Electrical Stimulation With Different Currents: the Effects on Force, Tolerance and Fatigue in Healthy Subjects

Electrical Stimulation With Different Currents: the Effects on Force, Tolerance and Fatigue in Healthy Subjects

Effects on Isometric Force Induction, Tolerance and Fatigue of Burst-modulated Kilohertz Frequency (Neo-Russian and Aussie) and Low Frequency (Rectangular Biphasic Symmetrical) Neuromuscular Electrical Stimulation in Healthy Subjects

Muscle strength is the amount of force generated by muscle contraction. It could be measured with an isometric dynamometer. This is a validated tool that could be used to measure Maximal Voluntary Isometric Contraction (MVIC) and Maximal Electrical Induced Contraction (MEIC). It is claimed that higher MEIC values will result in more force gained. If a current is more tolerated it will be easier to achieve better MEIC values. Tolerance to an electrical stimulation could be measured with the Visual Analogue Scale (VAS). A ratio between Normalized MEIC / VAS is often used, implying that the current is better with a higher ratio. Muscle fatigue is defined as a temporary loss or decrease in force-generating ability due to previous contractions. It is claimed that medium frequency neuromuscular electrical stimulation (NMES) generates more fatigue than low frequency currents. Aussie is a medium-frequency alternating current, sinusoidal waveform, 1 KHz carrier frequency. Neo-Russian is a medium-frequency current, rectangular biphasic symmetrical waveform, 2,5 KHz carrier frequency. Rectangular Biphasic symmetrical (RBS) waveform is a type of Low Pulsed Current (LPC), claimed to be better than classical Russian Current. Purpose: As it has been claimed that LPC is better in MEIC and tolerance, the aim of this study is to compare it with two newer medium frequency currents in terms of MEIC, tolerance and fatigue. Methods: Thirty male subjects, right leg dominant, will receive randomly the 3 types of electrical stimulation. Before that, the MVIC will be measured for data normalization. The MVIC and MEIC will be measured with an isometric dynamometer. In both measurements, subjects will be asked to perform three reps (5 sec work x 120 sec rest) and the best one will be used. Whenever the third one was the best, additional measurements will be taken until a decrease in torque will be obtained to determine the maximum. To apply Aussie electrical stimulation, an Aussie Sport (Ibramed) will be used. To apply Neo-Russian, a Neurodyn III (Ibramed) will be used. To apply RBS, a Genesy (Globus) will be used. The VAS will be used to assess tolerance to each treatment. One week later, the subjects will receive, randomly, a fatigue protocol that consists in 21 reps (5 sec work x 5 sec rest) of electrical stimulation with the three types of current. The data will be normalized with the MVIC and the reps equal or below 50 % of the first rep will be considered as a fatigue rep.

Thirty male subjects, right leg dominant, will receive 3 types of electrical stimulation in a randomized order. Aussie current will be delivered by Aussie Sport (Ibramed) device, Neo-Russian by Neurodyn III (Ibramed) device and RBS by a Genesy (Globus) device. MVIC and MEIC will be measured with an isometric dynamometer (3 reps x 5 sec work x 120 sec rest). The best rep will be used. Whenever the third one was the best, additional measurements will be taken until a decrease in torque will be obtained to determine the maximum. MVIC will be used for data normalization. The VAS will be used to assess tolerance to each treatment. A ratio between MEIC and VAS will be calculated. One week later, subjects will receive, ramdomly, a fatigue protocol with the three types of electrical stimulation that consists in 21 reps (5 sec work x 5 sec rest). The data will be normalized with the MVIC and the reps equal or below 50 % of the first rep will be considered as a fatigue rep.

MVIC will be measured for data normalization. The subjects will receive Neo-Russian electrical stimulation. The Maximal Elicited Induced Contraction (MEIC) will be measured. One week later, after a washout period, the fatigue will be measured with this type of current.

MVIC will be measured for data normalization. The subjects will receive Aussie electrical stimulation. The Maximal Elicited Induced Contraction (MEIC) will be measured. One week later, after a washout period, the fatigue will be measured with this type of current.

MVIC will be measured for data normalization. The subjects will receive RBS electrical stimulation. The Maximal Elicited Induced Contraction (MEIC) will be measured. One week later, after a washout period, the fatigue will be measured with this type of current.

Subjects will receive Neo-Russian electrical stimulation with three reps (5 sec work x 120 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured. They will be asked how uncomfortable the stimulation was, using Visual Analogue Scale (VAS). One week later, subjects will receive a fatigue protocol that consists in 21 reps (5 sec work x 5 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured for each contraction.

Subjects will receive Aussie electrical stimulation with three reps (5 sec work x 120 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured. They will be asked how uncomfortable the stimulation was, using Visual Analogue Scale (VAS). One week later, subjects will receive a fatigue protocol that consists in 21 reps (5 sec work x 5 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured for each contraction.

Subjects will receive RBS electrical stimulation with three reps (5 sec work x 120 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured. They will be asked how uncomfortable the stimulation was, using Visual Analogue Scale (VAS). One week later, subjects will receive a fatigue protocol that consists in 21 reps (5 sec work x 5 sec rest), and the Maximal Electrical Induced Contraction (MEIC) will be measured for each contraction.

Force generated by the patient during a maximal voluntary isometric contraction, measured by an isometric dynamometer with load cell and computer interface. The best of the 3 repetitions was considered. Whenever the third one was the best, additional measurements were taken until a decrease in torque was obtained in order to determine the maximum. Unit: Newtons (N)

Force generated in the muscle while applying electrical stimulation, measured by an isometric dynamometer with load cell and computer interface. This data (in Newtons) was normalized with the MVIC. Unit: percentage of MVIC

MEIC was measured on Day 1. Order: MVIC - Rest: 120 sec. - MEIC current 1 - Rest: 120 sec. - MEIC current 2 - Rest: 120 sec. - MEIC current 3 - Rest: 120 sec. - Assessed in an average of 21 min.

Visual Analogue Scale (VAS): Magnitude of pain, marked in a analogue scale by participants, to determine how unpleasant was each type of electrical stimulation (applied in randomized order). Expresed in centimeters. Minimum value: 0 Maximum value: 10 A higher score implicates a worse outcome. VAS was evaluated 3 times, 1 per type of electrical stimulation.

Asked after evaluation of MEIC wiht each type of current. VAS current 1 - VAS current 2 - VAS current 3 - Assessed in average of 15 seconds for each current.

Number of repetitions, while applying electrical stimulation, equal to or lower than 50% of the first of 21 reps, previously normalized with MVIC Units: units on scale. Range: from 0 to 21. A higher value represents a worse outcome.

Washout: 1 Week. Fatigue current 1 - Rest: 120 sec. - Fatigue current 2 - Rest: 120 sec. - Fatigue current 3 - Assessed in an average of 21 min.

Inclusion Criteria: Healthy volunteers Male Right leg dominant Exercising regularly Exclusion Criteria: History of injuries in the right leg Skin lesions Having a pacemaker Having a cardiovascular disease. Having a neurological disorder. Exercise 72 h before the procedure.