Biomehanički rad i koordinacijska struktura vožnje bicikla: pregled literature

In this review paper there three models to calculate mechanical work, the pattern of joint power during steady-state cycling and some theories regarding energy transfer through the joints and coordinative pattern analysis by joint mechanical work distribution will be briefly presented. Finally, there will be a report on the effects of workload, pedalling cadence and saddle height management on joint mechanical work. The first result that emerges from the management of the workload is that the positive mechanical work produced by the joints increases which is mostly related to the concentric muscle contraction. The contribution of hip and knee joints seems to be different from the ankle joint with changes in workload during cycling because the ankle joint muscles should be tuned to optimize stiffness and maximize the effective transmission of mechanical energy to the crank. When changing pedalling cadence, the authors have only agreed with the unchanged contribution of the ankle joint to the total mechanical work, while the hip and knee contribution results differ in the reported research. Lack of evidence in ankle joint function when the resistive force and pedalling cadence relationship are changed during fatigue as the mechanical energy transfer and stiffness function need further research. Controversial results have been reported in the analysis of joint contribution to the total mechanical work for different cycling expertise. Unfortunately, we cannot find conclusive research regarding the effects of saddle height on coordinative pattern mainly based on simultaneous analysis of joint moment distribution, joint kinematics and joint reaction forces.Uvod Bicikl je prijevozno sredstvo iznimno korišteno u cijelom svijetu. Kada je riječ o potrošnji energije tijekom vožnje biciklom, može se primijetiti da su mehaničke karakteristike (geometrija) bicikla unapređivane tijekom vremena kako bi se smanjila potrošnja energije, poboljšala brzina prijenosa i, očigledno, povećala ekonomičnost kretanja. Mehanički rad tijekom vožnje biciklom trebalo bi također analizirati u kontekstu poboljšanja ekonomičnosti kretanja, i to analizom koordinacijskog obrasca pokreta. Na taj način, optimizacija mišićne funkcije predstavljena je kao učinkovito rješenje za poboljšanje ravnoteže između mehaničkog rada i metaboličke energije. Mi još uvijek ne razumijemo potpuno kontrolu generiranja mišićne sile iz središnjeg živčanog sustava (koordinacijski obrazac pokreta), no ipak se dosta toga zna. U skladu s navedenim, u ovom radu pokušali smo ukratko predstaviti tri modela izračunavanja mehaničkog rada, koncept generiranja snage u mišićima zglobova koji sudjeluju u okretanju pedala tijekom vožnje standardnom brzinom te neke teorije koje se odnose na transfer energije kroz zglobne sustave i analizu koordinacijskog obrasca promatranjem distribucije mehaničkog rada u zglobovima. Naposljetku, izvijestili smo o učincima opterećenja, ritma okretanja pedala i visine sjedala na mehanički rad zglobova. Da bismo prikupili članke vezane uz glavni problem ovog preglednog članka obavljeno je kompjutersko pretraživanje najkorištenijih baza podataka ili agregatora baza (MEDLINE, SCOPUS, ISI Web of Knowledge, EBSCO i GOOGLE SCHOOLAR), kao i brojnih pojedinačnih časopisa dostupnih u papirnatom obliku. Ključne riječi za pretraživanje relevantnih članaka bile su: mišićni mehanički rad, koordinacijski obrazac, snaga mišića u zglobovima, visina sjedalice, opterećenje i ritam okretanja pedala. Modeli za izračunavanje mehaničkog rada: Na temelju promjena kinetičkih i potencijalnih energija svakog segmenta (unutarnji rad), model koji je predstavio Fenn (1930a,b) prilagođavao se godinama. Elftman (1939) je predstavio drugačiji pristup za izračunavanje mehaničkog rada u zglobovima koji je koristio rezultante zglobnih momenata i kutne brzine za izračunavanje snage svakog zgloba (kinetički model). Kompleksniji model izračunavanja mehaničkog rada kod okretanja pedala predstavili su Neptune i Van Den Bogert (1998) koji su u kompjutersku simulaciju gibanja uključili 28 mišića i njihove karakteristike sile-dužine-brzine. Ovaj model bio je naveden kao najosjetljiviji za objašnjavanje mišićne koordinacije tijekom okretanja pedala na biciklu, ponajviše stoga što analizira i mišićnu ko-kontrakciju. Generiranje snage u mišićima zglobova koji sudjeluju u okretanju pedala tijekom vožnje standardnim ritmom: Za razliku od hodanja i