Lower-Extremity Energetic Distribution During Rate-Controlled Ballet Jumps (Sautés) in Healthy Dancers.

Dancers frequently perform jumps in the context of a prolonged, continuous dance piece. The purpose of this study is to explore the lower-extremity energetics in healthy dancers performing repetitive dance jumps (sautés) before and after typical dance-specific choreography. Lower-extremity kinetic data were collected from 14 healthy female dancers during a series of sautés performed before and after 3 minutes of dance. Percent contributions of the lower-extremity joints to the whole-limb mechanical energy expenditure during ground contact were calculated. The jumps performed at the beginning were compared with the jumps at the end of the dance choreography. Dancers maintained the jump rate and consistent whole-limb mechanical energy expenditure between the jump series. As expected, for both jump series, the sautés had greater relative energetic contribution from the ankle and knee as compared with lesser contribution from the hip and toe. However, we observed lesser contribution from the knee and greater contribution from the hip after a 3-minute dance. After performing typical dance choreography, the dancers demonstrated a distal to proximal redistribution of individual joints' contribution to whole-limb mechanical energy expenditure.

Contributions of flexor hallucis longus and brevis muscles to isometric toe flexor force production.

PURPOSE: Morphological differences between the two primary great toe flexors - flexor hallucis longus (FHL) and flexor hallucis brevis (FHB) - likely drive differences in how these muscles contribute to functional toe flexor torque production. The aim of the study was to investigate FHL and FHB activation in two isometric toe flexion tasks - one called a "toe-pushing" task with the metatarsophalangeal (MTP) joints dorsiflexed and the interphalangeal (IP) joints in neutral and another called a "toe-gripping" task with the MTP joints in neutral and flexed IP joints. METHODS: Twenty participants' FHL and FHB muscles were instrumented with intramuscular electromyography electrodes. Muscle activation was normalized to a maximum voluntary contraction and compared between the two isometric toe flexor force production tasks. RESULTS: Overall, participants utilized these two toe flexors completely differently in the two tasks. In the toe-gripping task, the FHL was activated to a much greater extent than the FHB. In fact, 18 our of 20 participants activated FHL at more than 70% maximum voluntary contraction and half of participants activated FHB at less than 10%. In contrast, muscle activation during the toe-pushing task appeared more reliant on the FHB for most participants. CONCLUSIONS: Different contributions from the FHL and FHB to toe flexor force production in these two tasks are potentially driven by differences in muscle functional length among other factors. These findings help to inform the selection of rehabilitation and training exercises meant to preferentially target intrinsic or extrinsic foot musculature.

A Perspective on Reversibility of Tendinosis-Induced Multi-Level Adaptations.

Achilles tendinopathy is a well-known pathology that can display interindividual variations in chronicity, symptom presentation, and tendon morphology. Furthermore, symptoms may fluctuate within an individual throughout the stages of the pathology. Although pain is often used as a marker of condition severity, individuals may not consistently report pain due to periods of remission. Persons with tendinosis, which is characterized by advanced morphological alterations, have shown consistent changes in neuromechanics that indicate adaptations in the sensory-motor and the central nervous systems. The current treatment strategy involves repetitive resistance exercise aiming to achieve recovery of lost function. This treatment approach, however, has gauged such functional recovery through symptom relief and return to sport, which, in our opinion, may not suffice and may not prevent symptom recurrence or tendon rupture. In this physiologically informed perspective, we briefly review what is currently known about the consequences of Achilles tendon degeneration and examine the topic of reversing these changes. Shortcomings of contemporary treatment strategies are discussed and we therefore call for a new paradigm to focus on the whole-body level, targeting not only the tendon but also the reversal of the neuromotor control system adaptations.