Influence of Electrode Positioning and Current Type on Fatigue, Force and Discomfort
Condition: Electrical Stimulation
Study type: Interventional

Summary: 
      Introduction: Neuromuscular electrical stimulation (NMES) has the purpose of generating
      muscle contractions to minimize muscular atrophy and to improve neuromuscular performance.
      NMES has been performed using monophasic or biphasic currents, applied over a nerve trunk or
      muscle belly, and both can generate contractions by the peripheral and central nervous
      system. Pulse width (wide or narrow) is an essential parameter for NMES. Although NMES
      studies using wide pulses have been performed with monophasic currents, it is known that this
      current induces discomfort during NMES. Therefore, it is necessary to analyze if biphasic
      currents have the same effect as monophasic currents using the same parameters.

      Objectives:

      To compare the effects of NMES with narrow and wide pulse widths associated with monophasic
      and biphasic currents, applied over a tibial nerve and triceps surae muscles in healthy
      individuals in terms of muscle fatigue, central and peripheral contribution, voluntary and
      evoked force and sensory discomfort.

      Methods:

      A crossover, experimental controlled and randomized study will be developed with healthy male
      and female (age: 18-45 years). The following dependent variables will be: amplitude of
      H-reflex and M-wave (single and double pulses), voluntary and evoked triceps surae muscles
      torque, fatigability (force time integral), perceived discomfort and neuromuscular
      adaptations. The independent variables will be related to current phase, pulse width and
      location of electrical stimulation electrodes. There will be a familiarization session
      followed by 9 sessions with 7 rest days between them (10 weeks). Data will be reported as
      mean and standard deviation (± SD). Parametric tests will be used for the normally
      distributed data (Shapiro-Wilk test) that show homogeneous variations (Levene test). A
      repeated measure mixed-model ANOVA will be performed and, in the case of major effects or
      significant interactions, the Tukey post-hoc test will be applied. In addition, the power and
      size of the effect (reported as partial eta square, partial η2) will be calculated. The
      significance threshold will be set at p <0.05 for all procedures.

      Expected results: Biphasic currents will be more comfortable and will generate less muscle
      fatigue when compared to monophasic currents. There will be less fatigue and greater central
      contribution when wider pulse currents will be applied over a nerve trunk concerning the
      application with a wide pulse over a muscle belly.
    

Detailed description: 
      This is a randomized controlled trial, a crossover study, with healthy male and female
      participants. The procedures will take place in 10 distinct visits for a 7-day interval.

      The following visit in the lab will be:

        -  Familiarization session.

        -  Monophasic Current (100 Hz) with 1ms pulse width applied to the Tibial Nerve;

        -  Biphasic current (100 Hz) with pulse width 0.5ms applied to the Tibial Nerve;

        -  Biphasic current (100 Hz) with 1ms pulse width applied to the Tibial Nerve;

        -  Biphasic current (100 Hz) with 2ms pulse width applied to the Tibial Nerve;

        -  Monophasic (100 Hz) with 1ms pulse width applied to the Triceps Surae Muscle Belly;

        -  Biphasic current (100 Hz) with pulse width 0.5ms applied to the Triceps Surae muscle
           Belly;

        -  Biphasic current (100 Hz) with 1ms pulse width applied to the Triceps Surae Muscle
           Belly;

        -  Biphasic current (100 Hz) with 2ms pulse width applied to the Triceps Surae Muscle
           Belly;

        -  Biphasic current (25 Hz) with 0.5ms pulse width applied to the Triceps Surae Muscle
           Belly.

      The dependent variables will be:

        -  Muscle fatigability;

        -  Central and peripheral contribution (with H-reflex and M-wave amplitude analysis);

        -  Maximum voluntary isometric contraction;

        -  Force production for plantar flexion evoked by NMES;

        -  Perceived discomfort.
    

Intervention name(s): Monophasic Current (100 Hz) with 1ms pulse width applied to the Tibial Nerve; Biphasic current (100 Hz) with pulse width 0.5ms applied to the Tibial Nerve; Biphasic current (100 Hz) with 1ms pulse width applied to the Tibial Nerve; Biphasic current (100 Hz) with 2ms pulse width applied to the Tibial Nerve; Monophasic current (100 Hz) with 1ms pulse width applied to the Triceps Surae Muscle Belly; Biphasic current (100 Hz) with pulse width 0.5ms applied to the Triceps Surae muscle Belly; Biphasic current (100 Hz) with 1ms pulse width applied to the Triceps Surae Muscle Belly; Biphasic current (100 Hz) with 2ms pulse width applied to the Triceps Surae Muscle Belly; Biphasic current (25 Hz) with 0.5ms pulse width applied to the Triceps Surae Muscle Belly
Intervention type(s): Other; Other; Other; Other; Other; Other; Other; Other; Other
Intervention description(s): The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following NMES parameters: (Monophasic Current, 100 Hz, pulse duration 1 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current, 100 Hz, pulse duration 0.5 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current, 100 Hz, pulse duration 1 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current, 100 Hz, pulse duration 2 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Monophasic current, 100 Hz, pulse duration 1 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current, 100 Hz, pulse duration 0.5 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current , 100 Hz, pulse duration 1 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current , 100 Hz, pulse duration 2 ms, Ton: 6 s, Toff: 18 s); The participants will perform 36 contractions evoked by neuromuscular electrical stimulation with the following current parameters: (Biphasic current, 25 Hz, pulse duration 0.5 ms, Ton: 6 s, Toff: 18 s)
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Other