The Effects of Lifting Light or Heavy Weights on Muscle Growth and Strength in Trained Young Men
Condition: Skeletal Muscle Hypertrophy; Muscle Weakness
MeSH terms: Muscle Weakness; Hypertrophy
Study type: Interventional

Summary: 
      When practicing weightlifting regularly the body makes new proteins within the muscle.

      These new proteins can increase the size of the cells within the muscle to make them larger,
      a process called hypertrophy. The common convention surrounding gains in skeletal muscle size
      and strength is that heavy weights are needed. In contrast, lifting lighter weights are
      thought to be required to induce muscular endurance and not to promote growth. However, it
      has previously been shown in untrained men that lifting lighter weights results in similar
      gains in muscle mass and strength as lifting heavier weights. The purpose of this study is to
      examine how performing resistance training of different intensities (light or heavy weights)
      affects the degree of muscle growth and strength gain in individuals who are already
      resistance training.

      This information will be valuable when designing exercise protocols for increasing muscle
      size and strength at all ages, or in individuals returning from injury, as a way to stimulate
      muscle growth and promote strength gains without the need to lift heavy weights.
    

Detailed description: 
      Patients will visit the laboratory of Dr. Stuart Phillips at the Ivor Wynne Centre (IWC) at
      McMaster University for 14 weeks for a number of tests and exercise sessions.

      Each visit will be as follows:

      Visit 1:

      Upon obtaining consent, eligible participants will complete a medical screening questionnaire
      to determine their readiness to perform exercise as well as a filling out a form to determine
      subject characteristics. Participants will begin collecting data for their first 3-day diet
      record. They will record their diet (2 weekdays and a weekend day) again at 6 weeks
      (mid-protocol) and at 12 weeks of the study.

      Visit 2:

      Participants will report the lab between 08.00 and 10.00 h to undergo body composition scans
      including BodPod (to assess fat mass), bioelectrical impedance (BIA - to assess your total
      body water content), and Dual-energy x-ray- Absorptiometry (DXA- to determine bone mineral
      content). All tests will be performed in the post-absorptive state (12 hours). Participants
      will also have a familiarization with the lab and exercise equipment to determine preliminary
      resistance training (RT) loads.

      Visit 4:

      Participants will report to the lab to determine their one-repetition-maximum on the leg
      press, leg extension, bench press and shoulder press. This will be done by having
      participants attempt a weight based on their familiarization session; if they can complete
      this weight though a full range of motion with good form, they will rest 3-5 min and then
      attempt a higher weight until their 1RM is reached.

      Visit 5:

      Participants will report to the lab in the post-absorptive state (12 hours) for a resting
      muscle biopsy from the muscle on the outside of their thigh.

      Visits 6: Participants will be randomly assigned to one of two exercise intensity treatment
      groups: ~30% of 1RM (which equates to ~20-25 repetitions per set) for 3 sets to failure (25
      subjects) or 80% of 1RM for 3 sets to failure (another 25 subjects). All sets will have 60
      seconds of rest in between. On two occasions (one at the beginning of the study another at
      the end), participants will return to the lab in the post-absorptive state and a catheter
      (plastic tube with a small needle) will be inserted into a vein in your arm. A resting blood
      sample will be taken. Upon completion of their first exercise session, subsequent blood
      samples will be taken at 15 minutes, 30 minutes 60 minutes to determines an acute time course
      of the changes in blood metabolites and hormones.

      Visit 7-54:

      Participants will attend supervised exercise sessions 4 times per week (Monday, Tuesday,
      Thursday and Friday) alternating lower body and upper body focused sessions for 12 weeks.
      Participants in the 30% (LOW) group will perform approximately 20-25 repetitions per set
      while participants in the 80% (HIGH) group will perform approximately 8-12 repetitions per
      set. Immediately following each resistance training session as well as prior to sleep,
      participants will consume 30g of whey protein. 1RM testing will be repeated every three weeks
      throughout the protocol and will be conducted prior to beginning the last of every 12
      training sessions. Prior to completing their final training session (session number 48)
      participants will again arrive to the lab in the post-absorptive state for blood sampling
      procedure as described previously.

      Visit 55:

      Participants will arrive in the post absorptive (fasted) state 48 hours following their last
      training session. They will undergo a final BodPod, DEXA and BIA scan to determine body
      composition as well as a final resting biopsy of the vastus lateralis muscle.
    

Intervention name(s): 30% 1RM; 80% 1RM
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Participant exercises using a protocol tailored at 30% of their 1RM; Participant exercises using a protocol tailored at 80% of their 1RM
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Other