Muscle Strength in Severe Obese Patients in the Postoperative of Bariatric Surgery
Condition: Severe Obesity
MeSH terms: Obesity, Morbid
Study type: Observational

Summary: 
      Excessive fat mass (FM) contributes to changes in the strength and endurance of skeletal
      muscles. Mid-thigh muscle mass is approximately 2.5 times that of fat mass, but individuals
      who are obese have increased intra- (fat within muscle cells) and intermuscular fat (fat
      between muscle cells), establishing a negative influence on strength generation capacity and
      functional independence. The functional capacity of a skeletal muscle can be assessed based
      on the muscle's ability to produce strength. The relevance of this study is to
      identify/analyze the changes in segmental body composition (BC) which might better determine
      the association between fat free mass (FFM) of the lower limbs and maximum voluntary
      contraction (MVC), 36 months after bariatric surgery. This study was elaborated and will be
      performed at the Clinical Hospital in the Medical School of the University of Sao Paulo
      (HCFMUSP). The patients involved will receive the Informed Consent Form. The sample, consists
      of 155 adults selected at the ambulatory of the Bariatric and Metabolic Surgery Unit of the
      Department of Gastroenterology of HCFMUSP in the periods: preoperative, 6 and 36 months after
      surgery. Patients of both sexes, above 18 years of age, will undergo bariatric surgery
      performed at the institution. Adult patients over 60 years old, undergoing revision surgery
      and other surgical techniques will be excluded. Anthropometric variables will be obtained on
      the same day as the evaluation of BC by trained evaluators. The BC will be measured by In
      Body 230. BMI (kg/m2) shall be determined by dividing body weight (kg) by height (m) squared.
      Evaluation of Body Composition and Muscle Strength will be held between 8:00 am and 10:00 am
      in the Laboratory of Exercise and Movement Studies at the Institute of Orthopedics and
      Traumatology of FMUSP. BC measurements as FM (% and kg), FFM (% and kg), will be obtained by
      the indirect noninvasive method of electrical bioimpedance. The dynamometer will be used to
      evaluate muscle strength extension (Ext) and flexion (Flex) MVC torques for both legs will be
      carried. The MVC assessed variables should be absolute Ext and Flex torques (Nm), Ext and
      Flex torques relative to the body weight (Nm/Bw) and Ext and Flex torques relative to FFM
      (Nm/FFM).
    

Detailed description: 
      Anthropometric Assessment Anthropometric variables will be obtained on the same day as the
      evaluation of BC by trained evaluators. The body weight (kg) will be measured by In Body 230,
      2.0, (Biospace Seoul, Korea). The patient should be in the orthostatic position, facing the
      display, in the center of the scale, barefoot, in light clothes. The height measurement (m)
      will be performed in a stadiometer coupled to the scale W 300, Class III, with a maximum
      capacity of 2m. The patient will be kept with his back to the meter, with the feet united, in
      an erect position, looking at horizon and arms extended to the side of the body. The reading
      will be made in the nearest centimeter when the horizontal rod of the vertical bar of the
      stature scale rests against the individual's head. BMI (kg/m2) will be determined by dividing
      body weight (kg) by height (m) squared.

      Bioimpedance Body composition will be determined by bioelectrical impedance analysis (BIA)
      under constant conditions (with subjects appropriately hydrated and at the same time of
      day).The body composition analyzer (InBody230, Biospace Co., Gangnam-gu, Seoul, South Korea)
      was a segmental impedance device that uses a tetrapolar 8-point tactile electrode system, and
      the measured weight range was 10 to 250 kg. Impedance measurements were performed by
      utilizing 2 different frequencies (20 and 100 kHz) at each segment (the right arm, left arm,
      trunk, right leg, and left leg). The participant will be positioned in orthostatic position
      on a platform with lower electrodes for the feet and two brackets (the upper electrodes)
      gripped on hands. Data output was calculated in percentages (%) and included FM, FFM, trunk
      FFM, and appendicular FFM (the sum of the FFM values for the right arm, left arm, right leg,
      and left leg).

      Isokinetic dynamometer The muscular strength evaluation will be performed on the isokinetic
      dynamometer, Biodex ® Multi-joint System 3 (Biodex Medical Systems Inc, Shirley, New York,
      USA). The dynamometer is calibrated thirty minutes before the start of the tests.

      Participants are positioned for evaluation in the concentric / concentric mode of knee joint
      extension and flexion movements. Individuals remain seated with their hip at 90º of flexion,
      affixed to the chair with chest X-belts, a strap around the pelvic girdle, a strap over the
      distal third of the thigh and one at the distal third of the assessed leg, way to free the
      movements of the ankle.

      All participants are instructed to perform four movements with submaximal force to
      familiarize themselves with the equipment. The test is performed first on the dominant limb
      and later on the non-dominant limb. The assessed limb is positioned with the lateral femoral
      condyle (axis of the knee joint movement) aligned to the mechanical axis of the dynamometer.
      The member that is not being evaluated will be aligned with the other member. The volunteers
      are instructed to perform two sets of 4 uninterrupted repetitions of knee extension and
      flexion with interval of 60 seconds. Throughout the period of the test, standardized and
      constant verbal encouragement is performed to obtain as much force as possible during
      contractions.

      The tests are performed with concentric movements of flexion and extension of the knee,
      starting from 90º of flexion and reaching 20º of extension, with correction of the force of
      gravity.

      The angular velocity used will be 60 degrees per second (60º / s).

      The variables that will be obtained through the evaluation of muscular strength are:

      Torque Peak (Nm): is the maximum force reached in each of the repetitions in which the test
      was performed. The peak torque represents the largest muscle contraction in the arc of
      movement and corresponds to the highest point of the force x distance curve.

      Peak torque relative to body weight (Nm / kg): maximum force corrected for body weight, the
      result being expressed in percent newton-kilogram.
    

Intervention name(s): Isokinetic Dynamometer; Bioimpedance
Intervention type(s): Other; Other
Intervention description(s): Participants then executed two series of four uninterrupted repetitions of Ext and Flex of both legs, first with the dominant member and subsequently with the non-dominant member, at an angular velocity of 60o/s, with a 60-second interval between series.; Bioimpedance The BC measurements as FM (% and kg), FFM (% and kg), will be obtained by the indirect noninvasive method of electrical bioimpedance (BIA) 230, 2.0, (Biospace Seoul, Korea). Those evaluated will be standing and positioned on the platform electrodes, barefoot and with their arms extended with their hands on the two supports (electrodes).
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients with severe obesity undergoing bariatric surgery in the Bariatric Metabolic
        Surgical Unit of the Hospital das Clínicas, University of São Paulo Medical School.
      
Keywords: Severe obesity; Body Composition; Muscle Strength; Electrical bioimpedance analysis