The straight leg calf raise is not simply a calf raise performed with a straight leg. The position of the knee fundamentally changes which calf muscle is most challenged, which is why the straight leg and bent knee versions are distinct exercises with different training effects rather than being interchangeable variations of the same movement.
Understanding the anatomy behind this difference explains why the straight leg version is specifically prescribed in Achilles tendinopathy rehabilitation, why it is the more sport-specific of the two calf raise variations, and how to use both strategically in a training programme.
The Anatomy That Makes Knee Position Matter
The calf is composed of two primary muscles: the gastrocnemius and the soleus.
The gastrocnemius: The larger, superficial calf muscle whose two heads (medial and lateral) originate from the posterior femoral condyles (the back of the knee). Because the gastrocnemius crosses both the knee and the ankle, its ability to produce plantarflexion (the pushing down of the foot) is affected by the position of the knee. With the knee straight (extended), the gastrocnemius is at a longer length and under greater tension, making it the dominant calf muscle during the plantarflexion movement. With the knee bent, the gastrocnemius is shortened and mechanically disadvantaged, reducing its contribution.
The soleus: The deeper, flatter calf muscle that originates entirely below the knee (from the posterior tibia and fibula). Because the soleus does not cross the knee joint, its length and mechanical advantage are not affected by knee position. The soleus is the dominant calf muscle when the knee is bent.
The practical implication:
- Straight knee calf raise: primarily targets the gastrocnemius (with soleus contribution)
- Bent knee calf raise: primarily targets the soleus (with minimal gastrocnemius contribution)
Both muscles insert together via the Achilles tendon into the posterior calcaneus (heel bone). The Achilles tendon transmits the force of both muscles to the foot, which is why Achilles tendinopathy rehabilitation addresses both the gastrocnemius (through straight knee work) and the soleus (through bent knee work).
Why the Gastrocnemius Matters for Athletes
The gastrocnemius is the primary calf contributor to explosive plantarflexion: the push-off during sprinting, the jump initiation during basketball and volleyball, and the rapid ankle stiffening during running that contributes to energy economy. Its fast-twitch fibre composition and its longer moment arm for plantarflexion (compared to the soleus) make it the power-generating calf muscle most relevant to athletic performance.
Straight leg calf raises are therefore the more athletically specific calf exercise, developing the muscle most responsible for the explosive plantarflexion that drives athletic power. The soleus is more important for sustained submaximal loading (endurance running) while the gastrocnemius is more important for explosive speed and power activities.
Muscles Targeted
Primary:
- Gastrocnemius (medial and lateral heads): The dominant muscle in the straight leg calf raise due to its lengthened position with the knee extended
Secondary:
- Soleus: Contributes throughout the plantarflexion range but is less dominant than in the bent-knee version
- Tibialis posterior and peroneal muscles: Provide ankle stability throughout the movement
Step-by-Step Technique
Standard Bilateral Straight Leg Calf Raise
Setup:
- Stand with the feet hip-width apart, toes pointing forward or very slightly outward
- The knees are fully extended (straight) throughout the movement
- Stand on a flat surface for the standard version, or with the heels off the edge of a step for the deficit version
- Hold a wall, rack, or support lightly for balance (not for support of the body weight)
The movement:
- Rise onto the toes by pushing through the ball of the foot and the big toe
- Drive as high as possible onto the toes at the top position
- Hold for 1 to 2 seconds at the top, feeling the gastrocnemius contracted strongly
- Lower slowly under control, taking 2 to 3 seconds
- For the flat-surface version, allow the heels to return to the floor before the next rep
- For the deficit version, lower the heels below the step edge to achieve the maximum calf stretch before the next rep
- Complete the prescribed reps
Key technique cues:
Full plantarflexion at the top: The single most important cue. Many people perform calf raises to a partial height, shortening the range and significantly reducing the training stimulus. Drive all the way onto the toes until the calves are at maximum contraction. The ankle should reach close to full plantarflexion at the top of each rep.
Knees remain locked throughout: Any bending of the knee during the movement shifts the load from the gastrocnemius toward the soleus, changing the muscle emphasis. Maintain full knee extension throughout both the up and down phases.
Controlled eccentric: The lowering phase should be slow and deliberate (2 to 3 seconds). The eccentric phase of the calf raise is particularly important for Achilles tendinopathy management and for the overall strength development of the calf.
Even load through the foot: The rise should be evenly distributed across the ball of the foot rather than rolling to the outer edge (supinating) or inner edge (pronating). The big toe should be the primary contact point at the top.
No bouncing at the bottom: Allow the heels to lower fully and pause briefly before the next rep. Bouncing uses elastic energy stored in the Achilles tendon to assist the rise, reducing the muscular demand.
