Notes: Exercise in girls during growth seems to confer a high peak bone mineral density (BMD). Exercise in adulthood, in the peri- and postmenopausal period, and in old age prevents bone loss or increases BMD with a magnitude of minor biological significance. However, these changes must be regarded as beneficial compared to the age-related bone loss, which inevitably will occur if no interventions are implemented. Prospective intervention studies also suggest that exercise improves muscle strength, coordination and balance, even in elderly women, all of which are improvements with a potential of reducing the number of falls. A randomised, controlled, prospective, blinded study (the only study design that tests a hypothesis) of exercise with fracture as end point is extremely difficult to conduct, due to the large sample sizes needed. At present, no such studies exist. Retrospective and prospective observational and case–control studies suggest that physical activity in women is associated with reduced fracture risk. This may be correct, but we must never forget that a consistently replicated sampling bias may produce the same outcome.The Achilles heel of exercise is the reduction or the cessation of physical activity, which commonly occurs among middle-aged women when family and work demands reduce the time available for exercise. A higher BMD or improvement in muscle size and muscle strength achieved by exercise during adolescence seems to be eroded on retirement, leaving virtually no remaining benefits in old age, the period when fragility fractures begin to be a problem of increasing magnitude. However, recreational activities seem to maintain some of the musculo-skeletal benefits, but to date we do not know the level of activity needed to retain these benefits. Dose–response relationships need to be quantified, as also the effects on bone size, shape and architecture. Another essential question that we must address is how many fewer fractures will be the result of a community-based exercise campaign. Will efforts by the community to encourage a higher level of physical exercise, with the aim of reducing bone fractures, be cost-effective? The higher level of proof, suggesting that exercise does reduce fragility fractures and thus reduces the total cost for the society, must come from well-designed and well-executed, prospective, randomised, controlled trials. The responsibility of executing these studies lies in the hands of both researchers and the community.

Notes: The purpose of this study was to examine the outcome after surgery for an acute Achilles tendon rupture. In particular, we wanted to study whether persons who have suffered an Achilles tendon rupture are at greater risk of a contralateral tendon rupture. From September 1990 to April 1997, 168 acute Achilles tendon ruptures in 26 women and 142 men were treated operatively. In August 1998 (median: 4.2 years post injury), 154 of these patients (92%) responded to a follow-up questionnaire. Local symptoms (pain, decreased strength and/or reduced range of motion) were reported pre injury by 25% of the patients; at follow-up this had increased to 52%. Ten patients (6%) experienced a rupture on the contralateral side during the follow-up period (OR: 176 [70–282] vs. the expected rate based on the general population risk of this injury, P〈0.001). Thus, this study suggests that patients with an Achilles tendon rupture are at significantly increased risk of a contralateral tendon rupture, as well. Also, as many as half of the patients suffered from post-injury problems at long-term follow-up.

