Exercises and muscles targeted

Exercise	Muscles Targeted
Seated Leg Extension	Quadriceps (Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius, all four heads, primary), Tibialis Anterior (stabiliser at ankle during full extension)
Leg Extension — Terminal Knee Extension (partial ROM)	Vastus Medialis Oblique (VMO) (primary in the last 30 degrees of extension), Rectus Femoris (secondary), commonly used in knee rehabilitation and VMO-focused programming
Leg Extension — Isometric Hold (peak)	Quadriceps (sustained isometric contraction at full knee extension), Tibialis Anterior (sustained stabiliser), Rectus Femoris (isometric at hip and knee simultaneously)
Prone Leg Curl	Biceps Femoris (long and short heads, primary), Semimembranosus (primary), Semitendinosus (primary), Gastrocnemius (secondary, assists knee flexion), Popliteus (stabiliser at knee initiation)
Prone Leg Curl — Toes Plantarflexed	Biceps Femoris (primary), Semimembranosus, Semitendinosus, Gastrocnemius (increased contribution when foot is pointed, secondary to primary depending on load)
Prone Leg Curl — Toes Dorsiflexed	Biceps Femoris (primary), Semimembranosus and Semitendinosus (primary), Gastrocnemius (reduced — dorsiflexed ankle shortens gastrocnemius and limits its contribution), greater isolated hamstring focus
Prone Leg Curl — Isometric Hold (peak flexion)	Hamstrings (all three heads, sustained isometric at full knee flexion), Gastrocnemius (isometric), Popliteus (knee joint stabiliser)

The leg extension and prone leg curl cover the two opposing movement functions of the knee joint in isolation: extension driven by the quadriceps, and flexion driven by the hamstrings. Neither movement can be adequately replicated by compound exercises alone, as squats and deadlifts always load these muscles in combination with the hip and require significant stabiliser involvement. The DSA031 isolates each muscle group purely through the knee joint with no hip involvement required, which makes it the appropriate tool for direct quad and hamstring hypertrophy work, knee rehabilitation programming, and addressing strength imbalances between the two muscle groups.

Who this machine is built for

Serious Home Gym Builders
Dedicated leg extension and prone leg curl machines are two of the most commonly omitted pieces of equipment in home gyms because they appear to serve narrow purposes at a high space cost. The DSA031 resolves this by putting both in a 45.4" × 62.1" footprint from a single weight stack. For a home gym that already covers squatting and hip hinge patterns with compound equipment, the DSA031 adds the quad and hamstring isolation layer that compound movements alone cannot deliver.

Bodybuilders and Physique Athletes
Quad sweep, VMO fullness, and hamstring separation are the specific aesthetic outcomes that leg extensions and prone leg curls develop, and they require dedicated isolation volume that barbell squats and Romanian deadlifts cannot produce in the same training effect. The DSA031 covers both from the same station, which allows a complete quad and hamstring isolation circuit without moving to a second machine. The foot angle variation on the prone curl also allows the gastrocnemius contribution to be increased or reduced depending on whether the session priority is pure hamstring isolation or broader posterior chain work.

Commercial Gym Owners and Operators
Leg extension and leg curl machines are two of the highest-traffic stations in any commercial facility. A dual-function machine that covers both from one unit reduces the footprint required for complete lower body isolation coverage and keeps members cycling through the station faster when one mode is occupied. The DSA031's 503 lb total weight keeps it grounded under continuous bilateral and unilateral use, and the fully enclosed shroud system protects the cable and pulley components from the accumulation that high-use stations experience in commercial environments.

Physical Therapists and Sports Medicine Practitioners
The leg extension in its terminal range (the final 30 degrees of knee extension) is a standard VMO activation exercise in knee rehabilitation protocols following patellofemoral conditions and ACL recovery, depending on the clinical protocol in use. The prone leg curl is similarly used for progressive hamstring loading in rehabilitation contexts where hip-loaded hamstring exercises cannot yet be tolerated. The DSA031's selectorized precision allows exact load prescription per session, and the pop pin mode switch allows the same machine to deliver both exercises within a single rehabilitation session. Exercise selection and loading must always follow the specific clinical programme and practitioner guidance for each patient.

