Effect of orthoses on changes in neuromuscular control and aerobic cost of a 1-h run

The effects of foot orthoses and sensory facilitation on lower limb electromyography: A scoping review

Foot orthoses (FO) are used as a treatment for biomechanical abnormalities, overuse injuries, and neuropathologies, but study of their mechanism remains inconclusive. The neuromotor paradigm has proposed that FOs may manipulate sensory input from foot sole skin to reduce muscle activity for movement optimization. This review argues that a FO likely alters the incoming mechanical stimuli transmitted via cutaneous mechanoreceptors and nociceptors as the foot sole interfaces with the surface of the orthotic. Thus, all FOs with or without intentional sensory facilitation, likely changes sensory information from foot sole cutaneous afferents. Additionally, in light of understanding and applying knowledge pertaining to the cutaneous reflex loop circuitry, FO's increasing sensory input to the motorneuron pool can change EMG to either reflex sign (increase or decrease). The purpose of this scoping review was to synthesize FO and sensory augmentation literature and summarize how FO designs can capitalize on foot sole skin to modulate lower limb electromyography (EMG). Six database searches resulted in 30 FO studies and 22 sensory studies that included EMG as an outcome measure. Results revealed task and phase specific responses with some consistencies in EMG outcomes between testing modalities, however many inconsistencies remain. Electrical stimulation reflex research provides support for a likely sensory-to-motor factor contributing to muscle activity modulation when wearing FOs. The discussion divides trends in FO treatment modalities by desired increase or decrease in each compartment musculature. The results of this review provides a benchmark for future academics and clinicians to advance literature in support of a revised neuromotor paradigm while highlighting the importance of foot sole skin in FO design.

Acute intense fatigue does not modify the effect of EVA and TPU custom foot orthoses on running mechanics, running economy and perceived comfort

We determined whether fatigue modifies the effect of custom foot orthoses manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), on running mechanics, running economy, and perceived comfort. Eighteen well-trained, males ran on an instrumented treadmill for 6 min at the speed corresponding to their first ventilatory threshold (13.8 ± 1.1 km/h) in three footwear conditions (CON, EVA, and TPU). Immediately after completion of a repeated-sprints exercise (8 × 5 s treadmill sprints, rest = 25 s), these run tests were replicated. Running mechanics, running economy and perceived comfort were determined. Two-way repeated measures ANOVA [condition (CON, EVA, and TPU) × fatigue (fresh and fatigued)] were conducted. Flight time shortened (P = 0.026), peak braking (P = 0.016) and push-off (P = 0.032) forces decreased and vertical stiffness increased (P = 0.014) from before to after the repeated-sprint exercise, independent of footwear condition. There was a global fatigue-induced deterioration in running economy (- 1.6 ± 0.4%; P < 0.001). There was no significant condition × fatigue [except mean loading rate (P = 0.046)] for the large majority of biomechanical, cardio-respiratory [except minute ventilation (P = 0.020) and breathing frequency (P = 0.019)] and perceived comfort variables. Acute intense fatigue does not modify the effect of custom foot orthoses with different resilience characteristics on running mechanics, running economy and perceived comfort.

Assessment of a New Lateral Cushioned Casting Orthosis: Effects on Peroneus Longus Muscle Electromyographic Activity During Running

Background:

Classical medial wedge (CMW) orthoses have been prescribed to treat overpronation foot pathologies in runners. The effects of a novel supination orthosis (NSO) on the surface electromyography (EMG) activity of the peroneus longus (PL) muscle during a complete cycle of running have yet to be tested.

Purpose/Hypothesis:

The purpose of this study was to compare the EMG activity of the PL in participants wearing CMW orthoses and NSOs versus neutral running shoes (NRS) during a full cycle of running gait. It was hypothesized that the PL muscle activity would be lower for the NSO compared with CMW or NRS.

Study Design:

Controlled laboratory study.

Methods:

Included were 31 healthy recreational runners of both sexes (14 male and 17 female; mean age, 38.58 ± 4.02 years) with a neutral Foot Posture Index and standard rearfoot-strike pattern. Participants ran on a treadmill at 9 km/h while wearing NSO (3-, 6-, and 9-mm thicknesses), CMW (3-, 6-, and 9-mm thicknesses), and NRS, for a total of 7 different conditions randomly selected, while the EMG signal activity of the PL was recorded for 30 seconds. Each trial was recorded 3 times, and the intraclass correlation coefficient (ICC) to test reliability of the measurements was calculated. The Wilcoxon pair to pair nonparametric test with Bonferroni correction was performed to analyze differences among the conditions.

