research Update 31.01.14

Proof of concept: enthesitis and new bone formation in spondyloarthritis are driven by mechanical strain and stromal cells.

Jacques et al Ann Rheum Dis 2014;73:437-445

Objectives Spondyloarthritides (SpA) are characterised by both peripheral and axial arthritis. The hallmarks of peripheral SpA are the development of enthesitis, most typically of the Achilles tendon and plantar fascia, and new bone formation. This study was undertaken to unravel the mechanisms leading towards enthesitis and new bone formation in preclinical models of SpA.

Conclusions These findings provide a formal proof of the concept that mechanical strain drives both entheseal inflammation and new bone formation in SpA.

Commentary: This paper looks specifically at spondyloarthropathy and so cannot be amortised to planta fasciitis, however, the finding is important, and is the first to show a mechanical as well as inflammatory basis to enthesitis in spondyloarthritis.

The pursuit of improved running performance: Can changes in cushioning and somatosensory feedback influence running economy and injury risk?

Moore et al,  Footwear Science 2014 Article in Press

Abstract

There is currently no consensus regarding the effect that barefoot (BFT) running has on running economy (RE). Stride length and shoe mass are confounding variables, with a BFT stride length being shorter than a shod (SH) stride length. Comparison of SH, minimalist shod (MS) and BFT allows controlled variation of cushioning and somatosensory feedback to determine the effect that either and/or both have on RE and running mechanics.

Methods: Fifteen female habitually shod, recreational runners visited the laboratory twice. Familiarisation with BFT and SH treadmill running occurred during visit one, in addition to determining SH stride length and BFT stride length. During visit two participants ran BFT, SH and MS with BFT stride length and MS with SH stride length at 10 km·h−1 for six minutes with 10-minute rest periods between each condition. Lower limb kinematics, electromyography, impact acceleration and O2 were recorded during the final two minutes of each run.

Results: BFT RE was significantly better than SH and MS with BFT stride length. SH RE was significantly worse than MS with SH stride length, but similar to MS with a BFT stride length. Low vertical oscillation, peak eversion and peak dorsiflexion, less plantarflexion at toe-off, in addition to an earlier occurrence of heel off, higher impact accelerations and greater tibialis anterior activity were observed during the most economical condition.

Conclusions: Heightened somatosensory feedback and lack of cushioning (BFT) offered an advantage to economy over less somatosensory feedback (MS) and cushioning (SH). Whilst the low vertical oscillation and low plantarflexion at toe-off appear to contribute to the improved RE, other changes to running mechanics whilst BFT could potentially influence injury risk.

Commentary: Small sample size, and I am a little concerned at the manipulation of stride length on a treadmill, and how this is achieved in one session. All the same, this paper goes against the flow a bit, and i shall be interested to see what the feedback is.

Soccer Boots Elevate Plantar Pressures in Elite Male Soccer Professionals

Carl et al, Clin J Sport Med 2014;24:58–61

OBJECTIVE:: The present study measured the difference in peak plantar pressure between running shoes and soccer shoes in male soccer professionals [mean (SD): age, 23 (4) years; height, 184 (7) cm; weight, 81 (6) kg]. DESIGN:: Case series. SETTING:: Institutional study.

PARTICIPANTS:: A total of 17 elite male soccer professionals [mean (SD): age, 23 (4) years; height, 184 (7) cm; weight 81 (6) kg].

INTERVENTIONS: Fifteen right and left steps with sensor-loaded insoles (99 sensors, 50 Hz) while running (3.3 m/s) in running shoes and then chosen soccer shoes (12-stud profile). The players were equipped with running shoes from the supplier without any medical supervision.

MAIN OUTCOME MEASURES: Changes of peak plantar pressure for 9 defined foot portions between soccer boots and running shoes. RESULTS:: A statistically significant increase of peak plantar pressure was found for the lateral midfoot (P < 0.001 for preferred and nonpreferred foot), the first metatarsal head (preferred foot: P < 0.001, nonpreferred foot: P = 0.002), the metatarsal heads 4/5 (preferred foot: P = 0.001, nonpreferred foot: P = 0.002), and the big toe (preferred foot: P = 0.001, nonpreferred foot: P < 0.001), but not for the lateral and medial hindfoot, the medial midfoot, and lesser toes.

CONCLUSIONS: In running, soccer boots generate excessive foot loadings predominantly under the lateral midfoot, as compared with running shoes. Players should be trained with a thoughtfully designed workout regimen that allows performing as many straight running exercises as possible in running shoes instead of soccer boots. This may help to prevent fifth metatarsal stress fractures in elite male soccer players.

Commentary: No rocket science here guys and girls, but to my knowledge, this is the first published paper making a specific recommendation to mix training footwear, and more importantly to use running footwear instead of football boots for soccer based training. Important for this alone.