trčanja, kod okretanja papučica bicikla veći se dio mehaničke energije, povezane s cikličnim kretnjama, dobiva iz koncentričnih mišićnih akcija donjih ekstremiteta. Rezultati također pokazuju da se u pedaliranju skladišti elastična energija, istina, manja nego u trčanju. Transfer mehaničke energije kroz zglobne sustave i koordinacijski obrazac gibanja: Biciklizam, kao višezglobni zatvoreni kinetički lanac, razvija silu i prenosi snagu kroz kukove, koljena i gležnjeve. Broker i Gregor (1994) proveli su analizu transfera energije koristeći kinetički model mehaničke energije. Fregly i Zajac (1996) stvorili su simulacijski model koristeći samo kinematičke podatke. Neptune, Kautz i Zajac (2000) također su stvorili simulacijski model za analizu najvažnijih mišićnih grupa povezanih s cikličnim gibanjem u biciklizmu. Rezultati njihovih istraživanja otkrili su nam da mišići zgloba stopala (m. soleus, m. gastrocnemius i m. tibialis anterior) imaju vrlo važnu funkciju u transferu mehaničke energije ekstremiteta na papučicu bicikla, dok se mišići kvadricepsa i m. gluteus maximus povezuju s proizvodnjom mehaničke energije. Bolje razumijevanje funkcioniranje mišićnih grupa u biciklizmu omogućilo je i kvalitetnije objašnjavanje koordinacijskog obrasca kretanja pri samom okretanju pedala. Učinci opterećenja na mehanički rad zglobova i koordinacijski obrazac kretanja: Prvi rezultat, posljedica upravljanja opterećenjem, jest da dolazi do povećanja pozitivnog mehaničkog rada koji proizvode mišići zglobova uključenih u okretanje papučica bicikla, što je povezano s koncentričnom mišićnom kontrakcijom. Čini se da je doprinos mišića kukova i koljena promjenama opterećenju tijekom vožnje bicikla različit od doprinosa mišića zgloba stopala, budući da mišići zgloba stopala moraju biti prilagođeni za optimizaciju čvrstoće i maksimiziranja učinkovitosti transmisije mehaničke energije na pedalu bicikla. Učinak ritma okretanja papučica na mehanički rad zglobova i koordinacijski obrazac gibanja: Također je analiziran učinak ritma okretanja pedala na mehanički rad zglobova radi objašnjenja koordinacijskog obrasca gibanja tijekom vožnje biciklom. Pri jednakom izlazu snage, povećani unutarnji rad s povećanjem ritma okretanja pedala povezan je s negativnom snagom ekscentrične kontrakcije mišića koja se proizvodila zbog pokušaja kontroliranja primjene sile na papučice. Izabran je najprihvatljiviji ritam okretanja pedala koji će odgovarati omjeru između proizvodnje sile i brzine skraćivanja mišića. Dok male promjene u ritmu okretanja pedala (od 90 do 100 o/min) ne utječu na distribuciju mehaničkog rada, čini se da velike promjene ritma okretanja pedala ili mijenjaju ili ne utječu na doprinos kuka, koljena i gležnja na ukupni mehanički rad. Autori su se jedino složili oko činjenice da se doprinos mišića gležnja na ukupni mehanički rad ne mijenja s promjenama ritma okretanja pedala. Učinak visine sjedala na mehanički rad zglobova i koordinacijski obrazac kretanja: Provedena su i istraživanja o upravljanju visinom sjedala bicikla radi utvrđivanja obrasca opterećenja zglobova pri različitim visinama, budući da je dokazano kako je većina ozljeda u biciklizmu povezana s lošim pozicioniranjem vozača na biciklu. Također je objavljen i podatak da distribucija snage zgloba nije pod utjecajem smanjenja visine sjedalice na biciklu. Nažalost, nije pronađeno nijedno istraživanje koje se bavilo ispitivanjem utjecaja visine sjedalice na distribuciju mehaničkog rada zglobova, a isto tako nisu pronađeni ni simulacijski modeli koji analiziraju generiranje mišićne sile pri različitim visinama sjedalice bicikla. Objavljeni su samo EMG podaci kojima su se pokušali objasniti i razumjeti koordinacijski obrasci kretanja tijekom vožnje bicikla na različitim visinama sjedalice. Prijedlozi budućih istraživanja: U ovom preglednom članku predstavljeni su različiti modeli koji se primjenjuju za mjerenje mehaničkog rada u biciklizmu. Većina rezultata tih istraživanja bazirani su na kinetičkim modelima zbog toga što omogućuju usporedbu doprinosa zgloba kuka, koljena i gležnja ukupnom mehaničkom radu. Predstavljeni su i neki dokazi koji se temelje na proračunskim simulacijskim modelima, a koji predlažu povećanje pouzdanosti analize gibanja u biciklizmu pomoću procjene ko-kontrakcije mišića. Buduća istraživanja trebala bi se orijentirati na upotrebu proračunskih simulacijskih modela za analizu različitih opterećenja vožnje bicikla, ritma okretanja pedala, utjecaja visine sjedalice i sličnih znastvenih problema

