The effect of 26 versus 29-inch wheel diameter in the transmission of vibrations in cross-country mountain biking.

Vibrations experienced by cyclists can affect their performance and health. We analysed the vibrations transmitted by mountain bike (26 or 29-inch wheels), in a 2,110 m circuit with a sample of 55 cyclists. The results indicate that the 29"-wheel increases speed (p < 0.001) and thus performance but it also increases exposure to vibrations as the root mean square (RMS) indicate (p = 0.001). The wheel diameter significantly affected the accelerometer-related dependent variables (p < 0.01), specifically seen in the RMS variable (p < 0.01). Regarding vibration transmission variables, it was found that the LW/FH, RW/FH, LA/RH, and RA/RH ratios were higher in the 29" bicycle than in 26" one. Average heart rate (p = 0.01) and maximum heart rate (p < 0.01) values were higher for the 29" bike with no significant differences in the average power values recorded. In conclusion, bicycles with 29" wheels transmit higher levels of vibration to riders.

Effect of fatigue and gender on kinematics and ground reaction forces variables in recreational runners.

The presence of fatigue has been shown to modify running biomechanics. Overall in terms of gender, women are at lower risk than men for sustaining running-related injuries, although it depends on the factors taken into account. One possible reason for these differences in the injury rate and location might be the dissimilar running patterns between men and women. The purpose of this study was to determine the effect of fatigue and gender on the kinematic and ground reaction forces (GRF) parameters in recreational runners. Fifty-seven participants (28 males and 29 females) had kinematic and GRF variables measured while running at speed of 3.3 m s-1 before and after a fatigue test protocol. The fatigue protocol included (1) a running Course-Navette test, (2) running up and down a flight of stairs for 5 min, and (3) performance of alternating jumps on a step (five sets of 1 minute each with 30 resting seconds between the sets). Fatigue decreased dorsiflexion (14.24 ± 4.98° in pre-fatigue and 12.65 ± 6.21° in fatigue condition, p < 0.05) at foot strike phase in females, and plantar flexion (-19.23 ± 4.12° in pre-fatigue and -18.26 ± 5.31° in fatigue condition, p < 0.05) at toe-off phase in males. These changes led to a decreased loading rate (88.14 ± 25.82 BW/s in pre-fatigue and 83.97 ± 18.83 BW/s in fatigue condition, p < 0.05) and the impact peak in females (1.95 ± 0.31 BW in pre-fatigue and 1.90 ± 0.31 BW in fatigue condition, p < 0.05), and higher peak propulsive forces in males (-0.26 ± 0.04 BW in pre-fatigue and -0.27 ± 0.05 BW in fatigue condition, p < 0.05) in the fatigue condition. It seems that better responses to impact under a fatigue condition are observed among women. Further studies should confirm whether these changes represent a strategy to optimize shock attenuation, prevent running injuries and improve running economy.

Effects of functional resistance training on fitness and quality of life in females with chronic nonspecific low-back pain.

BACKGROUND: Exercise is important as adjuvant in the chronic low back pain (CLBP) treatment. Functional training could involve benefits for low back pain (LBP) patients. OBJECTIVE: To evaluate the effects of a 12-week period of functional resistance training on health-related quality of life (HRQOL), disability, body pain, and physical fitness in CLBP females. METHODS: Nineteen females CLBP were recruited according to Paris Task Force on Back Pain criteria. Participants were randomly assigned to an exercise group (EG); and a control group (CG). Subjects were tested at baseline and at week 12 after 24 sessions, 2 days per week. Body pain was assessed using visual analog scale (VAS), disability with Oswestry Disability Index (ODI) and HRQOL with Short Form 36 questionnaire. Physical fitness was measured using: flamingo test, back endurance test, side bridge test, abdominal curl-up tests, and 60-s squat test. RESULTS: EG showed significant improvements in physical function (10%; p< 0.05), body pain (42%; p< 0.05), vitality (31%; p< 0.05), physical component scale (15%; p< 0.05), VAS (62.5%; p< 0.01), ODI (61.3%; p< 0.05), balance (58%; p< 0.05), curl-up (83%; p< 0.01), squat (22%; p< 0.01), static back (67%; p< 0.01), and side bridge (56%; p< 0.01). CONCLUSION: Periodized functional resistance training decreased pain and disability and improved HRQOL, balance and physical fitness in females with CLBP, and can thus be used safely in this population.

