International SportMed Journal - Volume 11, Issue 1, 2010
Volume 11, Issue 1, 2010
Lower back pain in cyclists : a review of epidemiology, pathomechanics and risk factors : review articleAuthor Mandy MarsdenSource: International SportMed Journal 11, pp 216 –225 (2010)More Less
Lower back pain (LBP) appears to be a common overuse injury in cycling. However, there are few scientific studies that report on the epidemiology and risk factors associated with LBP in cyclists. The prolonged flexed posture that a cyclist maintains may lead to increased mechanical strain of the lumbar spine, causing LBP. In this article, the epidemiology, pathomechanics and risk factors associated with LBP in cyclists will be critically reviewed.
An extensive literature review was conducted using an evidence-based approach. Using selective keywords (lower back pain, cyclists, bicycle set-up, risk factors) a search was undertaken on the PubMed database to identify all research publications that relate to lower back pain in cyclists.
Although epidemiological studies were limited, LBP was shown to be a common cycling overuse injury. The point prevalence of LBP in cyclists ranged from 10-60%. It has been suggested that LBP in cyclists may be prevented by adjusting certain bicycle parameters to match the anthropometric measurements of the cyclist. Pathomechanical hypotheses for the development of LBP in cyclists are poorly supported, and most studies were conducted over time periods shorter than one hour. Monitoring cyclists over a longer period of cycling may yield more accurate data. There is strong evidence supporting the incorrect saddle angle as an intrinsic risk factor is associated with LBP in cyclists.
In conclusion, additional research on the epidemiology of LBP in cyclists is necessary. Further research studies, such as case control and intervention studies are necessary to study pathomechanics and risk factors associated with LBP in cyclists.
A workload equation for a bicycle ergometer is not sufficient to elicit exercise-induced bronchoconstriction in athletes : original research articleSource: International SportMed Journal 11, pp 226 –234 (2010)More Less
Background: Elite athletes often experience exercise-induced bronchoconstriction (EIB). However, this generally occurs during long-duration, repetitive, high-intensity exercise in dry air. Respiratory symptoms and laboratory tests are not adequate to predict and to diagnose EIB in athletes. Establishing the level of exercise intensity necessary to induce bronchoconstriction is important in both athletes and sedentary subjects. Research question: The study attempted to evaluate the heart rate responses of seventeen male athletes and eighteen male sedentary subjects by using a target workload equation for a bicycle ergometer. Type of study: An experimental study, using human subjects, was designed. Methods: Seventeen volunteer male elite athletes and eighteen male sedentary subjects participated in the study. Subjects performed an exercise challenge test on an electromagnetically braked bicycle ergometer. The equation used to establish the target workload was in watts = 53.76 x measured forced expiratory volume in 1 s (FEV1) - 11.07. Results: 88.2% of the athletes and 72.2% of the sedentary subjects reported at least one symptom of EIB. The difference between the percentage of maximal heart rate achieved in four minutes by athletes (81.4%) and sedentary subjects (86.3%) was statistically significant, but 5 of 18 sedentary subjects could not reach the target workload by the fourth minute. Only 1 of the 18 sedentary subjects demonstrated decrements greater than 10% in FEV1. Conclusion: This study demonstrated that a bicycle ergometer exercise challenge test using a workload equation is not suitable for EIB assessment for elite athletes because they cannot attain desired work intensity. It can be concluded that this equation may lead to a misdiagnosed or underdiagnosed athletic population.
Effect of different resistance exercise repetition velocities on excess post-exercise oxygen consumption and energetic expenditure : original research articleSource: International SportMed Journal 11, pp 235 –243 (2010)More Less
Background: The excess post-exercise oxygen consumption (EPOC) consists of the excess oxygen consumed above a resting state following exercise. Performance of resistance exercise can significantly disrupt the body's homeostasis, with the EPOC being dependent on the specific combination of prescriptive variables. Presently, the effects of different repetition velocities on VO2 and caloric expenditure during and following resistance exercise bouts have not been completely elucidated. Objective: To examine the effect of different repetition velocities on EPOC and total energetic expenditure during and following resistance exercise bouts. Methods: Twenty women (34.6 ± 5.5 years; 159 ± 4.1 cm; 55.1 ± 3.4 kg; 24±2.5 kg/m-2; 18.9 ± 4.3 % body fat) performed two resistance exercise bouts that differed only in the velocity of repetitions: sequence 1 (SEQ1) involved 1 second concentric and eccentric phases and sequence 2 (SEQ2) involved 2 second concentric and eccentric phases. Both bouts utilized a 70% of 1-RM load for all exercises, performed for 3 sets of 10 repetitions. The respired gas analysis was assessed before, during, and for 60 minutes following each bout. Results: None of the variables assessed (i.e. VO2, VCO2, VE/VO2, VE/ VCO2, VE, RQ) were significantly different between bouts (p > 0.05). Conclusion: A relatively slower repetition velocity will produce similar energy expenditure during and following resistance exercise as a relatively faster repetition velocity, as long as the total volume is equal between resistance exercise bouts.
Chronic hypoxia and exercise training affect the NO content and NOS activity of rat skeletal muscle : original research articleSource: International SportMed Journal 11, pp 244 –257 (2010)More Less
Background: Nitric oxide (NO) plays a critical role in the recovery stage, in maintaining a large blood flow in skeletal muscle and in promoting recovery after exercise. Research question: This study observed the NO level, NOS activity and the expression of NOS in rat skeletal muscle under normoxic and hypoxic training conditions. Type of study: Randomised controlled study. Methods: Sixty-four male Sprague-Dawley rats were randomly divided into normoxic control group, two-week training, four-week training, six-week training groups; hypoxic control group, two-week hypoxic training, four-week hypoxic training, six-week hypoxic training groups. The classic Griess method was used to test nitric oxide in the homogenate of skeletal muscle. Moreover, methods such as RT-PCR, western blot, etc. were utilised to test the change of the all types of nitric oxide synthase expression. Results: The results showed that the NO content of rat skeletal muscle was significantly increased in two, four, and six-week training subgroups compared with the control group under normoxic conditions; NO content increased in the four-weeks and six-weeks hypoxic training group compared with the hypoxic control group (p <0.05, p <0.01). Under hypoxic conditions, with increasing exercise time, the cNOS activity and the expression cNOS protein was significant different between the training group and the control group, while there was no change in iNOS expression. Conclusions: The data in this study suggested that the hypoxic exercise may promote increases in the NOS and NO levels, counteract the blood vessel contractile effect of hypoxia, and improve the relaxed tone of blood vessels.