Macrophage depletion reduces cell proliferation and extracellular matrix accumulation but increases the ultimate tensile strength of injured Achilles tendons.

de la Durantaye et al, Journal of Orthopaedic ResearchVolume 32, Issue 2, pages 279–285, February 2014

ABSTRACT

Macrophages are present in large numbers and display specific and distinct phenotypes during the various phases of tissue repair. However, their role following tendon injury and during repair has never been investigated. We injected C57BL/6 mice daily for 4 days with liposome-encapsulated clodronate to deplete circulating monocytes/macrophages. Placebo mice were injected with PBS (phosphate buffered saline). The left Achilles tendons of the mice were transversely sectioned and sutured using the 8-strand technique. Macrophage accumulation and cell proliferation were significantly lower in the tendons of clodronate-treated mice than in those of PBS-treated mice on days 3 and 7 post-injury. TGF-β1 staining was significantly more intense in the tendons of PBS-treated mice on day 7 post-injury. Edema and the dry mass of the Achilles tendons were also higher in the PBS-treated mice on days 7 and 14 post-injury. No differences in absolute strength and stiffness were observed, but Young's modulus and maximal stress were significantly greater for tendons from the clodronate-treated mice than those from PBS-treated mice after 14 days of tendon repair. Overall, our findings showed that macrophages promote cell proliferation and extracellular matrix accumulation but their presence leads to inferior ultimate tensile strength of the Achilles tendons

Commentary: A very interesting animal study. While nonsteroidal anti-inflammatory drugs are commonly prescribed to dampen the acute phase of inflammation, there are few tangible clinical benefits. There is thus an urgent need to understand the healing response and to find new therapeutic strategies to improve tendon healing.

The effect of lateral banking on the kinematics and kinetics of the lower extremity during lateral cutting movements

Wannop, J.W., et al. The effect of lateral banking on the kinematics and kinetics of the lower extremity during lateral cutting movements. Human Movement Science (2013), http://dx.doi.org/

Abstract

There are many aspects of cutting movements that can limit performance, however, the implementation of lateral banking may reduce some of these limitations. Banking could provide a protective mechanism, placing the foot and ankle in orientations that keep them out of dangerous positions. This study sought to determine the effect of two banking angles on the kinematics and kinetics of the lower extremity during two athletic maneuvers.

Kinematic and kinetic data were collected on 10 recreational athletes performing v-cuts and side shuffle movements on different banked surfaces (0°, 10°, 20°). Each sample surface was rigidly attached to the force platform. Joint moments were calculated and compared between conditions using a repeated measures ANOVA.

Banking had a pronounced effect on the ankle joint. As banking increased, the amount of joint loading in the transverse and frontal planes decreased likely leading to a reduction in injury risk. Also an increase in knee joint loading in the frontal plane was seen during the 20° bank during the v-cut. Conversely loading in the sagittal plane at the ankle joint increased with banking and coupled with a reorientation of the ground reaction vector may facilitate a performance increase. The current study indicates that the 10° bank may be the optimal bank, in that it decreases ankle joint loading, as well as increases specific performance variables while not increasing frontal plane knee joint loading. If banking could be incorporated in footwear it may be able to provide a protective mechanism for athletes.

Commentary: this is a very interesting paper, with authors including Stefan Graf and Darren Stefanyshyn, fro The Human Performance Laboratory in Calgary. Darren has had a long association with adidas, so do not be surprised to see some of the results of this work in future adi product! Banking, or "canting' of footwear in my opinion is one of the great performance and injury prevetion sleeper technolgies out there rightt now. I look forward to reading more.

Foot posture, foot function and low back pain: The Framingham Foot Study

Menz et al, Rheumatology (2013) 52 (12): 2275-2282.

Objective. Abnormal foot posture and function have been proposed as possible risk factors for low back pain, but this has not been examined in detail. The objective of this study was to explore the associations of foot posture and foot function with low back pain in 1930 members of the Framingham Study (2002-05).Methods. Low back pain, aching or stiffness on most days was documented on a body chart. Foot posture was categorized as normal, planus or cavus using static weight-bearing measurements of the arch index. Foot function was categorized as normal, pronated or supinated using the centre of pressure excursion index derived from dynamic foot pressure measurements. Sex-specific multivariate logistic regression models were used to examine the associations of foot posture, foot function and asymmetry with low back pain, adjusting for confounding variables.Results. Foot posture showed no association with low back pain. However, pronated foot function was associated with low back pain in women [odds ratio (OR) = 1.51, 95% CI 1.1, 2.07, P = 0.011] and this remained significant after adjusting for age, weight, smoking and depressive symptoms (OR = 1.48, 95% CI 1.07, 2.05, P = 0.018).Conclusion. These findings suggest that pronated foot function may contribute to low back symptoms in women. Interventions that modify foot function, such as orthoses, may therefore have a role in the prevention and treatment of low back pain

Commentary: Distinguished researcher hylton Menz goes out on a limb here to suggest the link between foot posture, orthoses and low back pain. there are a number of limitations to this study, all of which the authors outline in their discussion.