Influence of custom-made and prefabricated insoles before and after an intense run.

Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact loading during running. The aim of the study was to analyse the acute differences in stride and shock parameters while running on a treadmill with custom-made and prefabricated insoles. Stride parameters (stride length, stride rate) and shock acceleration parameters (head and tibial peak acceleration, shock magnitude, acceleration rate, and shock attenuation) were measured using two triaxial accelerometers in 38 runners at 3.33 m/s before and after a 15-min intense run while using the sock liner of the shoe (control condition), prefabricated insoles and custom-made insoles. No differences in shock accelerations were found between the custom-made and the control insoles. The prefabricated insoles increased the head acceleration rate (post-fatigue, p = 0.029) compared to the control condition. The custom-made reduced tibial (pre-fatigue, p = 0.041) and head acceleration rates (pre-fatigue and post-fatigue, p = 0.01 and p = 0.046) compared to the prefabricated insoles. Neither the stride nor the acceleration parameters were modified as a result of the intense run. In the present study, the acute use of insoles (custom-made, prefabricated) did not reduce shock accelerations compared to the control insoles. Therefore, their effectiveness at protecting against injuries associated with elevated accelerations is not supported and remains unclear.

The location of the tibial accelerometer does influence impact acceleration parameters during running.

Tibial accelerations have been associated with a number of running injuries. However, studies attaching the tibial accelerometer on the proximal section are as numerous as those attaching the accelerometer on the distal section. This study aimed to investigate whether accelerometer location influences acceleration parameters commonly reported in running literature. To fulfil this purpose, 30 athletes ran at 2.22, 2.78 and 3.33 m · s-1 with three accelerometers attached with double-sided tape and tightened to the participants' tolerance on the forehead, the proximal section of the tibia and the distal section of the tibia. Time-domain (peak acceleration, shock attenuation) and frequency-domain parameters (peak frequency, peak power, signal magnitude and shock attenuation in both the low and high frequency ranges) were calculated for each of the tibial locations. The distal accelerometer registered greater tibial acceleration peak and shock attenuation compared to the proximal accelerometer. With respect to the frequency-domain analysis, the distal accelerometer provided greater values of all the low-frequency parameters, whereas no difference was observed for the high-frequency parameters. These findings suggest that the location of the tibial accelerometer does influence the acceleration signal parameters, and thus, researchers should carefully consider the location they choose to place the accelerometer so that equivalent comparisons across studies can be made.

Disinfection by-products effect on swimmers oxidative stress and respiratory damage.

Disinfection by-products (DBPs) are generated through the reaction of chlorine with organic and inorganic matter in indoor swimming pools. Different DBPs are present in indoor swimming pools. This study evaluated the effects of different chlorinated formations in oxidative stress and lung damage in 20 swimmers after 40 min of aerobic swimming in 3 indoor pools with different characteristics. Biological samples were collected to measure lung damage (serum-surfactant-associated proteins A and B), oxidative stress parameters (plasma protein carbonylation and malondialdehyde, and whole-blood glutathione oxidation), and swimming exertion values (blood lactate) before and after exercise. Free chlorine and combined chlorine in water, and chlorine in air samples were determined in all the swimming pools. Chlorination as disinfection treatment led to the formation of chloramines in water samples, mainly mono- and dichloramine. However, free chlorine was the predominate species in ultraviolet-treated swimming pool. Levels of total chlorine increased as a function of the swimming activity in chlorinated swimming pools. The lower quality of the installation resulted in a higher content of total chlorine, especially in air samples, and therefore a higher exposure of the swimmer to DBPs. However, the concentration level of chlorinated DBPs did not result in significant variation in serum-surfactant-associated proteins A and oxidative stress parameters in swimmers. In conclusion, the quality of the installation affected the DBPs concentration; however, it did not lead to lung epithelial damage and oxidative stress parameters in swimmers.

