Transient Forefoot Compression Neuropathy with Chronic Elliptical Trainer Exercise Use

Many patients use elliptical trainers as part of their fitness program and the vast majority of them have reported few complaints with their proper use. Unfortunately, some individuals complain of an uncomfortable tingling or “pins and needles” sensation in the plantar forefoot that seems to be peculiar to the use of the elliptical trainer exercise machine.

In February 2012, Dr. Kirby described this “plantar forefoot pins and needles sensation” that comes with patients who exercise with elliptical trainers regularly as a medical condition which he named Transient Forefoot Compression Neuropathy (TFCN). Patients with TFCN will typically complain of a tingling or “pins and needles” sensation in their plantar forefoot after a certain length of time of exercising on the elliptical trainer. TFCN may also occur in cyclists and in patients with cavus feet with ankle/gastrocnemius/soleus equinus deformities presumably due to the large magnitudes of chronic compression forces acting on the forefoot of these individuals.

The plantar forefoot tingling sensation of TFCN may begin either before or immediately after cessation of elliptical trainer activity, but will normally gradually subside over the next five to ten minutes after ending elliptical trainer exercise. In the more severe cases, the plantar forefoot tingling sensation not only persists for the rest of the day, but may also persist for days or weeks if the individual uses the elliptical trainer as their primary form of daily aerobic exercise.

The most mechanically coherent explanation for the temporary tingling sensation seen in TFCN is the relatively constant and high magnitudes of plantar pressures that occur between the plantar forefoot and the foot platform of the elliptical trainer. Many individuals, especially those who are unfamiliar with elliptical trainer exercise machines, will often tend to lean their bodies forward toward the handle-levers which are often used to balance the body more forward on the trainer. By improperly leaning forward on the elliptical trainer, the forefoot will be subjected to significant increases in plantar pressure that would not occur if the individual kept their body in a more upright posture on the exercise machine.

Research published on the plantar pressures exerted on the forefoot of ten subjects doing five different types of cardiovascular exercises demonstrated that the highest peak forefoot plantar pressures occurred in walking (253 kPA), running (251 kPa), and with the elliptical trainer (213 kPa). Significantly decreased peak forefoot plantar pressures occurred in stair climbing (130 kPa) and recumbent biking (41 kPa) when compared to the elliptical trainer. Further analysis of the research shows that the peak plantar forefoot pressures seen in the elliptical trainer are 15-16% less than that experienced in walking and running, but are also 64% higher than stair climbing and recumbent biking (Burnfield JM, Jorde AG, Augustin TR, Augustin TA, Bashford GR: Variations in plantar pressure variables across five cardiovascular exercises. Med Sci Sports Exerc, 39:1012-2020, 2007).

Even though the peak pressures plantar to the forefoot in elliptical trainers are not as great as in walking and running, one must remember that in walking and running, the forefoot plantar pressures are eliminated intermittently during the swing phase of walking and during the forward recovery phase of running. With the elliptical trainer, however, the plantar forefoot is always in constant forceful contact with the foot plate of the machine. As a result, it is likely that the constant and unrelenting increased forefoot plantar pressure that occurs with elliptical trainer exercise, and especially occurs with improper forward body lean on the machine, will greatly increase the risk of TFCN developing.

The cause of the sensation of “pins and needles” and tingling in TFCN is likely due to the relatively high magnitudes of plantar forefoot pressure of continuous duration which creates a pathologic compression force on the plantar nerves of the forefoot during elliptical trainer exercise. The local compression of the plantar forefoot nerves creates a transient compression neuropathy, which causes the tingling sensation in the plantar metatarsal heads and digits. The mechanical compression of nerves is similar in mechanism to other common entrapment neuropathies of the lower extremity where chronic high magnitudes of pressure on nerves may cause sensory and/or motor nerve dysfunction. Common examples of other nerve pathologies in the lower extremity caused by chronic, excessive mechanical pressure on nerves include entrapment neuropathies of the saphenous, common, superficial and deep peroneal, sural, and posterior tibial nerves (McCrory P, Bell S, Bradshaw C: Nerve entrapments of the lower leg, ankle and foot in sport. Sports Med, 32(6):371-391, 2002).

Fortunately, the TFCN seen with elliptical trainers is normally easy to treat. First of all, patients should be instructed to lean as far backward on the elliptical trainer as possible so that more weight is placed on their heels to reduce forefoot pressure. Often times it is helpful to demonstrate to them how they may need to extend their arms as much as possible while they are grasping the handle-levers of the elliptical trainer exercise machine which will, in turn, force their upper torso backwards, reduce the force on their forefoot and increase the force on their rearfoot. Another solution is to have the patient simply wear heel lifts in their athletic shoes or wear athletic shoes with larger heel-height differential (i.e. larger heel drop) while on the elliptical trainer to increase plantar heel pressures and to decrease plantar forefoot pressures. If the tingling pain persists for more than an hour after the activity, patients should discontinue using the elliptical trainer for two to four weeks to reduce the risk of more serious and chronic injuries to the plantar nerves of the forefoot.

[Reprinted from Kirby KA: Kirby KA: Foot and Lower Extremity Biomechanics IV: Precision Intricast Newsletters, 2009-2013. Precision Intricast, Inc., Payson, AZ, 2014, pp. 135-136.]

Source: Facebook page of  Kevin A. Kirby, DPM