Acute Effect of a Gluteal Activation Warm-up on Hip Muscle Activity and Kinematics During a Single Leg Squat
Condition: Hip Adduction; Gluteus EMG Activity
Study type: Interventional

Summary: 
      Gluteal activation warm-up is one of the modalities being investigated recently. Although
      widely used in clinical and sports practice, it is unclear whether, in fact, performing
      gluteal activation exercises in warm-up is effective in increasing electromyographic
      activation (EMG), as well as the mechanisms that explain eventual gluteal activation
      improvement of neuromuscular function. Thus, the aim of this study is to verify the acute
      effect of a gluteal activation warm-up protocol on gluteus maximus (superior fibers) and
      gluteus medius EMG activation and kinematics during single leg squat. The hypotheses of this
      study are that after a gluteal activation warm-up program, there will be an increase in the
      muscle recruitment (mean) levels of the gluteus maximus (superior fibers) and gluteus medium.
      About kinematics, the hypotheses is that a decrease on hip adduction absolute angle and hip
      and knee frontal plane ROM on maximum knee flexion during single leg squat will occur.
      Physically active adults from 18 to 35 years old, with no history of previous injury or
      surgery on the lower limbs, who present excessive hip adduction during single-leg squat on
      the dominant limb in previous evaluation via visual scoring scale will participate in this
      study. The design adopted will be performed in the following order: (1) Preparation and
      familiarization. (2) Intervention protocol (standard warm-up protocol or the gluteal
      activation warm-up protocol), (4) immediately after the intervention protocol, the subjects
      will perform 3 single-leg squats and (5) EMG and MIVC strength test. The standard warm-up
      consist 5 minutes on a stationary bike and 30 seconds calf, hamstrings and quadriceps
      stretch. The gluteal activation warm-up protocol consists of performing the standard warm-up
      protocol and 3 sets of 12 repetitions clam exercise, using a elastic band (Perform Better®,
      USA). Exertion perception will be controlled using an exertion perception scale (OMNI). From
      kinematic and EMG data, absolute values of the hip adduction, hip and knee ROM in the frontal
      plane of the dominant limb and mean EMG activation data from the gluteus maximus (superior
      fibers) and gluteus medius muscles we will extracted, respectively. All data will be analyzed
      using descriptive and inferential statistics. (p <0.05).
    

