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.
None
Severe cardiovascular or pulmonary disease
Oncological disease
Lower limb disabilities
Neurological disorders
Parallel
Strength training with an internal focus of attention
Other interventionA 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
Other interventionA 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
Other interventionA 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.
Change from Baseline in Non-linear Force Variability after each Week during Intervention and 2 Weeks Follow-Up
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
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
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
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 Antagonist Co-Contraction Index after 2Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up
The antagonist co-contraction index (CCI) of the soleus as well as of the lateral and medial gastrocnemius heads with tibialis anterior will be calculated based on the formula: CCI=lowEMG/highEMG×(highEMG+lowEMG).
Change from Baseline in Linear Force Variability after each Week during Intervention and 2 Weeks Follow-Up
The linear measure of variability is analyzed with the coefficient of variation (CV), which indicates the amount of variability within the force signal.
Change from Baseline in Linear Gait Variability after each Week during Intervention and 2 Weeks Follow-Up
The linear measure of variability is analyzed with the coefficient of variation (CV), which indicates the amount of variability within the gait signal.
Change from Baseline of Hip, Knee, Ankle Range of Motion during Gait after 2Weeks, 4 Weeks of Intervention and 2 Weeks Follow-Up
Hip, knee, ankle range of motion during gait will be assessed using a motion capture system. This analysis assesses the angular displacement of each joint through the different phases of the gait cycle. For the hip and knee joint the ROM involves flexion and extension, while for the ankle joint dorsiflexion and plantarflexion are measured.
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Egas Moniz - Cooperativa de Ensino Superior, CRL
Lead sponsor
Fundação para a Ciência e a Tecnologia
Collaborator
