Bottom line: If you have an injured limb and are unable to train as normal (or train at all), training the other side can still yield benefits of the injured side
 
Question time….Let’s say you injure your left knee. What is the best strategy for your training plan?
 
1 Push through pain no matter how bad it is. Don’t change your training plan. Rest is for sissies
2 Continue to train the right knee, so long as it doesn’t further injure or provoke symptoms in the left
3 Stop training both legs because you don’t want you’re right leg to become too strong relative to your left and develop an asymmetry
 
There is a “best” answer here and that answer is number 2. Answer number 1 is ridiculous, so we’ll put that one aside. Number 3 sounds compelling and while it wouldn’t necessarily be “wrong” to go that direction, there are several reasons why number 2 is better.
 
Again, this is all based on the caveat that the training you do for the uninjured limb doesn’t put the injured limb at further risk of injury or delay healing. For example, let’s say you were doing some single leg activities on the uninjured leg, but each impact sent a “shock” through the injured leg. Your best bet is to either find different activities or delay training the uninjured limb until it can be done safely without provoking the injured limb.
 
In the literature, the concept of training effects on one limb being felt on the opposite side limb is called cross education. And to the surprise of some, the evidence is quite clear that cross-education works. Unfortunately, what should be the standard of care (training the rest of the body at the highest level possible in a way that supports the healing process), is instead a novel concept to many.

There are several reasons why cross-limb education is not promoted more. One is that the medical process is often siloed and sees the world with tunnel vision. For example, most orthopedic surgeons are going to just look at the injury and not even consider. That’s not meant to be critical, it’s just the nature of their job. They’re good at going into a damaged body part and making structural corrections using surgical techniques. They aren’t paid to tell you how to train. Similarly, most PT’s in a “traditional” outpatient setting aren’t getting paid to consider the opposite leg (and in some cases are actively discouraged from looking anyplace other than the site of the injury…Not their fault, that’s just the nature of the system in which they work). uninjured limb.
 
What does the evidence say?....A meta-analysis by Green (2018) reviewed 96 studies on cross education involving healthy young adults, healthy older adults and patients, finding an average strength gain via cross education of 18% in young adults, 15% in older adults, and 29% in a patient population. Although prior meta analyses had shown conflicting results on gender differences and upper versus lower limb effects, the studies compiled by in the Green meta-analysis revealed no significant differences. Overall, the average cross body transfer ranged from 48%-77% in the compiled studies, meaning that the immobilized limb experienced strength gains of 48%-77% of the trained limb. Again, this isn’t just one study on a homogenous group of subjects…this is 96 studies in a variety of populations. (Another interesting finding was that electrically stimulation of muscles appeared to have a greater cross-education effect than voluntary stimulation).
 
WHY cross education works remains up for debate but most evidence points to neurological mechanisms as the primary factors. Per Cirer-Sastre (2017), “this owes to the fact that no significant vascular adaptations have been found, nor were any histological changes in hypertrophy levels, in enzyme concentration, in contractile protein composition alteration, in fiber type or in cross-sectional area.” In short, strength is function of the nervous system, and the effects of nervous system output are global, meaning not specific to any single body part.
 
Although the evidence has been relatively settled that cross-education does exist via single sided training, HOW to facilitate cross-education is less clear although a meta-analysis of ten studies by Cirer-Sastre, “to optimize contralateral strength improvements, cross-training sessions should involve fast eccentric sets with moderate volumes and rest intervals.
 
Finally, approaching this from a pragmatic standpoint, if you sustain an injury to a limb, you could continue training the other limbs and have three “good” limbs or you could stop training both the injured and non-injured arm/leg and have two “good” limbs. Which sounds better?
 
The concern about developing asymmetries is logical, but overall is far overblown. As we know from the research, the cross-education effect will mitigate strength losses from inactivity by an injured limb. Further, even if cross-education did not exist, you’re better off having to bring one limb up to speed rather than losing strength in both sides have having two limbs to return to normal. Simply makes no sense why you would voluntarily weaken a perfectly healthy limb. Even if an asymmetry develops during a recovery period, its not as though you were going to hop right back into peak training after you get over the injury. You might as well give yourself the highest “baseline” with a strong, healthy limb rather than let both sides regress.
 
REFERENCES
Lara A. Green & David A. Gabriel (2018) The effect of unilateral training on contralateral limb strength in young, older, and patient populations: a meta-analysis of cross education, Physical Therapy Reviews, 23:4-5, 238-249, DOI: 10.1080/10833196.2018.1499272
 
Cirer-Sastre R, Beltrán-Garrido JV, Corbi F. Contralateral Effects After Unilateral Strength Training: A Meta-Analysis Comparing Training Loads. J Sports Sci Med. 2017;16(2):180–186. Published 2017 Jun 1.

