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ACUTE STRETCHING INHIBITS STRENGTH ENDURANCE PERFORMANCE
Abstract
Since strength and muscular strength endurance are linked, it is possible that the inhibitory influence that prior stretching has on strength can also extend to the reduction of muscle strength endurance. To date, however, studies measuring muscle strength endurance poststretching have been criticized because of problems with their reliability. The purpose of this study was twofold: both the muscle strength endurance performance after acute static stretching exercises and the repeatability of those differences were measured. Two separate experiments were conducted. In experiment 1, the knee-flexion muscle strength endurance exercise was measured by exercise performed at 60 and 40% of body weight following either a no-stretching or stretching regimen. In experiment 2, using a test-retest protocol, a knee-flexion muscle strength endurance exercise was performed at 50% body weight on 4 different days, with 2 tests following a no-stretching regimen (RNS) and 2 tests following a stretching regimen (RST). For experiment 1, when exercise was performed at 60% of body weight, stretching significantly (p < 0.05) reduced muscle strength endurance by 24%, and at 40% of body weight, it was reduced by 9%. For experiment 2, reliability was high (RNS, intraclass correlation = 0.94; RST, intraclass correlation = 0.97). Stretching also significantly (p < 0.05) reduced muscle strength endurance by 28%. Therefore, it is recommended that heavy static stretching exercises of a muscle group be avoided prior to any performances requiring maximal muscle strength endurance.
... exercise performance is mainly due to a reduction in muscle stiEness or increased compliance (Wilson et al., 1994). Most investigations have focused on measures of maximal muscle force generation, either through the measurement of isokinetic peak torque or a onerepetition maximum (1-RM); few studies have addressed the impact of acute muscle stretching on fatigue (Kokkonen et al., 2001). ...
... A relative 'muting' of the sensory response may result and, therefore, be manifest in the rating of perceived exertion to a given muscle contraction. T o date, the impact of acute muscle stretching on fatigue and the corresponding estimate of subjective effort has received little attention (Kokkonen et al., 2001). The aim of this study was to examine the effects of an acute stretching regime on hamstring muscle fatigue and perceived exertion during a dynamic, submaximal bout of resistance exercise. ...
... A general reduction in maximal muscle force after muscle stretching has been observed (Kokkonen et al., 1998(Kokkonen et al., , 2001Fowles et al., 2000;Behm et al., 2001). Kokkonen et al. (2001) examined muscle fatigue in 26 individuals who performed a single bout of resistance hamstring exercise at a load equivalent to 60% of individual body mass. ...
The objective of this study was to examine the effects of acute static muscle stretch on hamstring muscle fatigue and perceived exertion between young adult men and women. Twenty volunteers participated in two experimental sessions, in which we assessed maximal-effort isokinetic knee flexor force (90 degrees x s(-1)) and the number of sub-maximal (50% maximal) knee flexor repetitions to the point of failure. Immediately before the sub-maximal contractions on one randomly selected session, participants received ten 30-s passive knee flexor muscle stretches. Perceived exertion was sampled with a modified Borg category-ratio scale following each sub-maximal repetition. Each participant's perceived exertion response was estimated every 10% across the sub-maximal repetitions, via linear interpolation and power-function modelling. The men generated significantly greater force than the women during both experimental sessions, while muscle stretching had no significant effect on the number of sub-maximal repetitions. When estimated via power-function modelling, perceived exertion increased at a significantly greater rate following muscle stretch. Perceived exertion was significantly greater for the women following muscle stretch than the men. The findings suggest that the elevation in perceived exertion following knee flexor muscle stretching may be greater in women than men, despite no significant alterations in mechanical measures of muscle fatigue.
... exercise performance is mainly due to a reduction in muscle stiEness or increased compliance (Wilson et al., 1994). Most investigations have focused on measures of maximal muscle force generation, either through the measurement of isokinetic peak torque or a onerepetition maximum (1-RM); few studies have addressed the impact of acute muscle stretching on fatigue (Kokkonen et al., 2001). ...
... A relative 'muting' of the sensory response may result and, therefore, be manifest in the rating of perceived exertion to a given muscle contraction. T o date, the impact of acute muscle stretching on fatigue and the corresponding estimate of subjective effort has received little attention (Kokkonen et al., 2001). The aim of this study was to examine the effects of an acute stretching regime on hamstring muscle fatigue and perceived exertion during a dynamic, submaximal bout of resistance exercise. ...
... A general reduction in maximal muscle force after muscle stretching has been observed (Kokkonen et al., 1998(Kokkonen et al., , 2001Fowles et al., 2000;Behm et al., 2001). Kokkonen et al. (2001) examined muscle fatigue in 26 individuals who performed a single bout of resistance hamstring exercise at a load equivalent to 60% of individual body mass. ...
The aim of this study was to examine the effects of an acute stretching regime on hamstring muscle fatigue and rating of perceived exertion during a dynamic, sub-maximal bout of resistance exercise. Sixteen healthy males (age 25.7 +/- 4.3 years, height 1.81 +/- 0.06 m, body mass 87.5 +/- 15.1 kg; mean +/- s) and 16 healthy females (age 24.9 +/- 4.5 years, height 1.67 +/- 0.06 m, body mass 62.9 +/- 9.4 kg) volunteered to participate in two experimental sessions. After establishing their one-repetition maximum for the hamstring curl, the participants were assigned at random to one of two groups. Group 1 performed three bouts of 20 s hamstring stretches with the assistance of one of the investigators, while group 2 did not perform the stretches; instead, they sat resting for 3 min. Then, after stretching or resting, the participants performed as many hamstring curls as they could at 60% of their one-repetition maximum established earlier. All participants were assessed for their perceived exertion using a modified Borg category ratio (CR-10) scale. The participants returned within 1 week to complete the experiment. This time group 1 did not perform hamstring stretches, whereas group 2 did. As on the first occasion, all participants performed hamstring curls after stretching or resting. The participants in group 1 were able to perform more curls on the second day of testing than their counterparts in group 2. There were no significant differences between males and females or between the stretch and non-stretch conditions. There was a significantly higher first repetition rating of perceived exertion for the stretch condition (2.88 +/- 1.01) than for the non-stretch condition (2.50 +/- 0.95); there was no significant difference in the median ratings of perceived exertion between the stretch and non-stretch conditions. Significantly higher power function exponents were exhibited in the non-stretch (0.57 +/- 0.16) than in the stretch condition (0.51 +/- 0.12). In addition, females exhibited significantly higher power function exponents than males, irrespective of stretch condition and day (females: 0.59 +/- 0.12; males: 0.49 +/- 0.11). In conclusion, we found a small but statistically significant effect of an acute bout of stretching on ratings of perceived exertion during fatiguing hamstring muscle resistance exercise.
... In regard to the influence of acute SS on athletic performance, studies over the last 25 years have introduced evidence that acute SS may produce performance decrements (5,13,18,29,43,45). Studies have shown that acute SS reduced force production (18); sprint performance (36,43); depthjump performance; vertical jump height; long jump distance (13,45); strength endurance (29); and balance, reaction, and movement times (5). ...
... In regard to the influence of acute SS on athletic performance, studies over the last 25 years have introduced evidence that acute SS may produce performance decrements (5,13,18,29,43,45). Studies have shown that acute SS reduced force production (18); sprint performance (36,43); depthjump performance; vertical jump height; long jump distance (13,45); strength endurance (29); and balance, reaction, and movement times (5). ...
Static stretching (SS) has shown decreases in many areas including strength, anaerobic power, and sprinting time. Dynamic stretching (DS) has shown increases in anaerobic power and decreases in sprinting time. Research on the effects of stretching on agility performance is limited. The purpose of this study was to determine the effect of SS and DS on performance time of a sport agility test. Sixty male subjects consisting of collegiate (n = 18) and recreational (n = 42) basketball athletes volunteered for the study. Subjects were randomly assigned to 1 of 3 intervention groups: SS, DS, or no stretching (NS). All groups completed a 10-minute warm-up jog followed by a 3-minute rest. The SS and DS groups then completed an 8.5-minute stretching intervention. Next, all subjects completed 3 trials of the 505 agility test with 2-5 minutes of rest between trials. A 2-way repeated-measure analysis of variance (Stretch group, athlete category, group × athlete interaction) was used to determine statistical significance (p < 0.05). A Tukey post hoc test was performed to determine differences between groups. For all athletes, the DS group produced significantly faster times on the agility test (2.22 ± 0.12 seconds, mean ± SD) in comparison to both the SS group (2.33 ± 0.15 seconds, p = 0.013) and NS group (2.32 ± 0.12 seconds, p = 0.026). Differences between the SS and NS groups revealed no significance (p = 0.962). There was a significant difference in mean times for the type of athlete (p = 0.002); however, interaction between the type of athlete and stretching group was not significant (p = 0.520). These results indicate that in comparison to SS or NS, DS significantly improves performance on closed agility skills involving a 180° change of direction.
... Static stretching (SS) increases ROM [11][12][13] and may limit strength, maximum force, running velocity, balance or sprint performance, with an average reduction in performance of 3.7% 16 . Studies have shown that acute SS reduced force production 17 ; sprint performance 18,19 ; depth jump performance; vertical jump height; long jump distance 20,21 ; strength endurance 22 ; and balance, reaction, and movement times 23 . Consequently, Dynamic stretching (DS) has a minor effect on flexibility, but may well increase muscular strength with an average improvement in performance of 1.3% 24,25 . ...