Deficit Straight Leg Calf Raise
The most complete version, performed with the heels off the edge of a step to allow the calf to be fully stretched at the bottom.
How to do it:
- Stand on a step with only the forefoot on the step and the heels free to lower below the step level
- Hold the rail or wall for balance
- Lower the heels as far as comfortable below the step edge
- Rise all the way onto the toes
- Complete the full range from maximum dorsiflexion to maximum plantarflexion
Why the deficit version is superior for most applications: The full range from maximum stretch at the bottom to maximum contraction at the top provides a more complete training stimulus for the gastrocnemius than the flat-surface version, which has a limited bottom range. The deep stretch at the bottom position is particularly relevant to Achilles tendinopathy rehabilitation, where training the tendon at its longest length is specifically therapeutic.
Variations and Progressions
Level 1: Bilateral Flat-Surface Calf Raise
The starting point for people new to calf training or in early rehabilitation.
Sets and reps: 3 sets of 15 to 20
Tempo: 1 second up, 1 second hold, 2 seconds down
Level 2: Bilateral Deficit Calf Raise
The step elevation adds the full stretch range that makes the exercise significantly more demanding and more complete.
Sets and reps: 3 sets of 15
Tempo: 1 second up, 1 second hold, 3 seconds down
Level 3: Slow Eccentric Bilateral Deficit Calf Raise
Adding a significantly slowed eccentric phase (5 to 6 seconds down) is the specific protocol used in Achilles tendinopathy management (the Alfredson protocol, discussed below).
Sets and reps: 3 sets of 15
Tempo: 1 second up, 3-second hold, 5 seconds down
Level 4: Single-Leg Straight Leg Calf Raise
The most important progression for athletic performance and unilateral strength development. The single-leg version approximately doubles the load per calf compared to the bilateral version.
How to do it:
- Stand on one leg on the edge of a step
- The knee remains fully extended
- Lower the heel as far as comfortable below the step
- Rise as high as possible onto the single tiptoe
- Lower slowly under control
- Complete all reps on one side before switching
Sets and reps: 3 sets of 8 to 12 per side (fewer reps than bilateral due to the doubled demand)
Tempo: 1 second up, 1 second hold, 3 seconds down
Common finding: Many people discover a significant strength asymmetry between sides when first attempting the single-leg version. If the single-leg calf raise cannot be performed initially, use a light fingertip assist from a wall or rail while developing the strength.
Level 5: Loaded Single-Leg Calf Raise
Adding a dumbbell or holding a barbell on the shoulders provides progressive overload beyond body weight.
How to do it:
- Hold a dumbbell in the ipsilateral hand (same side as the working leg) or in both hands
- Stand on the step on one leg
- Perform the single-leg calf raise with the added load
- Begin with a light weight (5 to 10 kilograms) and progress gradually
Sets and reps: 3 sets of 8 to 10 per side
Level 6: Explosive Calf Raise (Plyometric Application)
For athletes specifically developing the fast-twitch gastrocnemius power relevant to sprint push-off and jumping.
How to do it:
- Stand on both legs on a flat surface
- Lower the heels briefly (slight bend at the ankle, not a full stretch)
- Explode upward onto the toes as rapidly as possible
- Focus on the rate of force development rather than the height achieved
- Land softly and repeat
Sets and reps: 4 sets of 10 with maximum effort on each rep and full rest between sets
This is the bridge between calf strengthening and sport-specific power development: it develops the fast-twitch gastrocnemius function most relevant to sprint and jump performance.
The Achilles Tendinopathy Application
Straight leg calf raises are the primary exercise in Achilles tendinopathy rehabilitation. The specific protocol, developed by Hakan Alfredson and colleagues in the 1990s, has become one of the most evidence-supported conservative interventions in musculoskeletal medicine.
The Alfredson protocol:
- Bilateral or single-leg calf raise (straight knee) for the gastrocnemius: 3 sets of 15 reps, twice daily
- Bent-knee single-leg calf raise for the soleus: 3 sets of 15 reps, twice daily
- The eccentric (lowering) phase is performed slowly (3 to 5 seconds)
- Training continues into mild pain (the original protocol specifies continuing despite pain, though current modifications suggest keeping pain at or below 5 out of 10 during the exercise)
- Load is added progressively (via a weighted backpack or dumbbell) when the protocol becomes too easy
Why this works for Achilles tendinopathy: As covered in the gluteus medius tendon article on this site in the context of another tendinopathy, progressive tendon loading drives the structural remodelling of pathological tendon tissue toward healthier collagen organisation. The slow eccentric phase of the calf raise specifically loads the Achilles tendon at its longest length and under maximal eccentric tension, which is the specific mechanical stimulus that promotes this remodelling.
