Specific Aims and Hypotheses:~Specific Aim 1: To examine the changes of type I and II (different types of muscle fibers) muscle fiber cross-sectional areas in the leg extensor muscles (vastus lateralis) pre- to post- 6 weeks of high-intensity resistance training and low-intensity resistance training with blood flow restriction. Hypothesis 1: Type I and II fiber cross-sectional area will increase following low-intensity resistance training with blood flow restriction, however, only cross-sectional area of type II fibers will increase post high-intensity resistance training.~Specific Aim 2: To examine changes in the size of the motor units that are active during low and high intensity contractions in the leg extensor muscles (vastus lateralis) pre- to post- 6 weeks of high-intensity resistance training and low-intensity resistance training with blood flow restriction. Hypothesis 2: The motor units that are active during low and high intensity contractions will increase in size from low-intensity resistance training with blood flow restriction, but only the motor units that are active during high intensity contractions will increase in size from high-intensity resistance training.~Specific Aim 3: To examine changes in whole muscle cross-sectional area as measured via ultrasound pre- to post- 6 weeks of high-intensity resistance training and low-intensity resistance training with blood flow restriction. Hypothesis 3: Whole muscle cross-sectional area will increase to similar degrees from both high-intensity resistance training and low-intensity resistance training with blood flow restriction.
The primary purposes of the proposed study is 1) To examine the changes of muscle fiber cross-sectional areas in the leg extensor muscles (vastus lateralis) pre- to post- 6 weeks of high-intensity resistance training and low-intensity resistance training with blood flow restriction and 2) To examine changes in motor unit size (a non-invasive measure of muscle fiber size) in the leg extensor muscles (vastus lateralis) pre- to post- 6 weeks of high-intensity resistance training and low-intensity resistance training with blood flow restriction.