Skeletal Muscle Hypertrophy
Conditions
Keywords
Skeletal Muscle, Hypertrophy, Strength, Muscle Endurance
Brief summary
When you perform weightlifting, your body makes new proteins within your muscle. These new proteins can increase the size of the fibers within your muscle to make your muscle larger, a process called hypertrophy. The common convention surrounding gains in muscle mass and strength are that higher-loads (i.e. heavier weights) used for fewer repetitions are better for increasing strength and lower-loads (i.e. lighter weights) used for higher repetitions are better for increasing muscle mass. However, recent research has found that when higher- and lower-loads are used when participants exercise until volitional fatigue (i.e. cannot perform another repetition), muscle mass and strength increases are similar regardless of using a higher- or lower-load. Many of these studies have examined this effect in males with fewer studies examining the effects of higher- and lower-load training in females when assessing changes in muscle mass, strength, and muscle endurance. Further, it has been shown that there is substantial individual variation in response to resistance exercise training where individuals can be broadly categorized as higher- or lower-responders to resistance exercise training. This study aims to explore how the muscle mass, strength, and muscle endurance of females are impacted by both higher- and lower-loads while also exploring how individuals may respond to the training interventions.
Detailed description
The study will be a total of 12 weeks in total duration. Weeks 1 and 12 will include testing assessments of skeletal muscle mass, muscle strength, and muscle endurance. Weeks 2-11 will be comprised of the resistance training intervention wherein participants will train thrice weekly at the Chan Gunn Pavilion research laboratory at the University of British Columbia. Resistance training sessions will include unilateral knee extensions and unilateral dumbbell bicep preacher curls with each being performed for three sets. Limbs assigned to train with higher-loads will perform between 8-12 repetitions per set and limbs assigned to train with lower-loads will perform between 20-25 repetitions per set. Participants will rest 90 seconds between sets and 120 seconds between exercises. Each exercise will be performed in its entirety before moving on to the next. Participants will also be supplemented with whey protein which will be ingested twice daily during the resistance training phase.
Interventions
OTHERHigher-load resistance training
This intervention will have one arm and one leg of each participant training with \ 80% of their one repetition maximum
OTHERLower-load resistance training
This intervention will have one arm and one leg of each participant training with \ 30% of their one repetition maximum
Sponsors
University of British Columbia
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
A within participant design will be used wherein each participant will be assigned to both training conditions. One arm and one leg will train with higher-loads and one arm and one leg will train with lower-loads; limb allocation will be randomized.
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 30 Years
Healthy volunteers
Yes
Inclusion criteria
1. Female 2. 18-30 years of age 3. Can fluently read and write in English 4. Able to commit to three training sessions per week for a continuous 10-week period as well as testing one week before and one week after this 10-week training period 5. All No answers on the Canadian Society for Exercise Physiology Get Active questionnaire or doctors' approval to participate
Exclusion criteria
1. Allergic to dairy products or are lactose-intolerant (participants will be supplemented with whey protein twice daily for the 10-week training period) 2. Allergic to any of the following ingredients which are present in the whey protein concentrate supplement: Bos taurus - Milk, Cocoa, Natural and Artificial Flavours, Xanthan Gum, Sucralose, Non-genetically modified organism Sunflower Lecithin 3. Any major uncontrolled cardiovascular, muscular, metabolic, and/or neurological disorders 4. Lung or kidney disease 5. Medical conditions impacting on their ability to undertake strenuous physical activity 6. Regular use of any mental health medications that may lead to excessive weight gain (selective serotonin reuptake inhibitors, second generation antipsychotics, antiepileptic drugs) 7. Participated in consistent resistance exercise training more than twice per month in the previous 12 months 8. Participated in consistent vigorous aerobic training more than twice per week in the previous 12 months 9. Significant gain or loss of body mass in the past 6 months (greater than 2 kg) 10. Current smoker 11. BMI less than 18 or over 30
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in upper- and lower-body skeletal muscle mass between weeks 1 and 12 | Weeks 1 and 12 | The total skeletal muscle mass measured in each individual arm and leg quantified using dual-energy x-ray absorptiometry scanning |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in unilateral knee extension one repetition maximum between weeks 1 and 12 | Weeks 1 and 12 | The maximum amount of weight that an individual can move for one full repetition during the unilateral knee extension exercise |
| Change in unilateral dumbbell bicep preacher curl relative muscle endurance between weeks 1 and 12 | Weeks 1 and 12 | The maximum number of repetitions that can be completed with 30% and 80% of the individuals current one repetition maximum for the unilateral dumbbell bicep preacher curl exercise |
| Change in unilateral dumbbell bicep preacher curl absolute muscle endurance between weeks 1 and 12 | Weeks 1 and 12 | The maximum number of repetitions that can be completed with 30% and 80% of the individuals baseline one repetition maximum for the unilateral dumbbell bicep preacher curl exercise |
| Change in unilateral knee extension relative muscle endurance between weeks 1 and 12 | Weeks 1 and 12 | The maximum number of repetitions that can be completed with 30% and 80% of the individuals current one repetition maximum for the unilateral knee extension exercise |
| Change in unilateral dumbbell bicep preacher curl one repetition maximum between weeks 1 and 12 | Weeks 1 and 12 | The maximum amount of weight that an individual can move for one full repetition during the unilateral dumbbell bicep preacher curl exercise |
| Change in Vastus Lateralis and Biceps Brachii Cross Sectional Area between weeks 1 and 12 | Weeks 1 and 12 | The cross sectional area of the vastus lateralis and biceps brachii muscles measured using ultrasonography |
| Change in Vastus Lateralis and Biceps Brachii Muscle Thickness between weeks 1 and 12 | Weeks 1 and 12 | The thickness of the vastus lateralis and biceps brachii muscles measured using ultrasonography |
| Change in Vastus Lateralis Pennation Angle between weeks 1 and 12 | Weeks 1 and 12 | The pennation angle of the vastus lateralis muscle fibers measured using ultrasonography |
| Change in Vastus Lateralis Fascicle Length between weeks 1 and 12 | Weeks 1 and 12 | The length of the fascicles of the vastus lateralis muscle measured using ultrasonography |
| Change in unilateral knee extension absolute muscle endurance between weeks 1 and 12 | Weeks 1 and 12 | The maximum number of repetitions that can be completed with 30% and 80% of the individuals baseline one repetition maximum for the unilateral knee extension exercise |
Countries
Canada
Outcome results
None listed