Results:

The reliability of all assessments was almost perfect (ICC, >0.81). For both the CMW and NSO, regardless of thickness, the PL activity was statistically significantly lower compared with the NRS (P < .05 for all). For all CMW thicknesses, the PL activity was lower compared with the respective NSO thicknesses, with the 3-mm thickness having the largest difference (CMW_3mm, 18.63 ± 4.64 vs NSO_3mm, 20.78 ± 4.99 mV; P < .001).

Conclusion:

Both CMW and NSO produced reduced EMG activity of the PL muscle; therefore, they can be prescribed to treat overpronation pathologies without associated PL strain concerns. In addition, the NSO saved the enhancement material placed on the medial-rear side of CMW, making it easier to wear sports shoes.

Clinical Relevance:

Knowing the safety of CMW and NSO will aid in understanding treatments for overpronation pathologies.

Rate of Force Development as an Indicator of Neuromuscular Fatigue: A Scoping Review

Because rate of force development (RFD) is an emerging outcome measure for the assessment of neuromuscular function in unfatigued conditions, and it represents a valid alternative/complement to the classical evaluation of pure maximal strength, this scoping review aimed to map the available evidence regarding RFD as an indicator of neuromuscular fatigue. Thus, following a general overview of the main studies published on this topic, we arbitrarily compared the amount of neuromuscular fatigue between the “gold standard” measure (maximal voluntary force, MVF) and peak, early (≤100 ms) and late (>100 ms) RFD. Seventy full-text articles were included in the review. The most-common fatiguing exercises were resistance exercises (37% of the studies), endurance exercises/locomotor activities (23%), isokinetic contractions (17%), and simulated/real sport situations (13%). The most widely tested tasks were knee extension (60%) and plantar flexion (10%). The reason (i.e., rationale) for evaluating RFD was lacking in 36% of the studies. On average, the amount of fatigue for MVF (−19%) was comparable to late RFD (−19%) but lower compared to both peak RFD (−25%) and early RFD (−23%). Even if the rationale for evaluating RFD in the fatigued state was often lacking and the specificity between test task and fatiguing exercise characteristics was not always respected in the included studies, RFD seems to be a valid indicator of neuromuscular fatigue. Based on our arbitrary analyses, peak RFD and early phase RFD appear even to be more sensitive to quantify neuromuscular fatigue than MVF and late phase RFD.

An exploratory study investigating the effect of foot type and foot orthoses on gluteus medius muscle activity

Background

Abnormal gluteus medius muscle activity is associated with a number of musculoskeletal conditions. Research investigating the effect of foot type and foot orthoses on gluteus medius muscle activity is both conflicting and limited. The primary aim was to investigate the relationship between foot type and gluteus medius muscle activity during shod walking. The secondary aims of this study were to explore the effect and amount of usage of a pair of unmodified prefabricated foot orthoses on gluteus medius muscle activity during shod walking.

Methods

Foot type was determined using the foot posture index and gluteus medius muscle activity was measured with surface electromyography in 50 healthy adults during shod walking. Participants were then fitted with prefabricated foot orthoses and required to return after 4 weeks. Pearson’s correlation and one-way ANOVA were used to determine effect of foot type. Paired t-tests and ANCOVA were used to determine effect of foot orthoses.

Results

Participants with a cavus foot type demonstrated significantly more gluteus medius mean (p = 0.04) and peak amplitude (p = 0.01), and a greater range in amplitude (p = 0.01) compared to participants with a neutral foot type. Compared to a planus foot type, participants with a cavus foot type demonstrated significantly larger mean (p = 0.02) and peak amplitude (p = 0.01), and a greater range in amplitude (p = 0.01). Prefabricated foot orthoses did not change the gluteus medius muscle activity.

Conclusion

When assessing healthy adults with a cavus foot type, clinicians and researchers should be aware that these participants may display higher levels of gluteus medius muscle activity during gait compared to neutral and planus type feet. Additionally, clinicians and researchers should be aware that the type of prefabricated foot orthoses used did not change gluteus medius muscle activity over 4 weeks. Future research should aim to explore this relationship between foot type and gluteus medius muscle activity in larger sample sizes, consider the potential role of other lower extremity muscles and biomechanical variables, and investigate if these findings also occur in people with pathology.

