Differences between the sexes and age-related changes in orienteering speed

The aim of this study was to assess the effects of the age and sex of the competitor on orienteering speed during competitive events. The results of the fastest three male and fastest three female competitors in each 5-year age band (21-79 years), from four national orienteering events, were analysed. The data for age and orienteering speed were log-transformed and regression analyses were conducted to determine the relationships between age and sex and orienteering speed. For comparison, data for the fastest Great Britain finisher in the 10,000-m track and 10-km cross-country events for age groups 40-69 years at the World Masters Championships were also analysed. The results showed that, before the age of 40 years, there was no substantial slowing in orienteering speed for males (0.5-4.2% per decade) but a moderate decline (4.7-10.0% per decade) for females. After the age of 45 years, the orienteering speed of males and females slowed by 13 - 2% and 16 - 4% per decade (mean - s ), respectively, until around the age of 69, after which the deterioration was accentuated. The orienteering speed of the females was 81 - 4, 74 - 6 and 69 - 7% that of the males at ages 21, 45 and 65 years, respectively. The magnitudes of the age-related slowing of orienteering speed and of the difference in orienteering speed between males and females aged 45 years and over were greater than those reported for the other endurance running events. This may reflect the physical demands of running in orienteering terrain, tactical and cognitive aspects of the sport, or sociocultural aspects of the participating population.     

Caffeine lowers perceptual response and increases power output during high-intensity cycling

The aim of this study was to determine the effects of caffeine ingestion on a ‘preloaded’ protocol that involved cycling for 2?min at a constant rate of 100% maximal power output immediately followed by a 1-min ‘all-out’ effort. Eleven male cyclists completed a ramp test to measure maximal power output. On two other occasions, the participants ingested caffeine (5?mg?·?kg^?1) or placebo in a randomized, double-blind procedure. All tests were conducted on the participants' own bicycles using a Kingcycle? test rig. Ratings of perceived exertion (RPE; 6–20 Borg scale) were lower in the caffeine trial by approximately 1 RPE point at 30, 60 and 120?s during the constant rate phase of the preloaded test (P?<0.05). The mean power output during the all-out effort was increased following caffeine ingestion compared with placebo (794±164 vs 750±163?W; P?=?0.05). Blood lactate concentration 4, 5 and 6?min after exercise was also significantly higher by approximately 1?mmol?·?l^?1 in the caffeine trial (P?<0.05). These results suggest that high-intensity cycling performance can be increased following moderate caffeine ingestion and that this improvement may be related to a reduction in RPE and an elevation in blood lactate concentration.     

Empowering teams through social network ties

Effective teamwork and knowledge coordination are becoming increasingly important for all kinds of organizations given the growing use of teams to tackle competitive challenges and sustain competitive advantage. In this study, we develop and validate a model of how two types of social network ties – expressive and instrumental – contribute to team efficacy and performance, mediated by three dimensions of a transactive memory system (TMS) – specialization, credibility and coordination within teams. We test the model in an empirical study drawing on data from 66 teams in a variety of organizations. The results suggest that both instrumental and expressive ties within teams can facilitate the formation of TMS and the three dimensions of TMS are all, even though to different extents, positively related to team efficacy. Team efficacy is also a powerful predictor of team performance. The findings in our study bridge the literature gap about social networks and TMS and explain the underlying process and mechanisms by which social network ties exert their influence on team outcomes. The results have implications for organizations that wish to leverage teams to take advantage of team members’ differentiated expertise and coordinate their work more effectively and efficiently.     

Exercise training and impaired glucose tolerance in obese humans

Individuals with impaired glucose tolerance (IGT) are at greater risk of developing diabetes than in normoglycaemia. The aim of this study was to examine the effects of 12-weeks exercise training in obese humans with IGT. Eleven participants (6 males and 5 females; 49±9 years; mean Body Mass Index (BMI) 32.4 kg · m(-2)), completed a 12-week brisk walking intervention (30 min per day, five days a week (d · wk(-1)), at 65% of age-predicted maximal heart rate (HR(max)). Anthropometric measurements, dietary intake, pulse wave velocity (PWV, to determine arterial stiffness) and blood pressure (BP) were examined at baseline and post intervention. Fasting blood glucose, glycosylated haemoglobin, insulin, blood lipids, indices of oxidative stress and inflammation (lipid hydroperoxides; superoxide dismutase; multimeric adiponectin concentration and high-sensitivity C-reactive protein) were also determined. Post intervention, PWV (9.08±1.27 m · s(-1) vs. 8.39±1.21 m · s(-1)), systolic BP (145.4±14.5 vs. 135.8±14.9 mmHg), triglycerides (1.52±0.53 mmol · L(-1) vs. 1.31±0.54 mmol · L(-1)), lipid hydroperoxides (1.20±0.47 μM · L(-1) vs. 0.79±0.32 μM · L(-1)) and anthropometric measures decreased significantly (P < 0.05). Moderate intensity exercise training improves upper limb vascular function in obese humans with IGT, possibly by improving triglyceride metabolism, which may subsequently reduce oxidative stress. These changes were independent of multimeric adiponectin modification and alterations in other blood biomarkers.     

Editorial

Ohne Zusammenfassung

---

Editorial

     

Neuromuscular characteristics of endurance- and power-trained athletes

In response to chronic physical training, the human neuromuscular system undergoes significant and specific adaptations. More importantly, these influences are the result of the type and quantity of physical activity. One of the simplest neuromuscular mechanisms is the spinal stretch reflex. The reflex system was previously viewed as inflexible, with a relatively fixed response that could vary only slightly. However, more recent data have identified an adaptive plasticity in the reflex system. In this respect, the reflex system can be used to assess training and aging adaptations of the human neuromuscular system. Due to their methodological simplicity, both the tendon-tap reflex and the electrically evoked Hoffmann reflex (H-reflex) can be used to assess training adaptations of the human neuromuscular system. The purpose of this paper is to review briefly the tendon-tap and H-reflex paradigms and delineate the research findings pertaining to changes in the reflex system with physical training. For purposes of clarity, this discussion will be divided into the following: (a) differences observed in the tendon-tap reflex, (b) differences observed in the H-reflex, and (c) role of interneurons in mediating these changes.     

Sodium bicarbonate ingestion does not alter the slow component of oxygen uptake kinetics in professional cyclists

We examined the effects of pre-exercise sodium bicarbonate (NaHCO3) ingestion on the slow component of oxygen uptake (VO2) kinetics in seven professional road cyclists during intense exercise. One hour after ingesting either a placebo or NaHCO3 (0.3 g x kg body mass(-1)), each cyclist (age, 25 +/- 2 years; VO2max, 74.7 +/- 5.9 ml x kg(-1) x min(-1); mean +/- s) performed two bouts of 6 min duration at an intensity of 90% VO2max interspersed by 8 min of active recovery. Gas exchange and blood data (pH, blood lactate concentration and [HCO3-]) were collected during the tests. In both bouts, the slow component of VO2 was defined as the difference between end-exercise VO2 and the VO2 at the end of the third minute. No significant difference was found in the slow component of VO2 between conditions in the first (NaHCO3, 210 +/- 69 ml; placebo, 239 +/- 105 ml) or second trial (NaHCO3, 123 +/- 88 ml; placebo, 197 +/- 101 ml). In conclusion, pre-exercise NaHCO3 ingestion did not significantly attenuate the VO2 slow component of professional road cyclists during high-intensity exercise.