ANALYSIS OF PEDALING TECHNIQUE DURING A MAXIMAL CYCLING EXERCISE

The purpose of this study was to analyze the effects of the fatigue process during a maximal cycling exercise on the pedaling technique. Eight elite competitive male cyclists were evaluated in a two days protocol. On day 1, the cyclists were submitted to a VO2MAX test, and on day 2, they cycled to exhaustion on a cycle ergometer equipped with two 2-D pedals dynamometer to measure the forces applied on the pedals. The workload was set at 100% of their VO2MAX, as measured on day 1. The resultant and effective forces were calculated from normal and tangential forces to obtain the index of effectiveness (IE). No differences were observed in the IE throughout the entire test. This study suggests that under a fatigue protocol, elite cyclists are able to sustain the IE, which can be an important strategy in order to sustain the power output

Functional taping effects on pain and electrical activation in patients with low back pain

Background: Low back pain (LBP) is a high prevalence health problem and it has several treatments available, among them it is the functional taping. Objective: To evaluate the influence of functional taping on the electrical activation of the erector spinae muscle, the degree of pain and the functionality in subjects with LBP. Methods: Twenty female with LBP participated in the study, and were divided in two groups: with and without the use of the functional taping. The electrical activity of the erector spinae muscle was obtained bilaterally by electromyography (EMG). The root mean square (RMS) value of the EMG was calculated for three maximum voluntary contractions (MVC) obtained before and 48 hours after the application of the taping. The RMS value of each MVC was normalized by the mean RMS value of the first test for each group. The visual analog pain scale was used to measure the pain, and the Roland Morris questionnaire to evaluate the functionality. Comparisons between groups (α=5%) were performed using the Mann Whitney test, and intra-group using the Wilcoxon test. Results: There was no decrease in muscular electrical activation, a significant decrease in pain, and an improvement in functionality. Conclusion: The use of functional taping in the lumbar spine promoted positive effects related to pain and functionality

