Quick Answer
The principle: Compound free-weight exercises (squats, deadlifts, lunges, split squats) are the foundation of leg training. Machines are most effective as accessory work — adding isolated volume, correcting specific weaknesses, and training to failure safely. Do compounds first; use machines to finish the session.
Leg Machines vs Free Weights: What the Research Shows
The practical debate — machines vs free weights — has a reasonably clear research answer. A 2020 study by Schwanbeck et al. in the Journal of Strength and Conditioning Research found no significant difference in muscle mass or strength gains between free-weight and machine training over 10 weeks. Both modalities produce hypertrophy effectively when volume and progressive overload are equivalent.
What differs is the type of adaptation. Free-weight exercises recruit stabiliser muscles — the core, hip stabilisers, and single-leg balance systems — that machines deliberately remove from the equation. This stabiliser recruitment transfers to functional athletic performance (running, cycling, sport) in ways that machine work does not fully replicate. Machines, by contrast, allow more precise muscle isolation, safer training to failure (the machine catches the weight if form breaks), and more consistent load across the full range of motion through a fixed movement pattern.
The practical recommendation: build your leg training around 2–3 free-weight compound movements (squat or split squat, deadlift variant, hip thrust or lunge), then use machines to add isolated volume to specific muscles. A typical well-structured leg session might be: barbell squat → Romanian deadlift → leg press → lying leg curl → standing calf raise. The free-weight compounds do the heavy lifting (literally and physiologically); the machines add targeted volume without the neural fatigue of more free-weight work. Our gym exercises for runners guide and strength training programme for runners both cover how machines fit into a runner’s weekly gym structure specifically.
The Leg Machines: A Complete Reference
| Machine | Primary muscles | Type | Best for | Sets × Reps |
|---|---|---|---|---|
| Leg press (45°) | Quads, glutes, hamstrings | Compound | High-volume lower body load without spinal stress | 3–4 × 8–15 |
| Hack squat | Quads (dominant), glutes | Compound | Deep quad development with controlled ROM | 3–4 × 8–12 |
| Leg extension | Quadriceps (isolation) | Isolation | VMO activation; quad finisher | 3 × 12–15 |
| Lying leg curl | Hamstrings (lengthened) | Isolation | Best hamstring isolation; injury prevention | 3–4 × 10–12 |
| Seated leg curl | Hamstrings (shortened) | Isolation | Hamstring volume; less hip flexor involvement | 3 × 12–15 |
| Standing calf raise | Gastrocnemius | Isolation | Calf mass and Achilles resilience | 3–4 × 10–15 (slow eccentric) |
| Seated calf raise | Soleus | Isolation | Deep calf/soleus strength; essential for runners | 3 × 12–15 |
| Hip abductor machine | Glute medius, TFL | Isolation | Hip stability; knee valgus correction | 3 × 15–20 |
| Hip adductor machine | Adductors (inner thigh) | Isolation | Groin strength; hip stability balance | 3 × 15–20 |
| Hip thrust machine | Gluteus maximus | Isolation | Direct glute loading; push-off strength | 3–4 × 10–15 |
Leg Press
The leg press is the most productive leg machine in most gyms. It trains the quadriceps, glutes, and hamstrings simultaneously through a large range of motion under significant load, with the back supported — removing the spinal compression of barbell squats. This makes it ideal for adding high-volume lower body work after squat and deadlift variations have already loaded the spinal erectors.
Setup: Adjust the seat so that when feet are on the platform, knees are bent at approximately 90 degrees. Feet hip-width apart, toes slightly turned out (10–15 degrees).
Execution: Lower the weight by bending the knees until they approach 90 degrees (or slightly below if hip mobility allows), then press through the whole foot — not just the toes — to return to the start. Never lock the knees out fully at the top; keep tension in the muscles throughout.
Foot position variations: High foot placement (feet near the top of the platform) increases glute and hamstring involvement. Low foot placement (feet near the bottom) increases quad demand. Wide stance with toes out targets the inner quad and adductors more. Narrow stance emphasises the outer quad. Experimenting with these positions lets you target specific weaknesses without changing machines.
Key warning: Never allow the lower back to peel off the seat at the bottom of the range. This is almost always a sign that the range of motion has exceeded hip mobility, creating lumbar flexion under load. Reduce the depth until the spine stays neutral throughout.
Hack Squat
The hack squat machine places the body in a fixed inclined position, with feet on a platform and the back and shoulders against a padded surface. The movement closely mimics a squat but with the trunk angle fixed, which places a greater emphasis on the quadriceps than the standard leg press. The range of motion is also typically larger, producing a deeper knee flexion and more thorough quad stimulus.
