The Forgotten Plantar Flexor: Training the Soleus

The soleus is one of the most neglected muscles in athletic training programs. Many coaches feel that due to the considerable amounts of force exerted on the calves during sprints, jumps (landings), and plyometrics, there is no need to further train the calves in the gym, since it’s unlikely we’ll be able to load them with anything near the 3-5x bodyweight level forces they experience in these movements. If any additional calf exercises are ever programmed, you can bet your lunch money that it’ll be some variation of a standing calf raise. While all of the aforementioned movements are all great, they fail to address one muscle group: the soleus.

I’ll give you a breakdown of some relevant literature, and then we’ll get into what most of you actually came here for (some new exercises to put in your toolbox). While the gastrocnemius (gastroc) and soleus are both synergists, as they share roles in plantar flexion, they are also anatomically unique in that the gastroc crosses both the knee and ankle joints while the soleus only crosses the ankle. This creates an interesting relationship between the two muscles.

Beyond this anatomical difference allowing the gastroc to function as both a plantar and knee flexor, the neural drive to the gastroc decreases as you enter deeper and deeper positions of knee flexion (Cresswell et al., 1995). Conversely, neural drive to the soleus remains the same regardless of joint angle at the knee. Lauber et al. (2014) found that at between 0 and 60 degrees of knee flexion, fascicle lengths of the soleus remain relatively unchanged, while the fascicle lengths of the gastroc progressively shorten 3.5 +/- 1.9 millimeters until around 21 degrees, and then remain around this length as you continue to go further into knee flexion. Further, they also found that motor units in the gastroc began to be de-recruited at a knee angle of 21.1 degrees when passively flexed.

These results are supported by Baumbach et al. (2014), who found that flexing the knee to a joint angle of 20 degrees removes any inhibition of the gastroc on ankle dorsiflexion. Interestingly, the same motor unit that was de-recruited at 21.1 degrees during passive flexion was re-recruited at a knee angle of 35.1 degrees while undergoing passive knee extension. They found activation levels of the gastroc and soleus actually switch at different joint angles and in accordance with gastroc fascicle length. Meaning, when the joint angle of the knee allows the fascicles of the gastroc to be at a length optimal for producing force, the gastroc will be the primarily activated calf muscle, and vice versa once the fascicles are in a shortened position.

These results suggest that the “bulk of the burden” of eccentric plantar flexion shifts onto the soleus at knee angles deeper than 20 degrees, and that the soleus will also be the primary plantar flexor of the two plantar flexors up until around a knee angle of 35 degrees when going back into knee extension. This supports the classical view that the soleus is more of an “eccentric muscle,” since it is primarily active throughout a larger percentage of knee flexion than knee extension.

I explain all of that to say: Your pogo hops, drop jumps, and calf raises aren’t doing jack squat for training the soleus. Sure, they’re great for the Achilles. They’re great for the gastroc. But the knee angles just aren’t deep enough to shift the bulk of the demands from the gastroc over to the soleus.

Your pogo hops, drop jumps, and calf raises aren’t doing jack squat for training the soleus. Sure, they’re great for the Achilles. They’re great for the gastroc…, says @Brandon_L_Pigg. Share on X

The question now moves to the ever important one: Does this even matter?

If you’re concerned with reducing knee injury risk among your athletes, well then, my answer would be “yes.”

Both Elias et al. (2003) and Mokhtarzadeh et al. (2013) found that the gastroc serves as an antagonist to the ACL ligament, and the soleus acts as an agonist for it. Elias went on to state that when only the soleus is activated, the tibia translates posteriorly in relation to the knee, but when just the gastroc or both the gastroc and soleus are active, the tibia translates anteriorly. In case it’s been a while since you took an anatomical kinesiology class, excessive anterior translation of the tibia in relation to the femur = bad.