A warm-up performed with proper-weight sandbags on the leg improves the speed and RPE performance of 100 m sprint in collegiate male sprinters

BACKGROUND

Muscle performance can be notably improved following a preloading maximal or near maximal stimulus due to the induction of postactivation potentiation, but the success of a preloading exercise in generating a postactivation potentiation response depends on the balance between fatigue and potentiation. However, the optimal warm-up strategy for sprint runners before a match may be not well established until now.

METHODS

Fifteen well-trained male sprint runners performed four different warm-up protocols: warm-up with 0% body mass; warm-up with 2% body mass; warm-up with 4% body mass; warm-up with 8% body mass. The weight-bearing sandbag was tied about 3~5 cm above each ankle joint. During the 100-meter test, the time and rating of perceived exertion (RPE) in the first 30 meters, time in the first 60 meters, and time in the 100 meters were recorded, respectively. Two-high-speed digital video cameras were separately set in the sagittal planes on the left side of a line drawn at a distance of 30 m and 60 m from the start line to record the sprint motion.

RESULTS

A warm-up performed with a sandbag weighted 4% of body mass could significantly improve the time and the RPE score of 100 m sprint by improving average velocity, stride frequency, average stride length, and average accelerated velocity during the sections of 0~30 m, 30~60 m and 60~100 m. This positive effect was better than that of 2% body-weigh effect. However, a warm-up performed with a sandbag weighted 8% of body mass had no significant influence on the performance of a 100 m sprint.

CONCLUSIONS

Current results indicated that a warm-up performed with proper-weight(4% body mass) sandbags on the leg was beneficial to the improvement of 100 m sprint performance, and the mechanism might be that it effectively activated the main muscles and neuromuscular regulation of running and produced a better postactivation potentiation.

Custom foot orthoses improve performance, but do not modify the biomechanical manifestation of fatigue, during repeated treadmill sprints

PURPOSE

We determined the effect of custom foot orthotics manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to a control condition (CON; shoes only) during repeated sprints on running mechanical alterations.

METHODS

Eighteen males performed eight, 5-s sprints with 25-s recovery on an instrumented sprint treadmill in three footwear conditions (EVA, TPU and CON). Mechanical data consisted of continuous (step-by-step) measurement of running kinetics and kinematics, which were averaged for each sprint for further analysis.

RESULTS

Distance ran in 5 s decreased from first to last sprint (P < 0.001), yet with higher sprints 1-8 values for both EVA (P = 0.004) and TPU (P = 0.018) versus CON. Regardless of footwear condition, mean horizontal forces, step frequency, vertical and leg stiffness decreased from sprint 1 to sprint 8 (all P < 0.001). Duration of the propulsive phase was globally shorter for both EVA (P = 0.002) and TPU (P = 0.021) versus CON, while braking phase duration was similar (P = 0.919). In the horizontal direction, peak propulsive (P < 0.001), but not braking (P = 0.172), forces also decreased from sprint 1 to sprint 8, independently of conditions.

CONCLUSION

Compared to shoe only, wearing EVA or TPU custom foot orthotics improved repeated treadmill sprint ability, yet provided similar fatigue-induced changes in mechanical outcomes.

A systematic review of the effect of footwear, foot orthoses and taping on lower limb muscle activity during walking and running

BACKGROUND

External devices are used to manage musculoskeletal pathologies by altering loading of the foot, which could result in altered muscle activity that could have therapeutic benefits.

OBJECTIVES

To establish if evidence exists that footwear, foot orthoses and taping alter lower limb muscle activity during walking and running.

STUDY DESIGN

Systematic literature review.

METHODS

CINAHL, MEDLINE, ScienceDirect, SPORTDiscus and Web of Science databases were searched. Quality assessment was performed using guidelines for assessing healthcare interventions and electromyography methodology.

RESULTS

Thirty-one studies were included: 22 related to footwear, eight foot orthoses and one taping. In walking, (1) rocker footwear apparently decreases tibialis anterior activity and increases triceps surae activity, (2) orthoses could decrease activity of tibialis posterior and increase activity of peroneus longus and (3) other footwear and taping effects are unclear.

