Caffeine gum improves 5 km running performance in recreational runners completing parkrun events.

PURPOSE: The purpose of this study was to determine whether caffeine gum improves the performance of recreational runners completing parkruns (weekly, 5 km, mass participant running events). METHODS: Thirty-six recreational runners (M = 31, F = 5; age 33.7 ± 10.7 y; BMI 23.1 ± 2.4 kg/m2) capable of running 5 km in < 25 min were recruited to a study at the Sheffield Hallam parkrun, UK. Runners were block randomized into one of three double-blind, placebo-controlled, cross-over intervention trials with caffeine gum as the treatment (n = 6 per intervention trial) or into one of three non-intervention trials that ran concurrently with the intervention trials (n = 6 per non-intervention trial). Changes in conditions across different parkruns were adjusted for using data from the non-intervention trials. Runners in the randomized cross-over intervention trials chewed gum supplying 300 mg of caffeine or a placebo gum for 5 min, starting 30 min before each parkrun. RESULTS: Caffeine gum improved 5 km parkrun performance by a mean of 17.28 s (95% CI 4.19, 30.37; P = 0.01). Adjustment for environmental conditions using data from the non-intervention trials attenuated the statistical significance (P = 0.04). Caffeine gum also decreased RPE by 1.21 (95% CI 0.30, 2.13; P = 0·01) units relative to placebo. CONCLUSIONS: A 300 mg dose of caffeine supplied in chewing gum improved the performance of recreational runners completing 5 km parkruns by an average of 17 s. TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov: NCT02473575 before recruitment commenced.

Injury of flexor halluics longus tendon in amateur marathon runners results in abnormal plantar pressure distribution: observational study.

OBJECTIVE: To analyze the changes of plantar pressure in amateur marathon runners with flexor halluics longus (FHL) tendon injury using the Medtrack-Gait plantar pressure measurement system, and to explore whether the plantar pressure data can be used as an index for the diagnosis of injury. METHODS: A total of 39 healthy amateur marathon runners without any ankle joint symptoms were recruited. Dynamic and static plantar pressure data were measured using the pressure plate of Medtrack-Gait. According to MRI imaging findings, whether the FHL tendon was injured or not was judged, and the dynamic and static data were divided into the injury group and control group. The data with statistically significant differences between the two groups were used to make the receiver operating characteristic (ROC) curve. RESULT: The maximum contact area (PA) of the first metatarsal(M1) region, the maximum load-bearing peak value (PW) and the time pressure integral (PMPTI) of the second metatarsal(M2) region in the injury group were lower than those in the control group, respectively (P < 0.05). The maximum contact area (PA) of the fifth metatarsal(M5) region was higher than that in the control group (P < 0.05). The area under curve (AUC) value of the ROC curve of the PA of M1 region, the PW and PMPTI of M2 region were statistically (P < 0.05). CONCLUSION: FHL tendon injury resulted in decreased PA in M1, decreased PW and PMPTI in M2, and increased PA in the M5 region, suggesting that FHL tendon injury resulted in a force shift from the medial to the lateral side of the foot. The PA of M1, PW and PMPTI of M2 have certain diagnostic value for early FHL injury in amateur marathon runners.

Effects of Minimalist vs. Traditional Running Shoes on Abdominal Lumbopelvic Muscle Activity in Women Running at Different Speeds: A Randomized Cross-Over Clinical Trial.

This study aimed to investigate if the characteristics of different running shoes could influence intra-abdominal pressure during running. A single-centre, randomized, prospective cross-over clinical trial was performed measuring activity patterns of internal oblique (IO), lumbar erector (LE), and gluteus maximus (GM) muscles in healthy women when running with minimalist shoes (MS). Participants were randomly allocated into two-sequence (MS/TS or TS/MS) treadmill running at six, nine, and eleven km/h. The surface electromyographic activity of IO, LE, and GM muscles were recorded while running. A repeated measures ANOVA explored the interaction effects of three-muscle x three speeds x two shoes. Significance was set at p ≤ 0.05. Fifty-one healthy nulliparous women (mean age: 26.55 ± 5.11 years; body mass index: 21.29 ± 2.07 Kg/m2) were included. Our findings revealed lower activations of the LE compared to the internal oblique IO and GM, irrespective of running speed and footwear used. Electromyographic activation significantly increased with higher running speeds (p < 0.001) for all muscles, regardless of the type of footwear. Although electromyographic records with MS consistently showed higher values than those with TS, the differences were not statistically significant for all muscles at all speeds. Our results indicate that electromyographic activation patterns vary according to the muscle group, exhibiting higher values with increased running speed. No significant differences were observed between MS and TS.