Despite these limitations, this study has several important strengths. First, in contrast to previous investigations focusing on military or clinical  samples, this study was population-based and the findings are therefore more likely to be representative of the general population. Second, they used an objective measure of foot posture rather than relying on visual assessment by clinicians, which is known to have questionable reliability. Third, to the best of our knowledge this is first study to incorporate a measure of dynamic foot function. This is an important consideration, given that static measures of foot posture may not always provide an accurate indicator of dynamic foot function when walking.

Part 2 of the Foot and Leg in Sport begins!!

Finally, after you have diligently waded through all the percursors, I have prepared you for the beginning.. Part 2: Injuries to the foot and leg!

Chapter 8: We look at the skin  and nails, and this is stuff you need to know and know well, because these are the stuctures injured more in sport than any other.

Research update November 2013

Gender-based differences in the functional deformation of the foot longitudinal arch. Mako Fukanoa, Toru Fukubayashib, The Foot 22 (2012) 6– 9

Background: Gender differences in physical characteristics are associated with differing incidences of sports-related injuries. However, functional differences in the foot arch, which acts as a shock absorber under dynamic conditions, have not been investigated.

Objective: This study investigated gender-based differences in the medial and lateral longitudinal arches under static and dynamic conditions.

Methods: Eleven males and 8 females participated in this study. Radiographic images of the subjects’ feet were obtained under static conditions, with and without weight bearing. In addition, each subject performed single leg landing from 10 cm platform with the knee extended, and cineangiographic images in the sagittal plane were obtained during landing.

Results: In the weight bearing position, the medial and lateral arch angles of the females were significantly greater than those of the males, but neither of the angles differed between the males and females without weight bearing. The magnitude of the angular changes of each arch was significantly greater in the females than in the males.

Conclusion: These results suggest that females have a greater range of arch motion than males under static and dynamic loading conditions.

Comment: it is difficult to assign too much weight to this study since the sample size (8 females) is very small. In addition, arch height has been shown to vary according to the amount of circulating oestragen and the phases of the menstrual cycle. This is also significantly effected by the oral contraceptive pill (OCP). None of these variables were controlled, making the conclusions of the study dubious at best.

Anatomy of the anterolateral ligament of the knee, Claes et al, Journal of Anatomy, Volume 223, Issue 4, pages 321–328, October 2013

Abstract

In 1879, the French surgeon Segond described the existence of a ‘pearly, resistant, fibrous band’ at the anterolateral aspect of the human knee, attached to the eponymous Segond fracture. To date, the enigma surrounding this anatomical structure is reflected in confusing names such as ‘(mid-third) lateral capsular ligament’, ‘capsulo-osseous layer of the iliotibial band’ or ‘anterolateral ligament’, and no clear anatomical description has yet been provided. In this study, the presence and characteristics of Segond's ‘pearly band’, hereafter termed anterolateral ligament (ALL), was investigated in 41 unpaired, human cadaveric knees. The femoral and tibial attachment of the ALL, its course and its relationship with nearby anatomical structures were studied both qualitatively and quantitatively. In all but one of 41 cadaveric knees (97%), the ALL was found as a well-defined ligamentous structure, clearly distinguishable from the anterolateral joint capsule. The origin of the ALL was situated at the prominence of the lateral femoral epicondyle, slightly anterior to the origin of the lateral collateral ligament, although connecting fibers between the two structures were observed. The ALL showed an oblique course to the anterolateral aspect of the proximal tibia, with firm attachments to the lateral meniscus, thus enveloping the inferior lateral geniculate artery and vein. Its insertion on the anterolateral tibia was grossly located midway between Gerdy's tubercle and the tip of the fibular head, definitely separate from the iliotibial band (ITB). The ALL was found to be a distinct ligamentous structure at the anterolateral aspect of the human knee with consistent origin and insertion site features. By providing a detailed anatomical characterization of the ALL, this study clarifies the long-standing enigma surrounding the existence of a ligamentous structure connecting the femur with the anterolateral tibia. Given its structure and anatomic location, the ALL is hypothesized to control internal tibial rotation and thus to affect the pivot shift phenomenon, although further studies are needed to investigate its biomechanical function.

Comment: this is like finding the Lost Ark of the Covenant of anatomy! In terms of a cadaveric study, the cohort is huge, with 41 knees. Critically, the ALL was identified in 40 of these 41 knees. Often discussed in hushed tones, the anterolateral ligament of the knee is rapidly gaining repect as the 3rd (behind ACL and PCL) critical stabilising ligament of the knee.

Do high-top shoes reduce ankle inversion? A dynamic x-ray analysis of aggressive cutting in a high-top and low-top shoe. Bishop, J.L. , Nurse, M.A., Bey, M.J. Footwear Science 2013, Article in press.