CONCLUSION

Modifications in shoe or orthosis design in the sagittal or frontal plane can alter activation in walking of muscles acting primarily in these planes. Adequately powered research with kinematic and kinetic data is needed to explain the presence/absence of changes in muscle activation with external devices.

CLINICAL RELEVANCE

This review provides some evidence that foot orthoses can reduce tibialis posterior activity, potentially benefitting specific musculoskeletal pathologies.

Controlled trial to compare the Achilles tendon load during running in flatfeet participants using a customized arch support orthoses vs an orthotic heel lift

Background

Achilles tendinopathy is one of the most common overuse injuries in running, and forefoot pronation, seen in flatfeet participants, has been proposed to cause additional loading across the Achilles tendon. Foot orthoses are one of the common and effective conservative treatment prescribed for Achilles tendinopathy, it works by correcting the biomechanical malalignment and reducing tendon load. Previous studies have shown reduction of Achilles Tendon load (ATL) during running by using customized arch support orthosis (CASO) or an orthotic heel lift (HL). However, there are still little biomechanical evidence and comparative studies to guide orthotic prescriptions for Achilles tendinopathy management. Therefore, this study seeks to investigate the two currently employed orthotic treatment options for Achilles tendinopathy: CASO and HL for the reduction of ATL and Achilles tendon loading rate (ATLR) in recreational runners with flatfeet.

Methods

Twelve participants were recruited and run along the runway in the laboratory for three conditions: (1) without orthoses, (2) with CASO (3) with HL. Kinematic and kinetic data were recorded by 3D motion capturing system and force platform. Ankle joint moments and ATL were computed and compared within the three conditions.

Results

Participants who ran with CASO (p = 0.001, d = 0.43) or HL (p = 0.001, d = 0.48) associated with a significant reduction in ATL when compared to without orthotics while there was no significant difference between the two types of orthoses, the mean peak ATL of CASO was slightly lower than HL. Regarding the ATLR, both orthoses, CASO (p = 0.003, d = 0.93) and HL (p = 0.004, d = 0.78), exhibited significant lower value than the control but similarly, no significant difference was noted between them in which the use of CASO yielded a slightly lower loading rate than that of HL.

Conclusions

Both CASO and HL were able to cause a significant reduction in peak ATL and ATLR comparing to without orthotics condition. There were subtle but no statistically significant differences in the biomechanical effects between the two types of orthoses. The findings help to quantify the effect of CASO and HL on load reduction of Achilles tendon and suggests that foot orthoses may serve to prevent the incidence of Achilles tendon pathologies.

Trial registration

NCT04003870 on clinicaltrials.gov 1 July 2019.

The Effect of EVA and TPU Custom Foot Orthoses on Running Economy, Running Mechanics, and Comfort

Custom made foot orthoses (CFO) with specific material properties have the potential to alter ground reaction forces but their effect on running mechanics and comfort remains to be investigated. We determined if CFO manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), improve running economy (RE), running mechanics, and comfort at two running speeds. Eighteen well-trained, male athletes ran on an instrumented treadmill for 6 min at high (HS) and low (LS) speeds corresponding to and 15% lower than their first ventilatory threshold (13.8 ± 1.1 and 11.7 ± 0.9 km.h⁻¹, respectively) in three footwear conditions (CON, EVA, and TPU). RE, running mechanics and comfort were determined. Albeit not reaching statistical significance (P = 0.11, η² = 0.12), RE on average improved in EVA (+2.1 ± 4.8 and +2.9 ± 4.9%) and TPU (+0.9 ± 5.9 and +0.9 ± 5.3%) compared to CON at LS and HS, respectively. Braking force was decreased by 3.4 ± 9.1% at LS and by 2.7 ± 9.8% at HS for EVA compared to CON (P = 0.03, η² = 0.20). TPU increased propulsive loading rate by 20.2 ± 24 and 16.4 ± 23.1% for LS and HS, respectively compared to CON (P = 0.01, η² = 0.25). Both arch height (P = 0.06, η² = 0.19) and medio-lateral control (P = 0.06, η² = 0.16) showed a trend toward improved comfort for EVA and TPU vs. CON. Compared to shoes only, mainly EVA tended to improve RE and comfort at submaximal running speeds. Specific CFO-related running mechanical adjustments included a reduced braking impulse occurring in the first 25% of contact time with EVA, whereas wearing TPU increased propulsive loading rate.

