The Effect of Loading Speed and Intensity During Exercise on the Immediate Structural Changes in the Achilles Tendon
Condition: Achilles Tendinopathy
MeSH terms: Tendinopathy
Study type: Interventional

Summary: 
      Aim: To assess the influence of loading speed and intensity during eccentric heel drop
      exercise on the immediate changes in Achilles tendon thickness and stiffness in healthy
      controls.

      Intervention: Three eccentric heel drop exercise protocols, different in loading speed and/or
      loading intensity will be compared. Each participant will perform a single protocol per
      session in a random sequence at 1-week intervals.

      Participants: a total of 30 healthy athletes will be included.

      Outcome measure: tendon thickness and stiffness will be measured at baseline and immediately
      following intervention with ultrasound imaging (B-mode) and shear wave elastography,
      respectively.

      Discussion: the study will determine whether an eccentric exercise intervention involving a
      low loading speed and high intensity could maximize the immediate reduction in thickness and
      associated increase in stiffness of the Achilles tendon compared with interventions involving
      a higher loading speed and lower intensity.
    

Detailed description: 
      Mechanical loading of the Achilles tendon during isolated eccentric contractions induces
      immediate changes in its structural properties. However, it is not known whether the loading
      speed and intensity has any impact on these changes. Therefore, this study aims to
      investigate the influence of loading speed and intensity during eccentric heel drop exercises
      on the immediate changes in Achilles tendon thickness and stiffness in healthy controls.

      Each participant will perform eccentric heel-drops on their dominant leg with and a fully
      extended knee, and with additional 20% body weight (added via a weighted backpack).
      Participants will stand with the forefoot of the tested limb on the edge of a step, with the
      ankle maximally plantar flexed and with body weight centred on this limb. Eccentric loading
      occurs when the participant lowers the heel to a predetermined angle and speed (depending on
      the type of intensity and speed cfr infra). In order to return to baseline, the body mass
      will therefore be shifted to the non-dominant leg to raise the body. Visual feedback
      (monitor) will be in front of the subjects and the exercise parameters (velocity and ankle
      angle) will be guided by software guidelines (Ultium Motion).

      Three protocols will be compared that differ in execution speed (namely a fast protocol; 1
      Hz: 1 second per repetition versus a slow protocol; 0.33 Hz: 3 seconds per repetition) and
      loading intensity (namely heavy; exercise into maximal dorsiflexion versus light; exercise
      into neutral ankle position).

      Protocol 1 (=Heavy x Slow): subjects perform eccentric heel drops from a maximal
      plantarflexion position to a maximal dorsiflexion position at a speed of 0.33 Hz, i.e. 3
      seconds per movement cycle.

      Protocol 2 (=Heavy x Fast): subjects perform eccentric heel drops from a maximal
      plantarflexion position to a maximal dorsiflexion position at a speed of 3 Hz, i.e. 1 seconds
      per movement cycle.

      Protocl 3 (=Light x Slow): subjects perform eccentric heel drops from a maximal
      plantarflexion position to a neutral ankle position at a speed of 0.33 Hz, i.e. 3 seconds per
      movement cycle.

      Participants will perform one exercise protocol per session, in a random order, and the
      interval between each session is one week. Six sets will be performed per session, with one
      minute of rest between each set. In order to ensure that the Achilles tendon's time under
      tension is the same for each protocol (180 seconds), 30 repetitions will performed per set
      for the fast protocol and 10 repetitions for the slow protocol. The approximate duration of
      each intervention will be 15 minutes. Before and immediately after each protocol, the
      structural properties of the Achilles tendon, 25 mm proximal to the calcenal posterosuperior
      border, will be assessed. These properties include tendon thickness (anteroposterior diameter
      (mm) and cross-sectional arae (mm2)), tendon echogenicity (average grey value from 0 (black)
      to 255 (white) A.U.) and tendon stiffness by shear wave elastography (kPa).
    

Intervention name(s): Slow and heavy exercise therapy; Slow and light exercise therapy; Fast and heavy exercise therapy
Intervention type(s): Other; Other; Other
Intervention description(s): 6 sets of 10 single leg isolated eccentric heel drops into maximal dorsiflexion at an exercise speed of 0.33 Hz, with 1-min rest period between each set.; 6 sets of 10 single leg isolated eccentric heel drops into neutral ankle position at an exercise speed of 0.33 Hz, with 1-min rest period between each set.; 6 sets of 30 single leg isolated eccentric heel drops into maximal dorsiflexion at an exercise speed of 1 Hz, with 1-min rest period between each set.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Repeated measure design
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Achilles tendon