... Static stretching (SS) increases ROM [11][12][13] and may limit strength, maximum force, running velocity, balance or sprint performance, with an average reduction in performance of 3.7% 16 . Studies have shown that acute SS reduced force production 17 ; sprint performance 18,19 ; depth jump performance; vertical jump height; long jump distance 20,21 ; strength endurance 22 ; and balance, reaction, and movement times 23 . Consequently, Dynamic stretching (DS) has a minor effect on flexibility, but may well increase muscular strength with an average improvement in performance of 1.3% 24,25 . ...
Introduction:
The aims of study were: 1) to verify the effectiveness of different stretching methods and training; 2) to compare the effects with only training on the flexibility of joints in basketball players.
Methods:
30 males basketball players (age: 17±1yrs; BMI: 23.4±3.1), divided into 2 groups (15 experimental group - EG - and 15 control group, CG), participated to study. EG performed 5 different stretching method: passive stretching, active stretching, postural protocol, PNF and dynamic stretching. To assess differences (p<0.05) between groups, an ANOVA was applied to anthropometrics characteristic (age; height; weight and BMI) and flexibility performances (leg raise in a supine position; forward trunk bending). ANOVA for repeated measurements was conducted to asses differences in each group with time (i.e., pre-post).
Results:
Results showed a variation linked to time (F=21.9; p<0.0001) and an effect of the treatment of the leg raise in a supine position test (F=25.1; p<0.0001). Also in flexion test of trunk, the average values could be linked to time of measurement (F=9.96; p<0.0001) and group (F=8.65; p<0.0001).
Conclusion:
The results suggest that a specific different stretching protocol should be used in different part of body to offer performance benefit and decreasing of the incidents of injuries.
Level of evidence:
IV.
... There are essentially two categories of stretching employed on a regular basis among athletes as part of a complete flexibility procedure: pre-activity stretching (Behm, Button, & Butt, 2001; Fry, McLellan, Weiss, & Rosato, 2003; Nelson, Kokkonen, & Arnall, 2005) and post-activity stretching (Hunter & Marshall, 1992; Kerrigan, Xenopoulus-Oddson, Sullivan, Lelas, & Riley, 2003). Static stretching, ballistic stretching, proprioceptive neuromuscular facilitation stretching (PNF), and dynamic stretching are the specific types of stretching predominantly used by athletes, coaches, and athletic trainers in pre-or post-activity. ...
The purpose of this study was to determine if NCAA Division I and III men’s basketball programs were in compliance with recommended pre- and post-activity stretching protocols. Questionnaires were sent to 500 NCAA Division I and Division III programs in the United States. Seventy-six coaches (75 males & 1 female) participated in the study. Chi-Square analysis (χ ² (3,n=69) = 42.29, p≤0.001) indicated a greater combined percentage of static/pnf/ballistic stretches (10.14%, n=7) and combination of stretches (57.97%, n=40) than expected as compared to dynamic stretches (31.89%, n=22). Participants were asked during what period (pre- or post-activity) stretching should be emphasized. The results were significantly different from expected (χ ² (4,n=76) = 129.28, p≤0.001), with a greater percentage of pre-activity stretches (26.31%, n=20) and both pre- and post-activity of stretches (60.52%, n=46) being reported as compared to post-activity stretches (13.15%, n=10). Some results seemed to be in conflict with current recommendations in the literature regarding pre-activity stretching practices.
... A decrease between 4 and 30 percent has been observed in maximal strength tests (e.g. Kokkonen et al., 1998; Avela et al., 1999; Nelson and Kokkonen, 2001; Marek et al., 2005), jumping (Church et al., 2001; Cornwell et al., 2001; McNeal and Sands, 2003: Young and Behm, 2003), sprinting (Fletcher and Jones, 2004; Nelson et al. 2005a), muscular endurance (Nelson et al., 2005b), and throwing (Noffal et al., 2004). ...
This narrative review examined the biomechanical effect of stretching exercises on skeletal
muscles. While there is a long history of clinical research on the effect of stretching on flexibility,
there have only been a few years of research on the acute and chronic effects of stretching on the
biomechanical parameters of muscle function. The acute effect of stretching appears to be a
significant increase in range of motion primarily due to increased stretch tolerance and significant
reductions in most all forms of muscular performance. Stretching also creates significant acute
reductions in passive tension (stress-relaxation) in the muscle, but does not appear to affect its
stiffness/elasticity. Stretch training significantly increases range of motion, but it also tends to
increase the passive tension and stiffness of the musculature. Future research of human muscle in
vivo during stretching and normal movement using ultrasound promises to help clarify the effects
of stretching on the active and passive components of muscle and the many biomechanical
variables of muscular performance.
... In this case, the main reason for this reduction may be a change in the muscle length tension curve that would shift the zone of optimal force generation and thereby achieve muscle fatigue more quickly, 41, 43, 44 resulting in a concomitant reduction in conduction velocity of the action potential. In general, the increase in both fatigue variables from EMG signals observed in this study may explain the findings of Franco (2008) and Nelson et al. (2005), who reported a decrease of performance in tests of muscular endurance. ...
AIM: The purpose of this study was to examine the acute effects of a static stretching protocol on neuromuscular fatigue of the flexor carpi radialis (FC) and flexor digitorum (FD).
METHODS: Twenty-six healthy and right-handed men with a mean (SD) age of 27.1 (2.9) years volunteered for this study. The fatigue test was performed before (Pre) and after three sets of 50 s stretching (Post) applied to the right hand, and twice (T1 and T2) without stretching to the left hand as a control condition. Isometric handgrip fatigue exercise was maintained for 30s within the range 50-60% of the maximal voluntary contraction. From the electromyography (EMG), root mean squares (RMS) values and mean frequency (MF) were obtained for each 2s consecutive windows of test and normalized by the MVC obtained in 6s tests. From time series, coefficients of linear regression were determined used to compare Pre with Post and T1 with T2 by paired samples t-tests.
RESULTS: Higher rate of increase in EMG on Post compared to Pre was found in both FC (P=0.015) and FD (P=0.006). A higher rate of decrease of MF for FC (P=0.004) and FD (P=0.005) was observed with Post compared to Pre. Conversely, the differences between T1 and T2 were not significant (P>0.05).
CONCLUSION: These findings indicate that static stretching performed immediately before submaximal isometric muscle actions may increase neuromuscular fatigue assessed by EMG, suggesting that could reduce muscle’s endurance capacity.
... Nadměrný strečink redukuje kapacitu silově vytrvalostních schopností (Kokkonen, J., Nelson, A. G., & Arnall, D. A., 2001). Sapega et al (1981) doporučuje zařazení strečinku bezprostředně po hlavní části tréninku, protože teplota tkání je v této době nejvyšší, což přispívá ke zvýšení bezpečnosti a produktivity strečinku. ...
This publication consists of two parts. The first part contains 8 chapters of the
latest features, diagnosis and the development of coordination skills, the second
part of the information in 4 chapters of the characteristics, diagnosis and the
development of movement abilities.
The first chapter of both parts contain definitions and classification of
coordination and movement abilities, characteristics of individual components,
including biological and methods agents. The diagnosis of the items listed in
tests of three famous motor batteries Unifittest, Eurofittest and Fitnessgram. For
the development of individual components are described in this chapter the
method development. Examples of physical exercises will allow readers to a practical application for their personal development. The first two chapters also
contain a substantive sub-chapter, entitled "Selected findings from the research
work, which lists the findings of the research work of individual authors, but
also knowledge of other Czech and foreign experts. At the end of the first
chapter in the coordination abilities are given the standard of test items and test
batteries Eurofittest IOWA - BRACE test and profile dough coordination
abilities at the end of the first chapter in part flexibility are the standard set of
test items from Unifittest, Eurofittest and Fitnessgram. The reader can compare
their personal performance with a normative set for the general population.
The first section of chapters 2 to 8 described a specific physical exercises to
develop coordination skills in aerobics, athletics, basketball, gymnastics, netball,
in downhill skiing and sport climbing. In the second part is then in Chapters 2 to
4 described a specific physical exercises to develop flexibility in athletics,
basketball and gymnastics. New in these chapters the authors proposed various
physical exercises including how to implement, the number of repetitions,
number of batches, duration of rest in a series of intervals, duration of rest
intervals between sets for both the general and the sports population.
... However, the practice of stretching as a part of warm-up has been questioned (19), and evidence indicates that stretching a muscle will reduce its stiffness, resulting in increased compliance (27), which could alter the force-generating characteristics of the muscle. Indeed, stretching as part of a warm-up has been shown to negatively affect subsequent strength or power performance (3,7,13,15,16) and some evidence also suggests that strength endurance (14) can be compromised. ...
