CrossFit is a fitness phenomenon that has taken the athletic community by storm. It is a regimen of constantly varied, functional movements performed at high intensities within a communal environment.1 CrossFit incorporates a variety of exercises into daily workout routines. These exercises include biking, swimming, rowing, gymnastics and plyometrics to name a few.
A large aspect of CrossFit is weightlifting. Olympic lifting and strength training programs take place in most CrossFit gyms on a daily basis. The two Olympic lifts, the snatch and “the clean and jerk” are complex body and barbell movements, requiring precision, accuracy and balance to land.1,2 The images at left illustrate the snatch progression from start to finish.
With CrossFit integrating so many different exercises, it is no surprise that athletes obtain a variety of shoe gear to participate. Since the cost of CrossFit shoes, weightlifting shoes and running shoes can add up quickly, beginner CrossFit athletes may not purchase the proper footwear necessary to perform the Olympic lifts.
Accordingly, it is important to be aware of weightlifting shoes, also called lifters, and their importance for the CrossFit or Olympic lifting athlete.
The International Weightlifting Federation requires sport footwear. The International Weightlifting Federation requires all athletes competing in Olympic lifting to wear sport footwear, called weightlifting shoes or boots. According to Rule 4.2.1 of the International Weightlifting Federation, all competitors must wear sport footwear to protect their feet, give them stability and provide a firm stance on the platform.2 Weightlifting shoes are generally fabricated with at least one strap, which extends over the midfoot toward the instep. Weightlifting shoes have a reinforced heel cup, which may be internal or external. The sole of the shoe, as defined by the International Weightlifting Federation, cannot extend beyond the upper or heel cup by more than 5 mm.2 There are no specifications on the style or shape of the shoe so the designs are often creative and colorful.
The elevated heel activates the quadriceps femoris muscles and lowers the risk of back injury. Interestingly, the International Weightlifting Federation does not specify a minimum or maximum height for the sole of the weightlifting shoe. Despite the lack of specifications, most lifters have a heel height elevated to approximately 2.5 cm. The elevated heel keeps the forefoot in a plantarflexed position relative to the rearfoot throughout the duration of the lift. This is important for a couple of reasons.
First, the plantarflexed position of the foot in the shoe leads to increased knee extensor muscle excitation and activity. A study by Kongsgaard and colleagues looked at electromyography activity and joint kinematics during a standard squat and a 25 degree decline eccentric squat.3 A total of 13 participants performed the standard and decline eccentric squat. The researchers studied the impact of these squats on the vastus lateralis, vastus medialis, rectus femoris, biceps femoris, semitendinosus, gastrocnemius, soleus and tibialis anterior muscles. They found the electromyography amplitudes of the quadriceps femoris muscles were statistically significant and greater for the 25-degree decline eccentric back squat. Increased activity of the quadriceps muscles enables an athlete to be more powerful as he or she reaches full extension through the lower extremity in the snatch or power clean lifts. Although this study was not examining people wearing weightlifting shoes, the 25-degree eccentric back squat simulates the effect that weightlifting shoes have on the body.
Second, the elevated heel reduces tension on the Achilles tendon, thus allowing for greater dorsiflexion at the ankle joint.4 The picture at left shows one manifestation of equinus in an athlete without weightlifting shoes. Note the elevated heel off the ground. When we adequately dorsiflex at the ankle, we are able to bring our shins into a more vertical position. This allows our bodies to sit into a squat easier and deeper, keeping the chest up, the trunk straight and the spine in neutral position without lifting our heels of the ground.
Moreover, the heel height in the weightlifting shoes aids in maintaining a more vertical position of the trunk, an important component to back injury prevention. Sato and coworkers examined the foot segment angle, trunk lean displacement and thigh segment peak flexion angle to determine the kinematic differences between weightlifting shoes and running shoes during the barbell back squat.4 A total of 25 male and five female injury-free, intercollegiate athletes performed two sets of back squats with one set in weightlifting shoes and one set in running shoes. The researchers examined the kinematic differences between the squats. They found a statistically significant difference in the trunk lean displacement between the two shoe types. When the study participants wore weightlifting shoes, there was far less forward lean of the trunk.
Too much forward flexion of the trunk leads to greater compressive force on the spine and a higher risk of low back injury. Wearing weightlifting shoes helps to combat the body’s natural tendency to lean forward in the bottom position of the back squat or snatch, preventing possible injuries. In the pictures at right, notice the difference in flexion of the trunk in and out of shoes.4
Weightlifting shoes provide a stable platform for push-off and landing. Some athletes may opt to wear running shoes with an elevated heel in lieu of lifters. Unfortunately, the sole of the running shoe is entirely different than the sole of the Olympic lifting shoe. We need to emphasize to CrossFit participants to avoid interchanging the two shoes. Running shoe soles are typically made of some form of lightweight rubber or foam, such as ethylene vinyl acetate (EVA). A foam sole is great in a running shoe when its primary function is to absorb vertical shock but this does not make for ideal weightlifting conditions.4 The foamy material deforms over time due to its compressible nature, leading to uneven shock absorption and dissipation.
In weightlifting, athletes require a firm, stable platform to push off and land on. The heel wedge of most weightlifting shoes is made of wood or thermoplastic polyurethane (TPU). The thermoplastic polyurethane or other plastic often extends into the heel cup, either internally or externally. This feature of the shoe offers stability without any compression or give. In addition, the wooden heel wedge with the rubber outsole is flat, allowing forces to spread out evenly through the sole. This is critical for a weightlifter. Athletes are required to pull their bodies under the barbell. For a brief moment in the clean and jerk or snatch lifts, both feet are off the ground simultaneously. Having a sturdy, flat and unyielding surface to land on allows the athletes to maintain their balance and complete the lift.
In summation, because of the popularity of CrossFit, podiatrists should begin to familiarize themselves with the sport and Olympic weightlifting. With over 11,000 CrossFit affiliated gyms worldwide, there is no doubt that you will see these patients in your office throughout your career. It is important to ensure that athletes are wearing adequate footgear for each aspect of CrossFit. In Olympic lifting, footgear should be supportive and unyielding with an elevated heel. The elevated heel in the lifting shoe helps prevent back injuries, improves overall form and increases activation of the quadriceps muscles.
1. What is CrossFit? Available at http://www.CrossFit.com/cf-info/what-is-CrossFit.html .
2. IWF Programme of the Competition. Available at http://www.iwf.net/doc/technical.pdf .
3. Kongsgaard M, Aagaard P, Roikjaer S, Olsen D, Jensen M, Langberg H, Magnusson SP. Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats. Clin Biomech. 2006; 21(7):748-754.
4. Sato K, Fortenbaugh D, Hydock DS. Kinematic changes using weightlifing shoes on barbell back squat. J Strength Conditioning Res. 2012; 26(1):28-33.
5. Bourget D, Millet GY, Fuchslocher J. Influence of shoes increasing dorsiflexion and decreasing metatarsus flexion on lower limb muscular activity during fitness exercises, walking and running. J Strength Conditioning Res. 2008; 22(3):966-973.
6. Queen RM, Abbey AN, Weigerinck JI, Yoder JC, Nunley JA. Effect of shoe type on plantar pressure: a gender comparison. Gait Posture. 2009; 31(1):18-22.
7. Clark DR, Lambert MI, Hunter AM. Muscle activation in the loaded free barbell squat: a brief review. J Strength Conditioning Res. 2012; 26(4):1169-1178.
Editor’s note; For a related article, see the March 2015 online-exclusive article, “Key Insights On Managing CrossFit Injuries,” at www.podiatrytoday.com/key-insights-managing-crossfit-injuries .