Toe Flexor StrengthNCT06589050
Improving Foot Strength in Vocational Ballet Dancers
A study testing "Toe flexor device" experimental group and "Inclined Heel Rise" experimental group in people with Toe Flexor Strength, run by University of Bern at 1 site in United Kingdom.
Trial 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. Read more about this study
- Who is it for?
- Ages 14 to 19 yearsHealthy volunteers can take part
- Conditions the study is for
- Toe Flexor Strength
- What is being tested?
- "Toe flexor device" experimental group and "Inclined Heel Rise" experimental group
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 49 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 10 Sep 2024to 15 Dec 2024
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 14 to 19 years
- All sexes
- Healthy volunteers accepted
- Child, Adult
Who may be able to join
- Being a ballet student at the Elmhurst Ballet School.
- Aged 14 to 19.
- Written informed consent (by the participant and/or their legal guardian).
Who cannot join
- Any recent lower leg or foot injuries.
- Chronic pain in the lower extremities.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: The Effects of Two Foot Strengthening Interventions on Toe Flexor Strength and Jumping Performance in Vocational Ballet Dancers: A Randomized Controlled Trial
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.
Read the 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.
- Conditions
- Toe Flexor Strength
- Being tested
- "Toe flexor device" experimental group, "Inclined Heel Rise" experimental group
- Keywords
- Toe flexor strength, Foot, Dance, Jumping performance
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
"Toe flexor device" experimental groupOther
This intervention group will perform toe flexion using a toe flexor (TF) device, which facilitates the shortening and stretching of the TF muscle-tendon units (MTUs) against resistance bands. While seated, participants will push a pedal down with their toes over two counts and release it over two counts.
"Inclined Heel Rise" experimental groupOther
This intervention group will perform single-leg heel rises on an inclined platform. Participants will place their hands against a barre for balance support, lift their heels over two counts, and lower them over two counts.
| Study group | Role | What they receive |
|---|---|---|
| "Toe flexor device" experimental group | Experimental | 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. Receives: Other: "Toe flexor device" experimental group |
| "Inclined Heel Rise" experimental group | Experimental | 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. Receives: Other: "Inclined Heel Rise" experimental group |
| Control group | No intervention | The control group will continue with the ballet school's normal training schedule. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Maximal voluntary isometric contraction (MVIC) of the toe flexors muscles
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).
Measured: Measurements will be performed one week prior to and one week after the intervention.
Secondary outcomes (5)
Vertical jump - Countermovement jump (CMJ) - Jump height (cm)
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.
Measured: Measurements will be performed one week prior to and one week after the intervention.
Vertical jump - CMJ - changes in force parameters
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).
Measured: Measurements will be performed one week prior to and one week after the intervention.
Vertical jump - Sauté jump - jump height (cm)
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.
Measured: Measurement will be performed one week prior to and one week after the intervention.
Vertical jump - Sauté - changes in force parameters
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).
Measured: Measurements will be performed one week prior to and one week after the intervention.
Horizontal jump - Long jump - jump distance (cm)
Participants will perform three horizontal long jumps with their hands positioned on their hips. The distance of the jumps will be measured (cm).
Measured: Measurements will be performed one week prior to and one week after the intervention.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Sep 2024
- Study start10 Sep 2024
- Primary completion5 Dec 2024
- Study completion15 Dec 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (7)Papers the sponsor has linked to this study.
- Other trials for Toe Flexor StrengthStudies of the same condition, open and under way.
- More trials run by University of BernThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This is a parallel-group randomized controlled study. Participants will be randomly assigned to one of three parallel groups (two experimental groups and one control group) with a 1:1:1 ratio. To balance the covariates of age and sex among the three groups, a computer-based program will perform stratified randomization within three blocks.