The effect of 3 warm-up routines on standing broad jump (SBJ) performance was investigated. Thirty-two men and women participated as subjects. Following the determination of 1-repetition maximum (1RM) squat, subjects completed warm-up routines and broad jumps on 4 occasions in a randomized order. Subjects performed SBJ immediately (POST) and 15 min following (POST15) the given warm-up routine. The routines were high force, consisting of high % 1RM, low repetition squats; high power, consisting of low % 1RM, low repetition speed squats; stretching, consisting of static stretches; and no activity, a control condition. Repeated measures analysis of covariance (ANCOVA) revealed no differences among broad jump performance following any of the warm-up routines (p = 0.157). A strong correlation (R = 0.805) was found between 1RM squat and SBJ. These data indicate that warm-up of any type has little effect on jump performance and that maximum strength is strongly related to jumping ability.
Stretching is used to increase joint range of motion, but the acute effects can decrease muscle strength. However, this may depend on the population or mode of stretching. The purpose of this study was to compare the acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance trained women. Fifteen resistance trained women (age 23.8 ± 1.80 yrs, mass 67.47 ± 7.77 kg, ht 168.30 ± 5.53 cm) and 12 ballet dancers (age 22.8 ± 3.04 yrs, mass 58.67 ± 5.65 kg, ht 168.00 ± 7.69 cm) performed 5 days of testing. The first day was control (no stretching) while the other four days were static or ballistic stretching in a counterbalanced order. Range of motion (ROM), strength and fatigue tests were also performed. Both groups demonstrated a significant decrease in hamstrings strength after static (102.71 ± 2.67 Nm) and ballistic stretching (99.49 ± 2.61 Nm) compared to control (113.059 ± 3.25 Nm), with no changes in quadriceps strength. For fatigue, only ballet dancers demonstrated a decrease from control (71.79 ± 4.88%) to ballistic (65.65 ± 8.19%), but no difference with static (65.01 ± 12.29%). These findings suggest that stretching decreases hamstrings strength similarly in ballet dancers and resistance trained women, with no differences between modes of stretching. However, ballistic stretching only decreased muscular fatigue in ballet dancers, but not in resistance trained women. Therefore, no stretching should be performed prior to strength performance. However, ballistic stretching may decrease acute muscular fatigue in ballet dancers.
The aim of this study is to investigate the effect of three different warm-up methods on flexibility, jumping and balance. 28 male students (age 22.002.00 years) from Faculty of Yasar Dogu Sport Sciences were enrolled in the study. Three different warm-up methods including static, dynamic and jogging were applied to the subjects at 24 hours intervals. Study group was subjected to flexibility, jumping and static and dynamic balance tests 4 minutes after each warm-up application. Data analysis showed that flexibility values measured after static warm-up were higher than those obtained after dynamic warm-up and jogging (p<0.01). Jumping values after static warm-up were found to be significantly higher than those obtained after jogging (p<0.05). In dynamic balance measurement, " average balance error after jogging " was found worse than dynamic warm-up (p<0.05). Static balance results showed that values after static and dynamic warm-up were better than those obtained after jogging (p<0.05). In conclusion flexibility values after static warm-up were found to be higher than those obtained after dynamic and jogging warm-up. Static warm-up was found to cause greater increase in jumping performance in comparison with jogging. Balance values after jogging were worse than those obtained after static and dynamic warm-up.
ÖZET
Bu çalışmanın amacı üç farklı ısınma yönteminin sıçrama, esneklik ve dengeye etkisini araştırmaktır. Bu çalışmaya Ondokuz Mayıs Üniversitesi Yaşar Doğu Spor Bilimleri Fakültesinde okuyan (yaş 22,002,00 yıl), 28 erkek öğrenci denek olarak katılmıştır. Deneklere 24 saat arayla üç farklı ısınma yöntemi olan statik ısınma, dinamik ısınma ve sadece ısınma koşusu uygulanmıştır. Araştırma grubu her ısınma uygulamasından 4dk sonra sıçrama, esneklik, statik ve dinamik denge testine tabi tutulmuştur. Verilerin analizi sonucunda, statik ısınma sonrası ölçülen esneklik değerlerinin, dinamik ısınma ve jogging ısınmaya göre daha yüksek olduğu tespit edilmiştir (p<0,01). Sıçrama değerleri incelendiğinde, statik ısınma sonrası değerlerin jogging ısınma sonrası değerlerden istatistiksel olarak daha yüksek olduğu tespit edilmiştir (p<0,05). Dinamik denge ölçümünde jogging ısınma sonrası ''ortalama denge hatası'' dinamik ısınmadan daha kötü bulunmuştur. (p<0.05). Statik denge sonuçlarında ise statik ve dinamik ısınma sonrası değerlerin jogging ısınma sonrası değerlere göre daha iyi olduğu görülmüştür (p<0,05). Sonuç olarak statik ısınma sonrasında esneklik değerlerinin dinamik ve jogging ısınmaya göre daha yüksek olduğu görülmüştür. Sıçrama performansını ise statik ısınmanın jogging ısınmaya göre daha fazla arttırdığı tespit edilmiştir. Jogging ısınma sonrası denge değerlerinin statik ve dinamik ısınmaya göre daha kötü çıktığı görülmüştür.
While some elements of the strength and conditioning portfolio have yet to achieve acceptance in the preparation of athletes in all sports, one area of practice which is almost universally accepted is the principle of the warm-up. Today, few athletes at any level train or compete without some attempt at a " warm-up ". However, while the general principles surrounding the need to warm-up remain valid, a large body of evidence is building up which both questions some of our current practices, and provides possible opportunities to improve practice. This article looks at current practice, and presents a model around which to construct effective warm-ups.
Introduction: Stretching exercises have been related to a performance deficit on strength-dependent activities. However, little is known about its effect on multiple sets of strength training. Objective: To determine the effect of an extensive stretching protocol on the performance of multiple sets and soreness in strength training. Methdos: The sample was composed by 12 trained-men, experienced in strength training. The protocol consisted of three sessions.The first session was used as a familiarization and load determination to 10 maximum repetitions (T10RM). The second and third conditions were randomized between subjects, and the bench press exercise (BP) was evaluated without previous stretching protocol (SEMA), and with previous stretching protocol (COMA). The stretching protocol consisted of six sets of 45 sec of stretch with 15 sec of resting intervals to the pectoralis major muscle. The stretching
intensity was kept between 70 and 90% of the subjective point of discomfort. The local soreness was evaluated before and after exercise by a brief stretching and palpation. The Analysis of Variance ANOVA (2x6) was used to compare the maximum number of repetitions. One-way ANOVA was used to compare the load of the first set of each condition (T10RM/SEMA/COMA). The Student t-test was used to compare the total load and soreness. Results: A decrease on maximum number of repetitions along the sets was observed in both conditions, without differences between them, for the load of the first set, total load and soreness. Conclusion: The number of repetitions in multiple sets was reduced in the same magnitude in the conditions with and without previous stretching; besides, it does not alter the total load or soreness.
The objective of this study was to evaluate the influence of the active static stretching on the sports performance in power and speed activities as “counter movement jump” (CMJ) and “20 meters sprint”. Twenty two males (24.0 ±6.2 years old), rugby7 and handball players, were randomly separated into two groups (A and B) and submitted to two protocols in two different days separated by 48 hours (1- general warm-up, active static stretching exercises followed by CMJ, and sprint test; 2- warm-up and only CMJ, and sprint test). The results did not show any acute effects of the static stretching on the CMJ and sprint performance (p>0.05). There were no significant differences in the average of speed in the sprint between the conditions “with active static stretching” and “without stretching” (6.12 ±0.32 m/s and 6.08 ±0.33 m/s, respectively; p=.828) and in the average of CMJ (35,71 ±6,20cm; 36,12 ±6,08cm, respectively, p=.788). It is concluded that the active static stretching does not influence the sports performance in power and speed activities in experienced high-level athletes.
Introdução: evidências prévias indicam que o treinamento de flexibilidade promove efeito deletério sobre a força muscular, todavia, são escassos achados relacionados aos efeitos potenciais de exercícios de alongamento muscular nos antagonistas sobre o desempenho dos agonistas. Objetivo: verificar o efeito do método de facilitação neuromuscular proprioceptiva-3S (FNP-3S) nos músculos antagonistas sobre a determinação da carga de 10 repetições máximas (RM) dos músculos agonistas no exercício de remada aberta sentada com pegada pronada (RA). Dezoito sujeitos (25 ± 5 anos de idade) do sexo masculino, praticantes de treinamento de força há no mínimo 1 ano participaram do estudo. Materiais e Métodos: dois protocolos foram aplicados para determinação das cargas de 10RM: 1) protocolo tradicional (TRAD) – teste e reteste de 10RM na RA; 2) Protocolo FNP-3S nos antagonistas (FNPA) - foi aplicada uma serie de FNP-3S nos antagonistas (peitorais) antes de cada tentativa de determinação de carga no teste de 10RM. Ao final de cada protocolo registrou-se a sobrecarga e tempo de tensão (TT). Resultados: houve aumento significativo na sobrecarga obtida durante o teste de 10RM no protocolo FNPA (54,3 ± 7,9 kg) quando comparado ao protocolo TRAD (47,94 ± 8,77 kg) de acordo com o teste T pareado (p < 0,05). Não houve diferença significativa no TT entre os protocolos. Conclusão: o método FNP-3S aplicado nos músculos antagonistas promoveu aumento significativo na sobrecarga de 10RM. Sugere-se a utilização deste método em novas pesquisas, possibilitando o surgimento de evidências que venham a contribuir para obtenção de melhores resultados em programas de treinamento e reabilitação.
