Flexibility has been controversially suggested as one of the biomechanical factors contributing to the variability observed in running economy among distance runners. The purpose of this investigation was to determine the magnitude of the relationship between sit-and-reach flexibility and running economy in men and women. Eight collegiate distance runners (4 men and 4 women) served as subjects for this correlational study (age = 19.9 +/- 1.25 years; VO2max = 63.2 +/- 3.4 mlxkgxmin). Each subject's flexibility was measured using the standard sit-and-reach test, and running economy was recorded during an incremental maximal treadmill test at both absolute (men = 241.2 mxmin; women = 198.32 mxmin) and relative (10-km pace) velocities. Statistical analyses indicated a significant relationship between sit-and-reach scores and running economy at an absolute velocity (r = 0.826, p <or= 0.05), as well as a significant sex difference in sit-and-reach scores (p <or= 0.05). The significant relationship demonstrates that the less flexible distance runners tended to be more economical, possibly as a result of the energy-efficient function of the elastic components in the muscles and tendons during the stretch-shortening cycle.
"It is estimated that storage and return of elastic energy during running approximates about half of the mechanical work performed during the eccentric phase of a running stride (Cavagna et al., 1964). In accordance with the latter assertion, stiffness of the musculoskeletal system in the lower-body is associated with enhanced running economy in a wide range of runners (Craib et al., 1996; Jones, 2002; Trehearn & Buresh, 2009). Muscle-tendon system is able to increase its stiffness through both explosive strength training (Foure et al., 2011) and heavy strength training (Kubo et al., 2001, 2002). "
[Show abstract][Hide abstract] ABSTRACT: Here we report on the effect of combining endurance training with heavy or explosive strength training on endurance performance in endurance-trained runners and cyclists. Running economy is improved by performing combined endurance training with either heavy or explosive strength training. However, heavy strength training is recommended for improving cycling economy. Equivocal findings exist regarding the effects on power output or velocity at the lactate threshold. Concurrent endurance and heavy strength training can increase running speed and power output at VO2max (Vmax and Wmax , respectively) or time to exhaustion at Vmax and Wmax . Combining endurance training with either explosive or heavy strength training can improve running performance, while there is most compelling evidence of an additive effect on cycling performance when heavy strength training is used. It is suggested that the improved endurance performance may relate to delayed activation of less efficient type II fibers, improved neuromuscular efficiency, conversion of fast-twitch type IIX fibers into more fatigue-resistant type IIA fibers, or improved musculo-tendinous stiffness.
Scandinavian Journal of Medicine and Science in Sports 08/2013; 4(4). DOI:10.1111/sms.12104 · 2.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, a comparison was made between muscle strength, power and muscle and tendon (km and kt respectively) stiffness of the triceps surae muscle group and running economy (RE) in trained male runners.
Twelve well-trained male runners (age = 21 +/- 2.7 y, height = 178.1 +/- 7.1 cm, body mass = 66.7 +/- 3.2 kg, VO2max = 68.3 +/- 4.3 mL x kg(-1) x min(-1), 5000-m time = 15:04 min:s) underwent passive stiffness testing using a free oscillation method. Muscle strength was determined via a maximal isometric squat test and power determined via a maximal countermovement jump (CMJ). On a separate day, subjects performed an incremental treadmill test and their RE, lactate threshold, and VO2max were determined. Fingertip blood lactate was determined at the end of each 3-min stage. Lactate threshold was defined as a nonlinear increase in lactate accumulation.
A statistically significant correlation was found between km and VO2 at stage 6 (r = -0.69, P = .01). In addition, statistically significant correlations were observed between CMJ peak force production and VO2 at stage 2 (r = .66, P = .02), stage 3 (r = .70, P = .01), and stage 4 (r = .58, P = .04). No other statistically significant correlations were observed.
These data suggest that greater muscle stiffness and less power are associated with greater RE. Future study in this area should focus on determining the mechanisms behind this relationship and how to best apply them to a running population through training techniques.
International journal of sports physiology and performance 06/2010; 5(2):249-61. · 2.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An objective of a warm-up prior to an athletic event is to optimize performance. Warm-ups are typically composed of a submaximal aerobic activity, stretching and a sport-specific activity. The stretching portion traditionally incorporated static stretching. However, there are a myriad of studies demonstrating static stretch-induced performance impairments. More recently, there are a substantial number of articles with no detrimental effects associated with prior static stretching. The lack of impairment may be related to a number of factors. These include static stretching that is of short duration (<90 s total) with a stretch intensity less than the point of discomfort. Other factors include the type of performance test measured and implemented on an elite athletic or trained middle aged population. Static stretching may actually provide benefits in some cases such as slower velocity eccentric contractions, and contractions of a more prolonged duration or stretch-shortening cycle. Dynamic stretching has been shown to either have no effect or may augment subsequent performance, especially if the duration of the dynamic stretching is prolonged. Static stretching used in a separate training session can provide health related range of motion benefits. Generally, a warm-up to minimize impairments and enhance performance should be composed of a submaximal intensity aerobic activity followed by large amplitude dynamic stretching and then completed with sport-specific dynamic activities. Sports that necessitate a high degree of static flexibility should use short duration static stretches with lower intensity stretches in a trained population to minimize the possibilities of impairments.
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