- Masking
- None (open label)
- Enrolment
- 49 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Bern
- Sponsor type
- University, hospital or other
- Collaborators
- Elmhurst Ballet School, Birmingham, German Sport University, Cologne
- Responsible party
- Sponsor
- Investigators
- Anna Schrefl, MSc, Principal investigator, University of BernDaniel Erlacher, PhD, Study chair, University of BernAndrea Schaerli, PhD, Study chair, University of BernNico Kolokythas, PhD, Study chair, Elmhurst Ballet School
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06589050
- Sponsor's protocol ID
- 5/24/AS/UOW
- Status last verified
- Mar 2025
- First submitted
- 5 Sep 2024
- Last updated
- 26 Mar 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Sensitive data of the students and the school.
Publications
Goldmann JP, Bruggemann GP. The potential of human toe flexor muscles to produce force. J Anat. 2012 Aug;221(2):187-94. doi: 10.1111/j.1469-7580.2012.01524.x.
PubMed 22747582Goldmann JP, Sanno M, Willwacher S, Heinrich K, Bruggemann GP. The potential of toe flexor muscles to enhance performance. J Sports Sci. 2013;31(4):424-33. doi: 10.1080/02640414.2012.736627. Epub 2012 Oct 30.
PubMed 23106289Chiu LZF, Daehlin TE. Midfoot and Ankle Mechanics in Block and Incline Heel Raise Exercises. J Strength Cond Res. 2021 Dec 1;35(12):3308-3314. doi: 10.1519/JSC.0000000000004145.
PubMed 34570059Jarvis DN, Kulig K. Kinematic and kinetic analyses of the toes in dance movements. J Sports Sci. 2016 Sep;34(17):1612-8. doi: 10.1080/02640414.2015.1126672. Epub 2015 Dec 21.
PubMed 26691227Smith R, Lichtwark G, Farris D, Kelly L. Examining the intrinsic foot muscles' capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping. J Sport Health Sci. 2023 Sep;12(5):639-647. doi: 10.1016/j.jshs.2022.07.002. Epub 2022 Jul 21.
PubMed 35872091Tourillon R, Gojanovic B, Fourchet F. How to Evaluate and Improve Foot Strength in Athletes: An Update. Front Sports Act Living. 2019 Oct 11;1:46. doi: 10.3389/fspor.2019.00046. eCollection 2019.
PubMed 33344969Willemse L, Wouters EJM, Pisters MF, Vanwanseele B. Plantar intrinsic foot muscle activation during functional exercises compared to isolated foot exercises in younger adults. Physiother Theory Pract. 2024 Aug;40(8):1656-1668. doi: 10.1080/09593985.2023.2204947. Epub 2023 Apr 26.
PubMed 37126537
Study at a glance
From the registry record, last updated by the sponsor on 26 Mar 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effects of Two Foot Strengthening Interventions on Toe Flexor Strength and Jumping Performance in Vocational Ballet Dancers: A Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT06589050
- Acronym / sponsor ID
- 5/24/AS/UOW
- Conditions
- Toe Flexor Strength
- Keywords
- Toe flexor strength, Foot, Dance, Jumping performance
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 49 participants (actual)
- Lead sponsor
- University of BernUniversity, hospital or other
- Collaborators
- Elmhurst Ballet School, Birmingham, German Sport University, Cologne
- Study start
- 10 Sep 2024 (actual)
- Primary completion
- 5 Dec 2024 (actual)
- Study completion
- 15 Dec 2024 (actual)
- First posted
- 19 Sep 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- This is a parallel-group randomized controlled study. Participants will be randomly assigned to one of three parallel groups (two experimental groups and one control group) with a 1:1:1 ratio. To balance the covariates of age and sex among the three groups, a computer-based program will perform stratified randomization within three blocks.
| Arm | Type | Receives |
|---|---|---|
| "Toe flexor device" experimental group | Experimental | Other: "Toe flexor device" experimental groupParticipants 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 | Experimental | Other: "Inclined Heel Rise" experimental groupParticipants 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. |
| Control group | No intervention | –The control group will continue with the ballet school's normal training schedule. |
Who may qualify
- Ages
- 14 to 19 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child, Adult
Key inclusion criteria (3 listed)
- Being a ballet student at the Elmhurst Ballet School.
- Aged 14 to 19.
- Written informed consent (by the participant and/or their legal guardian).
Key exclusion criteria (2 listed)
- Any recent lower leg or foot injuries.
