Use of Velocity Monitoring to Prescribe Appropriate Flywheel-based Inertial Training (FIT) Workloads for Exercise in Space Flight
Overview
- Phase
- N/A
- Intervention
- Not specified
- Conditions
- Muscle Atrophy
- Sponsor
- Lance Bollinger
- Enrollment
- 16
- Locations
- 1
- Primary Endpoint
- Voluntary activation
- Status
- Recruiting
- Last Updated
- 6 months ago
Overview
Brief Summary
This study aims to determine how flywheel-based inertial training (FIT) implemented according to principles of velocity-based training (VBT) and High-Intensity Interval Training (HIIT) affects disuse-induced physical de-conditioning including loss of voluntary muscle strength, aerobic capacity, and balance regulation.
Detailed Description
The primary objectives of this project are: 1. To assess how 30d of unilateral lower limb suspension (ULLS) with and without FIT exercise affects voluntary and electrically-evoked twitch force, motor unit recruitment, and anisotropic measures. 2. To determine how muscle anisotropy (assessed through diffusion tensor imaging) and motor unit action potential train (MUAPT) characteristics relate to contractile function in loaded and unloaded limbs Secondary objectives include: 1. To assess impact of ULLS with and without FIT on aerobic capacity 2. To assess impact of ULLS with and without FIT on balance regulation during single-leg stance This study aims to recruit 10 healthy, physically active participants (both male and female). Participants will undergo 30d of ULLS to unload the left limb during daily living activities. Subjects will wear a specially modified shoe with a 5cm rocker-style stack on the right leg and ambulate using crutches. Participants will be randomly assigned to either a control or exercise group. Those in the exercise group will perform Flywheel-based Inertial Training (FIT) leg press three times per week. Moment of inertia of the flywheel will be adjusted to elicit movement speeds of 0.4 m/s for resistance training (four sets of 10 repetitions). For High Intensity Interval Training, flywheel moment of inertia will be adjusted to elicit movement speed of 1.0m/s during upright squats (four sets of 3 min). Before and after the intervention, subjects will complete a series of tests including: 1. Body Composition - height, weight, waist circumference, and tetrapolar bioelectrical impedance analysis will be conducted. 2. Balance assessment - center of pressure will be assessed using portable force decks during single leg stance with eyes open and closed. This test will be repeated in the shod and unshod conditions. MUAPT data (high density surface electromyography) will be collected for the soleus and tibialis anterior during this test. 3. Aerobic capacity test - VO2max will be determined during a graded exercise test on a cycle ergometer (3 min per stage). Gas exchange and heart rate data will be collected continuously throughout the test. Pedal force will also be assessed. Additional outcomes such as ventilatory threshold and substrate utilization will be assessed. 4. Muscle Imaging - Diffusion tensor imaging (DTI), a magnetic resonance technique will be used to assess anisotropic measures, muscle volume, fascicle length, and fascicle orientation of the mid-thigh. 5. Muscle strength testing - Maximal voluntary isometric and isokinetic strength of the knee extensors, flexors, and ankle plantar- and dorsi-flexors will be assessed. Interpolated twitch (electrical stimulation of the femoral nerve) will be used to assess twitch characteristics and voluntary activation of the quadriceps
Investigators
Lance Bollinger
Associate Professor
University of Kentucky
Eligibility Criteria
Inclusion Criteria
- •Regularly engaging in aerobic exercise (\> 150min/wk) and resistance exercise (\>1 time per week) for the past 12 months
- •Education greater than or equal to bachelor's degree (any field)
Exclusion Criteria
- •Waist circumference \< 55cm or \> 90cm (F) and \< 75cm or \> 100cm (M)
- •Body mass index \< 18.5 or \> 29.9
- •Shoe size \< 25 or \>29cm.
- •Not regularly engaging in exercise for previous 12 months
- •Tobacco use within previous 6 months
- •Blood clotting disorder
- •Heart arrhythmia
- •Implanted device which could negatively be affected by electrical impulse or strong magnetic field such as pacemaker, internal defibrillator, or cochlear implant
- •Diagnosed cardiovascular, pulmonary, renal, or metabolic disease
- •Pregnancy (within previous 6 months)
Outcomes
Primary Outcomes
Voluntary activation
Time Frame: Baseline, day 13, and day 30
Voluntary activation of the quadriceps will be assessed with electrical stimulation of the femoral nerve before, during, and after a maximal voluntary isometric contraction (MVIC) using the interpolated twitch technique.
Twitch Properties-Electromechanical Delay
Time Frame: Baseline, day 13, and day 30
Electromechanical delay will be calculated as the time difference between the onset of electrical impulse and onset of torque development during femoral nerve stimulation. This will be measured before and after a maximal voluntary isometric contraction.
Twitch Properties-Rate of Torque Development
Time Frame: Baseline, day 13, and day 30
Rate of Torque Development will be calculated as the change in torque divided by the change in time in the linear phase between 20 and 80% of peak twitch torque during femoral nerve stimulation. This will be measured before and after a maximal voluntary isometric contraction.
Twitch Properties-Time to peak Tension
Time Frame: Baseline, day 13, and day 30
Time to peak tension will be calculated as the time difference between the onset of electrical impulse and peak twitch torque during femoral nerve stimulation. This will be measured before and after a maximal voluntary isometric contraction.
