October 2009

In the Moment: Sports Medicine

ITMsports-23262778By Jordana Bieze Foster

Alter footfall? Not so fast

Natural running pattern may be best

Websites all over the internet claim that runners who use a rearfoot strike pattern can run more efficiently and prevent injury by converting to a midfoot or forefoot strike pattern. But, as if we needed another reason to distrust information found online, studies of these variables suggest otherwise.

Although one epidemiologic study has found that faster long-distance runners are more likely to use a forefoot or midfoot strike pattern, other research suggests the relative biomechanical and physiological advantages over rearfoot running are unclear. Not only that, one recent modeling study actually predicted that the rearfoot strategy would be the most economic option, according to Joseph Hamill, PhD, a professor of kinesiology at the University of Massachusetts at Amherst, who presented a symposium on footfall patterns in October at the Prescription Foot Orthotic Laboratory Association’s annual conference on foot biomechanics and orthotic therapy.

“It turns out that the rearfoot pattern is least costly. This seems to argue against some of the programs you see on the internet,” Hamill said.

The recent attention to running footfall patterns may stem from a 2007 study of 415 participants in an elite-level half marathon, which found that although only 23.7% of runners used a midfoot pattern, the runners in that group tended to be faster than the rearfoot strikers who accounted for the majority of the study population.

Research from Hamill’s group has identified some biomechanical differences between the two strategies. A 2000 study presented at the Canadian Society of Biomechanics meeting found greater knee stiffness in forefoot running. A study presented in August at the annual meeting of the American Society of Biomechanics found significant differences in coordination patterns. And a third study confirmed that (not suprisingly) dorsiflexor activity differed as well.

But the latter study, which was scheduled to be presented at the International Society of Biomechanics meeting but was not because of passport issues, found no other differences in foot muscle activity. And research presented in May at the annual meeting of the American College of Sports Medicine found no significant differences in oxygen costs.

For Hamill, however, the piece de resistance was a second ASB study in which a computer model analyzed the energy costs for midfoot and rearfoot strike patterns, under the condition that overall energy expenditure be minimized (e.g., running as efficiently as possible for each particular footfall pattern). The researchers found that the energy rate for midfoot running was 1.2 kcal/min higher than for rearfoot running, a difference that would seem to take a toll over the course of the two-plus hours it takes an elite athlete to run a marathon, for example.

Even so, it may not make sense for midfoot or forefoot runners to try to switch to a rearfoot pattern either. The aforementioned ASB study on coordination patterns found that although the natural rearfoot strikers were able to mimic the coordination patterns of the forefoot strikers, the natural forefoot strikers were not able to alter their coordination patterns to match those of the rearfoot runners.

“I especially wouldn’t recommend a switch from a forefoot to a rearfoot style,” said Allison H. Gruber, a graduate student at UMass-Amherst who presented the findings at the ASB meeting. “I actually wouldn’t recommend anyone switching. It’s better to just do what’s normal for you.”

Hamill suggested that running shoe designs, currently optimized primarily for rearfoot runners, should feature different models for runners with other footfall patterns. The challenge in that regard, however, will be that the forefoot area of a running shoe offers less room for modification than the rearfoot area.

“Footwear ultimately should be designed for midfoot and forefoot runners,” Hamill said. “In the running industry, we haven’t paid much attention to this.”

Skateboarding shoes may test well but bail out on high-impact landing

Skateboarding shoes may not be providing athletes with the shock attenuation they need, in part because the shoes are being tested improperly, according to research presented in October at the annual PFOLA conference on foot biomechanics and orthotic therapy.

The standard method for measuring shock attenuation in footwear generates about 5 J of impact energy. That may be fine for relatively low-impact sports like running, but a skateboarder landing from a jump generates impacts between 40 J and 50 J, according to E.C. “Ned” Frederick, PhD, president of Exeter Research in Exeter, NH, who presented on skateboarding biomechanics at the PFOLA conference.

Frederick and colleagues have found that the impacts are even higher when a skateboarder “bails out” from a jump and lands on his or her feet instead of on the skateboard, which absorbs some of the shock during a successful landing.

With regard to testing, Frederick reported, the skateboarding shoes that performed best at 5 J actually performed worst at 44 J of impact, and vice-versa.

Repeat ACL surgery rates suggest poor compliance in young patients

Research from the Hospital for Special Surgery in New York City offers some evidence-based ammunition for practitioners hoping to enforce patient compliance after anterior cruciate ligament reconstruction: Those in the least-compliant age groups are most likely to need a repeat procedure.

The investigators reviewed data for more than 70,000 ACL reconstructions conducted in the state of New York, and found that 6.5% of patients underwent subsequent knee surgery within a year. Age was a significant predictor of repeat ACL reconstruction, with an 82% increased risk seen in patients under the age of 20, 43% in those between 20 and 29, and 19% in in those between 30 and 39. The findings were published in the October issue of the Journal of Bone & Joint Surgery.

Younger patients may be at higher risk for repeat surgery because they tend to be more active, or because they are less likely to comply with rehabilitation restrictions, according to Stephen Lyman, PhD, director of epidemiology and biostatistics at HSS and a co-author of the study.

Hip strengthening may complement orthoses, tendon loading for PTTD

A resistive exercise program for posterior tibial tendon disorder may be even more effective when a hip strengthening component is added, according to researchers from the University of Southern California.

In a study published in the January issue of Physical Therapy, the USC group analyzed the effects of custom foot orthoses wear and resistive exercise in 36 patients with stage I or II PTTD. Patients were randomized to orthoses and calf stretching only, orthoses and stretching plus concentric exercise, or orthoses and stretching plus eccentric exercise.

The custom foot orthoses were semi-rigid, full contact orthoses with medial rearfoot posting to decrease heel valgus and forefoot posting in the presence of bony deformities. Exercises were performed in shoes and orthoses, using a custom TibPost Loader device that allowed for targeted muscle training, twice a day for 12 weeks. A Theraband or similar resistive exercise device can be used in practice.

That study found that pain and functional scores improved significantly in all groups, least in the group that did not exercise and most in the eccentric exercise group. The researchers continued to see improvement six months later.

But the investigators suspected that more proximal variables might also play a role in PTTD, according to Kornelia Kulig, PhD, PT, an associate professor of clinical physical therapy at USC, who presented on the topic at the PFOLA conference. In particular, they noted that PTTD patients tend to have a difficult time standing on one foot, which is suggestive of hip weakness. A single-patient analysis indicated that hip extensor and abductor strength and hip extensor endurance were significantly greater on the uninvolved side than the involved side.

That led to a full-scale study of an intervention program including hip extension and abduction exercises in addition to the previously described tendon reloading exercises and the custom foot orthoses. Exercises are performed twice daily for 16 weeks.

Sixteen patients had completed the program as of early October, Kulig said. Although the results have not been published, she told the PFOLA attendees that the study subjects demonstrated significantly less pain with walking and significantly improved function, strength, endurance and balance.

It remains to be seen, however, whether adding hip exercises to the training protocol will have any effect on tendon structure. In the September issue of Foot & Ankle International, Kulig and colleagues reported that 10 weeks of the foot-specific eccentric tendon loading exercises combined with orthoses and stretching were not associated with any changes in tendon morphology or vascularization as assessed using grayscale and Doppler ultrasound, despite the improvement in symptoms.

“The exercises did not make a difference at the tendon level,” Kulig said.

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