Assessing the Impact of COVID-19 on Amateur Runners' Performance: An Analysis through Monitoring Devices.

This retrospective study aimed to analyze the return to running of non-professional runners after experiencing asymptomatic or mild COVID-19. Participants aged 18-55 years who maintained a training load of ≥10 km/week for at least three months prior to diagnosis and utilized Garmin/Polar apps were included. From these devices, parameters such as pace, distance, total running time, cadence, and heart rate were collected at three intervals: pre-COVID, immediately post-COVID, and three months after diagnosis. The Wilcoxon signed rank test was used for analysis (significance was set at ≤0.05). Twenty-one participants (57.1% male; mean age 35.0 ± 9.8 years) were included. The results revealed a significant decrease in running duration and distance two weeks after diagnosis, without significant changes in other parameters. Three months after infection, no differences were observed compared to pre-infection data, indicating a return to the pre-disease training load. These findings underscore the transient impact of COVID-19 on training performance among non-professional runners with mild or asymptomatic symptoms, highlighting the importance of tailored strategies for resuming running after infection.

Changes of bone turnover markers and testosterone in Japanese male endurance runners: a pilot study.

INTRODUCTION: The bone metabolism of male endurance runners during a competitive season has been little studied. Furthermore, Japanese runners have a special competitive season. This study aimed to investigate the change of bone turnover markers (BTMs) and other hormones in Japanese male endurance runners. MATERIALS AND METHODS: We investigated biochemical markers, bone formation and resorption markers and sex hormones, body composition using dual-energy X-ray absorptiometry (DXA), and training volume during a competitive season. 11 (age: 24.0 ± 4.3 years) Japanese male endurance runners were analyzed in this study. They participated in all measurements three times a year: the baseline (BL), the post-track period (PT), and the road race period (RR). RESULTS: Fat mass (FM) and percentage of body fat (% body fat) at RR (p = 0.009, p = 0.009) were lower than at BL. Specific bone alkaline phosphatase (BAP) decreased at PT (p = 0.004) and RR (p = 0.004) compared with BL. However, the bone resorption marker did not change. Free testosterone at PT (p = 0.032) was lower than BL. There was no correlation with blood variables and body composition or training volume. CONCLUSION: BAP and testosterone in Japanese male endurance runners decreased during the competitive season. However, there was no correlation between blood variables and training volume.

Achilles tendon dimensions, ankle stiffness and footfall patterns in recreational runners.

The main purpose of this study was to investigate the relationship among Achilles tendon (AT) dimensions, ankle joint stiffness, and footfall patterns in recreational rearfoot and non-rearfoot runners. Based on the foot strike index, a total of 107 runners were divided into rearfoot (47 females/40 males) and non-rearfoot runners (14 females/6 males). All participants had theirs AT dimensions (AT length, AT thickness, and AT moment arm) measured using a combination of ultrasound and motion capture systems. In addition, all performed running trials measured at self-selected speed in laboratory-neutral shoes. A partial correlation coefficient was used for correlations between the selected variables. The results revealed a significant relationship between ankle joint stiffness and level of footfall pattern in rearfoot (r = 0.232, p = 0.032) and non-rearfoot runners (r = -0.811, p < 0.001). The results also suggest a relationship between AT thickness and foot strike index (r = -0.486) in non-rearfoot runners. Runners whose footfall pattern is closer to the heel have greater ankle joint stiffness. Non-rearfoot runners whose footfall pattern is closer to the toe have a thinner AT. Non-rearfoot runners with thicker AT had greater ankle joint stiffness.

CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial.

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (TC). For such races, real-time feedback from pre-exercise and exercise TC may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of TC obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT. Twelve participants (25 ± 4 yrs) ingested 7.5 mL/kg fat-free mass of 4 °C water over the first 5 min of a 120 min sitting period, after which they completed a 5 km running TT at 30 °C, 50% relative humidity. A TC difference > ± 0.25 °C between sensors was deemed clinically unacceptable. Prior to water ingestion, the CORE-derived TC was 0.49 ± 0.25 °C lower than the GI pill. The CORE was irresponsive to the 0.26 ± 0.22 °C peak decline in TC captured with the GI pill 40 min following water ingestion. Prior to the TT, TC was 0.30 ± 0.25 °C lower with the CORE than the GI pill. During the TT, the CORE underestimated the rate of increase in TC by 0.0125 ± 0.019 °C/min compared with the GI pill, and mean absolute difference in TC between sensors was of 0.47 ± 0.34 °C. In conclusion, the CORE does not capture the cooling effect of cold water ingestion and provides a clinically relevant underestimation of TC during a 5 km running TT in the heat.