University and College Athletic Departments
Quad-to-hamstring strength ratio is a standard screening metric in athletic injury prevention programmes. Athletes with weaker hamstrings relative to their quadriceps carry a higher risk profile for knee and hamstring injuries during deceleration and cutting movements. The DSA031 allows S&C coaches to address both sides of the ratio from a single machine, testing and training each direction independently and tracking the balance across a training cycle. The dual-function format also improves session efficiency when multiple athletes are rotating through a lower body isolation circuit.

Private Personal Training Studios
The mode switch between leg extension and prone leg curl on the DSA031 requires no cable or pulley adjustment, only a change in body position and the two pop pin adjustments for the pivot frame. A trainer can move a client from quad extension to hamstring curl in under a minute without losing session momentum. The gas spring back pad holds the prone position without requiring the client to manually brace against it, which removes a common comfort barrier for clients who find prone machine positions uncomfortable on less well-designed alternatives.

How to setup and use

Setting Up the DSA031 for Leg Extension

Sit on the seat pad with your back against the back pad and your knees aligned with the pivot shaft of the pivot frame assembly, which is the correct contact point for the exercise to load through the knee joint correctly.
Position the front roller pads against the tops of the shins just above the ankle so the resistance contacts the lower leg at the correct drive point for knee extension.
Grip the front long handles (the longer grips positioned at the sides of the seat) for stability during the extension movement.
Adjust the seat position using the pop pin if needed so the back of the knees rest against the front edge of the seat pad without pressure cutting into the thigh during the movement.
Select your working weight using the selector pin and confirm it is fully seated before beginning the set.

Setting Up the DSA031 for Prone Leg Curl

Reposition from seated to prone by lying face-down on the back pad with the hips resting at the pad edge and the legs hanging over the roller end of the machine.
Position the rear roller pads under the ankles or lower calves so the resistance contacts the leg at the correct point for knee flexion without the rollers sitting too high on the calf muscle itself.
Grip the rear shorter handles positioned at the top of the machine near the back pad for stability during the curl movement.
Confirm the gas spring back pad is supporting the chest and abdomen comfortably in the prone position before selecting weight.
Adjust the weight if needed using the same selector pin, as the effective load for prone leg curl may differ from the leg extension weight due to the different leverage involved.

Performing Leg Extension

From the starting position with legs hanging at approximately 90 degrees, drive both legs upward simultaneously by straightening the knees until the legs are fully extended and the quadriceps are at peak contraction.
Pause at the top for one to two seconds to hold the peak contraction before beginning the controlled lowering phase.
Lower the legs back toward 90 degrees under control over at least two seconds rather than letting the weight stack drop, as the eccentric phase produces a significant training stimulus for quad development.
Complete all reps, then return legs to the resting position before dismounting.

Performing Prone Leg Curl

From the prone starting position with legs nearly extended on the rollers, curl both legs simultaneously toward the glutes by bending the knees as far as comfortable range allows.
Keep the hips pressed against the back pad throughout the curl to prevent the pelvis from lifting, which would shift load away from the hamstrings toward the hip flexors.
Pause briefly at peak flexion, then lower the legs back under control to the starting position over at least two seconds.
Complete all reps, then return legs to the extended starting position before dismounting from the prone position.

Owner's Manual

Access the complete assembly guide, parts list, and maintenance schedule below.

Download Owners Manual

Shipping & Delivery

All Dynasty Fitness equipment ships free across the 48 contiguous US states via freight carrier. If the product description says preorder, we'll send you an estimated delivery date via email.

Estimated delivery: 7–14 business days from order confirmation. You will receive a tracking number and a delivery window confirmation call before your shipment arrives. Deliveries are curbside standard, white glove delivery to room of choice is available at checkout.

Returns: Free within 30 days of delivery. Items must be in original condition and packaging. Refunds processed within 5 business days of return receipt.

