The impact of different step rate threshold methods on physical activity intensity in older adults

BackgroundOlder adults benefit most from engaging in higher-intensity physical activity, which is often determined using step rate thresholds. Fixed step rate thresholds that correspond to moderate (MPA) and vigorous-intensity physical activity (VPA) have been developed for heuristic activity promotion. The activPAL monitor uses step rate thresholds to determine activity intensity. Stepping thresholds may also vary based on body mass index (BMI) or aerobic fitness level in older adults. Despite the various thresholds used in the literature, it is unclear whether they produce similar outcomes.Research QuestionHow does time spent in physical activity intensities compare between different step rate thresholds in older adults?MethodsThirty-eight participants (24♀; 67 ± 4 years; BMI: 26.6 ± 4.4 kg/m²) wore an activPAL monitor 24-hr/day for up to 7-d (total: 205-d). Aerobic fitness (V̇O₂max: 23 ± 8 ml/kg/min) was determined via indirect calorimetry during a maximal, graded cycling test. Time spent in each intensity category (light-physical-activity [LPA], MPA, VPA) was determined using the fixed (MPA/VPA) 100/130, 110/130, and activPAL step rate thresholds (74/212), as well as BMI-adjusted absolute (108.5 ± 2.5/134.0 ± 4.8) and BMI-adjusted relative (40%/60% V̇O₂max; 111.4 ± 14.7/132.0 ± 19.0) cut-offs. Times spent in each intensity category were compared between methods.ResultsThe activPAL and 100/130 thresholds yielded less LPA and more MPA than all other methods. The activPAL had no time spent in VPA at all. The BMI-adjusted absolute and relative thresholds produced statistically equivalent time in LPA and MPA (via equivalence testing), but not VPA. No two methods yielded similar time spent in LPA, MPA, or VPA.SignificanceThe choice of step rate threshold has a major impact on physical activity intensity outcomes in older adults. Inherently, strategies that adjust for older adults’ body size and/or aerobic fitness level provide a more individualized data processing strategy than fixed thresholds that assume the same threshold for all older adults     

CROSSOVER COMPARISON BETWEEN THE DEPRESSOR EFFECTS OF LOW AND HIGH WORK-RATE EXERCISE IN MILD HYPERTENSION

1. The relationship between work-rate and the antihypertensive effect of exercise in hypertensives, and the mechanism of that effect, were investigated by a crossover clinical trial. 2. Ten mild hypertensives were randomly divided into two groups. One group performed low work-rate exercise (LWE) on a cycle ergometer for 10 weeks (blood lactate threshold; ～50% of maximum oxygen consumption [V?_O2max]). After a 10 week interval without exercise training, these subjects were then switched to a high work-rate exercise (HWE) regimen (4 mmol/ L of blood lactate; ～75% of V?_O2max) for another 10 weeks. In the other group, the order of exercise training was reversed. Since two patients withdrew from the protocol during HWE periods, statistical analysis was performed on the data from the remaining eight patients. There were no order effects observed in any of the data from the two groups. 3. During both LWE and HWE, resting blood pressure (BP) fell significantly after the initiation of exercise therapy (P<0.05). Furthermore, the overall effects of 10 weeks of LWE and HWE on BP were not significantly different. 4. The work-rate at the lactate threshold, which reflects physical fitness, had increased significantly by 16 W (P<0.01) after the LWE period and by 11 W (P<0.01) after the HWE. 5. During the LWE period, changes in haemodynamic and humoral variables were not significant, except for a reduction in plasma norepinephrine at week 10 (P<0.05). In the HWE period, changes in haemodynamic and humoral variables were not significant. 6. Based on these findings, LWE is recommended for mild hypertensives because of its safety.     

Influence of age on faecal carriage of P-fimbriated Escherichia coli and other gram-negative bacteria in hospitalized neonates

The aerobic faecal flora of 953 infants aged over 5 days was studied on discharge from 22 neonatal wards in Swedish hospitals. Klebsiella/enterobacter was isolated from 74% of infants and dominated the aerobic gram-negative flora in 19 wards. Escherichia coli was carried by 42% and showed a slight dominance in two wards. Initially klebsiella/enterobacter dominated the flora but became increasingly mixed with and taken over by E. coli, carriage increasing from 21% in infants discharged after 5-7 days to 57% after 3 weeks or later. Among infants with E. coli, P-fimbriated strains were demonstrated in 23% (range 0-67) and were independent of age. Occasional clustering of such strains was observed in 3/22 wards during the study period. It is postulated that the general and local colonization patterns observed reflect differences between individual strains of E. coli and klebsiella in both their capacity for transmission and their persistence in the newborn gut. The role of P-fimbriae in intestinal colonization of neonates by E. coli was, however, not supported.     

HEPATIC ZONATION OF CARBOHYDRATE METABOLISM

Periportal cells synthesize twice as much glucose from lactate than do cells from the perivenous zone.     

