Capillary Leveling of Freestanding Liquid Nanofilms.

We report on the capillary-driven leveling of a topographical perturbation at the surface of a freestanding liquid nanofilm. The width of a stepped surface profile is found to evolve as the square root of time. The hydrodynamic model is in excellent agreement with the experimental data. In addition to exhibiting an analogy with diffusive processes, this novel system serves as a precise nanoprobe for the rheology of liquids at interfaces in a configuration that avoids substrate effects.

Influence of muscle strength and total work on exercise-induced plasma growth hormone isoforms in women.

The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on human growth hormone (GH) variants to a heavy resistance exercise protocol in untrained women. From a distribution of 100 healthy, untrained women, the strongest 10 women (S) and the weakest 10 women (W) were compared for GH responses pre- and post an acute heavy resistance exercise test (AHRET, 6 sets of 10 RM squats, 2 minutes rest between sets). Blood samples were obtained pre-exercise and immediately post-exercise and subsequently analysed in total as well as fractionated by Sephacryl S-100R column chromatography into three molecular weight size classes: fraction A: > 60 kD, fraction B: 30-60 kD, fraction C: < 30 kD. For each total sample as well as each fraction, immunoreactive GH was measured via the Nichols IRMA, while bioactive GH was measured via the hypox rat tibial line bioassay and Diagnostic Systems Laboratory's immunofunctional GH ELISA. No exercise-induced changes or differences between groups were observed in the tibial line bioassay. However, the S group displayed a significantly higher pre-exercise resting value in the total fraction than the W group. Conversely, the W group exhibited a significantly higher pre-exercise value in the smaller molecular weight fraction C. With regards to the immunofunctional and immunoreactive assays, the total fraction, fraction A, and fraction B demonstrated significant (P < or = 0.05) exercise-induced increases in both the S and W group despite no group differences. For the Nichols and immunofunctional assays significant exercise-induced changes were observed in the smaller molecular weight C fraction in the W group but not the S group. However, the S group displayed a significantly higher pre-exercise value in fraction C relative to the W group. These data demonstrate for the first time that differences exist in the GH molecular weight variants between strong and weak untrained women, with the lower molecular weight variants seemingly less responsive to greater amounts of exercise in stronger women, thus suggesting differential regulation of GH molecular weight variants during resistance exercise due to pre-existing physical parameters.

Strength, workload, anaerobic intensity and the immune response to resistance exercise in women.

AIM: The mechanism linking exercise intensity to the magnitude of the immune response is not completely understood. The purpose of this investigation was to determine whether the immune response to resistance exercise was associated with (1) changes in workload or (2) anaerobic exercise intensity. METHODS: Previously untrained women underwent 6 months of resistance training for lower and upper body (TOTAL, n = 34) or for upper body alone (UPPER, n = 30). Lymphocyte subsets [T (CD3+), CD4+, CD8+, NK and B], functional markers (CD45RA+ and CD45RO+), and mitogen (phytohemagglutinin-M, concanavalin A and pokeweed mitogen) and superantigen (staphylococcus a. cowans)-stimulated proliferation were measured from blood samples collected pre- and post-exercise for a squat resistance exercise consisting of six sets of 10 repetitions at 75% of one repetition maximum. This protocol was performed before (T0) and after 3 (T3) and 6 months (T6) of training. RESULTS: Lymphocyte recruitment to the circulation and proliferation following resistance exercise did not differ between training groups at any time, although the TOTAL group performed at a higher workload as training progressed. With respect to anaerobic intensity, exercise-induced increases in NK, CD4+, CD8+ and B lymphocyte concentrations were 42 (P = 0.07), 76 (P < 0.05), 72 (P < 0.05) and 242% (P < 0.01) greater in women in the highest compared with the lowest post-exercise lactate quartiles. Lymphocyte proliferation did not differ between lactate quartiles. CONCLUSIONS: Anaerobic intensity, rather than increased strength and workload, is associated with the number of lymphocytes recruited to the circulation, but not T and B cell proliferation responses.

The relationship of natural killer cell counts, perforin mRNA and CD2 expression to post-exercise natural killer cell activity in humans.