Questions? Contact our team at:
📧Email: info@thedynastyfitness.com
📞Call: +1 (213)-584-0858

Need a buying guide?

Looking for one to one support before making final decision?
Feel free to contact us. Our expert support team would love to assist you.

Need Installation Help?

We have partnered with another company to help provide installation around the country. Please use the link below to see the price per machine for installation
See Installation Rates

Payment & Security

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Save 10%

Leg Extension Prone Leg Curl DSA031

$2,429.00

$2,429.00 ~~$2,699.00~~ 10% off (Save$270.00 )

Commercial Grade
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The Dynasty Fitness DSA031 Leg Extension Prone Leg Curl is a dual-function selectorized machine that trains the quadriceps through seated leg extension and the hamstrings through prone leg curl from the same pivot frame and weight stack. A pivot frame assembly running on two 6005-2Z bearings with two independent pop pins manages the transition between modes, while dual roller sets and two separate handle configurations orient the body correctly for each exercise without requiring any cable or pulley adjustment. Built from Q235A cold-rolled steel with a 200 lb selectorized weight stack and a gas spring back pad for comfortable prone positioning, the DSA031 covers both primary knee joint isolation movements in a single 45.4" × 62.1" footprint. It is built for commercial facilities, private training studios, and home gyms where complete quad and hamstring isolation training is a programme requirement without the floor space cost of two separate dedicated machines.

Dual-function selectorized machine covering seated leg extension for quadriceps and prone leg curl for hamstrings from the same pivot frame and 200 lb weight stack
Two independent pop pins and a precision pivot frame assembly on 6005-2Z bearings switch between exercise modes without cable adjustment, attachment changes, or pulley reconfiguration
Dedicated front handles for leg extension and separate rear handles for prone leg curl orient the body correctly for each movement so grip position actively supports the exercise rather than being neutral
Gas spring back pad holds the prone position comfortably during hamstring curl sets so the lumbar spine stays supported without the user having to brace against the pad throughout the set

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Exercises and muscles targeted

Exercise	Muscles Targeted
Seated Leg Extension	Quadriceps (Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius, all four heads, primary), Tibialis Anterior (stabiliser at ankle during full extension)
Leg Extension — Terminal Knee Extension (partial ROM)	Vastus Medialis Oblique (VMO) (primary in the last 30 degrees of extension), Rectus Femoris (secondary), commonly used in knee rehabilitation and VMO-focused programming
Leg Extension — Isometric Hold (peak)	Quadriceps (sustained isometric contraction at full knee extension), Tibialis Anterior (sustained stabiliser), Rectus Femoris (isometric at hip and knee simultaneously)
Prone Leg Curl	Biceps Femoris (long and short heads, primary), Semimembranosus (primary), Semitendinosus (primary), Gastrocnemius (secondary, assists knee flexion), Popliteus (stabiliser at knee initiation)
Prone Leg Curl — Toes Plantarflexed	Biceps Femoris (primary), Semimembranosus, Semitendinosus, Gastrocnemius (increased contribution when foot is pointed, secondary to primary depending on load)
Prone Leg Curl — Toes Dorsiflexed	Biceps Femoris (primary), Semimembranosus and Semitendinosus (primary), Gastrocnemius (reduced — dorsiflexed ankle shortens gastrocnemius and limits its contribution), greater isolated hamstring focus
Prone Leg Curl — Isometric Hold (peak flexion)	Hamstrings (all three heads, sustained isometric at full knee flexion), Gastrocnemius (isometric), Popliteus (knee joint stabiliser)

Who this machine is built for

How to setup and use

Setting Up the DSA031 for Leg Extension

Sit on the seat pad with your back against the back pad and your knees aligned with the pivot shaft of the pivot frame assembly, which is the correct contact point for the exercise to load through the knee joint correctly.
Position the front roller pads against the tops of the shins just above the ankle so the resistance contacts the lower leg at the correct drive point for knee extension.
Grip the front long handles (the longer grips positioned at the sides of the seat) for stability during the extension movement.
Adjust the seat position using the pop pin if needed so the back of the knees rest against the front edge of the seat pad without pressure cutting into the thigh during the movement.
Select your working weight using the selector pin and confirm it is fully seated before beginning the set.