Role of glycolysis in the genesis of early postocclusion arrhythmias

Antiarrhythmic effects of phosphorylated glycolysis intermediates glucose-1-phosphate, fructose-1,6-diphosphate, and phosphoenolpyruvate in early postocclusion arrhythmias are shown in rat experiments; in contrast to these, D-glucose, sodium pyruvate, and monoiodacetate, a glycolysis inhibitor, exert no appreciable antiarrhythmic effect. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 6, pp. 625–626, June, 1994 Presented by P. V. Sergeev, Member of the Russian Academy of Medical Sciences.     

血卟啉衍生物对癌细胞钠泵活性和糖酵解的光动力效应

血卟啉衍生物(YHpD)合并照光对S180瘤细胞摄取~(86)Rb,瘤细胞的钠泵活性及糖酵解具有明显的抑制作用,且抑制程度随YHpD剂量的增大而增强。瘤细胞的总ATP酶和(Na-K)-ATP酶活性对YHpD的光动力效应也较敏感.YHpD对Mg—ATP酶活性有轻度抑制作用。YHpD并用哇巴因,对瘤细胞摄取~(86)Rb的光动力效应比两种药物单独应用的抑制作用大。     

Skeletal Muscle Adaptations to Physical Training in Type II (Non-insulin-dependent) Diabetes Mellitus

Seven middle-aged men with manifest type II diabetes mellitus underwent an endurance training programme for 10–15 weeks. The maximal aerobic capacity, as well as the endurance capacity, was improved by 10% (p<0.05). The intramuscular glycogen store increased by more than 80% (p<0.05) from 350 μmol/g dw (dry weight), and the activities of citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase increased by more than 50% (p<0.05) and 30% (p<0.05). The activity of glycogen synthase was decreased by approximately 20% (p<0.05), whereas lactate dehydrogenase remained unchanged. Capillaries/fibre and fibre area increased by more than 50% (p<0.05) and 30% (p<0.05) leaving the area of supply constant. Training did not influence fasting blood lipids and glucose, glycosylated hemoglobin, oral glucose tolerance, and insulin response to an oral glucose load measured 72 hours post-exercise. It is concluded that patients with manifest type II diabetes, as normoglycaemic individuals, adapt to physical training. However, no persistent effect on glucohomeostasis and lipaemia is produced by short-term training in the diabetic patients.     

Differential titin isoform expression in human skeletal muscle

Mammalian skeletal muscle expresses at least two isoforms of the cytoskeletal protein titin (connectin; MW ≈ 3000 kDa). These isoforms are associated with different passive force curves, and thus may affect physical performance. To study the distribution of titin and its possible influence on performance in humans, muscle biopsies were obtained from 15 males (X ± SE; age = 25.4 ± 2.9 years, height = 177.7 ± 1.8 cm, weight = 76.5 ± 2.2 kg). Two biopsies were obtained on separate occasions from both the right and left vastus lateralis, and one biopsy each from the lateral head of the right gastrocnemius and the right soleus, with all biopsies handled identically. Fibre type analyses were performed via mATPase histochemistry. Expression of titin and myosin heavy chain isoforms were determined by SDS-PAGE. Titin bands in the resulting gels were highly repeatable and were verified by migration patterns, as well as Western blot analysis. Two groups of subjects were identified: group 1 (n=10) expressed only one titin isoform (titin-1) in all biopsies, and group 2 (n=5) expressed two titin isoforms (titin-1 and titin-2) in all biopsies. No significant differences (P> 0.05) between groups were observed for percentage fibre types, percentage fibre type areas, fibre type cross-sectional areas, and percentage myosin heavy chain expression when comparing individual muscles, sampling times or bilateral comparisons. This is the first report of differential titin isoform expression in healthy, mature human skeletal muscle, but it is not clear why this occurs or what influence this may have on performance.     

不同强度运动对女子游泳运动员性激素水平的影响及特点

本研究以放兔分析法观察不同强度运动前后19名女子游泳运动员血清促卵泡激素(FSH)、黄体生成素(LH)、雌二醇(E_2)、孕酮(P)、睾酮(T)及胰岛素(Ins)的变化。受试者在卵泡及黄体两期分别进行短时间高强度间歇运动——6×50m全速力竭性游泳和长时间持续运动——1000m全速力竭性游泳。在运动前5分钟及运动后即刻分别采集静脉血测定各种激素含量。主要结果如下:受试者从事6×50m最大速度间歇游泳后,卵泡期各种激素浓度的变化均显著高于运动前安静状态,黄体期变化不一,FSH、LH降低,E_2、P、T及Ins升高。从事1000m全速游泳后,激素变化表现为卵泡期FSH、LH、E_2、P均升高,T及Ins降低;黄体期E_2、P、T升高,Ins降低,FSH、LH无显著变化,两期相比黄体期运动成绩优于卵泡期。上述结果提示:①受试者月经周期的黄体期机体有氧能力强于卵泡期,运动能力的增强与黄体期E_2、P、T水平升高有关。②FSH、LH与E_2、P分泌变化并非同步一致,说明运动中E_2升高并非受制于促性腺激素,而主要是卵巢分泌量升高所致。③运动中E_2、P、T具有协同效应,可抵抗疲劳,提高人体运动能力。