A Prolonged Bout of Running Increases Hepcidin and Decreases Dietary Iron Absorption in Trained Female and Male Runners.

BACKGROUND: Declines in iron status are frequently reported in those who regularly engage in strenuous physical activity. A possible reason is increases in the iron regulatory hormone hepcidin, which functions to inhibit dietary iron absorption and can be induced by the inflammatory cytokine interleukin-6 (IL-6). OBJECTIVES: The current study aimed to determine the impact of a prolonged bout of running on hepcidin and dietary iron absorption in trained female and male runners. METHODS: Trained female and male collegiate cross country runners (n = 28, age: 19.7 ± 1.2 y, maximal oxygen uptake: 66.1 ± 6.1 mL $\cdot$ kg -1$\cdot$ min-2, serum ferritin: 21.9 ± 13.3 ng/mL) performed a prolonged run (98.8 ± 14.7 min, 21.2 ± 3.8 km, 4.7 ± 0.3 min/km) during a team practice. Participants consumed a stable iron isotope with a standardized meal 2 h postrun and blood was collected 1 h later. The protocol was repeated 2 wk later except participants abstained from exercise (rest). RBCs were collected 15 d after exercise and rest to determine isotope enrichment. Differences between exercise and rest were assessed by paired t tests and Wilcoxon matched-pairs signed rank tests. Data are means ± SDs. RESULTS: Plasma hepcidin increased 51% after exercise (45.8 ± 34.4 ng/mL) compared with rest (30.3 ± 27.2 ng/mL, P = 0.0010). Fractional iron absorption was reduced by 36% after exercise (11.8 ± 14.6 %) compared with rest (18.5 ± 14.4 %, P = 0.025). Plasma IL-6 was greater after exercise (0.660 ± 0.354 pg/mL) than after rest (0.457 ± 0.212 pg/mL, P < 0.0001). Exploratory analyses revealed that the increase in hepcidin with exercise may be driven by a response in males but not females. CONCLUSIONS: A prolonged bout of running increases hepcidin and decreases dietary iron absorption compared with rest in trained runners with low iron stores. The current study supports that IL-6 contributes to the increase in hepcidin with prolonged physical activity, although future studies should explore potential sex differences in the hepcidin response.This trial was registered at Clinicaltrials.gov as NCT04079322.

Self-reported foot strike patterns and sonographic evidence of Achilles tendinopathy in asymptomatic marathon runners.

It is unknown whether ultrasound findings and symptoms of Achilles tendinopathy in runners correlate with foot strike patterns. We aimed to examine the relationships among Achilles tendon ultrasound findings in runners with or without Achilles tendinopathy, their foot strike patterns, and their training regimens. We recruited marathon runners 18 years of age or older with no history of Achilles tendon pain or surgery participating in the 2018 DONNA Marathon. Participants completed surveys and underwent Achilles tendon sonographic evaluations and were categorized by foot strike patterns. Seventy-nine runners were included; 22 (28%) with forefoot, 30 (38%) midfoot, and 27 (34%) hindfoot strike patterns. Foot strike pattern was not associated with tendon hyperaemia (P = 1.00) or hypoechogenicity (P = .97), and there was no association of cross-sectional area of the Achilles tendon with peak weekly distance while training. Sonographic characteristics of Achilles tendinopathy did not correlate with foot strike patterns or training regimens. Although not statistically significant, it is worth noting that cross-sectional area was 1 mm2 larger per every 1 kg/m2 increase in body mass index.

A systematic nutrition intervention for low iron status in collegiate distance runners.