The aim of this study was to further investigate the mechanism of suppression of natural killer (NK) cell cytotoxic activity in peripheral blood following strenuous exercise. Blood was collected for analysis of NK cell concentration, cytotoxic activity, CD2 surface expression and perforin gene expression from runners (RUN, n=6) and resting controls (CONTROL, n=4) pre-exercise, 0, 1.5, 5, and 24 h following a 60-min treadmill run at 80% of VO2 peak. Natural killer cytotoxic activity, measured using a whole blood chromium release assay, fluctuated minimally in the CONTROL group and increased by 63% and decreased by 43% 0 and 1.5 h post-exercise, respectively, in the RUN group (group x time, P < 0.001). Lytic index (cytotoxic activity per cell) did not change. Perforin mRNA, measured using quantitative real-time polymerase chain reaction (QRT-PCR) decreased from pre- to post-exercise and remained decreased through 24 h. The decrease from pre- to 0 h post-exercise was seen predominately in the RUN group and was inversely correlated (r=- 0.95) to pre-exercise perforin mRNA. The NK cell surface expression of CD2 (lymphocyte function-associated antigen-2) was determined using fluorescent antibodies and flow cytometry. There was no change in the proportion of NK cells expressing CD2 or CD2 density. We conclude that (1) numerical redistribution accounted for most of the change in NK cytotoxic activity following a strenuous run, (2) decrease in perforin gene expression during the run was inversely related to pre-exercise levels but did not parallel changes in cytotoxic activity, and (3) CD2 surface expression was not affected by exercise.

Differential response of muscle phosphocreatine to creatine supplementation in young and old subjects.

This study compared the effects of short-term creatine supplementation on muscle phosphocreatine, blood and urine creatine levels, and urine creatinine levels in elderly and young subjects. Eight young (24 +/- 1.4 years) and seven old (70 +/- 2.9 years) men ingested creatine (20 g day-1) for 5 days. Baseline muscle phosphocreatine measurements were taken pre- and post-supplementation using nuclear magnetic resonance spectroscopy (NMR). On the first day of supplementation subjects had blood samples taken immediately before and hourly for 5 h following ingestion of 5 g of creatine, and a pharmacokinetic analysis of plasma creatine levels was conducted. Twenty-four hour urine collections were conducted for 2 days prior to the supplementation period and for 5 days during supplementation. Old subjects had significantly higher baseline plasma creatine levels than young subjects (68.5 +/- 12.5 vs. 34.9 +/- 4.7 micromol L-1; P < 0.02). There were no significant differences between groups in plasma creatine pharmacokinetic parameters (i.e. area under the curve, elimination rate constant, absorption rate constant, time to maximum concentration, and maximum concentration) following the 5 g oral creatine bolus. Urine creatine, assessed pre and on 5 days of supplementation, increased (P < 0.001), with no difference between groups. Urine creatinine did not change as a result of creatine supplementation. Young subjects showed a significantly greater increase in muscle phosphocreatine compared with old subjects, and post-supplementation muscle phosphocreatine levels were greater in young subjects (young 27.6 +/- 0.5; old 25.7 +/- 0.8 mmol kg-1 ww) (P=0.02). There were no differences in blood or urine creatine between groups in response to supplementation, but old subjects had a relatively small increase (young 35% vs. old 7%) in muscle phosphocreatine after supplementation.

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work.

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Cytokine production by stimulated mononuclear cells did not change with aging in apparently healthy, well-nourished women.

Aging is often associated with a dysregulation of the immune system. We examined mitogen-stimulated production of interleukin (IL)-2 and proinflammatory cytokines, IL-1beta and IL-6, in apparently healthy and generally well-nourished old versus young women. Subjects were screened for health using the SENIEUR protocol and a panel of laboratory tests for inflammation, as well as for the adequacy of nutritional status using criteria related to undernutrition, and protein, iron, vitamin B(12), and folate status. Young (n=26, age: 20-40 years) and old (n=44, age: 62-88 years) cohorts did not differ on the number of circulating monocytes, granulocytes, B (CD19+) cells, and T (CD3+, CD4+, and CD8+) cells. No differences (P>0.10) were seen between the two age groups in IL-2, IL-1beta and IL-6 levels in whole blood cultures at 48 h after stimulation with PHA (5 mg/l). Furthermore, no age-related differences were noted in the absolute amounts (pg) of IL-1beta and IL-6 after normalizing for circulating monocytes, B cells, or T cells (P>0.10). Similarly, no age-related decline in absolute amount of IL-2 (pg) after normalizing for circulating T cells was noted (P>0.10). Thus, contrary to most previous reports, our results do not support an increase in the production of proinflammatory cytokines IL-1beta and IL-6, and a reduced production of IL-2 with aging when health and nutritional status are maintained. These findings support our previous results of no change in monocyte function and few alterations in acquired immune response in a carefully selected group of healthy and well-nourished elderly women.

Blood leukocyte and glutamine fluctuations after eccentric exercise.

