-joint SSC performance, maximal isometric and isokinetic plantarflexion strength, and maximal Achilles tendon force and elongation differ between dancers, endurance runners, and untrained controls; 2) to determine the relationship between saut de chat weighted parameter rankings, leap height, maximal voluntary isometric plantarflexion strength, medial gastrocnemius stiffness, Achilles tendon stiffness, and leaping peak power; 3) to investigate the effect of an ankle-focused block progression training program (24 sessions) on saut de chat leaping performance, maximal plantarflexion strength, and Achilles tendon stiffness. and 4) to successfully perform single fibre and fibre bundle mechanics on micro-biopsy samples from medial gastrocnemii of dancers.

Study one demonstrated that dance is likely a stimulus for enhanced ankle-joint SSC function, plantarflexion isometric and isokinetic strength, and Achilles tendon elongation. Endurance running also appeared to be a possible stimulus for increased muscular strength. Study two revealed that relative peak power during leaping, maximal voluntary isometric plantarflexion strength, and medial gastrocnemius stiffness strongly and moderately predicted saut de chat performance as defined by a novel weighted parameter ranking tool. Study three showed that twelve weeks of ankle-specific block progression training appears to benefit saut de chat leaping performance, peak power output, ankle-joint kinetics, maximal strength, and Achilles tendon stiffness, while not affecting kinematic aesthetic measures. We found that by employing additional training that targets ankle-specific stretch-shortening cycle, neuromechanical, and muscle-tendon unit development, dancers are capable of improving already well-engrained movement execution strategies. Study four discovered that muscle fibre mechanics can be performed on micro-biopsy samples from medial gastrocnemius muscle, which will allow for future research on dancers’ basic muscle force-length and force-velocity properties to be more feasibly investigated.

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