Background: Iron is a trace mineral that plays a significant role in oxygen transport and energy production during exercise. In deficiency, iron can have a significant negative impact on sports performance. Due to its relative simplicity, supplementation is a common treatment to combat deficiency. However, there is a paucity of analyses combining supplementation with dietary education as a method of treatment. Objective: To assess the effectiveness of a systematic iron intervention combining nutrition education and supplementation stages to combat low ferritin levels in collegiate runners. Methods: Twenty four distance runners (13 women; 11 men; 19.5 ± 0.8 years of age) were measured for serum ferritin, daily iron, calcium and vitamin C intake at the start of the fall semester and again after 100 days of supplementation. A dependent groups t-test was applied to delineate changes in Ferritin levels and iron, vitamin C and calcium intake. Alpha levels were maintained a priori at p < 0.05. Results: Ferritin levels averaged 40.0 ± 22.6 ng/mL in Fall and 33.7 ± 14.7 ng/mL in Spring. There were no statistical differences in ferritin levels from Fall to Spring (p = 0.074). Weekly Iron intake (# of foods) significantly increased from Fall (110.8 ± 43.1) to Spring (123.3 ± 43.9), (p = 0.028). There were no significant changes in Vitamin C or Calcium intake between time points (p = 0.441), (p = 0.901). Conclusion: We found no significant differences in serum ferritin measures but dietary intake of iron increased as a result of the intervention.

Variations in the Thickness of the Plantar Fascia After Training Based in Training Race. A Pilot Study.

Plantar fascia (PF) is a connective tissue made up of mostly type 1 collagen that is subjected to constant loads. This study evaluated the effect of continuous running on tissue stress in the PF by measuring changes in the thickness of the PF using ultrasound scans. It was a cross-sectional study involving 24 runners from the University of Valencia, recruited as volunteers between December 2018 and February 2019. A variety of data was recorded: (age, body mass index, type of footwear, number of workouts per week, KM run per week, sports injuries in the last year, pre and postrace ultrasound PF measurements). There were significant differences in the 3 postrace measurements of the left foot (<0.001). PF thicknesses were measured before and after running, with a minimal average difference of 0.4 mm in the medial and central fascicles, and 0.3 mm in the lateral fascicle. We observed PF thicknesses above 4mm in asymptomatic patients with no signs of vascularisation, proving that increased PF thickness is not the only criterion for diagnosis of plantar fasciitis.

Gait Retraining With Visual Biofeedback Reduces Rearfoot Pressure and Foot Pronation in Recreational Runners.

CONTEXT: Running is a popular sport globally. Previous studies have used a gait retraining program to successfully lower impact loading, which has been associated with lower injury rates in recreational runners. However, there is an absence of studies on the effect of this training program on the plantar pressure distribution pattern during running. OBJECTIVE: To investigate the short-term effect of a gait retraining strategy that uses visual biofeedback on the plantar pressure distribution pattern and foot posture in recreational runners. DESIGN: Randomized controlled trial. SETTING: Biomechanics laboratory. PARTICIPANTS: Twenty-four recreational runners were evaluated (n = 12 gait retraining group and n = 12 control group). INTERVENTION: Those in the gait retraining group underwent a 2-week program (4 sessions/wk, 30 min/session, and 8 sessions). The participants in the control group were also invited to the laboratory (8 times in 2 wk), but no feedback on their running biomechanics was provided. MAIN OUTCOME MEASURES: The primary outcome measures were plantar pressure distribution and plantar arch index using a pressure platform. The secondary outcome measure was the foot posture index. RESULTS: The gait retraining program with visual biofeedback was effective in reducing medial and lateral rearfoot plantar pressure after intervention and when compared with the control group. In the static condition, the pressure peak and maximum force on the forefoot and midfoot were reduced, and arch index was increased after intervention. After static training intervention, the foot posture index showed a decrease in the foot pronation. CONCLUSIONS: A 2-week gait retraining program with visual biofeedback was effective in lowering rearfoot plantar pressure, favoring better support of the arch index in recreational runners. In addition, static training was effective in reducing foot pronation. Most importantly, these observations will help healthcare professionals understand the importance of a gait retraining program with visual biofeedback to improve plantar loading and pronation during rehabilitation.

Differential weight loss with intermittent fasting or daily calorie restriction in low- and high-fitness phenotypes.

NEW FINDINGS: What is the central question of this study? How does intrinsic aerobic capacity impact weight loss with 50% daily caloric restriction and alternate-day fasting? What is the main finding and its importance? Intermittent fasting is effective for weight loss in rats with low fitness, which highlights the importance of how intermittent fasting interacts with aerobic fitness. ABSTRACT: Recent interest has focused on the benefits of time-restricted feeding strategies, including intermittent fasting, for weight loss. It is not yet known whether intermittent fasting is more effective than daily caloric restriction at stimulating weight loss and how each is subject to individual differences. Here, rat models of leanness and obesity, artificially selected for intrinsically high (HCR) and low (LCR) aerobic capacity, were subjected to intermittent fasting and 50% calorie restrictive diets in two separate experiments using male rats. The lean, high-fitness HCR and obesity-prone, low-fitness LCR rats underwent 50% caloric restriction while body weight and composition were monitored. The low-fitness LCR rats were better able to retain lean mass than the high-fitness HCR rats, without significantly different proportional loss of weight or fat. In a separate experiment using intermittent fasting in male HCR and LCR rats, alternate-day fasting induced significantly greater loss of weight and fat mass in LCR compared with HCR rats, although the HCR rats had a more marked reduction in ad libitum daily food intake. Altogether, this suggests that intermittent fasting is an effective weight-loss strategy for those with low intrinsic aerobic fitness; however, direct comparison of caloric restriction and intermittent fasting is warranted to determine any differential effects on energy expenditure in lean and obesity-prone phenotypes.