It’s also worth noting that since strengthening the soleus theoretically would result in less anterior translation of the tibia during jump landings, it’s potentially possible that soleus training could assist in decreasing risk of patellar tendinitis. The two hypothetical mechanisms here would be: 1) the obvious one that increasing another muscle’s capacity to handle load during the jump landing would take some stress off the quad and patellar tendons; and 2) that decreasing anterior tibial translation would result in less of a stretch on the patellar tendon.

Training the Soleus

Alright, as promised, here are some exercises to add to your toolbox for soleus training. I’ll give you five different exercises with various outcome goals, as well as alternatives for movements that require special equipment. Since I tied injury prevention into the importance of lower leg training, I’ll throw in a more gastric-focused lift that may assist in these efforts as well. Many of these movements will be isometric in nature, which may be appreciated by anyone with Achilles issues who feels discomfort when training the ankle through dynamic ranges of motion.

Disclaimer: All of the above research was conducted by performing isometric plantar flexion, not ballistic movements. While I’m sure the dynamics change once the stretch-shortening cycle begins to play a role, we’re simply going to use the aforementioned research as a reference and assume things stay somewhat similar as we shift to dynamic movement.

Adding Bands to Target Function

As I mentioned earlier about how the soleus acts to pull the tibia posteriorly and as an agonist to the ACL, it would make sense to try and target that function in the gym. By anchoring a band anteriorly in relation to the body and looping it behind the back of the calf, you can create an anterior pull on the tibia for the soleus to work against. While it will be easier to add this variation to some exercises more than others, I think it’s a method worth checking out. I won’t count this as an exercise since you can apply this concept as a modification/progression to any of the following lifts that are performed while stationary.

Exercise 1: The Seated Calf Raise

I figured I would start this section by discussing the most well-known means of training the soleus: the seated calf raise. The seated calf raise is to the soleus as the standing calf raise is to the gastroc. It’s a golden age bodybuilding staple, but unfortunately, it’s just not as common in the training of athletes.

The seated calf raise is to the soleus as the standing calf raise is to the gastroc. It’s a golden age bodybuilding staple, but unfortunately, it’s just not as common in the training of athletes. Share on X

In conjunction with the stigmas against calf training that I mentioned at the beginning of this article, this exercise’s lack of popularity is also likely coupled with the simple fact that most normally budgeted training facilities won’t allot their funds (or dedicate space) to a piece of equipment that largely only has one function. Thankfully, I’m here to provide you with some alternatives that involve far more common equipment.

Seated Calf Raise Pros and Cons:

Pros:

• Ease of use.
• Able to load it heavily without much difficulty.
• Allows for full range of motion training since most have an elevated bar to rest your forefoot on.

Cons:

• A rare sight to see at most training gyms that don’t have a focus on bodybuilding.
• Costly for coaches to add multiple units to their training facilities.
• Takes up a considerable amount of space for a machine that’s largely a one-trick pony.

Alternative 1: The Safety Squat Bar Seated Calf Raise

The safety squat bar has gained a lot of popularity over the years and made its way into the big three of barbells (the Olympic straight bar and hex bar being the other two). This is good news for the sake of this article, because it is probably the best alternative to serve as a replacement for a seated calf raise machine. You can play around with where you seat the bar on the thigh, but I tend to prefer placing it toward the knee so that the load is closer to the ankle joint. In case you don’t have a safety squat bar, you could probably do these with a straight bar as well. I’d definitely recommend either using a pad or wrapping a towel around it, so you aren’t just setting a bare bar on your thigh.

Pros:

• Safety squat bars are commonly found pieces of equipment.
• Only being able to load one leg at a time forces you to train unilaterally.
• Can have athletes at each rack go at the same time instead of rotating people onto a seated calf raise machine.

Cons:

• Requires racking and un-racking the bar, plus seating it on the knee. Not a deal breaker, but certainly not as simple as the machine variant.
• Due to the constraint listed above and increased instability, you won’t be able to load it as heavily as you would the machine.
• Some athletes may find the bar being placed on their leg to be uncomfortable.