Setup: Adjust shoulder pads to fit snugly on the trapezius. Feet hip-width, toes slightly out, positioned mid-platform (experimenting with higher or lower changes the muscle emphasis similarly to the leg press).
Execution: Unlock the weight and lower slowly to the bottom of the range — typically until thighs are below parallel to the platform. Drive through the heels to return. Keep the core braced throughout and avoid letting the knees cave inward at any point.
The hack squat is particularly useful for athletes who want to develop deep quad strength and those who find barbell back squats uncomfortable due to shoulder mobility restrictions. It is a more demanding machine than the leg press and should typically come before rather than after it in a session.
Leg Extension Machine
The leg extension isolates the quadriceps — specifically by extending the knee against resistance through the terminal range of motion. It is the only machine that trains the quads in the shortened position (fully extended knee) and specifically activates the vastus medialis oblique (VMO), the teardrop-shaped inner quad muscle that is frequently undertrained and important for knee tracking and stability.
Setup: Adjust the seat so the knee joint aligns with the machine’s pivot point. Adjust the shin pad so it sits just above the ankle, not mid-shin.
Execution: Extend the legs fully, pause briefly at the top (this isometric hold at full extension specifically activates the VMO), then lower slowly — 3–4 seconds on the descent. Avoid letting the hips lift off the seat, which indicates the weight is too heavy.
Context: There has been debate about whether leg extensions are harmful to the knee due to the shear force they create at the joint. Current evidence suggests they are safe for most people at moderate loads and with controlled technique. They are best used as an accessory exercise after compound work — not as the primary leg exercise. For runners, the leg extension serves as a useful tool for building VMO strength that supports knee stability on single-leg landing, though it should be supplemented with single-leg exercises that train this in a functional context. Our runner’s lunge guide covers the hip flexor flexibility work that pairs with quad isolation to create balanced lower body training.
Lying and Seated Leg Curl
The hamstrings are among the most injury-prone muscles in runners and most undertrained in gym-goers who focus predominantly on quad-dominant exercises. Both lying and seated leg curl machines address this gap, but through slightly different mechanisms.
The lying (prone) leg curl — performed face-down with the shin pad behind the ankles — trains the hamstrings in a stretched, hip-extended position. This lengthened position produces greater muscle damage and hypertrophic stimulus, making it the preferred variant for building hamstring mass and strength. The lying position also means the hip flexors don’t significantly interfere with the movement.
The seated leg curl — performed sitting upright — trains the hamstrings in a more shortened position at the hip. This variant is useful for adding additional volume and provides variety across the week.
Setup (lying): Lie face-down with the knee joint aligned with the machine’s pivot and the shin pad resting comfortably above the ankles. Grip the handles lightly for stability.
Execution: Curl the ankles toward the glutes with control, pause at the top, then lower slowly over 3 seconds. Avoid letting the hips lift or the lower back arch — this indicates the load is too heavy. For runners, a slow 3–4 second eccentric (lowering phase) directly trains the type of hamstring strength most protective against running-related hamstring strains.
Standing and Seated Calf Raise
The calf complex consists of two primary muscles: the gastrocnemius (the larger, more superficial muscle that creates the visible shape of the calf) and the soleus (the deeper muscle beneath it). They are trained differently because the gastrocnemius crosses the knee joint while the soleus does not.
Standing calf raise (knee straight): With the knee extended, the gastrocnemius is in an optimal position to contribute maximally. This is the primary machine for gastrocnemius and overall calf mass development. Stand on the edge of the platform with heels dropping below the level of the step for a full range eccentric, rise onto the ball of the foot, pause, then lower slowly. The eccentric loading (slow lowering) is the most important phase for Achilles tendon resilience — a critical training priority for any runner.
Seated calf raise (knee bent): With the knee bent at approximately 90 degrees, the gastrocnemius is shortened and contributes less, placing more demand on the soleus. The soleus is predominantly slow-twitch and responds well to higher rep ranges and consistent training. It is a key muscle for endurance running and is often undertrained because people assume calf raises are calf raises — without understanding the knee position distinction.
For runners and endurance athletes, both machines are essential. Our tibialis anterior exercises guide covers the complementary front-of-shin work that pairs with calf machine training for complete lower leg balance.