Important note: Achilles tendinopathy management should ideally be supervised by a physiotherapist, particularly for insertional Achilles tendinopathy (pain at the tendon attachment on the heel bone), where the full stretch range of the deficit calf raise may not be appropriate initially. Mid-portion Achilles tendinopathy (pain in the middle section of the tendon) is the primary indication for the deficit protocol.
Athletic and Sport-Specific Applications
Running Performance
The gastrocnemius contributes to the spring-like energy storage and return mechanism of running that accounts for a significant proportion of running economy. Runners with stronger gastrocnemii have been shown to have better running economy (less oxygen cost for the same speed) because the tendon stores more elastic energy per stride.
Calf raise programming for runners:
- Single-leg deficit calf raise: 3 sets of 10 per side, twice per week
- Progress to loaded single-leg as body weight becomes insufficient
- Include the explosive calf raise in speed-focused training phases
Jumping Athletes (Basketball, Volleyball, Triple Jump)
The gastrocnemius is specifically active during the plantarflexion component of jumping. The explosive calf raise and the loaded single-leg calf raise are the primary calf exercises for maximising jump height.
Calf raise programming for jumping:
- Loaded single-leg deficit calf raise: 3 x 10 per side (strength)
- Explosive bilateral calf raise: 4 x 10 (power)
- Both should be part of a comprehensive plyometric and strength programme
Sprint Athletes
Sprint push-off requires maximal gastrocnemius force production in a very short ground contact time. Both the strength and the rate of force development of the gastrocnemius are relevant.
Calf raise programming for sprinters:
- Heavy bilateral deficit calf raise: 3 x 6 to 8 (maximum strength)
- Single-leg explosive calf raise: 4 x 8 (power and rate of force development)
- Include these as accessory work within a comprehensive sprint training programme
Programming Straight Leg Calf Raises
For general fitness and calf development:
- Bilateral deficit calf raise: 3 sets of 15 to 20, 2 to 3 times per week
- Progress to single-leg when bilateral is easy, then add load
For Achilles tendinopathy rehabilitation:
- The Alfredson protocol as described above: 3 x 15 twice daily (both straight and bent knee)
- Under physiotherapy guidance for optimal management
For athletic performance:
- Single-leg deficit calf raise: 3 x 8 to 10 per side, twice per week
- Explosive calf raise: 4 x 10 once per week in speed or power training sessions
- Loaded progression as strength improves
Combining straight and bent knee:
A complete calf training programme includes both variations:
- Straight leg (gastrocnemius emphasis): 3 x 12 single-leg
- Bent knee (soleus emphasis): 3 x 15 single-leg
- Perform in the same session or on different days
Frequently Asked Questions
Why are single-leg calf raises harder than expected?
The load in a single-leg calf raise is not simply double the bilateral version: it is significantly more than double because the leverage and stability demands are compounded. The gastrocnemius must produce force to push up the full body weight while the other muscles of the ankle and foot stabilise a more demanding single-leg balance position. Many strong athletes who can easily perform 20 bilateral calf raises find single-leg calf raises very challenging. This asymmetry is normal and improves rapidly with consistent training.
How many reps should I do for calf raises?
The calf muscles are trained daily through walking and benefit from moderate to high rep training. For general strength: 3 sets of 10 to 12 at a challenging load. For endurance: 3 sets of 15 to 20 at a lighter load. For Achilles tendinopathy: 3 sets of 15 at the appropriate tempo as per the Alfredson protocol. The calves generally respond well to both high-rep endurance work and lower-rep loaded work.
Should I add weight to calf raises?
Yes, when body weight becomes insufficient to produce fatigue within the prescribed rep range. For bilateral calf raises, this may be quickly (within a few weeks for trained athletes). For single-leg calf raises, body weight may be sufficient for longer. A dumbbell held in the hand, a weighted backpack, or a barbell on the shoulders are all appropriate loading methods.
Is there a difference between machine calf raises and free-standing calf raises?
Seated calf raise machines specifically target the soleus (bent-knee position). Standing calf raise machines typically allow straight-knee positioning and target the gastrocnemius similarly to free-standing calf raises. The free-standing deficit version on a step is generally preferred for the gastrocnemius because it allows full range of motion and natural proprioceptive demands. Machine versions provide stability advantages that may be useful in rehabilitation contexts.
Can straight leg calf raises cause shin splints?
Straight leg calf raises themselves do not cause shin splints, but they can aggravate existing shin splints if the volume is increased too rapidly. Shin splints (medial tibial stress syndrome) are caused by overload of the tibial bone and surrounding muscles from training load errors. Calf raises are generally part of the rehabilitation programme for shin splints rather than a cause of them. If calf raises consistently aggravate shin pain, reduce the volume and seek assessment.