Effects of unstable shoes on trunk muscle activity and lumbar spine kinematics.

BACKGROUND: In patients with neuromuscular disease and a forced vital capacity (FVC) of <30% of the predictive value, scoliosis correction operation was Background. An unstable shoe was developed as a walking device to strengthen the lower extremity muscles and reduce joint loading. A large number of studies have reported increased electromyographic (EMG) activity throughout the gait cycle in most of the lower limb muscles, and significant kinematic changes in the lower extremity. However, no studies have investigated the effects of wearing unstable shoes on spine kinematics and trunk muscle activity during gait. AIM: To compare trunk muscle activity and lumbar spine range of motion (ROM) during gait using an unstable shoe and a conventional stable control shoe. DESIGN: Cross-sectional study. SETTING: A Biomechanics laboratory. POPULATION: Forty-eight healthy voluntary participants (24.5±5.6 years and 22.7±6.8 kg/m2). METHODS: Subjects underwent gait analysis while simultaneously collecting surface EMG data of erector spinae (ES) and rectus abdominis (RA) and lumbar spine sagittal plane ROM while treadmill walking wearing regular shoes and unstable shoes. RESULTS: The results showed that the unstable shoes resulted in significantly higher ES and RA EMG muscle activity levels in all gait phases compared to control shoes (P<0.001). In addition, the unstable shoe condition showed a significantly higher mean (mean difference: 3.1º; 95% CI 2.2º to 4º) and maximum (mean difference: 4.5º; 95% CI 2.6º to 6.5º) lumbar spine extension values (P<0.001). CONCLUSIONS: Unstable shoes increase trunk muscle activity (ES, RA) and lumbar lordosis during gait compared to control shoes. CLINICAL REHABILITATION IMPACT: Based on these findings, the use of unstable shoes may have potential implications in promoting spine tissue health, particularly in strengthening trunk muscles in healthy population or in low back pain treatment.

Differences in ground reaction forces and shock impacts between nordic walking and walking.

UNLABELLED: The regular practice of Nordic walking (NW) has increased in recent years, in part thanks to the health benefits described by the scientific literature. However, there is no consensus on the effects of shock-impact absorption during its practice. PURPOSE: The aim of this study was to compare the levels of impact and ground reaction forces (GRF) between NW and walking (W). METHOD: Twenty physically active and experienced participants were assessed using a dynamometric platform and accelerometry analysis. RESULTS: The results show statistically significantly higher levels of acceleration in the tibia (12%) and head (21%) during NW compared with W. Equally, GRF were significantly higher (27%) at the instant of strike compared with W, and a reduction of the forces at the instant of takeoff (8%) was observed. CONCLUSIONS: During NW, shock impacts and GRF levels increased compared with W, an aspect that should be considered when prescribing health improvement programs.

Effects of treadmill running and fatigue on impact acceleration in distance running.

The effects of treadmill running on impact acceleration were examined together with the interaction between running surface and runner's fatigue state. Twenty recreational runners (11 men and 9 women) ran overground and on a treadmill (at 4.0 m/s) before and after a fatigue protocol consisting of a 30-minute run at 85% of individual maximal aerobic speed. Impact accelerations were analysed using two lightweight capacitive uniaxial accelerometers. A two-way repeated-measure analysis of variance showed that, in the pre-fatigue condition, the treadmill running decreased head and tibial peak impact accelerations and impact rates (the rate of change of acceleration), but no significant difference was observed between the two surfaces in shock attenuation. There was no significant difference in acceleration parameters between the two surfaces in the post-fatigue condition. There was a significant interaction between surface (treadmill and overground) and fatigue state (pre-fatigue and post-fatigue). In particular, fatigue when running overground decreased impact acceleration severity, but it had no such effect when running on the treadmill. The effects of treadmill running and the interaction need to be taken into account when interpreting the results of studies that use a treadmill in their experimental protocols, and when prescribing physical exercise.

Effect of custom-made and prefabricated insoles on plantar loading parameters during running with and without fatigue.

