Muscle Hypertrophy, Muscle Strength
Conditions
Brief summary
This study compared the effects of two lower-body resistance training exercises - the barbell back squat and the barbell hip thrust - on muscle growth and strength in untrained young adults. Thirty-four participants were randomly assigned to train using either the back squat or the hip thrust, two times per week for nine weeks. Muscle size (via MRI) and strength (via weightlifting tests) were measured before and after training to determine whether one exercise produced greater improvements than the other, particularly in the gluteal muscles. Muscle activity during the first training session was also measured using surface electromyography (sEMG) to see whether early muscle activation could predict later muscle growth.
Interventions
BEHAVIORALResistance training
Participants performed training twice per week (non-consecutive days) for 9 weeks, totaling 15-17 supervised sessions. Training volume progressed weekly: 3 sets in week 1, 4 sets in week 2, 5 sets in weeks 3-6, and 6 sets in weeks 7-9, matching the set-volume scheme used in the hip thrust group. Each set consisted of 8-12 repetitions performed to volitional muscular failure (defined as the inability to complete another repetition with proper form); load was adjusted as needed to keep repetitions within this range. Repetitions were performed with a controlled tempo (\~1-second concentric, \~2-second eccentric). All training sessions were supervised by study personnel. Participants were instructed to refrain from any other lower-body resistance training for the duration of the study.
Sponsors
Auburn University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Outcomes Assessor)
Masking description
Participants were not blinded to group allocation, as blinding was not feasible given the distinct nature of the two training exercises (back squat vs. barbell hip thrust). Investigators supervising training sessions were also not blinded, as they administered the assigned exercise protocol. During strength testing (3-repetition maximum and isometric wall push assessments), investigators were not blinded to group allocation due to logistical constraints, and the authors note that potential bias in this context cannot be fully ruled out. However, investigators were blinded to group allocation during MRI data collection and analysis; muscle cross-sectional area measurements were performed by a single investigator who did not have knowledge of participants' training group assignments.
Eligibility
Sex/Gender
ALL
Age
18 Years to 30 Years
Healthy volunteers
Yes
Inclusion criteria
* Age 18-30 years * Body mass index (BMI) less than 30 kg/m² * Minimal resistance training experience, defined as averaging ≤1 day per week of resistance training over the preceding 5 years * Willing and able to provide written informed consent.
Exclusion criteria
* Participation in structured endurance training (e.g., running or cycling) more than 2 days per week over the past 6 months * Known overt cardiovascular or metabolic disease * Use of supplemental creatine and/or hormone-altering agents (e.g., testosterone boosters, growth hormone boosters) within the past 2 months * Any medical condition that would contraindicate participation in an exercise program * Any condition precluding MRI scanning (e.g., medically implanted devices)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Hypertrophy | Baseline and 9 weeks | Cross-sectional area of the upper, middle, and lower gluteus maximus was measured via magnetic resonance imaging (MRI) at baseline and following the 9-week training intervention. T1-weighted transverse images were obtained using a 3T MRI scanner, and muscle borders were manually traced using ImageJ software by a single investigator blinded to group allocation. Bilateral (left + right) mCSA values were summed at each of three standardized anatomical sites (upper, middle, and lower gluteus maximus) to assess site-specific hypertrophic response to training. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| 3RM strength testing | Baseline and 9 weeks | Dynamic lower-body strength was assessed via 3-repetition maximum (3RM) testing for the barbell hip thrust, barbell back squat, and barbell deadlift at baseline and following the 9-week training intervention |
| One-bout EMG gluteal maximus recordings | Single training session within the first week of the intervention. | Surface electromyography (sEMG) was used to assess muscle excitation of the right upper, middle, and lower gluteus maximus and the right gluteus medius during a single 10-repetition-maximum (10RM) set of both the barbell back squat and barbell hip thrust exercises, performed during participants' first training session. Wireless sEMG electrodes were placed at standardized anatomical sites, and signals were sampled at 1000 Hz, rectified, filtered, and smoothed before being normalized to each participant's maximum voluntary isometric contraction (MVIC) for the corresponding muscle. Mean and peak sEMG amplitudes were calculated for each muscle site during each exercise and compared between the back squat and hip thrust conditions. |
Countries
United States
Outcome results
None listed