Spectral properties of muscle activation during incremental cycling test

It is uncertain whether fatigue and workload would affect muscle recruitment during cycling. To infer on changes in priority for recruitment of motor units, we assessed the combined effects of fatigue and workload during an incremental cycling test to exhaustion on frequency components of lower limbs muscle activation. Competitive cyclists performed an incremental maximal cycling test while muscle activations were recorded from the right and left vastus lateralis, biceps femoris and gastrocnemius medialis. Muscle activation signals were assessed using frequency band analyses and decomposed into overall, high and low frequency bands. Combined effects from workload/fatigue were assessed using t tests and Cohen¿s effect sizes (ES). There were increases in the overall muscle activation due to increased workload/fatigue for biceps femoris (40% vs. 90%, p<0.01 and ES = 1.85) and vastus lateralis (40% vs. 70%, p=0.01 and ES = 0.96, and 40% vs. 90%, p<0.01 and ES = 2.03, and 70% vs. 90%, p<0.01 and ES = 0.96), but not for gastrocnemius medialis. There was also greater contribution from low frequency component for biceps femoris (40% vs. 90%, p = 0.01 and ES = 1.12). Similar workload/fatigue effects have been observed between lower limbs. In conclusion, incremental cycling test lead to an increase in activation of main knee joint flexors and extensors but not in plantar flexors during cycling. Biceps femoris changes its recruitment profile due to increases in low frequency content

Why Fast Velocity Resistance Training Should be Prioritized for Elderly People?

Because of recent demographic changes with a greater proportion of elderly people in the world, physical independence among older adults is becoming increasingly more important. This minireview summarizes and discusses neuromuscular adaptations in response to resistance training with different contraction velocities in untrained elderly. slow and fast velocity training can to a similar extent improve muscle mass and maximal force. However, fast velocity resistance training is superior for improving power output, explosive force, and functional capacity. Thus, fast velocity resistance training provides more efficient neuromuscular adaptations, increasing simultaneously strength, power, explosive force, muscle mass, and functional capacity of untrained elderly.</p

Editorial: Structural and mechanistic determinants of endurance performance

[no abstract available

KINEMATICAL AND NEUROMUSCULAR ASPECTS RELATED TOPERFORMANCE DURING THE SWIMMING START

The aim of this study was to relate kinematical and neuromuscular aspects with performance in the swimming start. Ten swimmers took part in this study. Kinematical analysis (flight distance, flight time, start and entry angle and maximum height) and the muscle power were evaluated. Pearson’s correlate with significance set at 5% was used. Significant correlation of the start angle with flight distance (r= -0.59; p< 0.05) and with flight time (r=0.88; p< 0.01) were found; between maximum height and flight time (r= 0.59; p< 0.05) were found too. We can conclude that performance in the swimming start was determined by the start angle and maximum height. Muscle power did not affect performance in swimmers in this study

Reliability of portable electrical impedance myograph SKULPT® for morphological measures of vastus lateralis/ Confiabilidade da impedância elétrica do miógrafo portátil SKULPT® a partir de medidas morfológicas do vastus lateralis

New devices with clinical applicability are needed to provide fast and precise diagnostics. In this way, the aim of this study was to verify the reliability of the portable electrical impedance myograph (PEIM) Skulpt® for morphological measures of the vastus lateralis (VL). MATERIALS AND METHODS: A cross-sectional evaluation was designed on an independent limb to verify reliability between the PEIM Skulpt® and ultrasound (US) for VL muscle morphological measures. Twelve health men (age=32.17±8.90 years) participated in the study, being evaluated muscle quality (MQ) and fat mass (%FAT) with the PEIM on the frontal thigh position, and echo intensity (EI) and muscle and fat thickness (MT and FT) with the US. RESULTS: Equipment reliability (US vs. PEIM) indicated a moderate correlation [r=-0.53; p=0.770] between MQ and EI. Conversely, intra-rater reliability indicated moderate consistency for EI (p=0.021) and excellent for MT (p=0.008) and FT (p&lt;0.001). In addition, excellent consistency was indicated for MQ (p&lt;0.001) and %FAT (p&lt;0.001). Proposed equations were applied in the contralateral lower limb (n=12). Subsequently, a Bland-Altman plot presented lower bias and higher agreement limits for both adjustment equations for PEIM between the MT and FT with MQ and %FAT, respectively. CONCLUSION: In summary, our results indicate moderate intra-rater reliability consistency for EI, excellent for MT and FT, and excellent for MQ, and %FAT. In addition, our proposed adjustment equation presents clinical application to control %FAT and MQ with different possibilities of application in adults, as it can be applied in aesthetics, health control, and even physiotherapeutic treatments