Skeletal muscle, as a producer of glutamine, is important for lymphocytes, monocytes and macrophages. Exercise-induced muscle damage could burden the immune system by concurrently eliciting a local inflammatory response and decreasing glutamine availability. The aim of this study was to determine whether blood leukocyte and glutamine concentrations were affected in individuals with high serum creatine kinase (CK) activity (indirect indication of muscle damage) compared to those with no change in CK. Twelve females performed maximal eccentric resistance exercise using one arm and one leg. Blood leukocyte subsets and glutamine were measured at 24 and 0 h pre-exercise, and post-exercise at intervals up to 9 d post-exercise. Eleven subjects were placed in High (n = 6) and Low CK (n = 5) groups. Lymphocytes, (total, natural killer, and T), monocytes, and granulocytes did not change significantly in either group, at any time. Whole blood glutamine concentration decreased (p < 0.05) from 437 microM pre-exercise to 332 microM 3 d post-exercise in both groups. The decrease in glutamine suggests that the metabolism of the muscle may be affected by this exercise, however, the occurrence of this decrease in both groups suggests that this change was not a response to muscle damage.

Immune function did not decline with aging in apparently healthy, well-nourished women.

Nutrition plays a crucial role in immune function. Most studies on age-associated changes in immunocompetence in healthy adults did not examine the nutritional status of participants extensively. Inadequate nutritional status may confound the relationship of aging and immune response. The purpose of this study was to examine age-related changes in parameters of acquired and innate immunity in healthy and generally well-nourished older (62-88 years) versus younger (20-40 years) women. Subjects were screened for participation using the health criteria of the SENIEUR protocol as well as a number of nutrition criteria related to undernutrition, and protein, iron, vitamin B12, and folate status. Young and old women did not differ in total T (CD3+), T-helper (CD4+), or T-cytotoxic (CD8+) cell number. However, older women tended to have lower T-cell proliferation response to concanavalin A (P < 0.10) and significantly reduced response to phytohemagglutinin (P < 0.05). No age-related changes were noted in natural killer cell number or cytotoxicity. Phagocytosis and subsequent oxidative burst activity also did not differ between young and old women. Most immune parameters were not compromised with aging in this cohort of apparently healthy, well-nourished women. These findings highlight the importance of simultaneous examination of health and nutritional status in studies of immune function with aging.

Leukocyte adhesion molecule expression during intense resistance exercise.

We hypothesized that expression of L-selectin and very late antigen-4 (VLA-4) integrin adhesion molecules would influence cell type-specific redistribution during exercise. Women subjects performed six sets of 10-repetition maximum squats. L-selectin and VLA-4 integrin were measured by using flow cytometry pre- and postexercise on peripheral blood neutrophils and lymphocytes (n = 29 subjects) and lymphocyte subsets (n = 70 subjects), respectively. Neutrophil concentration increased 41.8% (P < 0.001), whereas the percent expressing L-selectin was unchanged (79%). Lymphocyte concentration increased 61.8% (P < 0.001). The percent of T cells expressing L-selectin decreased from 73.5 +/- 8.9 to 68.2 +/- 11.4% (P < 0.001); the combined population of natural killer and B cells expressing L-selectin decreased from 80.4 +/- 22.5 to 62.7 +/- 25.8% (P < 0.001). VLA-4 integrin was expressed by nearly all lymphocytes both pre- and postexercise. The proportional decrease in L-selectin positive cells could have resulted from 1) shedding of L-selectin, 2) selective entry of L-selectin-negative subsets, or 3) selective removal of L-selectin-positive subsets.

Eccentric exercise augments the cardiovascular response to static exercise.

High-force eccentric exercise induces neuromuscular dysfunction and may augment the cardiovascular response to exercise. This investigation sought to determine whether changes in strength and sense of force following high-force eccentric exercise alter heart rate and blood pressure responses during isometric contractions. Subjects (4F,6M) performed 50 maximum resistance eccentric actions with one arm (ECC arm). Contractions at 10% of the ECC arm maximum were held for 7 min on two pre-exercise days. The force output perceived to be the same as 10% of the pre-exercise maximum was determined using a force matching task. This force, 35.6, 27.2, and 21.1% lower on days 1, 3, and 5 post-exercise, was held during isometric contractions on these days, respectively. Despite a lowering of absolute contraction force, heart rate (P < 0.05) and blood pressure (P < 0.001) responses during contractions using the ECC arm were consistently elevated relative to the control arm. However, subjects perceived that they were exerting forces similar to those achieved before eccentric exercise-induced neuromuscular dysfunction. These findings suggest that perceived effort following strength loss induced by mechanically stressful exercise dictates the cardiovascular responses during isometric contractions.

Neuromuscular control following maximal eccentric exercise.

