Central and Peripheral Changes in Quadriceps Femoris Function After Different Types of Isometric Strength Training

NCT ID: NCT04624438

Last Updated: 2020-11-10

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 52 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2018-04-09
• Study Completion Date: 2018-06-15

Brief Summary

The purpose of this investigation is to examine the effects of 6-week unilateral isometric training interventions over quadriceps femoris on maximal strength and RFD-SF parameters and cortical excitability. Isometric strength training involved either electromyostimulation, voluntary activation, or the combination of both. The second aim is to investigate the potential cross-over effect on a non-trained leg.

Detailed Description

A longitudinal pre-post design with random assignment of the participants to one of three experimental groups or the control group was used. Quadriceps femoris (QF) function and cortical excitability were assessed on four occasions: prior to the intervention (pre-test), after 3 weeks of training (served for the adjustment of exercise intensity), after 6 weeks of training (post-test), and three weeks after the competition of training intervention (detraining) (Figure 1). Isometric strength training involves activation of QF applying EMS, VOLUNTARY, or the combination of both EMS and VOLUNTARY (COMBINED). The pre-test also served to familiarize participants with the training protocols and to determine the intensity of EMS needed to achieve 60%MVC. Quadriceps femoris (QF) function was assessed by MVC and RFD-SF. Cortical excitability was assessed with transcranial magnetic stimulation applied over the M1 region. Prior to the pretest, body mass and percent of body fat were assessed using a bioelectric impedance method (In Body 720; USA) and body height with a standard stadiometer. After the pretest, the participants were randomly assigned to either one of the experimental groups (EMS, VOLUNTARY, or COMBINED) and the control group (CONTROL). Experimental groups performed unilateral isometric strength training three times per week for 6 weeks. All participants were advised to refrain from all resistance training targeting the legs between pre-test and post-test.

Conditions

Quadriceps Muscle Function

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: FACTORIAL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Electromyostimulation - EMS

Experimental group comprised of healthy young adults that undergoes unilateral isometric training using electromyostimulation over quadriceps femoris

Group Type: EXPERIMENTAL

Isometric training with electromyostimulation

Intervention Type: OTHER

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). The force intensity was determined individually during pretest where EMS was delivered at maximal tolerable dose. Electrical stimulation was 6.25-second long and was followed by a rest period of 20-second (duty cycle 15%). Stimulation characteristics were selected among the "Compex" commercially available strength programs. The stimulation intensity was monitored on-line and determined by the subject at the start of each EMS session according to his/her pain threshold to produce a force corresponding to at least 60% of the pretest MVC score.

Voluntary activation - VOLUNTARY

Experimental group comprised of healthy young adults that undergoes unilateral isometric training based on voluntary activation of quadriceps femoris

Group Type: EXPERIMENTAL

Isometric training with voluntary activation

Intervention Type: OTHER

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). Participants were required to reach the proscribed force level only through voluntary activation of QF. To attain the same contraction/rest ratio as in EMS, automated audible signals were delivered in accordance with the contraction-rest pattern produced by the muscle stimulation device. To ensure participants produced 60% of individual MVC during each contraction the force level was measured with a force transducer and real-time feedback was provided on a computer screen.

Combination of EMS and VOLUNTARY - COMBINED

Experimental group comprised of healthy young adults that undergoes unilateral isometric training that combines electromyostimulation and voluntary activation of quadriceps femoris.

Group Type: EXPERIMENTAL

Isometric training with combination of electromyostimulation and voluntary activation

Intervention Type: OTHER

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). The proscribed force level was reached by the simultaneous action of EMS and VOLUNTARY. Each contraction was 6.25-second long and was followed by a rest period of 20-second (duty cycle 15%). Electrical stimulation corresponded to 30% of MVC, while the remaining 30% was achieved through voluntary muscle activation. To ensure participants produced a force corresponding to 60% of MVC during each contraction the force level was measured with a force transducer and real-time feedback was provided on a computer screen.

Control group - CONTROL

Group of healthy young adults who received no intervention.

Group Type: NO_INTERVENTION

No interventions assigned to this group

Interventions

Isometric training with electromyostimulation

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). The force intensity was determined individually during pretest where EMS was delivered at maximal tolerable dose. Electrical stimulation was 6.25-second long and was followed by a rest period of 20-second (duty cycle 15%). Stimulation characteristics were selected among the "Compex" commercially available strength programs. The stimulation intensity was monitored on-line and determined by the subject at the start of each EMS session according to his/her pain threshold to produce a force corresponding to at least 60% of the pretest MVC score.

Intervention Type: OTHER

Isometric training with voluntary activation

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). Participants were required to reach the proscribed force level only through voluntary activation of QF. To attain the same contraction/rest ratio as in EMS, automated audible signals were delivered in accordance with the contraction-rest pattern produced by the muscle stimulation device. To ensure participants produced 60% of individual MVC during each contraction the force level was measured with a force transducer and real-time feedback was provided on a computer screen.

Intervention Type: OTHER

Isometric training with combination of electromyostimulation and voluntary activation

Each training session (18 in total) consisted of forty 4-s contractions separated by 20 s inter-contraction intervals. The exercise intensity was close-to-identical among the sessions (60 %MVC). The proscribed force level was reached by the simultaneous action of EMS and VOLUNTARY. Each contraction was 6.25-second long and was followed by a rest period of 20-second (duty cycle 15%). Electrical stimulation corresponded to 30% of MVC, while the remaining 30% was achieved through voluntary muscle activation. To ensure participants produced a force corresponding to 60% of MVC during each contraction the force level was measured with a force transducer and real-time feedback was provided on a computer screen.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• young healthy, physically active participants of both genders

Exclusion Criteria

• no history of injuries, muscle-skeletal or neurological disease, or medications intake

• Minimum Eligible Age: 19 Years
• Maximum Eligible Age: 30 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Primorska, Faculty of Health Sciences

UNKNOWN

Sponsor Role: collaborator

University of Belgrade

OTHER

Sponsor Role: lead

Responsible Party

Dragan Mirkov

Professor Dr.

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Faculty of Sport and Physical Education, University of Belgrade

Belgrade, , Serbia

Countries

Serbia

Other Identifiers

02-672-2/09-04-2015

Identifier Type: -

Identifier Source: org_study_id