Relação entre cinemática e antropometria de nadadores recreacionais e universitários

As swimming performance depends on many factors, the main purpose of this study was to verify the relationship among the mean stroke cycles rate (SR), mean stroke cycle length (SL), mean swimming velocity (SV), anthropometric variables and flexibility of recreational and college swimmers. Sixteen recreational swimmers (G1) and 10 college swimmers (G2) were evaluated in three replicates maximum bouts of 25 m swimming crawl. Results showed significant correlations between SL (G1 = 1.62 ± 0.22 m; G2 = 1.55 ± 0.19 m) and (1) body mass (G2 = 65.0 ± 11.9 Kg) and (2) upper limbs span (G1 = 177.2 ± 12.3 cm; G2 = 172.6 ± 15.8 cm) and (3) height (G1 = 172.9 ± 11.3 cm; G2 = 172.0 ± 14.3 cm). Regardless levels of flexibility, significant negative correlation was found between the magnitude of ankle joint (G1 = 4.68 ± 0.70; G2 = 4.80 ± 0.91) and SV (G1 = 1.31 ± 0.21 m.s-1; G2 = 1.57 ± 0.21 m.s-1), for both groups. We conclude that SL, even among no competitive level swimmers, seems to be an important evaluation component of swimming performance.Considerando a dependência que o desempenho em natação apresenta de diversos fatores, o objetivo deste estudo foi verificar a relação entre a freqüência média de ciclos de braçadas (FBr), a distância média percorrida por ciclo de braçadas (DBr), a velocidade média de nado (VN), variáveis antropométricas e flexibilidade de nadadores recreacionais e universitários. Participaram deste estudo 16 nadadores recreacionais (G1) e 10 nadadores universitários (G2), avaliados em três repetições máximas de 25 m nado crawl. Encontraram-se correlações significativas entre DBr (G1 = 1,62 ± 0,22 m; G2 = 1,55 ± 0,19 m) e (1) massa corporal (G2 = 65,0 ± 11,9 kg); (2) envergadura (G1 = 177,2 ± 12,3 cm; G2 = 172,6 ± 15,8 cm) e estatura (G1 = 172,9 ± 11,3 cm; G2 = 172,0 ± 14,3 cm) (ambos os grupos). Quando analisados especificamente os níveis de flexibilidade, foi encontrada correlação significativa negativa entre a amplitude da articulação do tornozelo (G1 = 4,68 ± 0,7; G2 = 4,80 ± 0,9) e VN (G1 = 1,31 ± 0,21 m.s-1; G2 = 1,57 ± 0,21 m.s-1), para ambos os grupos estudados. Conclui-se que, mesmo em nadadores que não sejam de alto nível competitivo, o DBr parece ser um componente importante em relação à avaliação do desempenho em natação

O gênero influencia a intensidade do eco do quadríceps femoral em indivíduos jovens e saudáveis? O gênero influencia a intensidade do eco muscular?