Setting Up the DSA031 for Prone Leg Curl

Reposition from seated to prone by lying face-down on the back pad with the hips resting at the pad edge and the legs hanging over the roller end of the machine.
Position the rear roller pads under the ankles or lower calves so the resistance contacts the leg at the correct point for knee flexion without the rollers sitting too high on the calf muscle itself.
Grip the rear shorter handles positioned at the top of the machine near the back pad for stability during the curl movement.
Confirm the gas spring back pad is supporting the chest and abdomen comfortably in the prone position before selecting weight.
Adjust the weight if needed using the same selector pin, as the effective load for prone leg curl may differ from the leg extension weight due to the different leverage involved.

Performing Leg Extension

From the starting position with legs hanging at approximately 90 degrees, drive both legs upward simultaneously by straightening the knees until the legs are fully extended and the quadriceps are at peak contraction.
Pause at the top for one to two seconds to hold the peak contraction before beginning the controlled lowering phase.
Lower the legs back toward 90 degrees under control over at least two seconds rather than letting the weight stack drop, as the eccentric phase produces a significant training stimulus for quad development.
Complete all reps, then return legs to the resting position before dismounting.

Performing Prone Leg Curl

From the prone starting position with legs nearly extended on the rollers, curl both legs simultaneously toward the glutes by bending the knees as far as comfortable range allows.
Keep the hips pressed against the back pad throughout the curl to prevent the pelvis from lifting, which would shift load away from the hamstrings toward the hip flexors.
Pause briefly at peak flexion, then lower the legs back under control to the starting position over at least two seconds.
Complete all reps, then return legs to the extended starting position before dismounting from the prone position.

Owner's Manual

Access the complete assembly guide, parts list, and maintenance schedule below.

Download Owners Manual

Shipping & Delivery

All Dynasty Fitness equipment ships free across the 48 contiguous US states via freight carrier. If the product description says preorder, we'll send you an estimated delivery date via email.

Returns: Free within 30 days of delivery. Items must be in original condition and packaging. Refunds processed within 5 business days of return receipt.

Questions? Contact our team at:
📧Email: info@thedynastyfitness.com
📞Call: +1 (213)-584-0858

Need a buying guide?

Looking for one to one support before making final decision?
Feel free to contact us. Our expert support team would love to assist you.

Need Installation Help?

We have partnered with another company to help provide installation around the country. Please use the link below to see the price per machine for installation
See Installation Rates

Payment & Security

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Leg Extension Prone Leg Curl DSA031

$2,429.00

$2,429.00 ~~$2,699.00~~ 10% off (Save$270.00 )

Key Features

Dual-Function Pivot Frame with Two Independent Pop Pins

The pivot frame assembly sits on two 6005-2Z sealed bearings and manages the transition between leg extension and prone leg curl modes through two separate pop pins (Pop Pin I and Pop Pin II) that adjust the roller position and the resistance path for each exercise. No cable adjustment, no attachment swap, and no pulley reconfiguration is required to switch between modes. Unlike combo machines that require significant mechanical setup to move between exercise functions, the DSA031 changes modes purely through body position changes and two pop pin adjustments, making the transition practical within a single training session rather than a setup exercise in itself.

Four Roller Pads Across Two Foam Frame Assemblies

Four individual roller pads are distributed across two foam frame assemblies, providing the contact points for both leg extension and prone leg curl from the same pivot arm. The roller sleeve construction allows each pad to rotate against the skin surface as the leg moves through its arc, which reduces friction and the pressure point that a fixed pad creates against the shin or calf at different positions in the movement. Unlike single roller designs that concentrate load at one point throughout the arc, the multi-roller setup distributes contact across a larger surface area regardless of which exercise mode is active.