Hip Abductor and Adductor Machines
The hip abductor machine (legs start together, push outward against resistance) targets the gluteus medius, gluteus minimus, and tensor fascia latae — the muscles responsible for stabilising the pelvis when on a single leg. Hip abductor weakness is a common finding in runners who present with IT band syndrome, patellofemoral pain, and knee valgus under fatigue. Building abductor strength through this machine directly addresses one of the most common injury mechanisms in endurance athletes.
The hip adductor machine (legs start wide, pull together against resistance) targets the adductor longus, brevis, magnus, and gracilis — the inner thigh muscles that provide medial hip stability. Adductor strengthening reduces groin strain risk and improves the overall hip stability that supports efficient running mechanics.
Setup: Both machines: set the pads to the appropriate width for the start position. Sit upright, not leaning forward. Focus on driving the movement from the hips rather than shifting the entire trunk.
Practical note: Both machines are best used at moderate loads with controlled tempo (2 seconds in each direction) rather than heavy loads that compromise range of motion. 3 × 15–20 reps builds the endurance strength these muscles need for their stabilising role during running.
Hip Thrust Machine
The hip thrust machine — increasingly common in commercial gyms — provides the most direct loading of the gluteus maximus available on a machine. The barbell hip thrust has strong research support for glute activation and hypertrophy; the machine version replicates the movement pattern with selectorized resistance and a fixed movement path, making it more accessible and appropriate for those new to the exercise.
Setup: Set the resistance pad to rest comfortably across the hip crease — not across the abdomen or mid-thigh. Back against the padded rest, feet flat on the floor and hip-width apart.
Execution: Drive the hips upward by squeezing the glutes, arriving at a straight line from shoulder to knee at the top position. Pause at the top with a strong glute contraction for 1–2 seconds. Lower slowly. The gluteus maximus is the primary driver of hip extension during running — strong glutes at full extension translate directly to push-off power and reduced lower back load across high-mileage training weeks.
How to Structure a Leg Machine Session
Most gym sessions should combine free-weight compounds with machine work. A practical template for an intermediate athlete doing 2 leg sessions per week might be:
Session 1 (quad emphasis): Barbell back squat or hack squat → leg press → lying leg curl → leg extension → standing calf raise.
Session 2 (posterior chain emphasis): Romanian deadlift → split squat or Bulgarian split squat → seated leg curl → hip thrust machine → hip abductor machine → seated calf raise.
Machines always follow the free-weight compound exercises — not precede them. Within the machine section, start with the larger compound-style machines (leg press, hack squat) before isolation work (leg extension, leg curl). This sequence ensures the highest-quality effort goes to the movements that produce the most total muscle stimulus.
For runners specifically, the highest-priority machines are the standing calf raise (Achilles resilience), the lying leg curl (hamstring injury prevention), and the hip abductor (glute medius and knee stability). These three address the specific muscular gaps most likely to produce injury under high running mileage.
Structure Your Strength Work Alongside Your Running
SportCoaching's running training plans and coaching integrate gym session scheduling alongside running — so your strength work supports your running, rather than competing with it for recovery.
FAQ: Leg Training Machines
What is the best leg machine at the gym?
The leg press is the most versatile — compound, heavy loading, adjustable foot position. For hamstrings, the lying leg curl is the most effective isolation machine. The hack squat provides superior quad development with greater ROM. No single machine covers all leg muscles; a complete session uses 2–3 machines alongside free-weight compounds.
Are leg machines as effective as free weights?
For muscle mass: research shows no significant difference (Schwanbeck et al. 2020, J Strength Cond Research). For functional strength and stabiliser development: free weights are superior. Best practice: compound free weights as the foundation, machines as accessory work for volume and isolation.
What muscles do leg machines work?
Leg press/hack squat: quads, glutes, hamstrings (compound). Leg extension: quads only. Lying/seated leg curl: hamstrings only. Standing calf raise: gastrocnemius. Seated calf raise: soleus. Hip abductor: glute medius, TFL. Hip adductor: inner thigh. Hip thrust machine: gluteus maximus.
How many sets should I do on leg machines?
3–4 sets per exercise for most machine work. Beginners start with 2–3 sets. 8–15 reps for compound-style machines (leg press, hack squat); 12–20 reps for isolation machines (leg curl, calf raise). Progressive overload over time — increasing load, reps, or sets — is the primary driver of results regardless of rep range.
Should I use leg machines before or after free weights?
Always after. Free-weight compounds (squats, deadlifts, lunges) require more neuromuscular coordination and should be done when the nervous system is freshest. Machines add isolated volume after the main compound work is complete. Exception: the leg press can serve as a primary exercise if squats aren’t in the session, but it still comes before isolation work.