Notes: Exercise-induced arterial hypoxaemia is defined as a reduction in the arterial O2 pressure (PaO2) by more than 1 kPa and/or a haemoglobin O2 saturation (SaO2) below 95%. With blood gas analyses ideally reported at the actual body temperature, desaturation is a consistent finding during maximal ergometer rowing. Arterial desaturation is most pronounced at the end of a maximal exercise bout, whereas the reduction in PaO2 is established from the onset of exercise. Exercise-induced arterial hypoxaemia is multifactorial. The ability to maintain a high alveolar O2 pressure (PAO2) is critical for blood oxygenation and this appears to be difficult in large individuals. A large lung capacity and, in turn, diffusion capacity seem to protect PaO2. A widening of the PAO2–PaO2 difference does indicate that a diffusion limitation, a ventilation–perfusion mismatch and/or a shunt influence the transport of O2 from alveoli to the pulmonary capillaries. An inspired O2 fraction of 0.30 reduces the widened PAO2–PaO2 difference by 75% and prevents a reduction of PaO2 and SaO2. With a marked increase in cardiac output, diffusion limitation combined with a fast transit time dominates the O2 transport problem. Furthermore, a postexercise reduction in pulmonary diffusion capacity suggests that the alveolo-capillary membrane is affected. An antioxidant attenuates oxidative burst by neutrophilic granulocytes, but it does not affect PaO2, SaO2 or O2 uptake (VO2), and the ventilatory response to maximal exercise also remains the same. It is proposed, though, that increased concentration of certain cytokines correlates to exercise-induced hypoxaemia as cytokines stimulate mast cells and basophilic granulocytes to degranulate histamine. The basophil count increases during maximal rowing. Equally, histamine release is associated with hypoxaemia and when the release of histamine is prevented, the reduction in PaO2 is attenuated.During maximal exercise, an extreme lactate spill-over to blood allows pH decrease to below 7.1 and according to the O2 dissociation curve this is critical for SaO2. When infusion of sodium bicarbonate maintains a stable blood buffer capacity, acidosis is attenuated and SaO2 increases from 89% to 95%. This enables exercise capacity to increase, an effect also seen when O2 supplementation to inspired air restores arterial oxygenation. In that case, exercise capacity increases less than can be explained by VO2 and CaO2. Furthermore, the change in muscle oxygenation during maximal exercise is not affected when hyperoxia and sodium bicarbonate attenuate desaturation. It is proposed that other organs benefit from enhanced O2 availability, and especially the brain appears to increase its oxygenation during maximal exercise with hyperoxia.

Notes: Movement is caused by force transmission from contracting muscles to bone via tendon. The collagen structure of tendon is organized in a very hierarchical manner. The collagen fibril is considered the basic force-transmitting unit of tendon, and it is embedded in a hydrophilic extracellular matrix of proteoglycans, glycoproteins and glycosaminoglycans. It has recently been shown in human peritendinous tissue is more metabolically active in response to activity than previously thought, although it remains to be established, if the level of activity influences affects fibril diameter and/or total tendon cross-sectional area. Moreover, it cannot be unequivocally concluded that tendon adaptation to physical activity is one of a quantitative and/or qualitative nature. The currently available information is almost exclusively obtained from animal data, however, techniques such as microdialysis for tendon metabolism and ultrasound combined with MRI for tendon mechanical properties has already provided information on human tendon behavior, and is likely to further add to our understanding of how tendon adapt to physical activity. This review will address the structure and function of tendon, and the current knowledge of how tendons respond to activity with respect to biomechanical properties.

Notes: We evaluated a short-term (3 months) and a long-term (8 months) effect of dance training on joint mobility and muscle flexibility of the spine, hip and ankle and on speed and agility in young cross-country skiers. Twenty elite cross-country skiers – aged 12–15 years – participated in the study. Five males and five females received dance training (intervention group) and five males and five females did not dance (reference group). Joint mobility and muscle flexibility of the spine, hip and ankle joints were measured using a goniometer, a kyphometer, a measuring tape and a ruler. Two sports-related functional tests – the slalom-test and the hurdle-test – were also performed. These measurements/tests were performed before the start of the dancing period and after 3 and 8 months. The subjects from the intervention group increased their speed with 0.3 s after 3 (P = 0.05) and 8 months (P = 0.02), respectively, when measured with the slalom-test. They also improved their speed and agility according to the hurdle-test after 3 months with 0.8 s (P = 0.000) and 8 months with 0.6 s (P = 0.01). Furthermore, they increased flexion–extension of the thoracic spine with 7.5° after 3 months (P = 0.05) and with 9°° after 8 months (P = 0.03) and lateral flexion of the spine with 0.04 m (P = 0.005) and 0.03 m (P = 0.02) after 3 and 8 months, respectively. The reference group was impaired or unchanged in the studied parameters after both 3 and 8 months. We conclude that dance training has a positive effect on speed and agility and on joint mobility and muscle flexibility in flexion–extension and lateral flexion of the spine in young cross-country skiers.