Improving Foot Strength in Vocational Ballet Dancers
- Conditions
- Toe Flexor Strength
- Interventions
- Other: "Toe flexor device" experimental groupOther: "Inclined Heel Rise" experimental group
- Registration Number
- NCT06589050
- Lead Sponsor
- University of Bern
- Brief Summary
Professional dancers subject their feet to high forces through frequent jumping, repeated heel rises, insufficient shoe cushioning, and a high degree of foot mobility. To prevent injuries and improve jumping performance, dancers are recommended to strengthen the muscles of the lower extremities.
The foot muscles, especially the toe flexors, play an important role as shock absorbers and motors for the foot by absorbing and generating mechanical energy, which is essential for human locomotion. Furthermore, they serve as a link between the powerful leg extensor muscles and the ground, transmitting the energy generated by the larger muscle groups. This makes them essential components of overall athletic performance. However, the impact of foot muscle strength on dancers´ jumping performance remains uncertain. Therefore, the aim of this study is to investigate the effectiveness of two training programs designed to strengthen the toe flexor muscles in dancers. For this project, a 6.5-week intervention with ballet students from a vocational ballet school is planned. Before and after the intervention, all study participants will perform tests to assess foot muscle strength and jumping performance.
- Detailed Description
This study aims to develop two different toe flexor (TF) exercise programs for vocational dancers to enhance TF strength and jumping performance. It is hypothesized that i) both training programs increase TF strength and jumping performance, ii) horizontal jumps are more affected than vertical jumps, and iii) the TF exercise program with the TF strengthening device has a greater impact on TF strength.
Participants
Participants will be recruited from a vocational ballet school via an email detailing the study outline. They and their legal guardians (for participants under 18 years old) will be informed of the potential risks and benefits of the study. They will provide written informed consent prior to the measurements. Participants will then be assigned to either a control group, a toe flexor device experimental group, or a heel rise experimental group. The schedule includes three and a half weeks of training, a 12-day break due to the school schedule, followed by another three weeks of training. This will result in a total of 26 training sessions. An experienced trainer will supervise all training sessions. The control group will continue with the ballet school´s normal training schedule.
Data collection and management
An intervention protocol will be kept to collect information on compliance and progression of the training, such as the number of repetitions and the resistance applied. Data analysis will be performed according to the intention-to-treat (ITT) principle, in which participants are analyzed according to their original treatment group assignment. An additional researcher will manage reporting for adverse effects (such as delayed onset muscle soreness) and adverse events. All data collected in this study will be anonymized, personal identifiers removed, and data coded to protect the identities of the participants.
Sample size
Due to the study´s novel character, no sample size calculations have been conducted. To the researchers' best knowledge, no comparable protocols to improve TF strength have been investigated, so a sample size calculation was not warranted. The study is, therefore, exploratory.
Statistical analysis
Variables will be presented as the mean ± standard deviation. The Shapiro-Wilk test will be performed to assess the normality of the measured variables. Repeated-measures Analysis of Variance (ANOVA) with Bonferroni correction will be used to analyze variables across different times and groups. Non-normally distributed variables will be analyzed using Friedman ANOVA and Kruskal-Wallis ANOVA, with multiple comparisons of mean ranks for individual comparisons. Statistical analyses will be performed using IBM SPSS Statistics for Windows (Version 29.0), and the statistical significance level will be set to .05. If the primary and/or secondary outcomes yield null findings, equivalence testing will be conducted to determine whether the intervention is equivalent to the usual training (control group). The two one-sided tests (TOST) procedure will be applied, using either standardized differences (e.g., Cohen's d) or raw differences.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 49
Not provided
- Any recent lower leg or foot injuries.
- Chronic pain in the lower extremities.
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- PARALLEL
- Arm && Interventions
Group Intervention Description "Toe flexor device" experimental group "Toe flexor device" experimental group Participants will complete: * 3 sets of 15 repetitions with a 90-second break between each set. * Tempo 2-0-2-0 * 4 times per week * Progression will be achieved by increasing the stiffness of the elastic band whenever the participant can perform 15 repetitions without great effort. "Inclined Heel Rise" experimental group "Inclined Heel Rise" experimental group Participants will complete: * 3 sets of 10 to 15 repetitions with a 90-second break between each set. * Tempo 2-0-2-0 * 4 times per week * Progression will be achieved by increasing the number of repetitions to 15 and then adding weights to be held in the ipsilateral hand.
- Primary Outcome Measures
Name Time Method Maximal voluntary isometric contraction (MVIC) of the toe flexors muscles Measurements will be performed one week prior to and one week after the intervention. The post-intervention difference between the three groups in MVIC of the toe flexors measured with a custom-made toe flexor dynamometer in a seated position (90° angle in the hips and knees) where the foot is secured with a strap. Participants will push with their toes against a pedal and hold this isometric contraction for 2-3 seconds. The strength will be normalized by body weight (N/kg).
- Secondary Outcome Measures
Name Time Method Vertical jump - Countermovement jump (CMJ) - Jump height (cm) Measurements will be performed one week prior to and one week after the intervention. Participants will perform three CMJs on a Hawkin Dynamics force plate. They will stand upright on the plate and be instructed to jump as high as possible with their hands positioned on their hips.
Vertical jump - CMJ - changes in force parameters Measurements will be performed one week prior to and one week after the intervention. Participants will perform three CMJs on a Hawkin Dynamics force plate. The variables collected will be peak power (W), peak propulsive force (N), and peak landing force (N).
Vertical jump - Sauté jump - jump height (cm) Measurement will be performed one week prior to and one week after the intervention. Participants will perform three sautés on a Hawkin Dynamics force plate. They will perform a ballet-specific jump in an upright position with the legs externally rotated. Participants will be instructed to jump as high as possible.
Vertical jump - Sauté - changes in force parameters Measurements will be performed one week prior to and one week after the intervention. Participants will perform three sautés on a Hawkin Dynamics force plate. The variables collected will be peak power (W), peak propulsive force (N), and peak landing force (N).
Horizontal jump - Long jump - jump distance (cm) Measurements will be performed one week prior to and one week after the intervention. Participants will perform three horizontal long jumps with their hands positioned on their hips. The distance of the jumps will be measured (cm).
Trial Locations
- Locations (1)
Elmhurst Ballet School
🇬🇧Birmingham, United Kingdom