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

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.

Conditions

• Quadriceps Muscle Function

Interventions

OTHER

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.

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.

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.

Sponsors & Collaborators

• University of Primorska, Faculty of Health Sciences

  collaborator UNKNOWN

• University of Belgrade

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Model

FACTORIAL

Eligibility

Min Age

19 Years

Max Age

30 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2018-04-09

Primary Completion

2018-06-15

Completion

2018-06-15

Countries

• Serbia

Study Locations