Lower and Higher Load Resistance Exercise Protocols: Acute Muscle Activation and Skeletal Muscle Hypertrophy

Lower and Higher Load Resistance Exercise Protocols: Acute Muscle Activation and Skeletal Muscle Hypertrophy

Muscle Fibre Activation is Unaffected by Load and Repetition Duration When Resistance Exercise is Performed to Task Failure

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.

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

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).

The study investigators that performed the histochemical analysis were masked to which participant and which condition they were assessing at the time of analysis.

Participants performed three sets of unilateral knee extension with a load that was 80 % of their one-repetition maximum (1RM) at a tempo of three seconds per repetition.

Participants performed three sets of unilateral knee extension with a load that was 80 % of their one-repetition maximum (1RM) at a tempo of seven seconds per repetition.

Participants performed three sets of unilateral knee extension with a load that was 30 % of their one-repetition maximum (1RM) at a tempo of three seconds per repetition.

Participants performed three sets of unilateral knee extension with a load that was 30 % of their one-repetition maximum (1RM) at a tempo of seven seconds per repetition.

Inclusion Criteria: healthy male 18-30 years of age Exclusion Criteria: Have any acute or chronic illness such as cardiac, pulmonary, liver, or kidney abnormalities, uncontrolled hypertension, insulin- or non-insulin dependent diabetes or other metabolic disorders-all ascertained through a medical history screening questionnaire Experience arthritic conditions Smoke tobacco products Consume any analgesic or anti-inflammatory drug(s), prescription or non-prescription, chronically Have a history of neuromuscular complications Are on any medications known to affect protein metabolism (i.e. corticosteroids, non-steroidal anti-inflammatories, or prescription strength acne medications). Have an extensive history of RE training in the year prior to study entry.