The effect of foot orthoses and insoles on running economy and performance in distance runners: A systematic review and meta-analysis

Foot orthoses and insoles are prescribed to runners, however their impact on running economy and performance is uncertain. The aim of this systematic review and meta-analysis was to determine the effect of foot orthoses and insoles on running economy and performance in distance runners. Seven electronic databases were searched from inception until June 2018. Eligible studies investigated the effect of foot orthoses or insoles on running economy (using indirect calorimetry) or running performance. Standardised mean differences (SMDs) were computed and meta-analyses were conducted using random effects models. Methodological quality was assessed using the Quality Index. Nine studies met the criteria and were included: five studies investigated the effect of foot orthoses on running economy and four investigated insoles. Foot orthoses were associated with small negative effects on running economy compared to no orthoses (SMD 0.42 [95% CI 0.17,0.72] p = 0.007). Shock absorbing insoles were also associated with negative effects on running economy, but an imprecise estimate (SMD 0.26 [95% CI -0.33,0.84] p = 0.83). Quality Index scores ranged from 4 to 15 out of 17. Foot orthoses and shock absorbing insoles may adversely affect running economy in distance runners. Future research should consider their potential effects on running performance.

Neuromuscular Fatigue Does Not Impair the Rate of Force Development in Ballistic Contractions of Submaximal Amplitudes

The effect of muscle fatigue on rate of force development (RFD) is usually assessed during tasks that require participants to reach as quickly as possible maximal or near-maximal force. However, endurance sports require athletes to quickly produce force of submaximal, rather than maximal, amplitudes. Thus, this study investigated the effect of muscle fatigue induced by long-distance running on the capacity to quickly produce submaximal levels of force. Twenty-one male amateur runners were evaluated before and shortly after a half-marathon race. Knee extensors force was recorded under maximal voluntary and electrically evoked contractions. Moreover, a series of ballistic contractions at different submaximal amplitudes (from 20 to 100% of maximal voluntary force) was obtained, by asking the participants to reach submaximal forces as fast as possible. The RFD was calculated for each contraction. After the race, maximal voluntary activation, resting doublet twitch, maximal force, and RFD during maximal contraction decreased (-12, -12, -21, and -19%, respectively, all P-values < 0.0001). Nevertheless, the RFD values measured during ballistic contractions up to 60% of maximal force were unaffected (all P-values > 0.4). Long-distance running impaired the capacity to quickly produce force in ballistic contractions of maximal, but not of submaximal, amplitudes. Overall, these findings suggest that central and peripheral fatigue do not affect the quickness to which muscle contracts across a wide range of submaximal forces. This is a relevant finding for running and other daily life activities that rely on the production of rapid submaximal contractions rather than maximal force levels.

Foot orthoses for plantar heel pain: a systematic review and meta-analysis

Objective

To investigate the effectiveness of foot orthoses for pain and function in adults with plantar heel pain.

Design

Systematic review and meta-analysis. The primary outcome was pain or function categorised by duration of follow-up as short (0 to 6 weeks), medium (7 to 12 weeks) or longer term (13 to 52 weeks).

Data sources

Medline, CINAHL, SPORTDiscus, Embase and the Cochrane Library from inception to June 2017.

Eligibility criteria for selecting studies

Studies must have used a randomised parallel-group design and evaluated foot orthoses for plantar heel pain. At least one outcome measure for pain or function must have been reported.

Results

A total of 19 trials (1660 participants) were included. In the short term, there was very low-quality evidence that foot orthoses do not reduce pain or improve function. In the medium term, there was moderate-quality evidence that foot orthoses were more effective than sham foot orthoses at reducing pain (standardised mean difference −0.27 (−0.48 to −0.06)). There was no improvement in function in the medium term. In the longer term, there was very low-quality evidence that foot orthoses do not reduce pain or improve function. A comparison of customised and prefabricated foot orthoses showed no difference at any time point.

Conclusion

There is moderate-quality evidence that foot orthoses are effective at reducing pain in the medium term, however it is uncertain whether this is a clinically important change.