Tactical behavior of high-level male marathon runners.

This study analyzes the strategy used by the best male runners who participated in one of the major city marathons (Frankfurt Marathon, 2008-2018), the all-time performances <2:04:00, the male world records achieved during the 21st century and the Nike Breaking2 Project and INEOS 1:59 Challenge (total = 235 races). The races of the best runners in the Frankfurt Marathon (top 10) were analyzed (n = 110 runners, range: 2:03:42-2:14:05 hours); the runners were divided into two groups according to the tactical used. The pace of Group A (stable pace) remained steady throughout the race, while in Group B (decrease in running speed toward the end of the race) a moderate, but significant drop in speed was detected (P ≤ .001), starting from halfway through the race and getting sharper from the 30th kilometer (30-35 km = 1.6%, P ≤ .001 - 35-40 km = 4.3%, P ≤ .001 - 40-42.195 km: 3.9%, P ≤ .001, total = ≈10%). In the races in which the world record is achieved, the running speed tends to be steady and relatively conservative during the first stretch of the race, increasing smoothly in the second half and achieving a significant increase in the last 2195 m of the race (P = .016, ES = 1.14). Among all the possible strategies, running at a steady pace throughout the race seems the most effective option, especially when priority is given to time rather than position (ie, world records and best all-time races).

Blood serum denaturation profile examined by differential scanning calorimetry reflects the effort put into ultramarathon by amateur long-distance runners.

The impact of participation in the ultramarathon on the health and mental and physical condition is very complex. Undoubtedly, exercise brings many benefits but also involves health risks. Especially such an extreme effort as the one associated with finishing the ultramarathon run, can be dangerous to the health of the runner. With the variety of possible biomarkers of excessive fatigue that threaten health and life, a question arises which of them are the best and which should be considered in amateur long-distance runners showing particularly high individual variability. In this study differential scanning calorimetry (DSC) has been applied to show the overall effect of the 12-h run on blood sera of participants. Serum samples were obtained from the blood of ten male amateur long-distance runners, collected before and immediately after the run. Distinct changes in the shape of DSC curves have been observed for serum after finishing the run relative to pre-race serum. Statistically significant differences between stages "before" and "after" ultramarathon running have been found for parameters of the endothermic transition associated with denaturation of serum proteins. An increase in the temperature (from 70.9 ± 0.9 to 75.8 ± 2.9 °C) and excess heat capacity (from 0.859 ± 0.201 to 1.102 ± 0.226 Jg-1 °C-1) at peak maximum, the enthalpy of serum denaturation (from 18.55 ± 6.52 to 22.08 ± 5.61 Jg-1) and the first moment of the thermal transition with respect to the temperature (from the value of 67.0 ± 2.1 to 72.6 ± 2.1 °C) has been observed. These results show a clear impact of running an ultramarathon on the participant's blood serum.

Morphological Characteristics of Passive and Active Structures of the Foot Across Populations With Different Levels of Physical Activity.

BACKGROUND: Imaging diagnosis plays a fundamental role in the evaluation and management of injuries suffered in sports activities. OBJECTIVE: To analyze the differences in the thickness of the Achilles tendon, patellar tendon, plantar fascia, and posterior tibial tendon in the following levels of physical activity: persons who run regularly, persons otherwise physically active, and persons with a sedentary lifestyle. DESIGN: Cross-sectional and observational. PARTICIPANTS: The 91 volunteers recruited from students at the university and the Triathlon Club from December 2016 to June 2019. The data were obtained (age, body mass index, and visual analog scale for quality of life together with the ultrasound measurements). RESULTS: Tendon and ligament thickness was greater in the runners group than in the sedentary and active groups with the exception of the posterior tibial tendon. The thickness of the Achilles tendon was greater in the runners than in the other groups for both limbs (P = .007 and P = .005). This was also the case for the cross-sectional area (P < .01) and the plantar fascia at the heel insertion in both limbs (P = .034 and P = .026) and for patellar tendon thickness for the longitudinal measurement (P < .01). At the transversal level, however, the differences were only significant in the right limb (P = .040). CONCLUSION: The thickness of the Achilles tendon, plantar fascia, and patellar tendon is greater in runners than in persons who are otherwise active or who are sedentary.