Detailed description: 
      Muscle pre-activation is the application of exercises to specific muscle groups performed in
      the warm-up phase in order to increase the neuromuscular response. Among different modalities
      of warm-up, gluteal activation warm-up is one of the modalities being investigated recently.
      The hip joint perform movements in the three planes of movement (sagittal, frontal and
      transverse), being the gluteus maximus and gluteus medius the main muscles that perform
      triple actions in this joint. Not only about the joint itself but, the research about the hip
      joint kinematics is of interest due to its importance on pelvic stability and trunk control,
      playing a key role on motor control during dynamic tasks. This also claim for the increase
      emphasis that has been put on strategies that could help clinicians to better understand
      factors associated with hip muscle dysfunction and injury occurrence. The literature has been
      shown that hip muscle weakness are associated with the occurrence of knee injuries like ACL
      (anterior cruciate ligament) tears or patellofemoral dysfunction and interventions focused on
      better activate hip muscles, specifically gluteus maximus and medium, have been demonstrating
      to be key strategies to reduce undesirable movement patterns associated to lower limb injury
      risk factors. Although widely used in clinical and sports practice, it is unclear whether, in
      fact, performing gluteal activation exercises in warm-up phase is effective in increasing
      electromyographic activation (EMG), as well as the mechanisms that explain eventual gluteal
      activation improvement of neuromuscular function. Thus, the aim of this study is to verify
      the acute effect of a gluteal activation warm-up protocol on gluteus maximus (superior
      fibers) and gluteus medius EMG activation and kinematics during single leg squat. The
      hypotheses of this study are that after gluteal activation warm-up program, there will be an
      increase in the muscle recruitment (mean) levels of the gluteus maximus (superior fibers) and
      gluteus medium. About kinematics, the hypotheses that a decrease on hip adduction absolute
      angle and hip and knee frontal plane ROM (range of motion) on maximum knee flexion during
      single leg squat will occur. Participants will perform the test procedures during two visits,
      with a minimum interval of 24 hours and maximum of one week. The study will be conducted in
      two stages. In the first stage, anthropometric data collection, intervention protocol
      application and biomechanical data collection will be performed. The intervention application
      order will be random and counterbalanced which half of the participants will receive the
      gluteal gluteal activation warm-up protocol and the other half a standard warm-up protocol at
      the first visit. In the second stage, the intervention will be applied and biomechanical data
      will be collected. In this context, the following design will be adopted on both days: (1)
      Preparation and familiarization (2) intervention protocol application (standard warm-up or
      gluteal activation warm-up) (3) Immediately after the protocol, three (3) repetitions of the
      single leg squats will be performed and (4) data collection of maximal voluntary isometric
      contraction will be extracted. Since the first visit, the participant's routine will be
      performed as follow: (1) Anamnesis; (2) Anthropometric assessment; (3) electromyography
      electrodes fixation; (4) retro-reflective markers fixation for kinematic evaluation. (5)
      intervention protocol execution; (6) Assessment of movement pattern during single leg squats
      and (7) evaluation of muscle strength by handheld dynamometry and muscle electrical activity
      by electromyography via maximal voluntary isometric contraction (MIVC). The participants will
      be invited to make a second visit to the laboratory, to be scheduled in advance, to repeat
      the procedures for assessing muscle strength, muscle electrical activity, performing another
      intervention protocol and assessing kinematic during the single leg squat. At first,
      participants will receive all information about the procedures. For all tests, participants
      will receive specific positioning and execution guidance. For the anamnesis, participants
      will answer general questions about past and current health history, dominant lower limb and
      physical exercise through a questionnaire. For anthropometric data, measurements of height
      and body mass will be performed. For EMG and kinematic, electromyography electrodes will be
      fixed to the region of the gluteus maximus and gluteus medius muscles in the hip for
      assessment of electrical activity and retro-reflexive markers will be placed on anatomical
      marks of interest (lower limbs and pelvis) to evaluate the kinematic on single leg squat. A
      intervention protocol will be decided by draw and familiarization will be given informing
      position and execution of the exercises. Immediately after the intervention protocol, a
      single leg squat test will be performed only on the dominant limb. For such, three
      consecutive trials will be performed, without intervals between them. Familiarization and
      information will be given about the performance of the test. Kinematic data will be processed
      using KINOVEA software (Creative Commons 3.0, France). From the reference points attached
      only on the dominant limb, four body segments will be virtually reconstructed: pelvis, thigh,
      leg and foot. From these segments, the angles will be calculated at a static position,
      representing the start position and deepest knee flexion degree representing the end of the
      movement. The absolute values of hip adduction at maximum knee flexion angle (primary
      outcome) and differences between the two moments (ROM) in each test will be calculated to
      obtain the following ranges of motion (secondary outcome): knee on sagittal plane (flexion /
      extension), knee on frontal plane (adduction / abduction), hip on frontal plane (adduction /
      abduction) and pelvis on frontal plane (pelvic drop / contralateral elevation). All the three
      squat repetitions will be analyzed. The average of the three repetitions will be used for
      statistical analysis. EMG raw signals will be assessed using an TeleMyo DTS Desk Receiver®
      electromyograph (Noraxon® USA, Inc., Scottsdale, AZ, USA). Data will be sent in real time to
      a computer via Bluetooth, recorded and analyzed by MyoResearch 3.6 Applications Clinical
      software (Noraxon USA, Inc., Scottsdale, AZ, USA). A 10-500 Hz bandpass filter will be
      applied to EMG data. The MIVC with maximum amplitude of the EMG signal during the MIVC of
      each muscle will be recorded and will represent 100% of muscle activity. Muscle activities
      recorded during squats will then be expressed as a percentage of MVIC.

      For statistical analysis, a IBM SPSS Statistics software, version 20.0 (IBM Corporation,
      Armonk, New York) will be utilized to process and calculate data. A descriptive analysis of
      anthropometric variables will be performed to characterize the subjects, mean and standard
      deviation will be adopted for numerical variables. For inferential statistics, tests for
      normality will be employed. From kinematic data, only absolute values of hip frontal angle
      and ROM for hip and knee on frontal plane (hip and knee adduction/abduction) and knee on
      sagittal plane (knee flexion/extension) will be calculated. For EMG, mean EMG activity
      (Gluteus maximus and medius) over the three single leg squat repetitions will be considered
      for statistical analysis. Data reliability between conditions will be based on the intraclass
      correlation coefficient (ICC).
    

Intervention name(s): Standard warm-up protocol; Gluteal activation warm-up protocol
Intervention type(s): Other; Other
Intervention description(s): Stationary cycling and lower limb stretching exercises; Standard warm-up protocol + Clam exercise (3 sets of 12 repetitions each)
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: This is a descriptive quantitative study with cross-over design of repeated measures.The study will be conducted in two stages. In the first stage, anthropometric data collection, intervention protocol application and biomechanical data collection will be performed. The intervention application order will be random and counterbalanced which half of the participants will receive the gluteal pre-activation protocol and the other half a standard warm-up protocol at the first visit. In the second stage, the intervention will be applied and biomechanical data will be collected. In this context, the following routine will be performed: (1) Preparation and familiarization (2) intervention protocol application (standard warm-up or gluteal pre-activation) (3) Immediately after the protocol, three (3) repetitions of the single-legged squat will be performed and (4) data collection of maximal voluntary isometric contraction will be extracted.
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: single leg squat; 2D kinematics; hip adduction; EMG; gluteal activation; warm-up