Abstract

Ankle strains and sprains are one of the most common basketball injuries. These injuries are often the result of excessive ankle inversion. High-top shoes are worn because it is thought that they limit inversion and, therefore, reduce the risk of inversion injuries. However, it is difficult to quantify inversion of the ankle inside the shoe with traditional measurement techniques, making comparison between footwear conditions difficult. The purpose of this study was to compare inversion of the ankle and shoe in a high-top and a low-top shoe during aggressive lateral cutting. It was hypothesised that ankle inversion would be lower than shoe inversion in both a high-top shoe and a low-top shoe. Six male basketball players were analysed over three dynamic cutting trials in each condition. As hypothesised, shoe inversion during aggressive cutting was higher than ankle inversion in the high-top shoe (17°) and the low-top shoe (25.5°). Future research should focus on determining the relative contribution of ankle inversion inside the shoe versus relative motion between the shoe and the body to ankle injuries.

Comment: From the Nike Sports Lab in Oregon, it investigates a very small sample of only 6 athletes. I begs the question, "how come players in the WNBL, who more often than not wear low cut basketball shoes, have no greater incidence of ankle inversion injury than players in the NBL"? Same goes for netball, where elite players almost exclusively wear low cut footwear, often based on a running shoe outsole, with not greater incidence of inversion ankle injury.

Impact attenuation during weight bearing activities in barefoot vs. shod conditions: A systematic review. Alycia Fong Yan, Peter J. Sinclaira, , Claire Hillerb, Caleb Wegener, Richard M. Smith., Gait & Posture. Volume 38, Issue 2, June 2013, Pages 175–186

Although it could be perceived that there is extensive research on the impact attenuation characteristics of shoes, the approach and findings of researchers in this area are varied. This review aimed to clarify the effect of shoes on impact attenuation to the foot and lower leg and was limited to those studies that compared the shoe condition(s) with barefoot. A systematic search of the literature yielded 26 studies that investigated vertical ground reaction force, axial tibial acceleration, loading rate and local plantar pressures. Meta-analyses of the effect of shoes on each variable during walking and running were performed using the inverse variance technique. Variables were collected at their peak or at the impact transient, but when grouped together as previous comparisons have done, shoes reduced local plantar pressure and tibial acceleration, but did not affect vertical force or loading rate for walking. During running, shoes reduced tibial acceleration but did not affect loading rate or vertical force. Further meta-analyses were performed, isolating shoe type and when the measurements were collected. Athletic shoes reduced peak vertical force during walking, but increased vertical force at the impact transient and no change occurred for the other variables. During running, athletic shoes reduced loading rate but did not affect vertical force. The range of variables examined and variety of measurements used appears to be a reason for the discrepancies across the literature. The impact attenuating effect of shoes has potentially both adverse and beneficial effects depending on the variable and activity under investigation.

Comment: seems to me this study out of the University of Sydney is looking where everyone else is.. the wrong way! The key highlighted text above is "During running, shoes reduced tibial acceleration but did not affect loading rate or vertical force." That is right.. accelerations are really important, because they give a direct indication of transmitted shock.. and running shoes unquestionably reduce transmitted shock. The vast body of opinion now agrees that impact loading is probably not that important.. but it is something the punters understand to a degree, and the graph is easy to read! That means it sexy and suitable for general consumption, but it doesn not mean it really matters...

Extracorporeal Shock Wave Therapy Is Effective In Treating Chronic Plantar Fasciitis: A Meta-analysis of RCTs. Adeel Aqil, Muhammad R. S. Siddiqui, Matthew Solan, David J. Redfern, Vivek Gulati, Justin P. Cobb 

Background

Plantar fasciitis is the most common cause of heel pain. It may remain symptomatic despite conservative treatment with orthoses and analgesia. There is conflicting evidence concerning the role of extracorporeal shock wave therapy (ESWT) in the management of this condition.

Questions/purposes

We investigated whether there was a significant difference in the change of (1) VAS scores and (2) Roles and Maudsley scores from baseline when treated with ESWT and placebo. Specifically we compared overall improvement from baseline composite VAS, reduction in overall VAS pain, success rate of improving overall VAS pain by 60%, success rate of improving VAS pain by 60% when taking first steps, doing daily activities, and during application of a pain pressure meter.

Conclusions

ESWT is a safe and effective treatment of chronic plantar fasciitis refractory to nonoperative treatments. Improved pain scores with the use of ESWT were evident 12 weeks after treatment. The evidence suggests this improvement is maintained for up to 12 months. We recommend the use of ESWT for patients with substantial heel pain despite a minimum of 3 months of nonoperative treatment.

Comment: It has taken the best part of 20 years, but I am now about 95% convinced that ESWT is a viable and useful therapy for chronic plantar heel pain when conservative management has failed. this is a meta analysis of RCT's, a high level of evidence.

Biomechanical and biochemical protective effect of low-level laser therapy for Achilles tendinitis Rodrigo Labat Marcos et al, Journal of the Mechanical Behavior of Biomedical Materials, Volume 29, January 2014, Pages 272–285

Highlights

• Drugs and laser treatments of tendinitis lead to different mechanical properties.

• Lower tendon elasticity after diclofenac (NSAID) treatment than untreated tendinitis.

• Laser treatment (1 J) exhibits the best effect against tendinitis after 7 days.