- Chronic pain in the lower extremities.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| "Toe flexor device" experimental groupThis intervention group will perform toe flexion using a toe flexor (TF) device, which facilitates the shortening and stretching of the TF muscle-tendon units (MTUs) against resistance bands. While seated, participants will push a pedal down with their toes over two counts and release it over two counts. | Other | "Toe flexor device" experimental group |
| "Inclined Heel Rise" experimental groupThis intervention group will perform single-leg heel rises on an inclined platform. Participants will place their hands against a barre for balance support, lift their heels over two counts, and lower them over two counts. | Other | "Inclined Heel Rise" experimental group |
Primary outcome
Maximal voluntary isometric contraction (MVIC) of the toe flexors muscles
Time frame: 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).
5 secondary outcomes
Vertical jump - Countermovement jump (CMJ) - Jump height (cm)
Time frame: Measurements will be performed one week prior to and one week after the intervention.
Vertical jump - CMJ - changes in force parameters
Time frame: Measurements will be performed one week prior to and one week after the intervention.
Vertical jump - Sauté jump - jump height (cm)
Time frame: Measurement will be performed one week prior to and one week after the intervention.
Vertical jump - Sauté - changes in force parameters
Time frame: Measurements will be performed one week prior to and one week after the intervention.
Horizontal jump - Long jump - jump distance (cm)
Time frame: Measurements will be performed one week prior to and one week after the intervention.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 26 Mar 2025.
- Background: PubMed 22747582Goldmann JP, Bruggemann GP. The potential of human toe flexor muscles to produce force. J Anat. 2012 Aug;221(2):187-94. doi: 10.1111/j.1469-7580.2012.01524.x.
- Background: PubMed 23106289Goldmann JP, Sanno M, Willwacher S, Heinrich K, Bruggemann GP. The potential of toe flexor muscles to enhance performance. J Sports Sci. 2013;31(4):424-33. doi: 10.1080/02640414.2012.736627. Epub 2012 Oct 30.
- Background: PubMed 34570059Chiu LZF, Daehlin TE. Midfoot and Ankle Mechanics in Block and Incline Heel Raise Exercises. J Strength Cond Res. 2021 Dec 1;35(12):3308-3314. doi: 10.1519/JSC.0000000000004145.
- Background: PubMed 26691227Jarvis DN, Kulig K. Kinematic and kinetic analyses of the toes in dance movements. J Sports Sci. 2016 Sep;34(17):1612-8. doi: 10.1080/02640414.2015.1126672. Epub 2015 Dec 21.
- Background: PubMed 35872091Smith R, Lichtwark G, Farris D, Kelly L. Examining the intrinsic foot muscles' capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping. J Sport Health Sci. 2023 Sep;12(5):639-647. doi: 10.1016/j.jshs.2022.07.002. Epub 2022 Jul 21.
- Background: PubMed 33344969Tourillon R, Gojanovic B, Fourchet F. How to Evaluate and Improve Foot Strength in Athletes: An Update. Front Sports Act Living. 2019 Oct 11;1:46. doi: 10.3389/fspor.2019.00046. eCollection 2019.
- Background: PubMed 37126537Willemse L, Wouters EJM, Pisters MF, Vanwanseele B. Plantar intrinsic foot muscle activation during functional exercises compared to isolated foot exercises in younger adults. Physiother Theory Pract. 2024 Aug;40(8):1656-1668. doi: 10.1080/09593985.2023.2204947. Epub 2023 Apr 26.
- Individual participant dataSharing planned: No. Sensitive data of the students and the school.
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Anna Schrefl, MSc principal investigator
University of Bern
Daniel Erlacher, PhD study chair
University of Bern
Andrea Schaerli, PhD study chair
University of Bern
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing "Toe flexor device" experimental group and "Inclined Heel Rise" experimental group in people with Toe Flexor Strength, run by University of Bern at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 26 Mar 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Maximal voluntary isometric contraction (MVIC) of the toe flexors muscles (time frame: Measurements will be performed one week prior to and one week after the intervention.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06589050, which also lists 7 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Mar 2025.