The Effects of Restriction Pressure on Muscle Damage Responses to Blood Flow Restriction Exercise
Condition: Muscle Damage; Muscle Soreness; Muscle Strength
MeSH terms: Myalgia
Study type: Interventional

Summary: 
      Blood flow restriction (BFR) exercise involves the application of a constriction device to
      the limbs to restrict muscle blood flow during exercise. In recent years, BFR has become
      increasingly popular due to its additive effects on low-load resistance training, often
      promoting greater increases in muscle strength and size compared to similar resistance
      training without BFR. However, like other exercise, it is possible that BFR exercise can
      cause exercise-induced muscle damage (EIMD) that results in short-term reductions in muscle
      function and increased muscle soreness and swelling. One major variable that may influence
      the onset of EIMD is the restriction pressure used to restrict blood flow; however, the
      influence of restriction pressure on resistance EIMD is unclear.

      The purpose of this study is to investigate effects of two different restriction pressures
      (low and high) on EIMD responses to a bout of low-load BFR resistance exercise in a sample of
      healthy, active adults. It is hypothesised that a higher restriction pressure will result in
      increased EIMD compared to a lower restriction pressure. To test this hypothesis,
      participants will perform a lower-body exercise protocol with and without BFR, and several
      markers of EIMD will be assessed before and immediately, 24, 48, and 72 hours after the
      exercise.
    

Detailed description: 
      Following screening for the inclusion and exclusion criteria of the study, eligible
      participants will be fully informed of the study purposes and procedures and written consent
      will be acquired. During this study, participants will be randomly allocated into one of two
      experimental groups, with each group performing blood flow-restricted knee extension exercise
      with one leg and the same exercise protocol without BFR with the contralateral leg.
      Experimental groups will be differentiated by the tourniquet pressure used during the BFR
      condition. Several indirect markers of EIMD will be assessed at baseline and 24, 48, and 72
      hours after the exercise bout. Additional neuromuscular assessments will be performed
      immediately post-exercise to provide insight into the fatiguability of the exercise protocol.

      Participants will be required to attend the laboratory on five separate occasions: one visit
      for screening, assessment of limb occlusion pressure (i.e., the lowest pressure required to
      occlude blood flow to the limb), and familiarisation of the exercise protocol and
      neuromuscular assessments, one visit for completion of the exercise protocol and
      baseline/post-exercise tests, and three follow-up visits. All participants will be asked to
      refrain from alcohol and exercise from 24 hours prior to the exercise trial up to their final
      visit. The consumption of any pain-relieving medications (e.g., anti-inflammatory drugs) and
      undergoing of any muscle damage treatments (e.g., massage) will be prohibited throughout the
      study. To minimise the effects of pre-exercise feeding on the outcome measures, visits will
      be scheduled for the morning and participants will attend the lab following an overnight fast
      of a minimum of 10 hours, although water may be consumed ad libitum. All post-exercise
      measures will be collected at the same time of day ± 1 hours.
    

Intervention name(s): Blood flow restriction at 40% limb occlusion pressure; Blood flow restriction at 80% limb occlusion pressure
Intervention type(s): Other; Other
Intervention description(s): A 13-cm-wide pneumatic cuff will be applied to the most proximal portion of the chosen thigh (as determined by randomisation), immediately distal to the inguinal fold, prior to a bout of lower-body resistance exercise. The cuff will be inflated to 40% of limb occlusion pressure pressure and will remain inflated throughout the exercise (total occlusion time: ~5 mins).; A 13-cm-wide pneumatic cuff will be applied to the most proximal portion of the chosen thigh (as determined by randomisation), immediately distal to the inguinal fold, prior to a bout of lower-body resistance exercise. The cuff will be inflated to 80% of limb occlusion pressure pressure and will remain inflated throughout the exercise (total occlusion time: ~5 mins).
Other intervention name(s): Vascular restriction; Vascular occlusion; Venous restriction; Vascular restriction; Vascular occlusion; Venous restriction
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: The study uses a within-between, unilateral design, in which participants will be randomly allocated into one of two experimental groups using a stratified random allocation technique. Each group will perform blood flow-restricted exercise with one leg and the same exercise protocol without BFR with the contralateral leg. Experimental groups will be differentiated by the tourniquet pressure used during the BFR condition: i) tourniquet pressure set to 40% of limb occlusion pressure or ii) tourniquet pressure set to 80% of limb occlusion pressure. Legs will be counterbalanced such that the BFR and control conditions in each study group contain an equal number of dominant and non-dominant legs. This study design allows comparison between the two experimental conditions (i.e., 40% vs. 80% limb occlusion pressure), while allowing participants to serve as their own control condition.
Masking: Single (Outcomes Assessor)
Primary purpose: Other
Keywords: Muscle Damage; Muscle Soreness; Muscle Strength; Blood Flow Restriction