Introduction: The analysis of the echo intensity (IE) can be obtained by ultrasound from reflections of ultrasound waves from the tissue and has been widely used to identify tissue damage in clinical and sports context. Women may have more adipose tissue than men, which may reflect in greater fat infiltration into the muscle and thus influence IE values. Objective: To verify whether gender influences the SI of the quadriceps femoris in young, healthy individuals. Materials and Methods: Nineteen young healthy subjects (9 females and 10 males; 26.0 ± 7.0 years; 28.0 ± 6.0 kg/m2) participated in the study. Six ultrasound images were acquired of the rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) muscles, bilaterally and at rest. The IE values were established by means of the histogram function of the ImageJ® software, whose gray scale ranges from 0 (black) to 255 (white). To compare IE between gender, the mixed model ANOVA statistical test was used with a significance level of ≤ 0.05. Results: No significant differences were found between the quadriceps IE of men and women (p = 0.679). The mean IE values found were 135.18 ± 11.86, 126.74 ± 14.05 and 131.36 ± 12.81 A.U. for RF, VL and VM, respectively. Conclusion: Gender does not seem to influence SI values of the femoral quadriceps in young healthy individuals, which may represent a similar muscle composition between men and women with normal body mass index. Further studies should investigate different ages and body mass index.Introducción: El análisis de la intensidad del eco (IE) puede obtenerse mediante ultrasonidos a partir de las reflexiones de las ondas ecográficas del tejido y se ha utilizado ampliamente para identificar el daño tisular en el contexto clínico y deportivo. Las mujeres pueden tener más tejido adiposo que los hombres, lo que puede reflejarse en una mayor infiltración de grasa en el músculo y, por tanto, influir en los valores del IE. Objetivo: Comprobar si el género influye en la IE del cuádriceps femoral en individuos jóvenes y sanos. Materiales y métodos: Diecinueve individuos jóvenes y sanos (9 mujeres y 10 hombres; 26,0 ± 7,0 años; 28,0 ± 6,0 kg/m2) participaron en el estudio. Se adquirieron seis imágenes ecográficas de los músculos recto femoral (RF), vasto lateral (VL) y vasto medial (VM), bilateralmente y en reposo. Los valores del IE se establecieron mediante la función de histograma del software ImageJ®, cuya escala de grises va de 0 (negro) a 255 (blanco). Para comparar la IE entre géneros, se utilizó la prueba estadística ANOVA de modelo mixto con un nivel de significación de ≤ 0,05. Resultados: No se encontraron diferencias significativas entre el IE de los cuádriceps de hombres y mujeres (p = 0,679). Los valores medios de IE encontrados fueron 135,18 ± 11,86, 126,74 ± 14,05 y 131,36 ± 12,81 U.A. para RF, VL y VM, respectivamente. Conclusión: El género no parece influir en los valores del IE del cuádriceps femoral en individuos jóvenes y sanos, lo que puede representar una composición muscular similar entre hombres y mujeres con un índice de masa corporal normal. Otros estudios deberían investigar las diferentes edades y el índice de masa corporal.Introdução: A análise da intensidade do eco (IE) pode ser obtida por meio da ultrassonografia a partir de reflexões de ondas ecográficas do tecido e vem sendo amplamente utilizada para identificar danos nos tecidos no contexto clínico e desportivo. As mulheres podem ter mais tecido adiposo que homens, o que pode refletir em maior infiltração de gordura no músculo e, dessa forma, influenciar os valores de IE. Objetivo: Verificar se o gênero influencia a IE do quadríceps femoral em indivíduos jovens e saudáveis. Materiais e Métodos: Dezenove jovens saudáveis (9 mulheres e 10 homens; 26.0 ± 7.0 anos; 28.0 ± 6.0 kg/m2) participaram do estudo. Foram adquiridas seis imagens de ultrassom dos músculos reto femoral (RF), vasto lateral (VL) e vasto medial (VM), bilateralmente e em repouso. Os valores de IE foram estabelecidos por meio da função histograma do software ImageJ®, cuja escala de cinza varia de 0 (preto) a 255 (branco). Para comparar a IE entre gênero, foi utilizado o teste estatístico ANOVA de modelo misto com nível de significância de ≤ 0,05. Resultados: Não foram encontradas diferenças significativas entre a IE do quadríceps de homens e mulheres (p = 0.679). Os valores médios de IE encontrados foram 135,18 ± 11,86, 126,74 ± 14,05 e 131,36 ± 12,81 A.U. para RF, VL e VM, respectivamente. Conclusão: O gênero não parece influenciar os valores de IE do quadríceps femoral em indivíduos jovens e saudáveis, o que pode representar uma semelhante composição muscular entre homens e mulheres com índice de massa corpórea normal. Mais estudos devem investigar diferentes idades e índice de massa corpórea