The purpose of this study was to compare the effect of a dynamic warm up (DWU) with a static-stretching warm up (SWU) on selected measures of power and agility. Thirty cadets at the United States Military Academy completed the study (14 women and 16 men, ages 18-24 years). On 3 consecutive days, subjects performed 1 of the 2 warm up routines (DWU or SWU) or performed no warm up (NWU). The 3 warm up protocols lasted 10 minutes each and were counterbalanced to avoid carryover effects. After 1-2 minutes of recovery, subjects performed 3 tests of power or agility. The order of the performance tests (T-shuttle run, underhand medicine ball throw for distance, and 5-step jump) also was counterbalanced. Repeated measures analysis of variance revealed better performance scores after the DWU for all 3 performance tests (p < 0.01), relative to the SWU and NWU. There were no significant differences between the SWU and NWU for the medicine ball throw and the T-shuttle run, but the SWU was associated with better scores on the 5-step jump (p < 0.01). Because the results of this study indicate a relative performance enhancement with the DWU, the utility of warm up routines that use static stretching as a stand-alone activity should be reassessed.
The purpose of this study was to examine the acute effects of different stretching exercises on the performance of the traditional Wingate test (WT). Fifteen male participants performed five WT; one for familiarization (FT), and the remaining four after no stretching (NS), static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF). Stretches were targeted for the hamstrings, quadriceps, and calf muscles. Peak power (PP), mean power (MP), and the time to reach PP (TP) were calculated. The MP was significantly lower when comparing the DS (7.7 ± 0.9 W/kg) to the PNF (7.3 ± 0.9 W/kg) condition (p < 0.05). For PP, significant differences were observed between more comparisons, with PNF stretching providing the lowest result. A consistent increase of TP was observed after all stretching exercises when compared to NS. The results suggest the type of stretching, or no stretching, should be considered by those who seek higher performance and practice sports that use maximal anaerobic power.
The purpose of this study was to examine the acute effects of static versus dynamic stretching on peak torque (PT) and electromyographic (EMG), and mechanomyographic (MMG) amplitude of the biceps femoris muscle (BF) during isometric maximal voluntary contractions of the leg flexors at four different knee joint angles. Fourteen men ((mean 6 SD) age, 25 6 4 years) performed two isometric leg flexion maximal voluntary contractions at knee joint angles of 41°, 61°, 81°, and 101° below full leg extension. EMG (mV) and MMG (mÁs 22) signals were recorded from the BF muscle while PT values (Nm) were sampled from an isokinetic dynamometer. The right hamstrings were stretched with either static (stretching time, 9.2 6 0.4 minutes) or dynamic (9.1 6 0.3 minutes) stretching exercises. Four repetitions of three static stretching exercises were held for 30 seconds each, whereas four sets of three dynamic stretching exercises were performed (12–15 repetitions) with each set lasting 30 seconds. PT decreased after the static stretching at 81° (p = 0.019) and 101° (p = 0.001) but not at other angles. PT did not change (p. 0.05) after the dynamic stretching. EMG amplitude remained unchanged after the static stretching (p. 0.05) but increased after the dynamic stretching at 101° (p , 0.001) and 81° (p , 0.001). MMG amplitude increased in response to the static stretching at 101° (p = 0.003), whereas the dynamic stretching increased MMG amplitude at all joint angles (p # 0.05). These results suggested that the decreases in strength after the static stretching may have been the result of mechanical rather than neural mechanisms for the BF muscle. Overall, an acute bout of dynamic stretching may be less detrimental to muscle strength than static stretching for the hamstrings.
Stretching is a technique that maintains or improves the range of movement in a joint or group of joints. It serves the muscle and sensory tissue due to an extended traction action. It is a technique that can be applied in the clinic or from a training perspective in health and injured athletes. The technique is indicated for the care, prevention and maintenance of the abilities of each individual or for their development. Not all stretches are done in the same way or seek the same objective.On reviewing the literature, it is seen that there is no consensus on the classification or way in which to apply stretches. There is doubt on the beneficial effects of stretching during warming up. A study needs to be done to provide scientific support. The aim of the review is to recognise stretching, develop the classification, show five stretching methods and propose their application: in warming up, cooling down and training, in the healthy athlete and the athlete with muscle injuries.
El estiramiento es una técnica que mantiene o mejora la amplitud de movimiento en una articulación o un conjunto de articulaciones. Solicita el tejido muscular y sensitivo gra-cias a una acción de tracción alargamiento. Supone una técnica que se puede aplicar en clínica o desde la perspectiva del entrenamiento en deportistas sanos o lesionados. Su-pone una técnica indicada para el cuidado, la prevención y el mantenimiento de las ca-pacidades de cada individuo o para su desarrollo. No todos los estiramientos se realizan de la misma manera o persiguen el mismo objetivo.Al revisar la literatura, se observa que no hay consenso en la clasificacióno en la manera de aplicar los estiramientos: se ponen en duda los efectos beneficiososdel estiramiento durante el calentamiento, y es necesario el estudio para dar respaldo científicoEl objetivo de la revisión es ubicar el estiramiento, desarrollar la clasificación,exponer cinco modalidades de estiramientos y hacer una propuesta de aplicación: en el calenta-miento, vuelta a la calma y entrenamiento, en el deportista sano y en el deportista que padece lesiones musculares.
The aim of this study was to examine the acute effects of static stretching (SS), dynamic stretching (DS), and a combined (static and dynamic) stretch protocol on vertical jump (VJ) height, balance, and range of motion (ROM) in dancers. A no-stretch (NS) intervention acted as the control condition. It was hypothesized that the DS and combination stretch protocols would have more positive effects on performance indicators than SS and NS, and SS would have negative effects as compared to the NS condition. Ten trained female dancers (27 ± 5 years of age) were tested on four occasions. Each session began with initial measurements of hamstring ROM on the dominant leg. The participants subsequently carried out a cardiovascular (CV) warm-up, which was followed by one of the four randomly selected stretch conditions. Immediately after the stretch intervention the participants were tested on VJ performance, hamstring ROM, and balance. The data showed that DS (p < 0.05) and the combination stretch (p < .05) produced significantly greater VJ height scores as compared to SS, and the combination stretch demonstrated significantly enhanced balance performance as compared to SS (p < 0.05). With regard to ROM, a one-way ANOVA indicated that SS and the combination stretch displayed significantly greater changes in ROM than DS (p < 0.05). From comparison of the stretch protocols used in the current study, it can be concluded that SS does not appear to be detrimental to a dancer's performance, and DS has some benefits but not in all three key area's tested, namely lower body power (VJ height), balance, and range of motion. However, combination stretching showed significantly enhanced balance and vertical jump height scores and significantly improved pre-stretch and post-stretch ROM values. It is therefore suggested that a combined warm-up protocol consisting of SS and DS should be promoted as an effective warm-up for dancers.
The purpose of this study is to determine the pre and post-activity stretching practices of Division I, II, and III track and field throws programs. A 33-item survey instrument was developed to collect data regarding the warm-up and flexibility practices at the NCAA Division I (n = 320), Division II (n = 175), and Division III (n = 275) universities. A total of 135 surveys were completed for a 17.5% return rate, and although the response rate was generally low it did mirror the distribution percentages of the three divisions. Significant differences were found for the level of USATF certification and the use of static stretching between throws (χ = 6.333, p = .048). Significance was also found for the USATF certification level and athletic trainer (AT) assistance in performing static stretching (χ = 13.598, p = .01). Significant differences were also found for the NCAA division levels and the use of soft tissue work (χ = 5.913, p = .026). Although research supports dynamic warm-up/stretching over other forms of pre-activity protocols (23, 36), it appears that some track and field throws coaches are reluctant to completely discontinue pre-activity static stretching. The results of this study suggest it is necessary for track and field throws coaches to re-evaluate their own practices, perhaps better aligning them with current research findings.
Improving the process of how physical performance is enhanced is one of the main topics evaluated by physiologists. This process often involves athletes as well as non-athletic populations. The purpose of this study was to assess the chronic response to ten weeks of static stretching exercises carried out before and during a strength training program for eight exercises on eight repetition maximum (8RM) test performance, and basal serum IGF-1 levels. Thirty recreationally trained volunteers were randomly assigned into one of three training groups: 1) SBST (performed a warm-up with a static stretching protocol before each strength training session); 2) SDST (before each training set, a static stretching exercise was performed); and 3) OST (entire session was performed without any type of stretching exercise). Strength and IGF-1 levels were collected at the beginning (pre-test) and end (post-test) of the entire experimental procedure. All exercises showed a significant increase in muscle strength for the OST group. However, the results revealed a significant increase in muscle strength for only a few exercises in the SBST (LP, LE) and SDST (LP) experimental conditions. Significant statistical differences were found between SBST and SDST for all exercises in the OST experimental condition. Furthermore, IGF-1 expression showed no significant differences in intragroup analysis. However, the OST group showed higher values (p<0.05) in post-test when compared to other groups (increased significantly only in the OST experimental condition). It has been concluded that, while all groups showed an increase in muscular strength, but the strength training performed without any type of stretching exercise, regardless of if the stretching is performed prior or during the lifting session, can more effectively increase muscle strength as well as basal serum IGF-1 levels. It was concluded that strength training, with or without the use of stretching exercises, increased muscular strength in the studied groups, and can induce an increase in IGF-1 levels.
