National Council on Strength & Fitness - NCSF

The same hip-flexor stretch reaches a different muscle depending on how much the knee is bent.

The re**us femoris is part of the quadriceps. It crosses both the hip and the knee, and it also extends the knee. The iliopsoas - iliacus and psoas major - acts at the hip only.

Because those two reach their length-tension limit at different knee angles, the knee position during a stretch or assessment decides which one is targeted. High knee flexion with hip extension loads the re**us femoris. A straighter leg shifts the emphasis to the iliopsoas.

For a working coach: "tight hip flexors" is two muscles with two stretch positions. If every hip-flexor stretch in the program uses the same knee angle, one of them is being left out.

In a survey sent to all NCSF Certified Strength Coaches, we found that 76% work under the title and in the practice of a Strength & Conditioning Coach. NCCA-accredited, the same gold-standard framework behind the field's leading credentials.

Each sling coordinates a specific locomotion pattern, and a different exercise menu trains it.

Anterior oblique sling — sagittal-plane locomotion (walking, jogging).

Bulgarian with single-arm dumbbell raise. Forward lunge with alternate-arm band punch.

Posterior oblique sling — propulsion and counter-rotation through the contralateral lat-glute connection. Reverse lunge with single-arm band row.

Reverse lunge with single-arm cable row. Dumbbell single-leg RDL to overhead swing.

Lateral sling — pelvis stabilized on an anchored base for climbing and stepping.
Lateral step-up with sandbag overs. Ballistic side-step overs.

Deep posterior longitudinal sling — forward acceleration via ground reaction force traveling across the erectors, thoracolumbar fascia, biceps femoris, and peroneals. Smith machine leg swings with plantar flexion. Power skip bounds.

For the working coach: each exercise trains coordination of strength across body segments, not isolation of a single muscle.

The body controls a joint with three systems.

Local stabilizers fire anticipatorily — before force arrives — to lock joint position.

They're small (pelvic floor, transverse abdominis, multifidus) and don't produce visible movement when they contract. They brace.

Global stabilizers tend to contract eccentrically. They control the range of motion at a segment and handle deceleration and rotational control.

Global movers tend to contract concentrically. They generate torque to produce movement, and absorb shock when external force arrives — the pectorals during a football block.

At the trunk — where the risk for inefficiency is greatest because of its high joint count — the local system forms a four-walled box around the spine. Transverse abdominis at the front, maintaining intra-abdominal pressure. Diaphragm at the top, contracting simultaneously with the TVA. Pelvic floor at the bottom, anchoring the pelvic girdle in response to abdominal bracing. Multifidus and internal obliques at the back, regulating spinal positioning and stiffening reactively to protect the discs.

For the working coach: training the local system is training the brace that fires before force arrives.

In a survey sent to all NCSF Certified Strength Coaches, we found that 90% perform strength and conditioning in their current role. The credential hiring managers and directors look for.

In a force couple, opposing muscles work as synergists.

Force couples are pairs of muscles that act on the same joint to produce rotational forces — often pulling in opposite directions — that maintain joint position while the joint moves. The pair is often prime mover plus stabilizer, or agonist plus antagonist. Either way, both qualify as synergists when their opposing pulls produce the rotation that centers the joint.

Three common examples:
Shoulder abduction. Deltoid and rotator cuff.
Scapular rotation. Upper and lower trapezius.
Trunk rotation. Internal and external obliques.

For a working coach: maintaining joint position is the work of the couple, not of the prime mover alone.

Force transfer runs on four slings.

Muscle force doesn't stop at the insertion site. Fascia carries contractile force across body segments, and four force-coupling systems — the slings — channel that transfer across the spine and pelvis during movements of the arms and legs.

Anterior oblique sling. External oblique, anterior abdominal fascia, contralateral internal oblique, and hip adductors. It creates cross-stabilization for the pelvis and trunk during sagittal-plane locomotion — walking and jogging — firing diagonally as the lower limb swings and the opposite arm counterbalances. Athletes who need to accelerate quickly depend on it.

Posterior oblique sling. Latissimus dorsi, thoracolumbar fascia, and gluteus maximus.

The counter cross-beam to the anterior system: the glutes fire for hip extension to drive propulsion while the contralateral lat provides counter-rotation through the thoracolumbar fascia.

Deep posterior longitudinal sling. Erector spinae, deep thoracolumbar fascia,
sacrotuberous ligament, biceps femoris, and peroneals. An elongated, top-down system for forward acceleration — ground reaction force travels from the erectors through the biceps femoris and out to the peroneals for ankle and foot stability.

Lateral sling. Gluteus medius/minimus, TFL, ipsilateral adductors, and contralateral QL. It stabilizes the hips on an anchored base for climbing and stepping. Most lifters have built the strength. Coordinating it across these systems is the part the weight room often leaves untrained.

In a survey sent to all NCSF Certified Strength Coaches, we found a 92% employment rate. The NCSF CSC is NCCA-accredited and cited in NCAA guidance for collegiate strength coaches.

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Fasting's downstream effects extend past the cellular and hormonal cascades into the gut microbiota.

In addition to fasting's many effects on cells throughout the body and brain, the literature notes that fasting may elicit changes in gut microbiota composition that carry their own protective effect against obesity. The mechanism isn't detailed in this article — the gut microbiota effect is named as one more pathway in fasting's downstream physiology.

The takeaway: fasting works through several mechanisms in parallel. The metabolic switch, the four-hormone cascade, the cellular protection in the nervous system, and gut microbiota changes are all on the list.