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art science

Research News

This page introduces the latest research findings in a brief and accessible form,
and offers you insights into the world of biomechanics and medical technology
(reviews written by Dr. Sophie Elixhauser)

The diagonal stride is a common uphill technique in cross-country skiing. It is well-known that increasing the velocity in skiing is linked to the cycle rate and cycle length. Based on studies from roller-skiing and on-snow skiing, researchers Andersson et al.  speculated that “an increased cycle rate at a long cycle length is the main factor for increasing a high sub-maximal velocity up to a maximal velocity” (2) in diagonal cross-country skiing on snow. Yet, the exact role of cycle rate, cycle length, and time for force generation at different velocities had not previously been tested for this type of skiing. Andersson et al. therefore examined cycle and force characteristics in 11 male elite cross-country skiers skiing uphill with the diagonal stride technique at three different velocities (moderate, high & maximal). Using novel’s pedar® mobile system, they analysed plantar leg force and pole force, which they combined with video analysis and photocell measurements. They found that cycle length and cycle rate increased from moderate to high velocity, and maximal velocity was attained by elevating cycle length and decreasing cycle rate. The tests further showed that “that the development of leg force was considerably faster during diagonal skiing on snow than for roller-skiing” (17). The researchers therefore conclude that when training roller-skiing athletes should “focus on generating high vertical leg forces early during the kick in order to avoid a technique adaptation that might result in ‘slipping’ when skiing on snow” (17). All in all, these tests show the high importance of rapid leg force generation in fast diagonal skiing.

Andersson, E; Pellegrini, B; Sandbakk, Ø; Stöggl, T and H-C Holmberg (2014):
The effects of skiing velocity on mechanical aspects of diagonal crosscountry skiing.
Sports Biomechanics, DOI: 10.1080/14763141.2014.921236

Squatting is a movement frequently carried out during many daily tasks. Due to its demands on knee and hip musculature, squatting remains a common goal in many rehabilitation programmes. Scientific studies have inquired into the effect of knee osteoarthritis and total knee arthroplasty on squatting, finding asymmetrical loading between affected and non-affected limbs or slow and unbalanced movement execution. The hip, nevertheless, has not been examined in this respect. Researchers Brauner et al. therefore decided to study the effects of unilateral total hip arthroplasty (THA) on people’s squatting abilities, particularly during early functional recovery of patients.

They examined 61 test subjects (34 men, 27 female) who had undergone THA, and the results were later compared to a healthy reference group. Before the trial, each person was asked to complete the Function Assessment Questionnaire Hannover for Osteoarthritis. By means of 2 pedar® posturo pressure mats, the researchers tested the interlimb vertical force distribution and the dynamic stability during the squat manoeuvre. Similar to the aforementioned studies about the knee, they found that “patients who had undergone THA perform squats with an unloading of the operated limb and reduced dynamic stability”. Yet though limb loading became more symmetric and stability improved with rehabilitation, anteroposterior stability remained impaired. These results provide quantitative information that can be used to monitor the clinical progression and early functional recovery of patients with THA.

Brauner, T; Wearing, S; Rämisch, E; Zillober, M; and T Horstmann (2014):
Can measures of limb loading and dynamic stability during the squat maneuver provide an index of early functional recovery after unilateral total hip arthroplasty?
Archives of Physical Medicine and Rehabilitation 95(10): 1946-1953

Patients with diabetic polyneuropathy (DPN) are more likely to develop planter ulceration due to alterations in the foot rollover process during walking and an overall worsening of foot-ankle muscular, articular and nervous function.  The Brazilian/Italian group of researchers around Cristina Sartor and Isabel Sacco have tested the effects of strengthening, stretching and functional training on foot function in patients with DPN. The study was based on the hypothesis that these interventions could lead to the recovery of muscles and joint functions and help DPN patients “to maintain, for as long as possible, the residual capability to interact safely with the ground while walking or standing.”

Sartor et al. recruited 55 patients with DPN between 45-65 years of age. The intervention group of 26 persons underwent administered foot-ankle and gait training twice a week for an overall period of 12 weeks, whilst the control group of 29 persons received standard medical care. Plantar loading distribution was measured using novel’s pedar® system and the collected data were analysed with the software novel-projects. In comparison to the control group, the researchers found that the intervention “discreetly changed foot rollover towards a more physiological process, supported by improved plantar pressure distribution and better functional condition of the foot ankle complex.“ They therefore recommend these exercises as a complementary intervention to patients with DPN to be repeated periodically.

Sartor, CD; Hasue, RH; Cacciari, LP; Butugan, MK; Watari, R; Pássaro, AC; Giacomozzi, C; Sacco, ICN (2014):
Effects of strengthening, stretching and functional training on foot function in patients with diabetic neuropathy: results of a randomized controlled trial.
BMC Musculoskeletal Disorders 15:137 doi:10.1186/1471-2474-15-137

While treatment of children born with clubfoot nowadays often follows well-described non-operative approaches, relapse is not uncommon following initial correction. In children older than 2.5 years, a recommended surgical approach is to transfer the anterior tibialis tendon (ATTT) laterally to the third cuneiform, third/fourth metatarsal or to the cuboid. The use of pedography has become quite common to test plantar pressures in children with clubfoot. However limited work has been done to assess functional outcome following ATTT.

Using novel’s emed® technology, the group of researchers around Kelly Jeans from Dallas, Texas, embarked on a study to objectively test whether plantar pressures normalize after ATTT. Between 2003 and 2010, thirty children with clubfoot (37 clubfeet) underwent gait analysis and plantar pressure tests, which implied walking on the emed® platform for a minimum of five trials for each foot both preoperatively and postoperatively, i.e. one to two years after the surgery. Contact area, contact time, and peak pressures were quantified for seven different regions of the foot. The researchers found significant differences between preoperative and postoperative outcomes. The changes after ATTT, as they conclude, show that “the foot is better aligned for a more even distribution of pressure throughout the foot, but is not fully normalized”.

Jeans, K; Tulchin-Francis, K.; Crawford, L. and L.A. Karol 2014:
Plantar pressures following anterior tibialis tendon transfers in children with clubfoot.
Journal of Pediatric Orthopaedics
34 (5): 552-558

Customised foot orthoses (FOs) featuring extrinsic rearfoot posting are widely used for the treatment of symptomatic pronated foot type. Various FOs exist differing mainly with regard to their customisation to the individual patient. Previous research using surface electromyography (EMG) has found that FOs can affect muscle activity during gait. Likewise, plantar pressure distribution may be altered by the use and dose of FOs. But the specific dose response effect on these parameters has not yet been quantified.

The group of researchers Telfer et al. thus decided to test the dose response effect of customised FOs on EMG activity of selected lower limb muscles and on the distribution of in-shoe plantar pressure, and the effect of foot types on these variables. They measured EMG and plantar pressure effects of varying the dose in two groups of participants, with normal and pronated foot types respectively. novel’s pedar® system was used for the in-shoe plantar pressure measurements. The outcomes of this study lead Telfer et al. to conclude that “there is a significant and linear dose response effect of FOs on plantar pressure variables at the rearfoot, midfoot and forefoot” (p. 6).  No such effect could be found for muscle activity.  Moreover, foot type appeared to play an important role in the effect of FOs on above-knee muscle activity.
Telfer, S; Abbott, M.; Steultjens, M.; Rafferty, D.; and J.Woodburn (2013)
Dose-response effects of customised foot orthoses on lower limb muscle activity and plantar pressures in pronated foot type.
Gait & Posture 38(3): 443-449

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