Walking with a weighted backpack, known as rucking, has become a popular fitness trend, moving from its military origins into the mainstream. This method involves carrying a load—often plates or similar dense items—to increase the physical demand of a walk or hike. As more people adopt this low-impact, accessible form of exercise, a frequent question arises: can rucking genuinely build muscle mass, or is it simply a form of endurance training? Understanding the physiological response to carrying a sustained, moderate load is the key to determining its effectiveness for building muscle.
Rucking vs. Hypertrophy: Targeting Specific Muscle Groups
Rucking provides resistance, which is the foundational requirement for building muscle, a process known as hypertrophy. However, the type of muscle growth stimulated by rucking differs from the growth achieved through traditional weightlifting. Rucking primarily engages Type I, or slow-twitch, muscle fibers, which are efficient at using oxygen and resisting fatigue over long periods. This leads to increases in muscular endurance and strength, but not necessarily significant increases in muscle size.
For substantial muscle bulk, the body needs to stimulate Type II, or fast-twitch, muscle fibers, which respond best to heavy loads and high-intensity work that cause muscle failure. While the added weight of the pack does increase the workload on the lower body, including the quadriceps, hamstrings, glutes, and calves, the stimulus is generally not intense enough to trigger maximum hypertrophy. The upper back muscles, specifically the trapezius and rhomboids, also see increased resistance as they support the weight of the pack, leading to potential tone and strength gains.
The Role of Core Stabilization and Posture
The act of carrying an external load on the back requires continuous, subtle engagement of the core musculature to maintain an upright posture and balance. This stabilization effect recruits muscles in the abdominals, obliques, and lower back, including the erector spinae. These muscles work isometrically, meaning they contract without significantly changing length, to keep the spine stable under the load.
Although rucking will not yield the same results as direct, high-intensity abdominal exercises, it significantly improves functional strength and endurance in the stabilizing muscles. The resistance forces the core to constantly adjust and prevent the body from leaning too far forward, which helps build a stronger foundation for all other movements. This sustained tension helps improve overall postural alignment, which can mitigate the risk of back strain and injury.
Endurance and Metabolic Advantages of Weighted Walking
While the muscle-building effect of rucking is primarily focused on endurance, its advantages for cardiovascular health and metabolism are more pronounced. The simple addition of weight to a walk dramatically increases the body’s energy expenditure compared to walking without a load. Research indicates that for every 10% of body weight added in a rucksack, the energy use increases by nearly 20%.
This increased metabolic demand forces the heart and lungs to work harder to deliver oxygen to the working muscles. Over time, this improves cardiovascular fitness by increasing the body’s maximal oxygen uptake, or VO2 max. Rucking is an excellent form of low-impact, high-intensity steady-state cardio, which supports fat loss and overall heart health. Furthermore, the load-bearing nature of the exercise promotes increased bone density, a significant benefit, particularly for aging populations.
Safe Implementation and Weight Progression
To safely integrate rucking into a fitness routine, proper setup and gradual progression are necessary to prevent orthopedic issues. The backpack, or ruck, should be positioned high and tight on the back, ensuring the weight is distributed evenly and close to the body’s center of gravity. A common starting point for the added weight is 10% of one’s body weight, though beginners can start with 10 to 15 pounds.
Progression should be slow, with no more than a 5-pound increase in weight every one to two weeks, or an increase in distance before adding more weight. Beginners should limit their sessions to two or three times per week, allowing for adequate muscle and joint recovery. Avoiding the common mistake of leaning forward or adding too much weight too quickly is imperative, as this can strain the lower back and joints.