The Effect of Different Focus of Attention Instructions on Resistance Training and Its Transfer to Gait Parameters in Older Adults

Condition(s) studied

Investigational drug(s) / intervention(s)

Strength training with an internal focus of attention: A 4 weeks strength training program of seated calf raises with progressive overload is carried out. A supervisor applies force specific internal focus instruction in three sessions per week with at least 48h rest time. One session consists of 3 series until failure with 75%RM. Rest intervals between series are defined as 2 minutes.

Strength training with a proprioceptive external focus of attention: A 4 weeks strength training program of seated calf raises with progressive overload is carried out. A supervisor applies force specific proprioceptive external focus instruction in three sessions per week with at least 48h rest time. One session consists of 3 series until failure with 75%RM. Rest intervals between series are defined as 2 minutes.

Strength training with a visual external focus of attention: A 4 weeks strength training program of seated calf raises with progressive overload is carried out. A supervisor applies force specific visual external focus instruction in three sessions per week with at least 48h rest time. One session consists of 3 series until failure with 75%RM. Rest intervals between series are defined as 2 minutes.

Study summary

The goal of this clinical trial is to investigate the effects of strength training with different focus of attention strategies on plantar flexor force and how this affects gait in apparently healthy older adults. The main questions it aims to answer are:

* Is there an acute effect of focus of attention on non-linear force variability and the subjacent neurophysiological mechanisms in apparently healthy young and older adults?
* Is there a training effect of focus of attention on non-linear force variability and does it transfer to non-linear gait variability as well as the respective subjacent neurophysiological mechanisms in apparently healthy older adults?

Researchers will compare two different external focus strategies with an internal focus to see if non-linear variability increases and subjacent neurophysiological mechanisms are more automized with an external focus of attention compared to an internal focus. In the acute study young adults are assessed as the differences between focus conditions are thought to be in the same direction as for older adults but attenuated.

Participants will carry out training and strength assessments of the calf muscles and walking on a treadmill.

Eligibility

Primary outcome measure(s)

• Change from Baseline in Non-linear Force Variability after each Week during Intervention and 2 Weeks Follow-Up — Baseline, Week1, Week2, Week3, Week4 and Follow-Up (Week6)
  The non-linear variability of the temporal structure of the force signal of a 50 seconds isometric task at 50% of the maximum voluntary isometric contraction is analyzed using sample entropy (SampEn), which indicates the probability that short sequences of data points are repeated throughout the signal length. Lower SampEn (towards 0) is the consequence of similar distances between repetitions of those sequences, which indicates a more regular force output. A higher SampEn value (towards infinity) results from large differences of distances between repetitions of sequences, which designates a more irregular, variable force output.
• Change from Baseline in Non-linear Gait Variability after each Week during Intervention and 2 Weeks Follow-Up — Baseline, Week1, Week2, Week3, Week4 and Follow-Up (Week6)
  The non-linear variability of the temporal structure of the gait signal from a 12 minutes gait trial is analyzed using sample entropy (SampEn), which indicates the probability that short sequences of data points are repeated throughout the signal length. Lower SampEn (towards 0) is the consequence of similar distances between repetitions of those sequences, which indicates a more regular gait output. A higher SampEn value (towards infinity) results from large differences of distances between repetitions of sequences, which designates a more irregular, variable gait output.
• Change from Baseline in Cortico-Spinal Excitability after 2 Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up — Baseline, Week2, Week4 and Follow-Up (Week6)
  The cortical measures are assessed with transcranial magnetic stimulation (TMS). A stimulator generates motor evoked potentials (MEP) in the active soleus muscle during a low-intensity plantarflexion. To assess cortico-spinal excitability single-pulse TMS is applied. For cortico-spinal excitability the mean of the MEP amplitude from 10 stimulations is calculated. The values will be presented in % normalized to the EMG maximum voluntary contraction.
• Change from Baseline in Cortico-Spinal Inhibition after 2 Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up — Baseline, Week2, Week4 and Follow-Up (Week6)
  The cortical measures are assessed with transcranial magnetic stimulation (TMS). A stimulator generates motor evoked potentials (MEP) in the active soleus muscle during a low-intensity plantarflexion. To assess cortico-spinal inhibition single-pulse TMS is applied. For cortico-spinal inhibition the mean of electromyographic silent periods from 10 stimulations is calculated. The values are presented in ms.
• Change from Baseline in Intra-Cortical Inhibition after 2 Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up — Baseline, Week2, Week4 and Follow-Up (Week6)
  The cortical measures are assessed with transcranial magnetic stimulation (TMS). A stimulator generates motor evoked potentials (MEP) in the active soleus muscle during a low-intensity plantarflexion. To assess intra-cortical inhibition paired-pulse TMS is applied. For intra-cortical inhibition the mean of the MEP amplitude from 10 stimulations is calculated. The values will be presented in % normalized to the cortico-spinal excitability.
• Change from Baseline in Intra-Cortical Facilitation after 2 Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up — Baseline, Week2, Week4 and Follow-Up (Week6)
  The cortical measures are assessed with transcranial magnetic stimulation (TMS). A stimulator generates motor evoked potentials (MEP) in the active soleus muscle during a low-intensity plantarflexion. To assess intra-cortical facilitation paired-pulse TMS is applied. For intra-cortical facilitation the mean of the MEP amplitude from 10 stimulations is calculated. The values will be presented in % normalized to the cortico-spinal excitability.

Trial sites (1)

More Egas Moniz - Cooperativa de Ensino Superior, CRL trials in Portugal

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