Lower and Higher Load Resistance Exercise Protocols: Acute Muscle Activation and Skeletal Muscle Hypertrophy
Condition: Muscle Hypertrophy; Muscle Fibre Activation
MeSH terms: Hypertrophy
Study type: Interventional

Summary: 
      How much weight an individual lifts per workout does not dictate the relative increase in
      muscle size the individual gains following weeks of training, which is contrary to current
      strength training dogma. Specifically, researchers have concluded that so long as an
      individual performs resistance exercise with maximum effort, it is not necessary to lift with
      relatively heavy loads. However, other laboratories, on the basis of surface electromyography
      measurements, have challenged the thesis that lighter loads can result in the hypertrophy of
      larger, type II muscle fibres. Therefore, the purpose of this study was to combine surface
      electromyography measurements with direct measurements of muscle fibre activation to see if
      muscle fibre activation was truly dependent on load. The investigators hypothesized that all
      muscle fibres would be activated when the resistance exercise was performed with maximal
      effort.
    

Detailed description: 
      PROCEDURES INVOLVED IN THE RESEARCH

      The total time commitment of this study will be ~7 hours. Each participant's first visit
      (familiarization) will include an interview through where the researchers will determine if
      there are any reasons that the participant cannot take part in the study. The researchers
      will explain the study protocol and, upon the participant's consent, the investigators will
      obtain the participant's knee extension maximum voluntary contraction (MVC) on a dynamometer
      (Biodex, Shirley, USA) and a 1 repetition-maximum (RM) test on a knee extension machine.
      Following that, the investigators will determine the next two dates (trial days) in which the
      participant will come in.

      The participant will be asked to come in fasted on two separate trial days, each separated by
      two weeks, after the participant's familiarization visit. The participant will be required to
      avoid physical activity 48 hours before each of the three visits. There are four conditions
      in this study, each varying in relative load and speed of contraction. The participant will
      complete two conditions on each trial day, one with each leg. The conditions include: 80%RM
      Normal (80N; 1 eccentric: 1 pause: 1 concentric), 80% Slow (80S; 3:1:3), 30% Normal (30N;
      1:1:1) and 30% Slow (30S; 3:1:3). Each condition will include three sets to voluntary failure
      on a knee extension machine. Before and after each set the participant will perform three
      MVCs on the dynamometer identical to what the participant did on the familiarization day. The
      investigators will record the participant's rating of perceived exertion and effort via the
      Borg scale and electromyography (EMG), respectively. The participant will have one biopsy
      taken pre-training and two, one per condition/leg, one hour post-training.

      The REB Project Number for this study is: 802
    

Intervention name(s): resistance exercise
Intervention type(s): Behavioral
Intervention description(s): unilateral knee extensions until fatigue with varying load and speeds of contraction
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Each individual performed four bouts of resistance exercise that varied in load and speed of contraction on two separate days (one condition each leg per visit).
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: muscle fibre activation; electromyography