The Posterior Chain: Why Your Hamstrings Are the Engine for Everything

If you took a survey of where athletes are weakest relative to where they need to be strong for the Struggle Standard Test, the answer would be nearly universal: the posterior chain. Specifically, the hamstrings, glutes, and spinal erectors — the muscles running from heel to base of skull along the back of the body, collectively responsible for every hip extension, every load transfer, and every stride that the six events demand.

This is a nearly universal weakness in both strength athletes and endurance athletes, and it exists for the same reason in both: the exercises they prioritize either don't train the posterior chain adequately, or they train it in a pattern that develops it for one specific task while leaving others underdeveloped.

What the Posterior Chain Is

The posterior chain is not a specific muscle. It is a functional classification of muscles that work together to extend the hip, extend the knee (through the hamstrings' hip extension role), and stabilize the spine under load:

• Hamstrings — The only muscles that cross both the hip and knee joint, simultaneously responsible for hip extension and knee flexion. This dual-joint function is why isolated leg curls are inadequate — they train only the knee flexion function, not the hip extension function that the hamstrings perform during running, squatting, and pulling.
• Gluteus maximus — The largest muscle by volume, and the primary hip extensor. Powers the deadlift lockout, the running drive phase, and the squat ascent.
• Spinal erectors — Maintain lumbar and thoracic extension under axial load. They are not primarily prime movers — they are postural stabilizers that allow the hips and legs to generate force without the spine collapsing.

Simmons is categorical: "The hamstrings, glutes, all back muscles, and hips — for squatting or deadlifting, the posterior chain must be developed." The posterior chain is the limiting factor in more lifts than most athletes realize.

The Posterior Chain in the Deadlift

A weak hamstring shows up as a forward lean in the first portion of the deadlift pull — the hips rise faster than the shoulders, the back angle increases, and the lift transitions from a leg-and-back movement to an almost entirely lower back movement. This is mechanically inefficient and injury-prone.

Simmons' solution is specific: glute-ham raises, reverse hyperextensions, Romanian deadlifts, banded good mornings — exercises that train the posterior chain in the pattern that the deadlift and squat demand, without the CNS cost of deadlifting itself. In the program, leg curls (Day 5, 3×15–20) and GHR variations (Day 3) cover both functions: the leg curl trains the isolated knee flexion function; the GHR trains the full dual-joint function simultaneously through the complete range of motion.

The Posterior Chain in Running

Running economy — the oxygen cost per unit of distance at a given speed — is significantly determined by the strength and power of the hip extension chain. Each running stride is powered primarily by hip extension: the glutes and hamstrings driving the leg backward, propelling the body forward. The quads, despite their prominence in running folklore, are primarily responsible for absorbing impact force and maintaining joint stability, not for generating propulsive force.

A well-trained posterior chain allows maintained hip extension power and forward propulsion as fatigue accumulates. A poorly-trained posterior chain produces an athlete whose stride length shortens markedly in the final portion of Event 5, whose hips drop and weight shifts forward, and whose running economy degrades faster than their aerobic capacity would predict.

The sled drag is the most direct posterior chain training tool for running economy — it trains the glutes and hamstrings in the exact contraction pattern used during the running drive phase, over distance, building endurance capacity in the specific movement pattern.

The Posterior Chain in Carry Events

Event 6's carry components demand sustained isometric tension in the erectors and sustained eccentric control in the hamstrings and glutes during each step under a load that simultaneously challenges grip, trunk, and posture. The collapse pattern in carries is predictable: first the grip starts to fail, then trunk flexion forward compensates, which inhibits the glutes and shifts more work onto the already-compromised lower back.

The fix is a strong posterior chain trained for sustained tension under load over distance — a sled drag adaptation, not a GHR adaptation. And trunk stability work: the anti-rotation work on Day 3 (cable anti-rotation, bear hug carries, pallof press variations) is critical because a stable trunk under load requires the erectors and obliques to co-contract isometrically throughout the carry.

Why the Good Morning Is in the ME Rotation

The Anderson Good Morning with Mini Bands as a Wave 3 ME lower exercise trains erector strength through a large range of motion under maximal load — with the erectors acting as prime movers, not stabilizers. This trains erector strength through the range of motion most vulnerable in the deadlift: the mid-pull, where the back angle is most prone to rounding under fatigue. The mini bands add accommodating resistance, forcing the erector to sustain maximum effort through the full range.

Build the posterior chain. Everything else gets stronger with it. Every event in the Struggle Standard Test is limited, at some point, by the strength and endurance of the muscles running up the back of the body. This is where the program pays the most attention. This is where you should too.