Twitch Properties-Peak Twitch Torque
Time Frame: Baseline, day 13, and day 30
Peak twitch torque during femoral nerve stimulation will be calculated as the highest torque output immediately (approximately 200ms) following femoral nerve stimulation. This will be measured before and after a maximal voluntary isometric contraction.
Twitch Properties-Relaxation Rate
Time Frame: Baseline, day 13, and day 30
Relaxation rate will be calculated as the change in torque divided by the change in time during the relaxation phase of twitch following femoral nerve stimulation. This will be measured before and after a maximal voluntary isometric contraction.
Post activation Potentiation
Time Frame: Baseline, day 13, and day 30
Post-activation will be calculated as the percentage difference in peak twitch torque in femoral nerve stimulation before and after a maximal voluntary isometric contraction.
Motor unit action potential train (MUAPT) firing rate
Time Frame: Baseline, day 13, and day 30
Firing rate of individual motor units of the vastus lateralis (VL) will be assessed with high density surface electromyography (EMG) using four-pin high density surface electromyography electrodes. Firing rate at 30, 60, and 90% MVIC will be reported. Motor unit firing rate will also be reported during static stance. Participants will use a screen displaying real-time torque output. Participants will voluntarily increase torque (5 seconds), hold at a pre-determined torque level (10 seconds), and gradually reduce force back to resting (5 seconds) with the knee held in a fixed position. This test will be completed with a 10s isometric hold at 30, 60, and 90% of maximal voluntary isometric force.
Motor unit action potential train (MUAPT) recruitment threshold.
Time Frame: Baseline, day 13, and day 30
Recruitment threshold of individual motor units of the VL will be assessed with high density surface electromyography using four-pin high density surface electromyography electrodes. Recruitment threshold will be measured during isometric ramp contractions of the quadriceps Participants will use a screen displaying real-time torque output. Participants will voluntarily increase torque (5 seconds), hold at a pre-determined torque level (10 seconds), and gradually reduce force back to resting (5 seconds) with the knee held in a fixed position. This test will be completed with a 10s isometric hold at 30, 60, and 90% of maximal voluntary isometric force.
Motor unit action potential train (MUAPT) de-recruitment threshold.
Time Frame: Baseline, day 13, and day 30
De-recruitment threshold of individual motor units f the VL will be assessed with high density surface electromyography using four-pin high density surface electromyography electrodes. Recruitment threshold will be measured during isometric ramp contractions of the quadriceps Participants will use a screen displaying real-time torque output. Participants will voluntarily increase torque (5 seconds), hold at a pre-determined torque level (10 seconds), and gradually reduce force back to resting (5 seconds) with the knee held in a fixed position. This test will be completed with a 10s isometric hold at 30, 60, and 90% of maximal voluntary isometric force.
Muscle size
Time Frame: Baseline and day 30
Muscle size will be measured by MRI. Anatomical MRI scans will allow for assessment of anatomical cross sectional area.
Muscle Physiological cross-sectional area
Time Frame: Baseline and day 30
Diffusion tensor imaging (DTI) will be used to assess muscle volume and fascicle length. Physiological cross-sectional area will be calculated as Muscle volume divided by fascicle length.
Muscle Fractional Anisotropy
Time Frame: Baseline and day 30
Diffusion tensor imaging (DTI) will be used to assess anisotropic measures. A ratio of the diffusivity in the principal planes will be used to calculate fractional anisotropy.
Muscle Diffusion properties
Time Frame: Baseline and day 30
Diffusion tensor imaging (DTI) will be used to assess rate of water diffusion in three principal planes. We will report rates of water diffusion in three ways: 1) mean diffusivity (average rate in all three plane), 2) axial diffusivity (rate of diffusion along primary axis), and 3) radial diffusivity (rate of diffusion perpendicular to the primary axis).
Muscle cross-sectional area (Ultrasound)
Time Frame: Baseline, day 13, and day 30
cross-sectional area of the vastus lateralis and rectus femoris will be measured by ultrasonography
Fascicle length
Time Frame: Baseline, day 13, and day 30
Panoramic views of the mid-portion of the VL will be measured by ultrasonography
Pennation angle
Time Frame: Baseline, day 13, and day 30
Pennation angle of the mid-portion of the vastus lateralis will be assessed by ultrasonography
Voluntary Isokinetic Muscle Strength
Time Frame: Baseline, day 13, and day 30
Maximal voluntary isokinetic concentric strength of the knee extensors/flexors and ankle dorsi-/plantar-flexors will be assessed at 60 deg/s
Voluntary Isometric Muscle Strength
Time Frame: Baseline, day 13, and day 30
Maximal voluntary isometric strength of the knee extensors/flexors and ankle dorsi-/plantar-flexors will be assessed during a (10 seconds) maximal effort contraction.
Secondary Outcomes
- Aerobic Capacity(Baseline and day 30)
- Ventilatory Threshold(Baseline and day 30)
- Substrate utilization(Baseline and day 30)
- Body Composition(Baseline and day 30)
- Postural sway area(Baseline, day 13, and day 30)
- Postural Sway Velocity(Baseline, day 13, and day 30)
- Motor unit firing rate - single leg stance(Baseline, day 13, and day 30)
- Change in heart rate at rest(Baseline and day 30)
- Change in blood pressure at rest(Baseline and day 30)
- Change in heart rate variability(Baseline and day 30)
- Change in heart rate recovery after exercise(Baseline and day 30)