Is There an Economical Running Technique? A Review of Modifiable Biomechanical Factors Affecting Running Economy

Running economy (RE) has a strong relationship with running performance, and modifiable running biomechanics are a determining factor of RE. The purposes of this review were to (1) examine the intrinsic and extrinsic modifiable biomechanical factors affecting RE; (2) assess training-induced changes in RE and running biomechanics; (3) evaluate whether an economical running technique can be recommended and; (4) discuss potential areas for future research. Based on current evidence, the intrinsic factors that appeared beneficial for RE were using a preferred stride length range, which allows for stride length deviations up to 3 % shorter than preferred stride length; lower vertical oscillation; greater leg stiffness; low lower limb moment of inertia; less leg extension at toe-off; larger stride angles; alignment of the ground reaction force and leg axis during propulsion; maintaining arm swing; low thigh antagonist–agonist muscular coactivation; and low activation of lower limb muscles during propulsion. Extrinsic factors associated with a better RE were a firm, compliant shoe–surface interaction and being barefoot or wearing lightweight shoes. Several other modifiable biomechanical factors presented inconsistent relationships with RE. Running biomechanics during ground contact appeared to play an important role, specifically those during propulsion. Therefore, this phase has the strongest direct links with RE. Recurring methodological problems exist within the literature, such as cross-comparisons, assessing variables in isolation, and acute to short-term interventions. Therefore, recommending a general economical running technique should be approached with caution. Future work should focus on interdisciplinary longitudinal investigations combining RE, kinematics, kinetics, and neuromuscular and anatomical aspects, as well as applying a synergistic approach to understanding the role of kinetics.

The Influence of Running on Foot Posture and In-Shoe Plantar Pressures

BACKGROUND

Running can be considered a high-impact practice, and most people practicing continuous running experience lower-limb injuries. The aim of this study was to determine the influence of 45 min of running on foot posture and plantar pressures.

METHODS

The sample comprised 116 healthy adults (92 men and 24 women) with no foot-related injuries. The mean ± SD age of the participants was 28.31 ± 6.01 years; body mass index, 23.45 ± 1.96; and training time, 11.02 ± 4.22 h/wk. Outcome measures were collected before and after 45 min of running at an average speed of 12 km/h, and included the Foot Posture Index (FPI) and a baropodometric analysis.

RESULTS

The results show that foot posture can be modified after 45 min of running. The mean ± SD FPI changed from 6.15 ± 2.61 to 4.86 ± 2.65 (P < .001). Significant decreases in mean plantar pressures in the external, internal, rearfoot, and forefoot edges were found after 45 min of running. Peak plantar pressures in the forefoot decreased after running. The pressure-time integral decreased during the heel strike phase in the internal edge of the foot. In addition, a decrease was found in the pressure-time integral during the heel-off phase in the internal and rearfoot edges.

CONCLUSIONS

The findings suggest that after 45 min of running, a pronated foot tends to change into a more neutral position, and decreased plantar pressures were found after the run.

Plantar flexor neuromuscular adjustments following match-play football in hot and cool conditions

We assessed neuromuscular fatigue and recovery of the plantar flexors after playing football with or without severe heat stress. Neuromuscular characteristics of the plantar flexors were assessed in 17 male players at baseline and ∼30 min, 24, and 48 h after two 90-min football matches in temperate (∼20 °C and 55% rH) and hot (∼43 °C and 20% rH) environments. Measurements included maximal voluntary strength, muscle activation, twitch contractile properties, and rate of torque development and soleus EMG (i.e., root mean square activity) rise from 0 to 30, -50, -100, and -200 ms during maximal isometric contractions for plantar flexors. Voluntary activation and peak twitch torque were equally reduced (-1.5% and -16.5%, respectively; P < 0.05) post-matches relative to baseline in both conditions, the latter persisting for at least 48 h, whereas strength losses (∼5%) were not significant. Absolute explosive force production declined (P < 0.05) 30 ms after contraction onset independently of condition, with no change at any other epochs. Globally, normalized rate of force development and soleus EMG activity rise values remained unchanged. In football, match-induced alterations in maximal and rapid torque production capacities of the plantar flexors are moderate and do not differ after competing in temperate and hot environments.

High-intensity running and plantar-flexor fatigability and plantar-pressure distribution in adolescent runners

CONTEXT

Fatigue-induced alterations in foot mechanics may lead to structural overload and injury.

OBJECTIVES

To investigate how a high-intensity running exercise to exhaustion modifies ankle plantar-flexor and dorsiflexor strength and fatigability, as well as plantar-pressure distribution in adolescent runners.

DESIGN

Controlled laboratory study.

