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

Not Applicable

Completed

• Conditions: Quadriceps Muscle Function
• Interventions: Other: Isometric training with electromyostimulation; Other: Isometric training with voluntary activation; Other: Isometric training with combination of electromyostimulation and voluntary activation

• Registration Number: NCT04624438
• Lead Sponsor: University of Belgrade

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.

Study Timeline

• Study Start: 2018-04-09
• Primary Completion: 2018-06-15
• Study Completion: 2018-06-15
• Status Verified: 2020-11
• Study First Submitted: 2020-11-02
• Study First Submitted QC: 2020-11-05
• Last Update Submitted: 2020-11-05
• Study First Posted: 2020-11-10
• Last Update Posted: 2020-11-10

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 52

Inclusion Criteria

• young healthy, physically active participants of both genders

Exclusion Criteria

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: FACTORIAL

Arm && Interventions

Group	Intervention	Description
Electromyostimulation - EMS	Isometric training with electromyostimulation	Experimental group comprised of healthy young adults that undergoes unilateral isometric training using electromyostimulation over quadriceps femoris
Voluntary activation - VOLUNTARY	Isometric training with voluntary activation	Experimental group comprised of healthy young adults that undergoes unilateral isometric training based on voluntary activation of quadriceps femoris
Combination of EMS and VOLUNTARY - COMBINED	Isometric training with combination of electromyostimulation and voluntary activation	Experimental group comprised of healthy young adults that undergoes unilateral isometric training that combines electromyostimulation and voluntary activation of quadriceps femoris.

Primary Outcome Measures

Name	Time	Method
Motor Evoked Potentials (MEP)	After 9 weeks	MEPs were elicited in quadriceps femoris by transcranial magnetic stimulation (TMS) over M1 area. Motor cortex excitability was estimated by measuring the MEP amplitude (Input-Output, IO) peak to peak, caused by 20 randomized individual TMS stimulates with 100% (IO1), 120% (IO2) and 130% (IO3) of active motor threshold (AMT) intensity.
MVC	After 9 weeks	Maximal isometric force and Rate of Force Development of quadriceps femoris muscle during isometric contractions with maximal effort
The slope of the rate-of-force development scaling factor (RFD-SF)	After 9 weeks	The slope of the relationship (RFD-SF) between muscle force and rate of force development during rapid isometric contractions of varying intensities

Secondary Outcome Measures

Name	Time	Method
M-wave	After 9 weeks	The tracing of the earliest electromyography (EMG) response to the stimulation of femoral nerve
The linearity of the rate-of-force development scaling factor (RFD-SF) relationship	After 9 weeks	The linearity, described by coefficient of determination (r-squared) of the relationship (RFD-SF) between muscle force and rate of force

Trial Locations

Locations (1)

Faculty of Sport and Physical Education, University of Belgrade; 🇷🇸 Belgrade, Serbia