• Gene expression analysis correlates mechanical properties observations.

Abstract

For three decades, low level laser therapy (LLLT) has been used for treatment of tendinitis as well as other musculoskeletal diseases. Nevertheless, the biological mechanisms involved remain not completely understood. In this work, the effects of LLLT and of the widely used nonsteroidal anti-inflammatory drug, diclofenac, have been compared in the case of collagenase-induced Achilles tendinitis. Wistar rats were treated with diclofenac or laser therapy. The tensile behavior of tendons was characterized through successive loading–unloading sequences. The method considered 11 characteristic parameters to describe the mechanical behavior. It was shown that during the acute inflammatory process of the tendon, the mechanical properties were significantly correlated to the high levels of MMP-3, MMP-9 and MMP-13 expression presented in a previous paper (Marcos, R.L., et al., 2012). The treatment by non-steroidal anti-inflammatory drugs such as diclofenac sodium produces a low protective effect and can affect the short-term biochemical and biomechanical properties. On the contrary, it is shown that LLLT exhibits the best results in terms of MMPs reduction and mechanical properties recovery. Thus, LLLT looks to be a promising and consistent treatment for tendinopathies.

Comment: this is a very nice animal study ( for those not familiar, rats share remarkably similar physiology and gene expression to humans, and so are often used in invasive studies like this). It is pretty hard to argue the outcomes, and LLLT appears to be gaining some fans.. and some evidence. Also check out this if you are interested.

The effect of stud configuration on rotational traction using the studded boot apparatus Dara M. Twomey, Monique Connell, Lauren Petrass, Leonie Otago Sports Engineering March 2013, Volume 16, Issue 1, pp 21-27

Abstract

Due to its associated injury risk, rotational traction is a frequently measured natural turf surface property. The most commonly used equipment, the studded boot apparatus (SBA), consists of a circular stud configuration that does not replicate the stud pattern on a regular football boot and may under or over estimate the surface traction. The aim of this study was to establish potential differences in the rotational traction measured between the current stud configuration on the SBA and the stud configuration on the most commonly used Australian football boots. The original studded boot had significantly higher rotational traction than the moulded stud sole or bladed sole. Location, quality and time tested all interacted significantly with the rotational traction measured. The current SBA may not accurately represent the rotational traction experienced by football players, and consequently may not be the most appropriate configuration to assess the relationship between rotational traction and injuries.

Comment: important paper underlining the importance of correct boot selection based on stud configuration for the football codes. Get this one wrong at your peril!

Stretch and activation of the human biarticular hamstrings across a range of running speeds  Schache, A.G., Dorn, T.W., Wrigley, T.V., Brown, N.A.T., Pandy, M.G. European Journal of Applied Physiology 2013 113 (11) , pp. 2813-2828

 Purpose: The human biarticular hamstrings [semimembranosus (SM), semitendinosus (ST) and biceps femoris long head (BFLH)] have an important role in running. This study determined how hamstrings neuro-mechanical behaviour changed with faster running, and whether differences existed between SM, ST and BFLH. Methods: Whole-body kinematics and hamstrings electromyographic (EMG) activity were measured from seven participants running at four discrete speeds (range: 3.4 ± 0.1 to 9.0 ± 0.7 m/s). Kinematic data were combined with a three-dimensional musculoskeletal model to calculate muscle-tendon unit (MTU) stretch and velocity. Activation duration and magnitude were determined from EMG data. Results: With faster running, MTU stretch and velocity patterns remained similar, but maxima and minima significantly increased. The hamstrings were activated from foot-strike until terminal stance or early swing, and then again from mid-swing until foot-strike. Activation duration was similar with faster running, whereas activation magnitude significantly increased. Hamstrings activation almost always ended before minimum MTU stretch, and it always started before maximum MTU stretch. Comparing the hamstrings, maximum MTU stretch was largest for BFLH and smallest for ST irrespective of running speed, while the opposite was true for peak-to-peak MTU stretch. Furthermore, peak MTU shortening velocity was largest for ST and smallest for BFLH at all running speeds. Finally, for the two fastest running speeds, the amount of MTU stretch that occurred during terminal swing after activation had started was less for BFLH compared to SM and ST. Conclusion: Differences were evident in biarticular hamstrings neuro-mechanical behaviour during running. Such findings have implications for hamstrings function and injury.

Comment: Although a small cohort, this is a ripping little study from Marcus Pandy's group that sheds important new light on hamstring muscle action during running.

Research update October 2013

Autologous Platelet-Rich Plasma Versus Dextrose Prolotherapy for the Treatment of Chronic Recalcitrant Plantar Fasciitis. Eunkuk Kim,  Jong Ha Lee. PM&R Available online 19 July 2013

Design - A single-blinded, randomized, controlled study.

Participants

Twenty-one patients with a clinical diagnosis of chronic PF confirmed by diagnostic ultrasound (plantar fascia thickness >4 mm) were randomly assigned to the PRP group (n = 10) or the DP group (n = 11).