What is plantar fasciitis (“PF”)? If you’ve had it, you certainly know it doesn’t feel very good! “Plantar fasciitis” is very broad term commonly applied to any pain on the bottom of the foot. Sometimes the condition is not plantar fasciitis at all, but instead a strained foot muscle or “fat pad syndrome” (more on that diagnosis later). Ultimately, for the patient, the specific diagnosis doesn’t matter too much because the treatment approach will be very similar (assuming we stay in the realm of orthopedics and aren’t dealing with a condition unrelated to muscles, tendons/ligaments or bones). 
 
I call plantar fasciitis an “equal opportunity offender” because you’ll find it in elite athletes who dedicate insane training volumes to their sport but also in sedentary people who walk no further than the bathroom, and of course every type of person in between. In other words, you can get it from doing too much or from not doing enough.
 
Practically speaking, you’ll find plantar fasciitis manifested in several different ways. First, the classic presentation of plantar fasciitis is isolated tenderness toward the front/middle of the heel, at a landmark called the medial calcaneal tubercle. Although the pain might extend along the entire foot, for this version of plantar fasciitis, the hallmark is localized pain at that specific point on the heel. Additionally, patients with this presentation will often feel pain at its worst in the first step of the morning.
 
Another similar common presentation is pain further back toward the heel but still on the bottom of the foot over a broader area. This is sometimes called fat pad syndrome if the primary source of pain is the fat pad on the heel rather than the plantar fascia. But again, the causes behind the condition are very similar so the treatment approach should look similar as well.
 
Plantar fasciitis may also refer to pain in the arch of the foot. Again, this may be a result of true plantar fascia inflammation or it could be referred pain patterns from elsewhere in the body. It could also be a strained muscle, as there are many muscles on the bottom of the foot that perform a variety of functions.
 
1. CHANGE YOUR CADENCE 

Changing to a faster cadence is one way to decrease stress on the foot. Cadence is a more complicated issue than footstrikes-per-minute, but do know that changing to a faster cadence is often accompanied by OTHER changes known to decrease loading, most notably a forward lean and shift to a more forefoot strike. My personal preference is that if you are going to change mechanics, let the mechanical changes emerge as a BYPRODUCT of focusing on cadence rather than flooding your mind with technical cues that may be difficult to implement in real time.
 
2. FIND SOFT RUNNING SURFACES 

This isn’t possible 100pct of the time for everyone, but the sacrifice can be worth it. When I’ve been on the cusp of injury, I’ve done endless loops around a grass soccer field to get the mileage in while minimizing the risk of further injury. There’s precedent for this too at the highest levels of running, as USA Olympians Galen Rupp and Dathan Ritzenheim (both historically injury prone) have been known to do up to 20 miles around a 600m grass loop! As a caveat, there isn’t as much evidence to support this strategy as we might think. That said, anecdotally countless runners report fresh and rejuvenated legs after dedicating the time and effort to run more on grass.

​Article: The Benefits of Running on Grass (Triathlete Magazine)
 
3. TRAIN SMART! 

Probably the most important strategy of all. Smart training provides the right amount of stimulus for the body to adapt and become stronger; excess training provides a stimulus too great for the body’s adaptive capabilities. This doesn’t necessarily mean physical breakdown though. Pain could be a warning signal, especially notable given the high density of nerve tissue in the feet. With excess loading, the foot can become more sensitive to pain, meaning it takes less of a stimulus to provoke a higher level of pain than before. All this information returns us to the concept that the first line of defense against plantar fasciitis (or any injury for that matter) is to pick the right training loads.
 
4. SELF-MASSAGE YOUR FOOT  

For self-massage, the simplest would be direct pressure. Just put your finger on a tender spot and hold it there. You can also massage along the foot, finding those “rough” spots or knotted areas and working them out. Though people often report mixed results from self-massage in other areas of the body, the foot tends to respond quite well, perhaps because the foot is so dense with nerve tissue.
 
Another form of self-massage is instrument assisted soft tissue mobilization. This is just a fancy term for using different objects to perform self-massage! There are plenty of commercial products on the market, some designed specifically for the feet. Everyone has their own preferences, from the hardness of a golf ball to the softness of the spikey ball. Of all the implements available the spikey ball seems to be the most well received.