Kinematic and electromyographic (EMG) analysis of a target-directed, maximal velocity movement was used to investigate the effects of high-force eccentric exercise on the neuromuscular control of elbow flexion. Ten non-weight-trained females [19.6 (1.6) years old] performed 50 maximal velocity elbow flexion movements from 0 to 1.58 rad (90 degrees), as rapidly as possible in response to a light stimulus, while kinematic and triphasic EMG parameters were measured. This was done three times pre-exercise, immediately and 1, 2, 3, 4, and 5 days following the 50 maximal eccentric elbow flexion actions. The eccentric exercise caused lengthening of kinematic parameters including total movement time and time to peak velocity. The EMG elements of the biceps brachii (b.) motor time, time to peak EMG, biceps b. burst duration, and the latency period between biceps b. and triceps b. bursts were lengthened post-exercise. These changes persisted for up to 5 days post-exercise. The exercise also caused a large increase in serum creatine kinase (CK) activity. It was concluded that high-force eccentric exercise in this population caused prolonged changes in neuromuscular control that were a function of exercise-induced disruption of the skeletal muscle. Compensation in the central motor program was such that the components of the triphasic EMG pattern were systematically lengthened.

Exercise-induced muscle pain, soreness, and cramps.

The three types of pain related to exercise are 1) pain experienced during or immediately following exercise, 2) delayed onset muscle soreness, and 3) pain induced by muscle cramps. Each is characterized by a different time course and different etiology. Pain perceived during exercise is considered to result from a combination of factors including acids, ions, proteins, and hormones. Although it is commonly believed that lactic acid is responsible for this pain, evidence suggests that it is not the only factor. However, no single factor has ever been identified. Delayed onset muscle soreness develops 24-48 hours after strenuous exercise biased toward eccentric (muscle lengthening) muscle actions or strenuous endurance events like a marathon. Soreness is accompanied by a prolonged strength loss, a reduced range of motion, and elevated levels of creatine kinase in the blood. These are taken as indirect indicators of muscle damage, and biopsy analysis has documented damage to the contractile elements. The exact cause of the soreness response is not known but thought to involve an inflammatory reaction to the damage. Muscle cramps are sudden, intense, electrically active contractions elicited by motor neuron hyperexcitability. Although it is commonly assumed that cramps during exercise are the result of fluid electrolyte imbalance induced by sweating, two studies have not supported this. Moreover, participants in occupations that require chronic use of a muscle but do not elicit profuse sweating, such as musicians, often experience cramps. Fluid electrolyte imbalance may cause cramps if there is profuse prolonged sweating such as that found in working in a hot environment. Thus, despite the common occurrence of pain associated with exercise, the exact cause of these pains remains a mystery.

Muscle function at the wrist following 9 d of immobilization and suspension.

The purpose of this study was to evaluate the effects of 9 d of immobilization and partial suspension on muscle function at the wrist. Twelve female subjects (19-27 yr) wore a cast suspended from the neck by a sling that immobilized muscles acting on the wrist. Atrophy, muscle damage indicators, isometric and isokinetic strength, reaction time, speed of movement, and fatigability were assessed. Forearm muscle cross-sectional area decreased by 4.1% following immobilization and suspension. There was no indication that significant muscle degeneration occurred during immobilization or when muscles resumed normal function. Isometric strength for flexion and extension decreased by 29.3 and 32.5%, respectively. Concentric strength decrements for flexion, extension, pronation, and supination ranged from 8.9-21.7% at 2.11 and 3.16 rad.s-1. Eccentric strength decrements at 2.11 rad.s-1 for the same movements ranged from 12.5-18.5%. Fatigability was unaffected. Greater relative strength losses compared to decreased muscle cross-sectional area may be the result of a decrease in contractile protein density or unidentified neural factors following immobilization and partial suspension. However, neuromuscular control of reaction time was not affected.

Creatine kinase isoenzyme MB may be elevated in healthy young women after submaximal eccentric exercise.

Elevations in serum creatine kinase isoenzyme MB (CK MB) after exercise may be of clinical importance for the diagnosis of myocardial infarction. However, CK MB has been observed to increase after exercise in highly trained endurance runners. No data exist relating to the effect of exercise in a heterogeneous female population with regard to CK MB. The purpose of the present investigation was to determine whether an elevation in serum CK MB can be measured in women (heterogeneous for aerobic capacity, estradiol, and lean body mass) and to make a preliminary analysis of the relationships of postexercise serum CK MB concentration and CK activity, estradiol, lean body mass, and peak oxygen consumption. Lean body mass and peak oxygen consumption were measured for 15 college-age women (19 to 29 years) after the performance of a stepping exercise for 40 minutes at 70% of peak oxygen consumption to elicit the efflux of intramuscular enzymes. Serum CK MB concentration, CK activity, and estradiol level were measured before exercise and 24 and 48 hours after exercise. Serum estradiol level was also measured immediately after exercise. Four of the 15 subjects had elevations in CK MB concentrations ranging from 18.4 to 101.2 micrograms/L, many times the upper normal limit (4.7 micrograms/L). All subjects with high serum CK MB concentrations had high CK activity, and the two measures were significantly related (p < 0.01) in the postexercise period. It was concluded that exercise can cause large elevations in serum CK MB in some women.(ABSTRACT TRUNCATED AT 250 WORDS)