Interventions

Each patient received 2 injections into the plantar fascia through a peppering technique under ultrasound guidance at an interval of 2 weeks, either with 2 mL of autologous PRP or 2 mL of 15% dextrose/lidocaine solution.

Main Outcome Measurements

The outcome measures included the pain, disability, and activity limitation subscales, measured by means of the Foot Functional Index. Data were collected before the first injection, at 2 weeks (before the second injection), and at the 2- and 6-month follow-ups.

Conclusions

Each treatment seems to be effective for chronic recalcitrant PF, expanding the treatment options for patients in whom conservative care has failed. PRP treatment also may lead to a better initial improvement in function compared with DP treatment.

Kinematic and electromyographic analysis of the Nordic Hamstring Exercise. Massimiliano Ditroilo, Giuseppe De Vito, , Eamonn Delahunt. Journal of Electromyography and Kinesiology. Volume 23, Issue 5, October 2013, Pages 1111–1118

The Nordic Hamstring Exercise (NHE) has been introduced as a training tool to improve the efficiency of eccentric hamstring muscle contraction. The aim of this study was to perform a biomechanical analysis of the NHE. Eighteen participants (20.4 ± 1.9 years) performed two sets of five repetitions each of the NHE and maximal eccentric voluntary contraction (MEVC) of the knee flexors on an isokinetic dynamometer whilst knee angular displacement and electrical activity (EMG) of biceps femoris were measured. EMG was on average higher during the NHE (134.3% of the MEVC). During the forward fall of the NHE, the angle at which a sharp increase in downward velocity occurred varied between 47.9 and 80.5 deg, while the peak knee angular velocity (pVelocity) varied between 47.7 and 132.8 deg s−1. A significant negative correlation was found between pVelocity and peak EMG (r = −0.62, p < 0.01) and EMG at 45 deg (r = −0.75, p < 0.01) expressed as a percentage of peak MEVC EMG. Some of the variables analyzed exhibited good to excellent levels of intra- and inter-session reliability. This type of analysis could be used to indirectly monitor the level of eccentric strength of the hamstring muscles while performing the NHE and potentially any training- or injury-related changes.

Commentary: The Nordic Hamstring protoocol has gained popularity as an eccentric hamstring training program, especially in the football codes. For those of you not familiar with the protocol, watch this video.

[video:1]

This study provides a level of evidence supporting the concept that this protocol is an effective training tool to specifically strengthen the knee flexor muscles The results showed that during the performance of the NHE the BF is highly activated, in fact for the majority of the participants the peak activation was higher during the NHE compared to a traditional maximal eccentric exercise performed on an isokinetic dynamometer.

Influence of midsole hardness of standard cushioned shoes on running-related injury risk. Daniel Theisen, Laurent Malisoux, Joakim Genin, Nicolas Delattre, Romain Seil,, Axel Urhausen. Br J Sports Med 2013-article in press.

Abstract

Background In this double-blind randomised controlled trial, we tested if leisure-time runners using shoes with less compliant midsoles have a higher running-related injury (RRI) risk.

Method We provided 247 runners with standard running shoes having either a soft study shoes (soft-SS) or a hard study shoes (hard-SS) midsole and followed them prospectively for 5 months regarding RRI. All information about sports practice and injuries was uploaded on a dedicated internet platform and checked for consistency and completeness. RRI was defined as any first-time pain sustained during or as a result of running practice and impeding normal running activity for at least 1 day. Cox proportional hazards regressions were used to identify RRI risk factors.

Result The type of study shoes used for running was not associated with RRIs (HR=0.92; 95% CI 0.57 to 1.48). The hard-SS had a 15% greater overall stiffness in the heel region. The two study groups were similar regarding personal and sports participation characteristics, except for years of running experience, which was higher (p<0.05) in the hard-SS group. Global RRI incidence was 12.1 RRI/1000 h of running. No between-group differences were found regarding injury location, type, severity or category. Nevertheless, the adjusted regression model revealed positive associations with RRI risk for body mass index (HR=1.126; 95% CI 1.033 to 1.227), previous injury (HR=1.735; 95% CI 1.037 to 2.902) and mean session intensity (HR=1.396; 95% CI 1.040 to 1.874). Protective factors were previous regular running activity (HR=0.422; 95% CI 0.228 to 0.779) and weekly volume of other sports activities (HR=0.702; 95% CI 0.561 to 0.879).

Conclusions Midsole hardness of modern cushioned running shoes does not seem to influence RRI risk.

Commentary: No surprises here at all, and goes to underline the need for athkletic footwear companies to modify the claims historiaccly made about midsole hardness!

Effect of overground vs treadmill running on plantar pressure: Influence of fatigue. Daniel Theisen, Laurent Malisoux, Joakim Genin, Nicolas Delattre, Romain Seil, Axel Urhausen. Gait & Posture, Volume 38, Issue 4, September 2013, Pages 929–933.