Alternative 2: Kettle Bells

This one will require a bit of jerry rigging, but I like to think all strength coaches are a bit of a MacGyver at heart. Essentially, you’re going to be suspending some kettle bells with some sort of a strap and then placing this strap over your thigh like you did with the safety squat bar variation. While I’m sure the possibilities are endless, here are the two methods I’ve tried.

The most common way would be using a dip/pull-up belt, where the belt is centered over the thigh, and then a kettle bell is suspended on both sides of the leg. The second is with my favorite exercise equipment: a combination of a $6 trailer carabiner and a $6-$9 pack of nylon tie-down straps that can be looped together. I’ll link one of my tweets here where I go into a whole host of uses for these bad boys. (I’m talking they can be used for anything from TRX straps, dip belts, and overcoming ISOs, to makeshift belt squats, Spanish squats—you name it.) But they can also be used for these kettle bell seated calf raises.

Pros:

• If you don’t have a safety squat bar/don’t enjoy that variation, this is a very cheap alternative.
• This same setup works great for hip thrusts. Just lay the straps/belt across your hips and suspend a kettle bell on either side. It’s far easier to balance than a barbell, which makes it my second favorite variation behind Smith machine hip thrusts.

Cons:

• It allows for the least amount of load of the three methods listed.
• The suspended kettle bells can, and likely will, smack into your leg/ankle if they start swaying.

Exercise 2: 90/90 Soleus ISO

Mock this exercise and call it wimpy at your own risk, because this will leave first-timers sore for three or more days. For anyone familiar with PRI, this exercise involves getting into a similar position as the 90/90 heel lift. The difference is that, instead of driving down through the heels, you’ll plantar flex onto the ball of your foot (first metatarsal head) and squeeze those calves as hard as you can. I’m a big fan of ISOs in three positions: 1) most shortened position, 2) most lengthened position, and 3) common joint angles experienced in sport/running/jumping.

This ISO is our most shortened position of the soleus, and I particularly like it for another reason: It allows us to target the soleus in full plantar flexion, says @Brandon_L_Pigg. Share on X

This one is our most shortened position of the soleus, and I particularly like it for another reason: It allows us to target the soleus in full plantar flexion. As stated in the section where I reviewed a few relevant literature sources, the gastroc usually will have already taken over as the main mover of the two calves by the time you enter the late ranges of plantar flexion. By being at a knee angle of 90 degrees in this exercise, we take the gastroc out of the equation and train the soleus in a position in which it’s especially weak.

Exercise 3: Seated Overcoming Calf Raise ISO

This one will probably be easiest using the safety squat bar setup mentioned earlier, but I suppose there are ways you could use the other two methods. Here, we’ll be getting our ISO at the most lengthened position of the soleus. You’ll perform this by setting up safety pins so that you’re barely able to plantar flex out of that dorsiflexed position.

Alternative: Single Leg Plantar Flexion ISO from Pronated Position

Yeah, I clearly don’t exactly have a catchy name for this one, but the exercise is still a worthwhile alternative for anyone who is without access to a gym due to COVID-19 or other circumstances. Although it still gets you into that lengthened position of the soleus, this one is a bit different because your knee angle will likely be at that tipping point where the primary mover shifts from gastroc to soleus, whereas the other exercises provided all take place at deeper ranges of knee flexion. That isn’t necessarily a bad thing, as this is a common position experienced in landings. All you do is perform a knee bend and get your knee out over your big toe while keeping a vertical torso.

Concentrate your weight onto the transverse arch of the foot, but still keep the heel in contact with the ground. From there, simply push the ground as hard as you can and try to plantar flex the ankle but stay in that knee bent position. This is an especially great movement to which to add the band variation I listed at the top of the exercise section. Since this is a position that you’ll experience in landings, it makes sense to train the soleus to pull posteriorly on the tibia to prevent excessive anterior tibial translation.