Stretching is a technique that maintains or improves the range of movement in a joint or group of joints. It serves the muscle and sensory tissue due to an extended traction action. It is a technique that can be applied in the clinic or from a training perspective in health and injured athletes. The technique is indicated for the care, prevention and maintenance of the abilities of each individual or for their development. Not all stretches are done in the same way or seek the same objective. On reviewing the literature, it is seen that there is no consensus on the classification or way in which to apply stretches. There is doubt on the beneficial effects of stretching during warming up. A study needs to be done to provide scientific support. The aim of the review is to recognise stretching, develop the classification, show five stretching methods and propose their application: in warming up, cooling down and training, in the healthy athlete and the athlete with muscle injuries.
The present study aimed to investigate the immediate effects of 15 min static or sub-maximal contract-relax stretching modalities on the neuromuscular properties of plantar flexor muscles. Ten male volunteers were tested before and immediately after 15 min static or contract-relax stretching programs of plantar flexor muscles (20 stretches). Static stretching consisted in 30s stretches to the point of discomfort. For the contract-relax stretching modality, subjects performed 6s sub-maximal isometric plantar flexion before 24s static stretches. Measurements included maximal voluntary isometric torque (MVT) and the corresponding electromyographic activity of soleus (SOL) and medial gastrocnemius (MG) muscles (RMS values), as well as maximal peak torque (Pt) elicited at rest by single supramaximal electrical stimulation of the tibial nerve. After 15 min stretching, significant MVT and SOL RMS decreases were obtained (-6.9+/-11.6% and -6.5+/-15.4%, respectively). No difference was obtained between stretching modalities. Pt remained unchanged after stretching. MG RMS changes were significantly different between stretching modalities (-9.4+/-18.3% and +3.5+/-11.6% after static and contract-relax stretching modalities, respectively). These findings indicated that performing 15 min static or contract-relax stretching had detrimental effects on the torque production capacity of plantar flexor muscles and should be precluded before competition. Mechanisms explaining this alteration seemed to be stretch modality dependent.
Since strength and muscular strength endurance are linked, it is possible that the inhibitory influence that prior stretching has on strength can also extend to the reduction of muscle strength endurance. To date, however, studies measuring muscle strength endurance poststretching have been criticized because of problems with their reliability. The purpose of this study was twofold: both the muscle strength endurance performance after acute static stretching exercises and the repeatability of those differences were measured. Two separate experiments were conducted. In experiment 1, the knee-flexion muscle strength endurance exercise was measured by exercise performed at 60 and 40% of body weight following either a no-stretching or stretching regimen. In experiment 2, using a test-retest protocol, a knee-flexion muscle strength endurance exercise was performed at 50% body weight on 4 different days, with 2 tests following a no-stretching regimen (RNS) and 2 tests following a stretching regimen (RST). For experiment 1, when exercise was performed at 60% of body weight, stretching significantly (p < 0.05) reduced muscle strength endurance by 24%, and at 40% of body weight, it was reduced by 9%. For experiment 2, reliability was high (RNS, intraclass correlation = 0.94; RST, intraclass correlation = 0.97). Stretching also significantly (p < 0.05) reduced muscle strength endurance by 28%. Therefore, it is recommended that heavy static stretching exercises of a muscle group be avoided prior to any performances requiring maximal muscle strength endurance.
This study examined the efficacy of short-term alpha-ketoisocaproic acid (KIC) monotherapy supplementation immediately prior to moderate- and high-intensity single bout exercise performance.
Thirteen resistance trained men (22.8 +/- 2.5 years; 81.6 +/- 12.6 kg) participated in a prospective, randomized, double blind, placebo controlled crossover experiment. Each subject completed one familiarization and four experimental trials with either 1.5 g or 9.0 g of either KIC or isocaloric placebo control (CONT), following an overnight fast. During the experimental trials, subjects consumed the supplement regimen and then completed leg and chest press repetitions to failure and 30 s of repeated maximal vertical jumping (VJ) on a force plate.
In this treatment regimen, no significant differences (p > 0.05) were observed between dosages or conditions for leg press (low CONT = 19.8 +/- 0.4 SEM, low KIC = 21.0 +/- 0.5, high CONT = 20.1 +/- 0.3, high KIC = 22.4 +/- 0.6) or chest press (low CONT = 18.1 +/- 0.2, low KIC = 18.5 +/- 0.3, high CONT = 17.8 +/- 0.3, high KIC = 18.0 +/- 0.3) repetitions to failure. Additionally, no significant differences were observed for peak or mean VJ performance (low CONT = 34.6 +/- 2.2 cm and 28.6 +/- 1.8 cm; low KIC = 35.6 +/- 2.0 cm and 29.4 +/- 1.6 cm; high CONT = 35.7 +/- 2.1 cm and 29.4 +/- 1.7 cm; high KIC = 34.8 +/- 2.3 cm and 28.3 +/- 1.7 cm), respectively.
Based on our results, we conclude that acute KIC ingestion by itself with no other ergogenic supplement, immediately prior to exercise, did not alter moderate- nor high-intensity single-bout exercise performance in young resistance-trained males. This study addressed single-dose single-bout performance events; the efficacy of KIC monotherapy supplementation on repeated high-intensity exercise bouts and long-term exercise training remains unknown.
Previous research has shown that passive muscle stretching can diminish the peak force output of subsequent maximal isometric and concentric contractions. The purpose of the present study was twofold: 1. to establish if the deleterious effect of stretching on performance also exists for a skill that relies on the rate of force production for success rather than peak force generation and 2. to determine if a similar effect exists for a movement that employs a stretch-shortening action. Ten participants performed two types of maximal vertical jump with and without prior stretching of the hip and knee extensors. Both static jumps (SJ) and countermovement jumps (CMJ) were executed from a force platform. Jump height was calculated from the velocity at takeoff determined from the force/time data. Stretching induced a significant (p<0.05) decrease in jump height for both the SJ (4.4 ± 1.3%) and CMJ (4.3 ± 1.3%). Thus, it appears that pre-performance stretching exercises might negatively impact skills that demand a high power output in addition to those that rely simply on maximizing peak force. Furthermore, it is possible that this detrimental effect is comparable for skills that take advantage of the stretch-shortening phenomenon and those that do not.
This study examined the effects of 4 different resistance training protocols on upper-body strength and local muscle endurance development in children. Untrained boys and girls (mean +/- SD age, 8.1 +/- 1.6 years) trained twice per week for 8 weeks using child-sized weight machines and medicine balls weighing 1-2.5 kg. In addition to general conditioning exercises, subjects in each exercise group performed 1 set of the following exercise protocols for upperbody conditioning: 6-8 repetitions with a heavy load on the chest press exercise (HL, n = 15); 13-15 repetitions with a moderate load on the chest press exercise (ML, n = 16); 6-8 repetitions with a heavy load on the chest press exercise immediately followed by 6-8 medicine ball chest passes (CX, n = 12); or 13-15 medicine ball chest passes (MB, n = 11). Twelve children served as nontraining controls (CT). After training, only the ML and CX groups demonstrated significant (p < 0.05) improvements in 1RM chest press strength (16.8% and 16.3%, respectively) as compared with the CT group. Local muscle endurance, as determined by the number of repetitions performed posttraining on the chest press exercise with the pretraining 1RM load, significantly increased in the ML group (5.9 +/- 3.2 repetitions) and CX group (5.2 +/- 3.6 repetitions) as compared with the CT group. In terms of enhancing the upper-body strength and local muscle endurance of untrained children, these findings favor the prescription of higher-repetition training protocols during the nitial adaptation period.
(C) 2001 National Strength and Conditioning Association
ACSM Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Adults. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 975-991, 1998. The combination of frequency, intensity, and duration of chronic exercise has been found to be effective for producing a training effect. The interaction of these factors provide the overload stimulus. In general, the lower the stimulus the lower the training effect, and the greater the stimulus the greater the effect. As a result of specificity of training and the need for maintaining muscular strength and endurance, and flexibility of the major muscle groups, a well-rounded training program including aerobic and resistance training, and flexibility exercises is recommended. Although age in itself is not a limiting factor to exercise training, a more gradual approach in applying the prescription at older ages seems prudent. It has also been shown that aerobic endurance training of fewer than 2 d·wk-1, at less than 40-50% of V˙O2R, and for less than 10 min-1 is generally not a sufficient stimulus for developing and maintaining fitness in healthy adults. Even so, many health benefits from physical activity can be achieved at lower intensities of exercise if frequency and duration of training are increased appropriately. In this regard, physical activity can be accumulated through the day in shorter bouts of 10-min durations.
In the interpretation of this position stand, it must be recognized that the recommendations should be used in the context of participant's needs, goals, and initial abilities. In this regard, a sliding scale as to the amount of time allotted and intensity of effort should be carefully gauged for the cardiorespiratory, muscular strength and endurance, and flexibility components of the program. An appropriate warm-up and cool-down period, which would include flexibility exercises, is also recommended. The important factor is to design a program for the individual to provide the proper amount of physical activity to attain maximal benefit at the lowest risk. Emphasis should be placed on factors that result in permanent lifestyle change and encourage a lifetime of physical activity.