Controversy exists whether custom-made insoles are more effective in reducing plantar loading compared to prefabricated insoles. Forty recreational athletes ran using custom-made, prefabricated, and the original insoles of their running shoes, at rest and after a fatigue run. Contact time, stride rate, and plantar loading parameters were measured. Neither the insole conditions nor the fatigue state modified contact time and stride rate. Addressing prevention of running injuries, post-fatigue loading values are of great interest. Custom-made insoles reduced the post-fatigue loading under the hallux (92 vs. 130 kPa, P < 0.05), medial midfoot (70 vs. 105 kPa, P < 0.01), and lateral midfoot (62 vs 96 kPa, P < 0.01). Prefabricated insoles provoked reductions in post-fatigue loading under the toes (120 vs. 175 kPa, P < 0.05), medial midfoot (71 vs. 105 kPa, P < 0.01), and lateral midfoot (68 vs. 96 kPa, P < 0.01). Regarding both study insoles, custom-made insoles reduced by 31% and 54% plantar loading under the medial and lateral heel compared to the prefabricated insoles. Finally, fatigue state did not influence plantar loading regardless the insole condition. In long-distance races, even a slight reduction in plantar loading at each foot strike may suppose a significant decrease in the overall stress experienced by the foot, and therefore the use of insoles may be an important protective mechanism for plantar overloading.

Supination control increases performance in sideward cutting movements in tennis.

The objective of this study was to explore the effects of tennis shoe characteristics on performance during sideward cutting movements followed by direction changes. Five tennis players (age = 21.5 +/- 0.8 years, mass = 75.2 +/- 2.8 kg, and height = 1.78 +/- 0.05 m) participated in the study and 10 tennis shoes were tested. Several footwear mechanical parameters were analyzed: Shore A hardness, longitudinal and transverse flexibility, midsole height at heel, presence of heel counters, and weight. A force plate was used to measure the kinetic variables, and two video cameras were used to perform a three-dimensional photogrammetric analysis. Results revealed that subject-footwear interaction was statistically not significant (p > 0.05) for the kinetic and kinematic variables. Only contact time (p = 0.008) and supination movement (p = 0.009) were footwear dependent. Positive correlations between contact time and first supination peak (r = 0.783, p = 0.007) and second supination peak (r = 0.730, p = 0.016) were observed. Impulse was not changed, which means shoes limiting supination allowed tennis players to perform faster sideward cutting movements.

Nordic walking practice might improve plantar pressure distribution.

Nordic walking (NW), characterized by the use of two walking poles, is becoming increasingly popular (Morgulec-Adamowicz, Marszalek, & Jagustyn, 2011). We studied walking pressure patterns of 20 experienced and 30 beginner Nordic walkers. Plantar pressures from nine foot zones were measured during trials performed at two walking speeds (preferred and 20% faster), and under two walking conditions (NW vs. normal walking). In comparison to normal walking, NW experience led to a significant (p < .05) pressure reduction of about 50% on the central metatarsals. No significant increases were detected in other foot regions. The differences between experienced and beginners during normal walking including a 40% pressure reduction on the metatarsal area, suggests that regular NW practice might also have a beneficial effect on plantar pressure when walking without poles.

Plantar pressures determinants in mild Hallux Valgus.

While podobarometric techniques have been applied to the study of pressures in Hallux Valgus (HV), little is known about its clinical and radiological determinants. So, the aim of the present study was to determine the plantar pressure pattern in participants with mild HV, comparing to a control group, and their clinical and anthropometric determinants. Biofoot/IBV(®) in-shoe system was used to evaluate 79 participants with mild HV. Computerized measurements of the 1st intermetatarsal angle (IMA) and the hallux abductus angle (HAA) were made on antero-posterior radiographs. The clinical outcome was assessed using the AOFAS score. The dependent baropodometric variables and the independent clinical and anthropometric variables were subjected to a multiple regression analysis. In both groups, the highest average pressure was in the 2nd metatarsal head (MTH). The mean pressure under the Hallux was significantly higher in HV group (controls, 146.5±92.5kPa; HV, 328.5±113.2kPa; p<0.001). An 18.6% of average pressure under the 1st MTH was accounted for pain, first ray alignment and total AOFAS score. Variations of the HAA explained 26.8% of the mean Hallux pressure. Women with mild HV present with pathologically increased pressure under the Hallux, which is caused by the altered alignment of the first ray. Pain and clinical result were associated with the pressure under the 1st MTH and the remaining variables were only moderate predictors of dynamic plantar pressures.