Abstract

The differences produced when running on a treadmill vs overground may call into question the use and validity of the treadmill as a piece of equipment commonly used in research, training, and rehabilitation.

The aim of the present study was to analyze under pre/post fatigue conditions the effect of treadmill vs overground on plantar pressures. Twenty-seven recreational runners (17 men and 10 women) ran on a treadmill and overground at two speeds: S1 = 3.33 m/s and S2 = 4.00 m/s, before and after a fatigue protocol consisting of a 30-min run at 85% of their individual maximal aerobic speed (MAS). Contact time (CT in seconds), peak pressure (PP in kPa), and relative load (RL in %) were analyzed under nine foot zones of the left foot using an in-shoe plantar pressure device.

A two-way repeated measures ANOVA showed that running on a treadmill increases CT (7.70% S1 and 9.91% S2), modifies the pressure distribution and reduces PP (25.98% S1 and 31.76% S2), especially under the heel, medial metatarsals, and hallux, compared to running overground. Moreover, on both surfaces, fatigue (S2) led to a reduced stride frequency (2.78%) and reduced PP on the lateral heel and hallux (15.96% and 16.35%, respectively), and (S1) increased relative load on the medial arch (9.53%). There was no significant interaction between the two factors analyzed (surface and fatigue). Therefore, the aforementioned surface effect, which occurs independently of the fatigue state, should be taken into account when interpreting the results of studies that use the treadmill in their experimental protocols, and when prescribing physical exercise on a treadmill.

AND

Three-dimensional kinematic comparison of treadmill and overground running. JONATHAN SINCLAIR, JIM RICHARDS, PAUL J. TAYLOR, CHRISTOPHER J. EDMUNDSON, DARRELL BROOKS & SARAH J. HOBBS.  Sports Biomechanics, Volume 12, Issue 3, 2013

Abstract

The treadmill is an attractive device for the investigation of human locomotion, yet the extent to which lower limb kinematics differ from overground running remains a controversial topic. This study aimed to provide an extensive three-dimensional kinematic comparison of the lower extremities during overground and treadmill running. Twelve participants ran at 4.0 m/s ( ± 5%) in both treadmill and overground conditions. Angular kinematic parameters of the lower extremities during the stance phase were collected at 250 Hz using an eight-camera motion analysis system. Hip, knee, and ankle joint kinematics were quantified in the sagittal, coronal, and transverse planes, and contrasted using paired t-tests. Of the analysed parameters hip flexion at footstrike and ankle excursion to peak angle were found to be significantly reduced during treadmill running by 12° (p = 0.001) and 6.6° (p = 0.010), respectively. Treadmill running was found to be associated with significantly greater peak ankle eversion (by 6.3°, p = 0.006). It was concluded that the mechanics of treadmill running cannot be generalized to overground running.

Commentary: Running on a treadmill compared to running overground significantly modifies the contact time as well as the magnitude and distribution of plantar pressures. On both kinds of surface, the runner's fatigue increases the relative load on the medial arch and reduces the peak pressure under the lateral heel and hallux. The effect of the kind of surface on plantar pressure seems to be independent of the runner's fatigue state, given that no significant interaction was found between the two factors. in addition, there is a kinematic change at the level of both the hip and ankle with repect treadmiull and overground running. In short, tyreadmill runningis different to overground running.

Gluteal muscle activity and patellofemoral pain syndrome: a systematic review. Barton CJ, Lack S, Malliaras P, Morrissey D. Br J Sports Med. 2013 Mar;47(4):207-14

Abstract

OBJECTIVE:

There is growing evidence to support the association of gluteal muscle strength deficits in individuals with patellofemoral pain syndrome (PFPS) and the effectiveness of gluteal strengthening when treating PFPS. In additiona, an impressive body of work evaluating gluteal electromyography (EMG) has recently emerged, further supporting the importance of gluteal muscle function in PFPS. This systematic review synthesises these EMG findings in order to better understand the role of gluteal muscle activity in the aetiology, presentation and management of PFPS.

METHODS:

MEDLINE, EMBASE, CINAHL, Web of Knowledge and Google Scholar databases were searched in September 2011 for prospective and case-control studies evaluating the association of gluteal EMG with PFPS. Two independent reviewers assessed each paper for inclusion and quality. Means and SDs were extracted from each included study to allow effect size calculations and comparison of results.

RESULTS:

Ten case-control, but no prospective studies were identified. Moderate-to-strong evidence indicates gluteus medius (GMed) activity is delayed and of shorter duration during stair negotiation in PFPS sufferers. In addition, limited evidence indicates GMed activity is delayed and of shorter duration during running, and gluteus maximus (GMax) activity is increased during stair descent.

CONCLUSIONS:

Delayed and shorter duration of GMed EMG may indicate impaired ability to control frontal and transverse plane hip motion. Further research evaluating the value of gluteal muscle activity screening in identifying individuals most likely to develop PFPS, and the effectiveness of interventions targeting changes to gluteal muscle activation patterns is needed.