Previous work has demonstrated that muscular injury in rat soleus muscles resulting from eccentric contractions (downhill walking) is accompanied by elevations in mitochondrial [Ca2+] (MCC). Muscles are stretched during eccentric contractions, and there is evidence in the literature that stretch of the cell membrane induces Ca2+ influx in various tissues, including skeletal muscle. The purpose of this study was to determine if passive stretch of rat soleus muscles will induce increases in total muscle [Ca2+] (TCC) and MCC. Soleus muscles from female rats (51-122 g) were isolated and incubated in vitro for 2 h at resting length (Lo) or at the maximal in situ length (S). TCC (+62%) and MCC (+56%) were elevated in the S muscles. Also, there was a 63% reduction in maximal twitch tension in the S muscles. ATP concentration, phosphocreatine concentration, and lactate release between Lo and S muscles were the same, indicating that impaired metabolism was not responsible for the observed differences in [Ca2+] and force production between Lo and S muscles. Increases in TCC in the S condition indicate that stretch results in Ca2+ influx from the extracellular space, which is supported by the observation that when S muscles were incubated in Ca(2+)-free buffer, TCC and MCC did not increase. High concentrations of verapamil (0.25-0.75 mM) blocked the elevations in TCC and MCC in the S muscles, but the magnitude of the drug concentration required makes it questionable whether the effect resulted from specific blockade of slow voltage-sensitive Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)
As muscles are stretched, blood flow and oxygen delivery are compromised, and consequently muscle function is impaired. We tested the hypothesis that the structural microvascular sequellae associated with muscle extension in vivo would impair capillary red blood cell hemodynamics. We developed an intravital spinotrapezius preparation that facilitated direct on-line measurement and alteration of sarcomere length simultaneously with determination of capillary geometry and red blood cell flow dynamics. The range of spinotrapezius sarcomere lengths achievable in vivo was 2.17 ± 0.05 to 3.13 ± 0.11 μm. Capillary tortuosity decreased systematically with increases of sarcomere length up to 2.6 μm, at which point most capillaries appeared to be highly oriented along the fiber longitudinal axis. Further increases in sarcomere length above this value reduced mean capillary diameter from 5.61 ± 0.03 μm at 2.4-2.6 μm sarcomere length to 4.12 ± 0.05 μm at 3.2-3.4 μm sarcomere length. Over the range of physiological sarcomere lengths, bulk blood flow (radioactive microspheres) decreased ~40% from 24.3 ± 7.5 to 14.5 ± 4.6 ml·100 g-1·min-1 . The proportion of continuously perfused capillaries, i.e., those with continuous flow throughout the 60-s observation period, decreased from 95.9 ± 0.6% at the shortest sarcomere lengths to 56.5 ± 0.7% at the longest sarcomere lengths and was correlated significantly with the reduced capillary diameter (r = 0.711, P < 0.01; n = 18). We conclude that alterations in capillary geometry and luminal diameter consequent to increased muscle sarcomere length are associated with a reduction in mean capillary red blood cell velocity and a greater proportion of capillaries in which red blood cell flow is stopped or intermittent. Thus not only does muscle stretching reduce bulk blood (and oxygen) delivery, it also alters capillary red blood cell flow dynamics, which may further impair blood-tissue oxygen exchange.
Flexibility measures can be static [end of ROM (range of motion)], dynamic-passive (stiffness/compliance) or dynamic-active (muscle contracted, stiffness/compliance). Dynamic measures of flexibility are less dependent on patient discomfort and are more objective. Acute and chronic changes in flexibility are likely to occur with stretching exercises, but it is difficult to distinguish between changes in stretch tolerance as opposed to changes in muscle stiffness. How flexibility is measured impacts these findings. There is no scientifically based prescription for flexibility training and no conclusive statements can be made about the relationship of flexibility to athletic injury.
The literature reports opposing findings from different samples, frequently does not distinguish between strain, sprain and overuse injury, and rarely uses the proper denominator of exposure.There is basic scientific evidence to suggest that active warm-up may be protective against muscle strain injury but clinical research is equivocal on this point. Typically, specific flexibility patterns are associated with specific sports and even positions within sports. The relationship of flexibility to athletic performance is likely to be sport-dependent. Decreased flexibility has been associated with increased in-line running and walking economy. Increased stiffness may be associated with increased isometric and concentric force generation, and muscle energy storage may be best manifested by closely matching muscle stiffness to the frequency of movement in stretch-shorten type contractions.
The purpose of this study was to assess strength performance after an acute bout of maximally tolerable passive stretch (PS(max)) in human subjects. Ten young adults (6 men and 4 women) underwent 30 min of cyclical PS(max) (13 stretches of 135 s each over 33 min) and a similar control period (Con) of no stretch of the ankle plantarflexors. Measures of isometric strength (maximal voluntary contraction), with twitch interpolation and electromyography, and twitch characteristics were assessed before (Pre), immediately after (Post), and at 5, 15, 30, 45, and 60 min after PS(max) or Con. Compared with Pre, maximal voluntary contraction was decreased at Post (28%) and at 5 (21%), 15 (13%), 30 (12%), 45 (10%), and 60 (9%) min after PS(max) (P < 0.05). Motor unit activation and electromyogram were significantly depressed after PS(max) but had recovered by 15 min. An additional testing trial confirmed that the torque-joint angle relation may have been temporarily altered, but at Post only. These data indicate that prolonged stretching of a single muscle decreases voluntary strength for up to 1 h after the stretch as a result of impaired activation and contractile force in the early phase of deficit and by impaired contractile force throughout the entire period of deficit.
The purpose of this study was to investigate the factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N=12) or a similar period of no stretch (control, N=6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity.
Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for "central" fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal changes in cortical excitability and inhibitability based on electromyographic (EMG) recordings, and a decline in supraspinal "drive" based on force recordings. Some of the changes in motor cortical behavior can be dissociated from the development of this "supraspinal" fatigue. Central changes also occur at a spinal level due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. Some intrinsic adaptive properties of the motoneurons help to minimize fatigue. A number of other central changes occur during fatigue and affect, for example, proprioception, tremor, and postural control. Human muscle fatigue does not simply reside in the muscle.
The interaction between running, stretching and practice jumps during warm-up for jumping tests has not been investigated. The purpose of the present study was to compare the effects of running, static stretching of the leg extensors and practice jumps on explosive force production and jumping performance.
Sixteen volunteers (13 male and 3 female) participated in five different warm-ups in a randomised order prior to the performance of two jumping tests. The warm-ups were control, 4 min run, static stretch, run + stretch, and run + stretch + practice jumps. After a 2 min rest, a concentric jump and a drop jump were performed, which yielded 6 variables expressing fast force production and jumping performance of the leg extensor muscles (concentric jump height, peak force, rate of force developed, drop jump height, contact time and height/time).
Generally the stretching warm-up produced the lowest values and the run or run + stretch + jumps warm-ups produced the highest values of explosive force production. There were no significant differences (p<0.05) between the control and run + stretch warm-ups, whereas the run yielded significantly better scores than the run + stretch warm-up for drop jump height (3.2%), concentric jump height (3.4%) and peak concentric force (2.7%) and rate of force developed (15.4%).
The results indicated that submaximum running and practice jumps had a positive effect whereas static stretching had a negative influence on explosive force and jumping performance. It was suggested that an alternative for static stretching should be considered in warm-ups prior to power activities.
The aim of this study was to examine the effects of an acute stretching regime on hamstring muscle fatigue and rating of perceived exertion during a dynamic, sub-maximal bout of resistance exercise. Sixteen healthy males (age 25.7 +/- 4.3 years, height 1.81 +/- 0.06 m, body mass 87.5 +/- 15.1 kg; mean +/- s) and 16 healthy females (age 24.9 +/- 4.5 years, height 1.67 +/- 0.06 m, body mass 62.9 +/- 9.4 kg) volunteered to participate in two experimental sessions. After establishing their one-repetition maximum for the hamstring curl, the participants were assigned at random to one of two groups. Group 1 performed three bouts of 20 s hamstring stretches with the assistance of one of the investigators, while group 2 did not perform the stretches; instead, they sat resting for 3 min. Then, after stretching or resting, the participants performed as many hamstring curls as they could at 60% of their one-repetition maximum established earlier. All participants were assessed for their perceived exertion using a modified Borg category ratio (CR-10) scale. The participants returned within 1 week to complete the experiment. This time group 1 did not perform hamstring stretches, whereas group 2 did. As on the first occasion, all participants performed hamstring curls after stretching or resting. The participants in group 1 were able to perform more curls on the second day of testing than their counterparts in group 2. There were no significant differences between males and females or between the stretch and non-stretch conditions. There was a significantly higher first repetition rating of perceived exertion for the stretch condition (2.88 +/- 1.01) than for the non-stretch condition (2.50 +/- 0.95); there was no significant difference in the median ratings of perceived exertion between the stretch and non-stretch conditions. Significantly higher power function exponents were exhibited in the non-stretch (0.57 +/- 0.16) than in the stretch condition (0.51 +/- 0.12). In addition, females exhibited significantly higher power function exponents than males, irrespective of stretch condition and day (females: 0.59 +/- 0.12; males: 0.49 +/- 0.11). In conclusion, we found a small but statistically significant effect of an acute bout of stretching on ratings of perceived exertion during fatiguing hamstring muscle resistance exercise.