Exercise 4: Prowler Bounds

As we transition to some more power-focused movements with the prowler bounds, you’ll notice the movements become more full body in nature. You’ll want to cue delaying knee extension here to make sure you make ground contact with a nice bent knee. From there, you just bound. It’s almost like squatted bounding.

Alternative: 10-Yard Hill Sprint

If you don’t have access to a prowler sled, you can just head over to a reasonable hill and get some 10-yard sprints in. Since you aren’t reaching top-end sprint mechanics here, you’ll still have enough of a knee bend to give the soleus some love.

Exercise 5: Squatted Depth Jumps

In a normal depth jump, the first few moments of ground contact will feature knee joints and fascicle lengths that allow the gastroc to blunt the impact before the knee bends deeply enough for the focus to shift over to the soleus. By landing in a squatted position, we take the crutch away and force the soleus to be the primary eccentric plantar flexor from the start. This helps prepare athletes to later perform change of direction maneuvers that involve the foot making contact with the ground while the knee is already bent at or beyond 20 degrees. Since we’re using it as a preparatory movement for change of direction progressions, it would be logical to progress these to squatted lateral depth jumps to add a change of direction component to the movement.

Bonus Gastroc Exercise: Overcoming Standing Calf Raise ISO

As alluded to in exercise 5, the gastroc will be the primary muscle for plantar flexion during the first milliseconds of ground contact in most movements. Because of this, we can train these positions with overcoming isometrics to increase the gastroc’s ability to produce force and dampen the amount of forces that the body will need to produce up the chain to be able to overcome the force imposed by landing. I would train these in both full plantar flexion and full dorsiflexion, as the full plantar flexion position will help train the gastroc for jump landings, and the dorsiflexed position will help prepare it for ground contacts in sprints with top-end mechanics.

Training Below the Knee for Performance

While training the soleus probably isn’t the one secret missing ingredient…I do believe it to be another important element when training a well-rounded and robust athlete, says @Brandon_L_Pigg. Share on X

All calf training isn’t created equal, and hopefully I’ve helped you discover newfound value in training the calves beyond exclusively plyometric movements. While training the soleus probably isn’t the one secret missing ingredient that’s stood between your athletes and world record PRs or playing 10 years straight without sustaining an injury, I do believe it to be another important element to consider when training a well-rounded and robust athlete. With the 11 total calf training variations I just explained, I hope I’ve given you some juice and ideas to help make training the calves cool again.

Since you’re here…
…we have a small favor to ask. More people are reading SimpliFaster than ever, and each week we bring you compelling content from coaches, sport scientists, and physiotherapists who are devoted to building better athletes. Please take a moment to share the articles on social media, engage the authors with questions and comments below, and link to articles when appropriate if you have a blog or participate on forums of related topics. — SF

References

Cresswell, A.G., Löscher, W.N., and Thorstensson, A. “Influence of gastrocnemius muscle length on triceps surae torque development and electromyographic activity in man.” Experimental Brain Research. 1995;105(2):283-290.

Lauber, Benedikt, Lichtwark, G.A., and Cresswell, A.G. “Reciprocal activation of gastrocnemius and soleus motor units is associated with fascicle length change during knee flexion.” Physiological Reports. 2014;2(6):e12044.

Baumbach, S.F., Brumann, M., Binder, J., Mutschler, W., Regauer, M., and Polzer, H. “The influence of knee position on ankle dorsiflexion – A biometric study.” BMC Musculoskeletal Disorders. 2014;15(1):246.

Elias, J.J., Faust, A.F., Chu, Y-H., Chao, E.Y., and Cosgarea, A.J. “The soleus muscle acts as an agonist for the anterior cruciate ligament. An in vitro experimental study.” American Journal of Sports Medicine. 2003;31(2):241-246.

Mokhtarzadeh, H., Yeow, R.C-H., Goh, J., Oetomo, D., Malekipour, F., and Lee, P. “Contributions of the Soleus and Gastrocnemius muscles to the anterior cruciate ligament loading during single-leg landing.” Journal of Biomechanics. 2013;46(11):1913-1920.