The hip thrust is a widely recognized exercise for developing the gluteal muscles and building lower body strength. As lifting techniques evolve, trainers have developed variations to target specific physiological goals. This drive for specialization led to the rise of the Kas Hip Thrust, a modified movement designed to maximize muscle growth through unique mechanical demands. Understanding its distinct purpose and proper execution is key.
Defining the Kas Hip Thrust
The Kas Hip Thrust is a specialized variation of the traditional hip thrust, named after fitness coach Kassem Hanson. The foundational difference lies in the deliberate reduction of the range of motion (ROM) compared to a standard hip thrust. Instead of lowering the hips all the way to the floor, the Kas version only utilizes the top third or half of the movement.
This limited ROM alters the exercise’s primary focus. While a full hip thrust engages the hamstrings and quadriceps and allows for heavier loads, the Kas variation emphasizes constant tension and a powerful peak contraction in the gluteus maximus. Remaining in the upper portion prevents the glutes from fully relaxing, shifting the goal from maximal strength to prolonged time under tension for hypertrophy.
Proper Execution and Form
Setting up for the Kas Hip Thrust begins similarly to the standard version. Position the upper back against a secure bench or box, typically 12 to 18 inches high. The edge of the bench should sit just below the shoulder blades, allowing the body to hinge effectively from the hips. Foot placement is crucial: the feet should be planted flat on the floor, spaced about hip-width apart. This ensures the shins are vertical, creating a 90-degree angle at the knee at the top of the movement.
Once the barbell is loaded and resting comfortably in the hip crease, the movement starts from the fully extended top position, where the hips, knees, and shoulders form a straight line. Execution is slow and controlled, focusing on a minimal eccentric (lowering) phase. The hips should only be lowered a few inches, stopping well before the knees track back behind the ankles.
The goal is to maintain tension, so the descent should be controlled, often recommending a slow three-second count, before immediately driving the hips back up. At the apex, perform a forceful squeeze of the glutes, often with a brief one- to three-second hold, before initiating the next short-range repetition. Maintaining a neutral spine and keeping the chin tucked throughout the set is essential to prevent the lower back from compensating.
Targeted Muscle Engagement
The physiological impact of the Kas Hip Thrust’s limited range of motion is its ability to maximize time under tension (TUT) specifically on the gluteus maximus. By eliminating the bottom portion of the lift, where the glutes are in a more lengthened, relaxed state, the muscle remains contracted throughout the entire set. This sustained mechanical tension is a primary driver of muscle hypertrophy, or growth.
The standard, full-range hip thrust recruits the glutes, hamstrings, and quadriceps, making it excellent for building maximal strength and power with heavy loads. In contrast, the Kas variation minimizes the involvement of the hamstrings and quads because the hips never descend far enough to utilize their full stretch reflex. This isolation ensures the glutes are the primary muscle group performing the work.
The exercise favors tension-focused lifting over strength-focused lifting. The slower tempo and shorter stroke create a prolonged engagement ideal for generating metabolic stress and a localized “pump,” which contributes significantly to muscle building. This makes the Kas Hip Thrust a preferred choice for individuals whose goal is to specifically develop the size and shape of the glutes without relying on the heavier weights typically used for full-range, strength-focused movements.