"There is currently moderate to strong evidence that GMed muscle activity is delayed and of shorter duration during stair ascent and descent in individuals with PFPS. In additiona, limited evidence indicates that GMed muscle activity is delayed and of shorter duration during running. "

For an excellent commentary on this paper and the issue in general, go to The Running Physio.

The effect of exercise repetition on the frequency characteristics of motor output force: Implications for Achilles tendinopathy rehabilitation. Nicole L. Grigg, Scott C. Wearing, John M. O’Toole, James E. Smeathers. Journal of Science and Medicine in Sport Available online 1 May 2013

Design

Controlled laboratory study, longitudinal.

Methods

Nine healthy adult males performed six sets (15 repetitions per set) of eccentric ankle exercise. Ground reaction force was recorded throughout the exercise protocol. For each exercise repetition the frequency power spectrum of the resultant ground reaction force was calculated and normalised to total power. The magnitude of peak relative power within the 8–12 Hz bandwidth and the frequency at which this peak occurred was determined.

Results

The magnitude of peak relative power within the 8–12 Hz bandwidth increased with each successive exercise set and following the 4th set (60 repetitions) of exercise the frequency at which peak relative power occurred shifted from 9 to 10 Hz.

Conclusions

The increase in magnitude and frequency of ground reaction force vibrations with an increasing number of exercise repetitions is likely connected to changes in muscle activation with fatigue and tendon conditioning. This research illustrates the potential for the number of exercise repetitions performed to influence the tendons’ mechanical environment, with implications for tendon remodelling and the clinical efficacy of eccentric rehabilitation programmes for Achilles tendinopathy..

Practical implication

•The increase in the magnitude and frequency of 8–12 Hz vibrations with an increasing number of exercise repetitions is likely the results of changes in muscle activation with fatigue.

•The number of eccentric exercise repetitions performed can influence the tendon's mechanical environment.

•Performing eccentric exercise to fatigue provides a patient specific method to increase the magnitude and frequency of vibrations in the 8–12 Hz bandwidth, which may influence tendon remodelling and the clinical effectiveness of eccentric rehabilitation protocols for Achilles tendinopathy..

Lower Body Determinants of Running Economy in Male and Female Distance Runners. Barnes, Kyle R.; Mcguigan, Michael R.; Kilding, Andrew E.

Journal of Strength & Conditioning Research: 11 October 2013

Quote:

A variety of training approaches have been shown to improve running economy in well-trained athletes. However, there is a paucity of data exploring lower-body determinants that may affect running economy as well as account for differences that may exist between genders. Sixty-three male and female distance runners were assessed in the laboratory for a range of metabolic, biomechanical and neuromuscular measures potentially related to running economy (ml.kg-1.min-1) at a range of running speeds. At all common test velocities women were more economical than men (effect size (ES) = 0.40), however, when compared in terms of relative intensity males had better running economy (ES = 2.41). Leg stiffness (r = -0.80) and moment arm length (r = 0.90) were large-extremely largely correlated with running economy and each other (r = -0.82). Correlations between running economy and kinetic measures (peak force, peak power and time to peak force) for both genders were unclear. The relationship in stride rate (r = -0.27 to -0.31) was in the opposite direction to that of stride length (r = 0.32 to 0.49), and the relationship in contact time (r = -0.21 to -0.54) was opposite of that of flight time (r = 0.06 to 0.74). While both leg stiffness and moment arm length are highly related to running economy, it appears that no single lower-body measure can completely explain differences in running economy between individuals or genders. Running economy is therefore likely determined from the sum of influences from multiple lower-body attributes.

Commentary: Whilst the effect of lower lomb stiffness and moment arch length (giving an indication of the mechanical efficiency of a segment), are well documented in terms of running economy, this paer highlights the complexity of the issue, and the summative quality of many different parameters combining to influence running economy. Moral to the story? Do not focus on one thing in isolation!

Chapter 5: Sports Injury – Basic Management Principles

Chapter 5 outlines the strategies for the coming chapters which will deal with specific injury. Go to 'member resources" to download The Foot And Leg in Sport: Chapter 5

Validation for Cortisone in plantar heel pain?

I must admit I have been far from convinced about either the evidence for, or the efficacy of, infiltration of corticosteroid for plantar heel pain. however a brand new study seems to provide some pretty good evidence to the contrary...

Use of Primary Corticosteroid Injection in the Management of Plantar Fasciopathy. Is It Time to Challenge Existing Practice?

The Foot and Leg in Sport: New chapter up.

This is important stuff, and if you hope to understand sports injury, this is the background information you need to diagnose and treat. Get into it!

Using Ultrasound for imaging lower limb stress fractures

Today a very interesting précis of a new diagnostic investigation for stress fracture.. Ultrasound. Cheap, easy, non ionising, and specific.

We all know that stress fractures are best imaged by isotopic bone scan, CT scan, or even better MRI right? Wrong, the old is new technique of diagnostic ultrasound is rapidly gaining traction as a relaible early diagnostic technique for stress fracture.