Pacing strategies during male 1500 m running world record performances.

The aim was to determine the pacing strategies used to achieve male 1500 m running world record performances. Lap times (three first laps and the last 300 m) for the last 37 male 1500 m world record performances achieved since 1917 until 1998 were collected. An analysis of variance with repeated measures and a Bonferroni post hoc test were conducted to determine differences between the percentages of race average speed at each lap. Lap 1 and last 300 m differed from lap 2 and 3, being the latter slower (P < 0.001, 1.44 ≤ ES ≤ 1.95), and displaying a U-shaped pacing profile. Whereas the pacing strategies observed differed from those previously determined for major championship races, a fast endspurt was always present and therefore athletes aiming for a world standard performance should train for developing their anaerobic capacity in addition to a high aerobic power.

Mechanical Power in Endurance Running: A Scoping Review on Sensors for Power Output Estimation during Running.

Mechanical power may act as a key indicator for physiological and mechanical changes during running. In this scoping review, we examine the current evidences about the use of power output (PW) during endurance running and the different commercially available wearable sensors to assess PW. The Boolean phrases endurance OR submaximal NOT sprint AND running OR runner AND power OR power meter, were searched in PubMed, MEDLINE, and SCOPUS. Nineteen studies were finally selected for analysis. The current evidence about critical power and both power-time and power-duration relationships in running allow to provide coaches and practitioners a new promising setting for PW quantification with the use of wearable sensors. Some studies have assessed the validity and reliability of different available wearables for both kinematics parameters and PW when running but running power meters need further research before a definitive conclusion regarding its validity and reliability.

Lower leg morphology in runners: forefoot strikers have longer heels but not bigger muscles than rearfoot strikers.

Foot strike pattern used during running may relate to lower leg morphology. We tested the hypotheses that forefoot strike (FFS) runners have longer plantarflexor moment arms (r) and larger plantarflexor muscles than rearfoot strike (RFS) runners. FFS runners had 17% longer r than RFS runners, but all runners had similarly sized medial and lateral gastrocnemius (MG and LG) muscles. Because muscle size also depends on activation pattern ( Ahn et al., 2011), we compared MG:LG activation bias during walking in 24 runners and 23 sedentary subjects. Half of all subjects activated their MG and LG muscles equally ('unbiased') while walking, while the other half activated their MG more strongly than their LG muscles ('MG-biased'). Unbiased sedentary subjects had 16-23% smaller MG muscles compared with MG-biased sedentary subjects, unbiased runners and MG-biased runners. Muscle contraction dynamics during FFS running may balance the effects of longer plantarflexor moment arms in determining MG and LG muscle size.

Differences in foot muscle morphology and foot kinematics between symptomatic and asymptomatic pronated feet.

PURPOSE: This study aimed to determine the differences in foot muscle morphology and 3D multisegmental foot kinematics during walking between symptomatic and asymptomatic individuals with pronated feet (pronators) in a physically active population. METHODS: A total of 30 young physically active adults with pronated feet participated in this study, with 15 of them having recurring overuse injuries in the lower extremity in the 6 months prior to the test. A pronated foot was identified as having a foot posture index score between 6 and 12. An ultrasound system was used to measure the cross-sectional area and thickness of foot muscles of interest, including peroneus muscles, flexor digitorum longus and brevis, and abductor hallucis. Foot kinematic data during walking was collected using a 3D motion capture system incorporating the Oxford Foot Model. RESULTS: The symptomatic pronators demonstrated smaller cross-sectional area of flexor digitorum longus and abductor hallucis, and thinner peroneus muscles and abductor hallucis than their asymptomatic counterparts. The symptomatic pronators also displayed higher forefoot peak abduction during the stance phase of walking. CONCLUSION: There are differences in both extrinsic and intrinsic foot muscle morphology between symptomatic and asymptomatic pronators in a physically active adult population. Strengthening foot muscles may contribute to injury prevention in pronators. Large forefoot abduction instead of large rearfoot eversion during walking might be the indicator of pain in physically active pronators. Findings of this study may have implications on the underlying mechanisms of overuse injuries in individuals with pronated feet.