SETTING

Academy research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eleven male adolescent distance runners (age = 16.9 ± 2.0 years, height = 170.6 ± 10.9 cm, mass = 54.6 ± 8.6 kg) were tested.

INTERVENTION(S)

All participants performed an exhausting run on a treadmill. An isokinetic plantar-flexor and dorsiflexor maximal-strength test and a fatigue test were performed before and after the exhausting run. Plantar-pressure distribution was assessed at the beginning and end of the exhausting run.

MAIN OUTCOME MEASURE(S)

We recorded plantar-flexor and dorsiflexor peak torques and calculated the fatigue index. Plantar-pressure measurements were recorded 1 minute after the start of the run and before exhaustion. Plantar variables (ie, mean area, contact time, mean pressure, relative load) were determined for 9 selected regions.

RESULTS

Isokinetic peak torques were similar before and after the run in both muscle groups, whereas the fatigue index increased in plantar flexion (28.1%; P = .01) but not in dorsiflexion. For the whole foot, mean pressure decreased from 1 minute to the end (-3.4%; P = .003); however, mean area (9.5%; P = .005) and relative load (7.2%; P = .009) increased under the medial midfoot, and contact time increased under the central forefoot (8.3%; P = .01) and the lesser toes (8.9%; P = .008).

CONCLUSIONS

Fatigue resistance in the plantar flexors declined after a high-intensity running bout performed by adolescent male distance runners. This phenomenon was associated with increased loading under the medial arch in the fatigued state but without any excessive pronation.

The influence of a new sole geometry while running

Running shoe construction influences the forces experienced by the human body while running. The aim of this study was to ascertain whether the new sole architecture of the On running shoe reduces ground reaction forces compared with running barefoot or with a conventional running shoe and whether it changes the physiological parameters of running in shoes. Thirty-seven trained male participants were studied while running at submaximal speeds wearing their conventional running shoe, wearing the On running shoe and while barefoot. Additional biomechanical and physiological values were investigated to determine whether the On running shoe induced any changes in these parameters compared with conventional running shoes. The On exhibited similar ground reaction forces as conventional shoes, and these were different from the forces experienced while running barefoot, showing that the On was more similar to typical shoed running. No difference was observed in running economy between the On and a conventional shoe model. However, a slightly lower heart rate (HR) (≈1.3%) and blood lactate concentration (≈5.5%) were observed during submaximal running with the On running shoe compared with a conventional running shoe, as well as a greater lateral deviation of the centre of pressure mid-stance. The ramifications of the reduced HR and blood lactate concentration for competitive performance are unknown.

Foot orthoses for adults with flexible pes planus: a systematic review

BACKGROUND

Foot orthoses are widely used in the management of flexible pes planus, yet the evidence to support this intervention has not been clearly defined. This systematic review aimed to critically appraise the evidence for the use of foot orthoses for flexible pes planus in adults.

METHODS

Electronic databases (Medline, CINAHL, Cochrane, Web of science, SportDiscus, Embase) were systematically searched in June 2013 for randomised controlled, controlled clinical and repeated measure trials where participants had identified flexible pes planus using a validated and reliable measure of pes planus and the intervention was a rigid or semi-rigid orthoses with the comparison being a no-orthoses (shoes alone or flat non-posted insert) condition. Outcomes of interest were foot pain, rearfoot kinematics, foot kinetics and physical function.

RESULTS

Of the 2,211 articles identified by the searches, 13 studies met the inclusion criteria; two were randomised controlled trials, one was a controlled trial and 10 were repeated measure studies. Across the included studies, 59 relevant outcome measures were reported with 17 calculated as statistically significant large or medium effects observed with use of foot orthoses compared to the no orthoses condition (SMD range 1.13 to -4.11).

CONCLUSIONS

No high level evidence supported the use of foot orthoses for flexible pes planus. There is good to moderate level evidence that foot orthoses improve physical function (medial-lateral sway in standing (level II) and energy cost during walking (level III)). There is low level evidence (level IV) that foot orthoses improve pain, reduce rearfoot eversion, alter loading and impact forces; and reduce rearfoot inversion and eversion moments in flexible pes planus. Well-designed randomised controlled trials that include appropriate sample sizes, clinical cohorts and involve a measure of symptom change are required to determine the efficacy of foot orthoses to manage adult flexible pes planus.