Acute responses to structured aerobic and resistance exercise in women with gestational diabetes mellitus.

Research on the acute responses to exercise in pregnancy is scarce, especially for women affected by gestational diabetes mellitus (GDM). The aim of this study was to investigate responses to a single bout of exercise performed multiple times throughout the pregnancy in women diagnosed with GDM. Data from 18 pregnant women (aged: 32.8 ± 3.8) diagnosed with GDM, treated with diet only, were analyzed. Participants' pre-pregnancy body mass index was 24.4 ± 4.9 kg/m2 , 50% of them were nulliparous, and 50% of the sample regularly exercised before the pregnancy. The exercise intervention consisted of an individual structured aerobic and resistance exercise program performed twice per week from the time of diagnosis until at least the 36th week of pregnancy. The exercise program included 20 minutes of aerobic exercise, 20-25 minutes of resistance exercise, and 10 minutes of cool down. Maternal heart rate, systolic and diastolic blood pressure, temperature and fetal heart rate were measured at every exercise session, along with blood glucose on 3 occasions. In total, 365 exercise sessions were analyzed (85 in the second trimester and 280 in the third trimester), on average 20.3 ± 7.7 per participant. Heart rate and fetal heart rate were elevated during both the aerobic and resistance parts of the exercise session (P < .01) in comparison with the baseline while systolic and diastolic blood pressure did not change in the total sample. There was a slight elevation in tympanic membrane temperature during the aerobic part of the session (P < .01). All parameters returned to baseline levels by the end of the session. Glucose levels dropped from the baseline, from 4.7 ± 0.6 to 3.9 ± 0.4 mmol/L (P < .01). There were no differences in responses to exercise between the second and third trimesters, nor between pre-pregnancy exercisers and non-exercisers. The combination of aerobic and resistance exercise for women diagnosed with GDM does not have harmful short-term effects if performed according to guidelines. Likewise, exercise can be considered useful for controlling hyperglycemia in pregnancy for women affected by GDM.

Markers of bone metabolism during 14 days of bed rest in young and older men.

OBJECTIVE: We aimed at comparing markers of bone metabolism during unloading in young and older men, and to assess countermeasure effectiveness. METHODS: 16 older (60±2 years) and 8 younger men (23±3 years) underwent bed rest (BR) for 14 days. A subgroup of the Older performed cognitive training during BR and supplemented protein and potassium bicarbonate afterwards. Biochemical markers of bone and calcium/phosphate metabolism were assessed. RESULTS: At baseline urinary NTX and CTX were greater in younger than in older subjects (P<0.001), but increased during BR (P<0.001) by a similar amount (P>0.17). P1NP was greater in young than in older subjects (P<0.001) and decreased during BR in the Young (P<0.001). Sclerostin increased during BR across groups (P=0.016). No systematic effects of the countermeasure were observed. CONCLUSION: In men, older age did not affect control of bone metabolism, but bone turnover was reduced. During BR formation markers were reduced only in younger men whereas resorption markers increased to a comparable extent. Thus, we assume that older men are not at an elevated, and possibly even at a reduced risk to lose bone when immobilized.

Single muscle fibre contractile properties differ between body-builders, power athletes and control subjects.

NEW FINDINGS: What is the central question of this study? Do the contractile properties of single muscle fibres differ between body-builders, power athletes and control subjects? What is the main finding and its importance? Peak power normalized for muscle fibre volume in power athletes is higher than in control subjects. Compared with control subjects, maximal isometric tension (normalized for muscle fibre cross-sectional area) is lower in body-builders. Although this difference may be caused in part by an apparent negative effect of hypertrophy, these results indicate that the training history of power athletes may increase muscle fibre quality, whereas body-building may be detrimental. We compared muscle fibre contractile properties of biopsies taken from the vastus lateralis of 12 body-builders (BBs; low- to moderate-intensity high-volume resistance training), six power athletes (PAs; high-intensity, low-volume combined with aerobic training) and 14 control subjects (Cs). Maximal isotonic contractions were performed in single muscle fibres, typed with SDS-PAGE. Fibre cross-sectional area was 67 and 88% (P < 0.01) larger in BBs than in PAs and Cs, respectively, with no significant difference in fibre cross-sectional area between PAs and Cs. Fibres of BBs and PAs developed a higher maximal isometric tension (32 and 50%, respectively, P < 0.01) than those of Cs. The specific tension of BB fibres was 62 and 41% lower than that of PA and C fibres (P < 0.05), respectively. Irrespective of fibre type, the peak power (PP) of PA fibres was 58% higher than that of BB fibres (P < 0.05), whereas BB fibres, despite considerable hypertrophy, had similar PP to the C fibres. This work suggests that high-intensity, low-volume resistance training with aerobic exercise improves PP, while low- to moderate-intensity high-volume resistance training does not affect PP and results in a reduction in specific tension. We postulate that the decrease in specific tension is caused by differences in myofibrillar density and/or post-translational modifications of contractile proteins.

Increased fatigability of the gastrocnemius medialis muscle in individuals with intermittent claudication.

BACKGROUND: We attempted to identify possible differences in the contractility of the gastrocnemius medialis (GM) muscle between healthy controls and individuals with peripheral arterial disease (PAD) and intermittent lower-limb claudication. METHODS: The GM muscles of 17 PAD patients and 17 healthy controls were examined with tensiomyography. Single or multiple electrical impulses were used to trigger muscle contractions, and the time and amplitude of contractions were measured. RESULTS: After single-impulse stimulation, the GM muscles of PAD patients showed significantly shorter contraction times (P < 0.001) than the GM muscles of controls. During 1 min of repetitive electrical stimulation, the contraction velocity of the controls' GM muscles typically showed a sustained increase throughout the stimulation period, whereas in PAD patients, a significant decrease in contraction velocity was observed after 30 s. The onset of muscle fatigue was unrelated to the ankle brachial index (ABI) of the examined leg. When the legs of PAD patients with higher and lower ABIs were compared to each other, no significant differences were found regarding the time and amplitude of contraction after single-impulse stimulation. CONCLUSIONS: The GM muscles of individuals with intermittent claudication contract more quickly and fatigue earlier than the GM muscles of healthy controls. Because the contraction time, measured with tensiomyography, reflects the individual's muscle fibre composition, our findings may reflect a shift from type I fibres to type II fibres in the GM muscles of PAD patients. Our data support the idea that calf myopathy is present in claudication-prone patients and, in part, determines the clinical manifestations of PAD.