The results of previous research have shown that passive muscle stretching can diminish the peak force output of subsequent maximal isometric, concentric and stretch-shortening contractions. The aim of this study was to establish whether the deleterious effects of passive stretching seen in laboratory settings would be manifest in a performance setting. Sixteen members (11 males, 5 females) of a Division I NCAA track athletics team performed electronically timed 20 m sprints with and without prior stretching of the legs. The experiment was done as part of each athlete's Monday work-out programme. Four different stretch protocols were used, with each protocol completed on a different day. Hence, the test period lasted 4 weeks. The four stretching protocols were no-stretch of either leg (NS), both legs stretched (BS), forward leg in the starting position stretched (FS) and rear leg in the starting position stretched (RS). Three stretching exercises (hamstring stretch, quadriceps stretch, calf stretch) were used for the BS, FS and RS protocols. Each stretching exercise was performed four times, and each time the stretch was maintained for 30 s. The BS, FS and RS protocols induced a significant (P < 0.05) increase (approximately 0.04 s) in the 20 m time. Thus, it appears that pre-event stretching might negatively impact the performance of high-power short-term exercise.
Several studies utilizing adult subjects have indicated that static stretching may reduce subsequent strength and power production, possibly for as long as an hour following the stretch. This observation has not been evaluated in children, nor in athletes accustomed to performing static stretches during strength/ power type training sessions. The purpose of this investigation was to determine if an acute bout of passive, static stretching of the lower extremity would affect jumping performance in a group of young, female gymnasts. Thirteen competitive gymnasts (age 13.3 ± 2.6 yrs) performed drop jumps under two conditions: immediately following stretching and without prior stretching. The jumps were performed on separate days. The conditions were randomly ordered among the subjects. Time in the air (AIR) and ground contact time (CT) were measured during the drop jumps using a timing mat. Three different stretches of the lower extremity were conducted on each gymnast twice, each stretch being held for 30 seconds. Following the stretching condition, AIR was significantly reduced (.44 vs .46 sec, p < .001), while CT was not different (.130 for both conditions, p > .05). This study demonstrates that children's lower extremity power is reduced when the performance immediately follows passive, static stretching, even in children accustomed to static stretching during training sessions involving explosive power.
The regional distribution and number of microspheres in the calf muscles of rat has been studied during isometric sustained contraction and in stretched uncontracted muscles in situ. Carbonized microspheres, 15 +/- 5 mum, were injected into the aortic arch and muscle blood flow arrested 6 sec later. The calf muscles were freeze sectioned (12 slices of 40 mum) and the microspheres counted microscopically. The microsphere concentration in the gastrocnemius and plantaris muscles during rest was 4.6 +/- 1.6 spheres/mm3 (mean +/- S.E.). One min after a standardized exercise programme the sphere concentration was increased to 20.5 +/- 3.9 spheres/mm3. At increasing force of contraction following the standard exercise programme, the microsphere concentration fell from 11.6 +/- 2.5 at 25% of maximal force of contraction (MFC) to 2.2 +/- 0.6 spheres/mm3 at 100% MFC (5.6 kg/cm2). Corresponding measurements in stretched, uncontracted muscles showed a similar fall in microsphere concentration in the central inner zone and in the peripheral outer zone was slightly higher than unity (1.08-1.16) in muscles at rest and at light postexercise hyperemia. At 75 and 100% MFC the ratio was 0.76 +/- 0.07 and 0.57 +/- 0.13, significantly lower than unity. Stretching of the uncontracted muscle group to 175% MFC reduced the ratio towards zero. The greater reduction in blood flow to the inner central zone of contracted calf muscles shown by microsphere distribution was confirmed by measurement of 125 I-antipyrine distribution. These results show an increased resistance against blood flow during active contraction or stretching of the calf muscles, most pronounced in the central inner zone at high tensions.
Muscular strength and fatigability of strength-trained (ST) and untrained (UT) women were compared during a 6-min bout of maximal rhythmic exercise involving the elbow flexor muscles given at a rate of 30 contractions.min-1. Fifteen ST and 15 UT subjects, aged 18-34 years and pair-matched for body size, were tested for differences in initial strength, final strength, absolute endurance, relative endurance, and rate of fatigue. Results revealed a significant difference in initial strength, final strength, and absolute endurance in favor of ST subjects. No significant difference was found for relative endurance, and rates of fatigue were similar for both groups. It is concluded that muscular strength and endurance are enhanced in women engaged in a training program designed primarily to increase muscular strength and hypertrophy, but fatigability is not affected.
Competitive and recreational athletes typically perform warm-up and stretching activities to prepare for more strenuous exercise. These preliminary activities are used to enhance physical performance and to prevent sports-related injuries. Warm-up techniques are primarily used to increase body temperature and are classified in 3 major categories: (a) passive warm-up - increases temperature by some external means; (b) general warm-up - increases temperature by nonspecific body movements; and (c) specific warm-up - increases temperature using similar body parts that will be used in the subsequent, more strenuous activity. The best of these appears to be specific warm-up because this method provides a rehearsal of the activity or event. The intensity and duration of warm-up must be individualised according to the athlete's physical capabilities and in consideration of environmental factors which may alter the temperature response. The majority of the benefits of warm-up are related to temperature-dependent physiological processes. An elevation in body temperature produces an increase in the dissociation of oxygen from haemoglobin and myoglobin, a lowering of the activation energy rates of metabolic chemical reactions, an increase in muscle blood flow, a reduction in muscle viscosity, an increase in the sensitivity of nerve receptors, and an increase in the speed of nervous impulses. Warm-up also appears to reduce the incidence and likelihood of sports-related musculoskeletal injuries. Improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance. Maintaining good flexibility also aids in the prevention of injuries to the musculoskeletal system. Flexibility is defined as the range of motion possible around a specific joint or a series of articulations and is usually classified as either static or dynamic. Static flexibility refers to the degree to which a joint can be passively moved to the end-points in the range of motion. Dynamic flexibility refers to the degree which a joint can be moved as a result of a muscle contraction and may therefore not be a good indicator of stiffness or looseness of a joint. There are 3 basic categories of stretching techniques: (a) ballistic--which makes use of repetitive bouncing movements; (b) static--which stretches the muscle to the point of slight muscle discomfort and is held for an extended period; and (c) proprioceptive neuromuscular facilitation - which uses alternating contractions and stretching of the muscles. Each of these stretching methods is based on the neurophysiological phenomenon involving the stretch reflex.(ABSTRACT TRUNCATED AT 400 WORDS)
The problem of the study was to investigate the relationship between maximum strength and muscular endurance; also the relationship between maximum strength and percentage of maximum strength held before and after an extended period of isometric training. The subjects (N = 60) were divided into two equal groups, control and experimental. The experimental group was further divided into two subgroups of high and low strength. The control group was tested for maximum strength and endurance once at the beginning of the experiment and once after 20 days. The subjects in the experimental group were tested for maximum strength and endurance before they embarked on a 20-day period of isometric training. They held tension for 100 sec. in the morning and again in the afternoon. Periodic tests were on the 5th, 10th, 15th, and 20th day. There was a significant relationship between maximum strength and endurance and a negative and generally significant relationship between maximum strength and percentage of maximum strength held.
The purpose of this study was to quantify the relationship between musculotendinous stiffness and performance in eccentric, isometric, and concentric activities. Thirteen trained subjects performed a series of maximal effort eccentric, concentric, and isometric muscular contractions in a bench press-type movement. Additionally, subjects performed a series of quasi-static muscular contractions in a bench press movement. A brief perturbation was applied to the bar while these isometric efforts were maintained, and the resulting damped oscillations provided data pertaining to each subject's musculotendinous stiffness. Musculotendinous stiffness was significantly related to isometric and concentric performance (r = 0.57-0.78) but not to eccentric performance. These results are interpreted as demonstrating that the optimal musculotendinous stiffness for maximum concentric and isometric activities was toward the stiff end of the elasticity continuum. A stiffer musculotendinous unit may facilitate such performances by improving the force production capabilities of the contractile component, due to a combination of improved length and rate of shortening, and additionally by enhancing initial force transmission.
Stretching exercises are either performed alone or with other exercises as part of the athlete's warm-up. The warm-up is designed to increased muscle/tendon suppleness, stimulate blood flow to the periphery, increase body temperature, and enhance free, coordinated movement. The purpose of this paper is to review the literature regarding stretching, with the aim of defining its role during the warm-up. Implications of stretching on muscle/tendon flexibility, minimizing injury, enhancing athletic performance, and generally preparing the athlete for exercise are discussed. Physiology applied to stretching is also discussed together with different related techniques and practical aspects. A proposed model stretching regime is presented based on the literature reviewed.