Effects of mat characteristics on plantar pressure patterns and perceived mat properties during landing in gymnastics.

Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction.

Análisis del patrón de las presiones plantares en gimnastas durante la recepción en una colchoneta / Analysis of plantar pressure pattern in gymnasts during land in different mats

En gimnasia, la recepción es la acción más frecuentes e importante para la puntuación final durante la competición, así como por las lesiones que podría producirse durante su ejecución. En la mayoría de los casos, la estabilidad del pie estará condicionada por la habilidad del gimnasta y las características y/o propiedades de la colchoneta, razón por la cual, en este estudio se han analizado el patrón y las magnitudes de presión plantar durante la recepción, así como su relación con la estabilidad y la percepción en la propiedades de la colchoneta. Para ello, se analizó mediante un sistema de plantillas instrumentado, la presión en el pie derecho de 5 gimnastas varones, tras5 saltos válidos en 6 colchonetas con diferencias estadísticamente significativas según test EN 12503-4: 2001, además de sus diferenciasen composición y estructura. También se evaluó mediante encuestas la percepción que el gimnasta había tenido en algunas de las propiedad es de la colchoneta tras la recepción. Considerando como variable dependiente la media de presión máxima en cada zona, se realizó un ANOVA tomando como factor aleatorio al gimnasta y fijo a las colchonetas, observándose diferencias significativas (p < 0.05) por zona y colchoneta. El análisis factorial identificó las relaciones entre las zonas del pie, reduciendo a 4 componentes o factores (mediopié, antepié, retropié y pie externo) con un 83.80% del total de la varianza. El ANOVA en la percepción no mostró diferencias significativas, sin embargo, el análisis de correlaciones entre las presiones plantares y percepción mostró relaciones significativas (p < 0.01 y p < 0.05). En conclusión, existe un mismo patrón de presión independientemente de la colchoneta empleada, con elevadas magnitudes en el talón (785 kpa) y primer metatarsiano (352.6 kpa), y similares magnitudes (cercanas a los 200 kpa) en el resto de zonas. En cuanto a la percepción de estabilidad y velocidad de recuperación, los resultados lo relacionan con aumento de presión en la parte delantera del pie y con colchonetas más blandas, mientras que la presión en el talón se asocia con la percepción de la deformación para amortiguar la recepción y con colchonetas de mayor densidad (AU)

Landing is the most frequency and important action during gymnastic score competition, as well as the injuries that happen during its execution too. Generally, foots stability will be provided by the gymnast ability and mat properties. For this reason, pattern and plantar pressure during landings were analyzed, besides its relation with the stability and mat property perception. Five male gymnasts were analyzed by means of a pressure plantar system in his right foot, during five valid jumps in six different mats with statistical differences according to EN 12503-4: 2001 standard. The gymnast perception was analyzed with a survey after each five jump in different mat. Results of the ANOVA indicated significant differences (p < 0.05) in plantar zones and mats, with gymnast as random factor, mats as random fix factor and as dependent variable, the average of pressure in each zone. The factorial analysis identified the relations between the foot zones, reducing to four components (middle foot, rear foot, front foot, external foot) with 83.80% explained variance. The ANOVA in perception did not show significant differences. The correlation analysis in a plantar pressures and perceptions, exhibited significant relations (p < 0.01 y p < 0.05). In conclusion, a same pattern of plantar pressure was showed for different mats, with high pressure in the heel (785 kpa) and first metatarsi an (352.6 kpa), and similar magnitude (near to 200 kpa) in rest zones .The stability and recovery speed perceptions were associated with high front pressures and soft mats, whereas high rear pressure and hard mats, was associated with the perception of the deformation to absorb the land (AU)