Dedicated Front and Rear Handle Sets

Two separate handle configurations serve the two exercise modes: longer front grips (STφ30×φ22×415mm) positioned at the sides of the seat for leg extension, and shorter rear grips (STφ30×φ22×130mm) positioned at the top of the back pad frame for prone leg curl. Having handles matched to each mode rather than a single universal grip means the hand position naturally supports the correct body alignment for each exercise. The front handles give the seated user a lateral brace during the extension drive, while the rear handles give the prone user a forward brace during the hamstring curl.

Gas Spring Back Pad for Prone Positioning

A gas spring mechanism supports the back pad frame, which holds the back pad at a fixed comfortable angle for the prone leg curl position. Without this support the pad would need to be manually positioned and could shift during the set as the user's body moves. The gas spring maintains consistent pad support throughout the prone curl without any user intervention, which keeps the chest and abdomen in a stable contact position from the first rep to the last. This is particularly relevant for heavier prone leg curl sets where any instability in the support surface translates directly into technique deviation.

Q235A Cold-Rolled Steel Frame with Dual Tubing Profile

The frame uses Q235A high-frequency cold-rolled steel in the DSA series construction standard: 40×140mm rectangular tubing for the primary structural members and 50×100mm oval tubing for the cross sections. The electrostatic powder coating passes 800 hours of salt spray testing. A dual-function machine carries more mechanical cycling than either single function alone, since the pivot frame and cable system serve two separate exercise patterns across the same daily volume. The DSA031's frame specification addresses this higher mechanical demand through the same commercial-rated construction used across the DSA series.

200 lb Selectorized Weight Stack with Full Shroud Enclosure

The 200 lb selectorized stack covers the full practical loading range for both leg extension and prone leg curl training, with pop pin selection allowing rapid weight changes between exercises and between warm-up and working sets. Front, top, and rear shrouds enclose the weight stack, cable, and pulley system from the training environment. The seven 4.5" pulleys routing the single cable through the weight stack frame and main frame assemblies are protected within the enclosure from the sweat and debris accumulation that accelerates wear in high-use commercial stations. Unlike open-frame alternatives, the full enclosure maintains both the mechanical integrity and the visual appearance of the machine under daily commercial training conditions.

Product Information
Product Name	Leg Extension Prone Leg Curl
Model	DSA031
Series	DSA Selectorized Series
Product Type	Dual-Function Selectorized Leg Extension and Prone Leg Curl Machine
Primary Function	Seated leg extension — quadriceps isolation
Secondary Function	Prone leg curl — hamstring isolation
Target Muscles	Quadriceps (leg extension), Hamstrings and Gastrocnemius (prone leg curl)
Grade	Commercial
Dimensions and Weight
Length	45.4 in (115.3 cm)
Width	62.1 in (157.8 cm)
Height	61.7 in (156.6 cm)
Total Weight	503 lbs (228 kg)
Resistance and Weight Stack
Maximum Weight Stack	200 lbs
Selector Mechanism	Pop pin with coil, tool-free
Cable System	Single cable
Pulley System	4.5" pulleys (x7 total — 3 in weight stack frame, 4 in main frame)
Adjustability and Mechanism
Mode Switching	Two independent pop pins (Pop Pin I and Pop Pin II) on pivot frame
Pivot Frame Bearings	6005-2Z sealed bearings (x2)
Back Pad Mechanism	Gas spring supported back pad frame
Roller Pads	4 rollers across 2 foam frame assemblies — serve both exercise modes
Handles and Pads
Front Handles (leg extension)	STφ30×φ22×415mm (x2)
Rear Handles (prone leg curl)	STφ30×φ22×130mm (x2)
Back Pad	Gas spring supported, serves prone curl position
Seat Pad	Fixed, serves seated leg extension position
Frame and Construction
Frame Material	Q235A high-frequency cold-rolled steel
Frame Tubing	40×140mm square tubing, 50×100mm oval tubing
Surface Finish	Electrostatic powder coating, 800+ hour salt spray rated
Weight Stack Finish	Cast iron with black textured powder coating
Shroud System	Front, top, and rear weight stack shrouds, fully enclosed
Indoor Use Only	Yes

Q: How do I switch between leg extension and prone leg curl mode?
A: Switching modes requires changing body position from seated to prone and adjusting the two pop pins on the pivot frame to reposition the rollers for the new exercise. No cable adjustment, attachment change, or pulley reconfiguration is needed. The front handles serve the seated leg extension position and the rear handles serve the prone leg curl. The full mode transition takes around one minute, which makes pairing leg extension and leg curl in a superset format practical from a single machine without significant session interruption.

