Stretching immediately before starting cycling appears to impair exercise efficiency and durability, warn researchers.
In a study involving nine men who performed acute stretching exercises before they began a high-intensity cycle, exercise efficiency and time-to-exhaustion were significantly decreased compared with when they did not perform the stretches, report Fabio Esposito (University of Milan, Italy) and team.
The stretching routine involved elongating knee extensors and flexors, plantar flexors of the ankle, and hip extensors during five 1-minute sessions lasting 45 seconds each, with 15 seconds rest inbetween. The participants, who were aged a mean of 24 years, performed a cycling task maintaining a constant pedal rate of 100 revolutions per minute for 5 minutes or until they felt exhausted, both with and without doing the stretches first.
As reported in the Scandinavian Journal of Medicine & Science in Sports, a sit-and-reach test showed that stretching significantly improved reach compared with not stretching, by an average of 3.5 cm, providing evidence that stretching significantly increases flexibility of the posterior muscular chain, note Esposito et al.
The team reports that mean values of cardiorespiratory and metabolic variables at maximum aerobic power (VO2max) were not significantly altered by the stretching maneuvers.
However, stretching did significantly decrease the maximum voluntary extension of the knee extensor muscles by 8%, suggesting that muscle activation and force production were impaired, say the researchers. This would have led to a need to exert a higher relative force on the pedals to maintain the same constant workload as in the control condition, they explain.
Exercise performance during tests performed at 85% of VO2max was also significantly affected, with the time to exhaustion being, on average, 26% shorter when the cycling exercise was preceded with stretching.
In addition, stretching before cycling showed a significant effect not only on expiratory ventilation, which increased by a mean of 5.9% over the entire duration of the exercise, but also on oxygen uptake, which increased by 4.3%, and carbon dioxide production, which increased by 4.6%.
Moreover, during the last minute of exercise, the net mechanical efficiency was a significant 4.1% lower when participants had stretched prior to exercise compared with when they had not stretched.
"These results are suggestive of an impairment in cycling efficiency due to changes in muscle neural activation and viscoelastic characteristics induced by stretching," says the team.
"Further studies are needed to clarify whether different stretching modalities could improve joint flexibility without impairing aerobic performance," the researchers conclude.
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