The question of whether a treadmill can contribute to a “bigger bum” relates directly to training the gluteal muscle group, which includes the gluteus maximus, gluteus medius, and gluteus minimus. The gluteus maximus is the largest, primarily responsible for hip extension and the shape of the buttocks. The medius and minimus stabilize the pelvis during movement and assist with hip abduction. This article explores the physiological requirements for muscle growth, known as hypertrophy, and how the treadmill can be strategically used to meet those demands.
The Science of Muscle Hypertrophy
Muscle growth, or hypertrophy, is a biological adaptation where muscle fibers increase in size, resulting in a physically larger muscle. This process is triggered by three primary factors that place a significant demand on the muscle.
Mechanical Tension
This involves applying a heavy load or high resistance to the muscle fibers. This tension causes the muscle to generate a strong force, which signals growth.
Metabolic Stress
This is often felt as the “burn” during high-repetition sets, involving the accumulation of byproducts within the muscle cell.
Muscle Damage
This refers to micro-tears in the muscle fibers caused by strenuous or unfamiliar exercise.
Hypertrophy occurs when the body repairs these micro-tears, rebuilding the muscle fibers thicker and stronger. This repair process requires adequate recovery time and nutritional building blocks. Muscle size gains happen more readily in Type II (fast-twitch) muscle fibers, which are primarily recruited during high-force, short-duration activities.
Glute Engagement During Standard Treadmill Use
When engaging in standard treadmill activity, such as walking or running on a flat or low-incline surface, the primary purpose is usually cardiovascular conditioning. This steady-state exercise primarily recruits Type I (slow-twitch) muscle fibers. These fibers are highly resistant to fatigue and built for prolonged activity, but they have a lower capacity for size increase compared to Type II fibers.
While the gluteal muscles provide hip extension and stabilization during standard running and walking, the mechanical tension is generally too low to induce hypertrophy. The resistance provided by moving body weight over a flat surface is sufficient for endurance, but it does not meet the overload requirement necessary for muscle growth. Consequently, steady-state cardio typically results in muscular endurance improvements rather than a noticeable increase in glute size.
The glutes are engaged primarily to control movement and stabilize the pelvis, particularly the gluteus medius and minimus. However, the gluteus maximus, the main muscle for size, is not challenged with enough resistance to adapt by getting bigger. Therefore, a basic, flat-surface treadmill routine is not an effective strategy for achieving gluteal muscle hypertrophy.
Optimizing Incline and Speed for Glute Development
To shift treadmill work from low-resistance endurance to high-resistance growth, settings must be adjusted to significantly increase mechanical tension on the gluteal muscles. This is best achieved by combining a steep incline with walking or incorporating high-speed interval training.
Incline Walking
Increasing the incline to 10% or higher mimics climbing a steep hill, which dramatically increases gluteus maximus activation. Walking at a steep incline forces the glutes to work harder to propel the body upward and forward, emphasizing hip extension. A pace of 3.0 to 3.5 miles per hour is effective for maintaining high glute engagement. To maximize contraction, consciously driving through the heel and slightly increasing stride length encourages fuller hip extension.
High-Intensity Interval Training (HIIT)
Short, all-out sprints recruit the Type II (fast-twitch) muscle fibers, which possess the greatest potential for size gain. A typical HIIT protocol involves alternating 30-second sprints with 60 to 90 seconds of recovery walking or jogging, repeated multiple times. The high-force requirement of sprinting provides the necessary mechanical tension and metabolic stress to stimulate hypertrophy in the glutes and hamstrings.
Nutritional Requirements for Glute Growth
Exercise alone is insufficient to build muscle mass; the process requires specific nutritional support to fuel the repair and rebuilding of muscle tissue. Protein is the foundational building block for muscle repair and growth, providing the amino acids necessary to synthesize new muscle proteins. To support hypertrophy, a daily intake of at least 1.4 grams of protein per kilogram of body weight is recommended, with some guidelines suggesting up to 1.6 grams or more.
The body must also be in a state of positive energy balance, known as a caloric surplus, for muscle growth to occur efficiently. This means consuming slightly more calories than the body expends each day to provide the energy needed for muscle repair and new tissue creation. A modest surplus of about 5% to 10% above maintenance calories is advised to maximize muscle gain while minimizing the accumulation of body fat. Without both adequate protein and a slight caloric surplus, muscle growth stimulated by treadmill workouts will be significantly limited.