Q: Does foot angle change which hamstring muscles are worked during prone leg curl?
A: Yes, and the difference is meaningful. When the toes are plantarflexed (pointed down) during the curl, the gastrocnemius is in a lengthened position at the ankle and contributes more to the knee flexion drive alongside the hamstrings. When the toes are dorsiflexed (pulled toward the shin), the gastrocnemius is shortened at the ankle and its contribution is reduced, placing more of the load on the biceps femoris, semimembranosus, and semitendinosus specifically. Most coaches recommend dorsiflexing the foot during prone leg curls when the goal is maximum hamstring isolation, and plantarflexing when a broader posterior chain response is the target.

Q: How does the seated leg extension compare to squats for quad development?
A: Squats develop the quadriceps as part of a compound movement pattern that simultaneously loads the glutes, hamstrings, and erectors, and requires the quads to work in coordination with those other muscle groups. The leg extension on the DSA031 isolates the quadriceps through the knee joint alone with no hip involvement, which means the quads work to failure independently of any other muscle group's contribution. The two movements are complementary rather than substitutes. Squats build overall leg mass and functional strength, while the leg extension adds isolated quad volume that compound movements alone cannot produce at the same muscle-specific intensity.

Q: Should I use the same weight for leg extension and prone leg curl?
A: Most users find they use a different weight for each exercise, as the quadriceps and hamstrings have different strength profiles and the lever arm differs between the two movements. Start each exercise at a conservative load on the first session, find the weight that allows controlled full-range reps with a two-second lowering phase, and track these separately. Comparing your leg extension and leg curl weights over time is also a useful indicator of the quad-to-hamstring strength ratio, which has implications for knee health and athletic injury risk.

Q: Can I use the DSA031 for single-leg training?
A: Single-leg leg extension and single-leg prone leg curl are both possible on the DSA031 by simply working one leg at a time with the other leg resting off the roller. This roughly doubles the effective resistance on the working leg relative to the selected weight, so reduce the stack by approximately half when moving from bilateral to unilateral sets. Single-leg work is particularly useful for identifying and addressing strength differences between the left and right leg, which can be masked during bilateral training where the stronger leg compensates for the weaker one.

Q: What Dynasty Fitness machines pair with the DSA031 for complete leg training?
A: The DSA031 covers knee joint isolation for both the quadriceps and hamstrings. For compound leg strength, the Belt Squat DPB312 adds squat pattern loading without spinal compression, and the Leg Press/Hack Squat DRE8016 covers the bilateral leg press and hack squat pattern from a selectorized station. For glute-specific training beyond what the prone leg curl provides, the Hip Thruster DPB401 or Hip Thruster DSH031 adds horizontal hip extension. The Standing Calf Raise DSA019 completes the lower leg picture with dedicated gastrocnemius isolation that the DSA031 does not address as a primary movement.

Q: Is 200 lbs enough stack for advanced leg extension and leg curl training?
A: For leg extension, 200 lbs is sufficient for the vast majority of training contexts. The quadriceps are a large and strong muscle group but leg extension loads them through a single-joint movement where the leverage is not favourable to extremely heavy loads, and most experienced lifters produce their best quad development at moderate loads with strict form and controlled eccentrics. For prone leg curl, the hamstrings typically work at even lower loads on isolation machines relative to their compound strength. The 200 lb ceiling covers both exercises across the full practical training range without becoming a limiting factor.

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Every machine that leaves Dynasty Fitness carries the same promise: it is built to the commercial standard that professional training environments demand, priced so that standard is no longer exclusive to them, and backed by the support and warranty coverage that a long-term training investment deserves.

We are committed to equipment that stands the test of time — and to making sure the people who train the hardest have access to the tools that match their effort.