Experiments were carried out to test the effect of prolonged and repeated passive stretching (RPS) of the triceps surae muscle on reflex sensitivity. The results demonstrated a clear deterioration of muscle function immediately after RPS. Maximal voluntary contraction, average electromyographic activity of the gastrocnemius and soleus muscles, and zero crossing rate of the soleus muscle (recorded from 50% maximal voluntary contraction) decreased on average by 23.2, 19.9, 16.5, and 12.2%, respectively. These changes were associated with a clear immediate reduction in the reflex sensitivity; stretch reflex peak-to-peak amplitude decreased by 84. 8%, and the ratio of the electrically induced maximal Hoffmann reflex to the maximal mass compound action potential decreased by 43. 8%. Interestingly, a significant (P < 0.01) reduction in the stretch-resisting force of the measured muscles was observed. Serum creatine kinase activity stayed unaltered. This study presents evidence that the mechanism that decreases the sensitivity of short-latency reflexes can be activated because of RPS. The origin of this system seems to be a reduction in the activity of the large-diameter afferents, resulting from the reduced sensitivity of the muscle spindles to repeated stretch.
Repeated activation of skeletal muscle causes fatigue, which involves a reduced ability to produce force and slowed contraction regarding both the speed of shortening and relaxation. One important component in skeletal muscle fatigue is a reduced sarcoplasmic reticulum (SR) Ca2+ release. In the present review we will describe different types of fatigue-induced inhibition of SR Ca2+ release. We will focus on a type of long-lasting failure of SR Ca2+ release which is called low-frequency fatigue, because this type of fatigue may be involved in the muscle dysfunction and chronic pain experienced by computer workers. Paradoxically it appears that the Ca2+ released from the SR, which is required for contraction, may actually be responsible for the failure of SR Ca2+ release during low-frequency fatigue. We will also discuss the relationship between gross morphological changes in muscle fibres and long-lasting failure of SR Ca2+ release. Finally, a model linking muscle cell dysfunction and muscle pain is proposed.
Recent research has shown that a regimen of stretching provides an acute inhibition of maximal force production by the stretched muscle group. To further characterize this phenomenon, the effect of an acute stretching regimen on maximal isokinetic knee-extension torque at 5 specific movement velocities (1.05, 1.57, 2.62, 3.67, and 4.71 rad x s(-1)) was examined in 10 men and 5 women (22-28 years). Each person's 5 baseline maximal isokinetic knee-extension torques (dominant leg) were measured on a Cybex NORM dynamometer. Following the baseline torque measurements, the participants stretched the dominant quadriceps for 15 minutes using 1 active and 3 passive stretching exercises. Once the stretching exercises were completed, the maximal torque measurements were repeated. Poststretch maximal torque at 1.05 rad x s(-1) was significantly reduced (p < 0.05) from 218 +/- 47 Nm (mean +/- SD) to 199 +/- 49 Nm (7.2% decrease). At 1.57 rad x s(-1), a similar decrease (p < 0.05) was also seen (204 +/- 48 Nm vs. 195 +/- 47 Nm; 4.5% decrease), but at the other velocities (2.62, 3.67, and 4.71 rad x s(-1)), poststretch maximal torque was unaltered (p > 0.05). It appears, therefore, that the deleterious impact of stretching activities on maximal torque production might be limited to movements performed at relatively slow velocities.
Although different warm-up and flexibility routines are often prescribed before physical activity, little research has been conducted to determine what effects these routines have on athletic performance in activities. The purpose of this investigation was to determine to what degree different warm-up routines affect performance in the vertical jump test. The 40 female participants were asked to perform a general warm-up only, a general warm-up and static stretching, and a general warm-up and proprioceptive neuromuscular facilitation (PNF) on 3 nonconsecutive days. Each of the treatments was followed by a vertical jump test. A 1-way repeated-measures analysis of variance revealed a significant difference in vertical jump performance. A post hoc analysis revealed decreased vertical jump performances for the PNF treatment group. Based on the results of this study, performing PNF before a vertical jump test would be detrimental to performance.
It is well established that altering O2 delivery to contracting skeletal muscle affects human performance. In this respect, a reduced O2 supply (e.g., hypoxia) increases the rate of muscle fatigue, whereas increasing O2 supply (e.g., hyperoxia) reduces the rate of fatigue. Interestingly, the faster onset of fatigue in moderate hypoxia does not appear to be a consequence of mitochondrial O2 limitation because these effects occur at submaximal rates of O2 consumption for these conditions and at O2 tensions well above that which impairs mitochondrial O2 uptake in vitro. Alterations in O2 supply modulate the regulation of cellular respiration and may affect the onset of impaired Ca2+ handling with fatigue. Specifically, changes in O2 supply alter the coupling between phosphocreatine hydrolysis and O2 uptake in contracting muscles, which by determining the rate of inorganic phosphate (Pi) accumulation may affect Ca2+ release. Partial ischemia differs somewhat in that the reduction in force could be due to reduced O2 supply and/or impaired removal of metabolic by-products secondary to insufficient blood flow. Nonetheless, recent evidence shows a parallel decline and restoration of force with alterations in O2 supply but not blood flow alone during submaximal contractions. Furthermore, the causes of fatigue are similar when O2 is plentiful and when it is reduced.
To determine the effects of stretching before and after exercising on muscle soreness after exercise, risk of injury, and athletic performance.
Systematic review.
Randomised or quasi-randomised studies identified by searching Medline, Embase, CINAHL, SPORTDiscus, and PEDro, and by recursive checking of bibliographies.
Muscle soreness, incidence of injury, athletic performance.
Five studies, all of moderate quality, reported sufficient data on the effects of stretching on muscle soreness to be included in the analysis. Outcomes seemed homogeneous. Stretching produced small and statistically non-significant reductions in muscle soreness. The pooled estimate of reduction in muscle soreness 24 hours after exercising was only 0.9 mm on a 100 mm scale (95% confidence interval -2.6 mm to 4.4 mm). Data from two studies on army recruits in military training show that muscle stretching before exercising does not produce useful reductions in injury risk (pooled hazard ratio 0.95, 0.78 to 1.16).
Stretching before or after exercising does not confer protection from muscle soreness. Stretching before exercising does not seem to confer a practically useful reduction in the risk of injury, but the generality of this finding needs testing. Insufficient research has been done with which to determine the effects of stretching on sporting performance.
The purpose of this study was to determine the effect of an acute static stretching bout of the biceps brachii on torque, electromyography (EMG), and mechanomyography (MMG) during concentric isokinetic muscle actions. Eighteen (men, n = 10; women, n = 8) adult subjects (M +/- SD age = 22.7 +/- 2.8 years; weight = 78.0 +/- 17.0 kg; height = 177.9 +/- 11.0 cm) performed maximal isokinetic (30 and 270 degrees.s(-1)) forearm flexion strength testing on 2 occasions while EMG and MMG were recorded. Subjects were randomly assigned to stretching (STR) or nonstretching (NSTR) protocols before strength testing. Two-way ANOVAs with repeated measures revealed significantly (p < or = 0.05) greater torque for NSTR (M +/- SEM = 36.9 +/- 3.3 N.m) vs. STR (35.2 +/- 3.3 N.m), significantly greater MMG amplitude for STR vs. NSTR for 30 degrees.s(-1) (STR = 93.5 +/- 14.4 mV; NSTR = 63.1 +/- 10.6 mV) and 270 degrees.s(-1) (STR = 207.6 +/- 35.6 mV; NSTR = 136.4 +/- 31.7 mV), and no difference in EMG amplitude. These results indicate that a greater ability to produce torque without prior stretching is related to the musculotendinous stiffness of the muscle rather than the number of motor units activated. This suggests that performing activities that reduce muscle stiffness (such as stretching), may be detrimental to performance.
Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function.
Six healthy males (age: 21.5 +/- 1.4, mean +/- SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization.
After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST.
In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.
HUNTER, S. K., J. DUCHATEAU, and R. M. ENOKA. Muscle fatigue and the mechanisms of task failure. Exerc. Sport Sci. Rev., Vol. 32, No. 2, pp. 44–49, 2004. An alternative approach in the study of muscle fatigue is to address the question, “What causes task failure during a fatiguing contraction?” This approach is described by considering how variation in the type of load supported and contraction intensity influence both the time to task failure and the centrally mediated adjustments in reflex activity and motor unit behavior.
The objective of this study was to conduct a systematic analysis of the literature to assess the efficacy of stretching for prevention of exercise-related injury. Randomized clinical trials (RCTs) and controlled clinical trials (CCTs) investigating stretching as an injury prevention measure were selected. A computer-aided search of the literature was conducted for relevant articles, followed by assessment of the methods of the studies. The main outcome measures were scores for methodological quality based on four main categories (study population, interventions, measurement of effect, and data presentation and analysis) and main conclusions of authors with regard to stretching. One RCT (25%) and three CCTs (100%) concluded that stretching reduced the incidence of exercise-related injury. Three RCTs (75%) concluded that stretching did not reduce the incidence of exercise-related injury. Only two studies scored more than 50 points (maximum score=100 points) indicating that most of the studies selected were of poor quality. Neither of the two highest scoring RCTs showed positive effects for stretching. Due to the paucity, heterogeneity and poor quality of the available studies no definitive conclusions can be drawn as to the value of stretching for reducing the risk of exercise-related injury.
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Relationship of maximum back and leg strength to back and leg strength endurance
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