CON Subjects Research Articles

Effects of an 8-month Yoga Intervention on Bone Markers and Muscle Strength in Premenopausal Women

Although the beneficial effects of Yoga in increasing psychological well-being and decreasing stress and reducing cardiovascular risks have been reported, no randomized controlled studies to date have investigated its effects on bone metabolic markers. PURPOSE: To examine the effects of an 8-month Yoga exercise program on bone biomarkers and muscle strength in premenopausal women (35 to 50 years). METHODS: Thirty-four women were randomly assigned either to a Yoga group (YE, n=16) or a control group (CON, n=18). Subjects in YE group performed 60 minutes of an Ashtanga Yoga series 2 times/week with one day between sessions for 8 months. Each Yoga session consisted of 15 minutes of warm-up exercises, 35 minutes of Ashtanga Yoga postures and 10 minutes of cool-down with relaxation; and the session intensity was progressively increased during the 8 months. CON subjects were encouraged to maintain their normal daily lifestyles monitored by the bone-specific physical activity questionnaire at 2 month intervals for 8 months. Body composition (DXA) and muscle strength (1RM) for leg press (LP), knee extension (KE), knee flexion (KF), lat pull down (LP), shoulder press (SP), and biceps curl (BC) were measured. Bone formation (Bone Alkaline Phosphatase, Bone ALP) and bone resorption (Tartrate-Resistant Acid Phosphatase, TRAP5b) markers were assessed at baseline and after the intervention. RESULTS: At baseline, there were no group differences in body composition, or strength variables (p>0.05) except for SP (p<0.05, YE<CON). YE group significantly (p<0.01) improved LP compared to CON (11.35% vs. -6.54%). A significant group x time interaction was observed for Bone ALP (p<0.01) with YE exhibiting greater increases than CON (9.05% vs. -7.11%).There were no significant (p>0.05) effects for serum TRAP5b concentrations after 8 months. CONCLUSIONS: Eight months of Ashtanga Yoga training was beneficial for increasing bone formation and for improving leg press strength in premenopausal women.

Low‐volume resistance exercise attenuates the decline in strength and muscle mass associated with immobilization

We determined the effectiveness of low-volume resistance exercise (EX) for the attenuation of loss of muscle mass and strength during leg immobilization. Men (N = 5) and women (N = 12, age 24 ± 5 years, body mass index 25.4 ± 3.6 kg/m(2)) were divided into two groups: exercise (EX; n = 12) and control (CON; n = 5). Subjects wore a knee brace on one leg that prevented weight bearing for 14 days. Resistance exercise (EX; 80% of maximal) was performed by the immobilized limb every other day. Immobilization induced a significant reduction (P < 0.05) in muscle fiber and thigh cross-sectional area (CSA), isometric knee extensor, and plantarflexor strength in the CON (P < 0.01) but not in the EX group. There were significant losses in triceps surae CSA in the CON and EX groups (P < 0.05), but the losses were greater in CON subjects (P < 0.01). A minimal volume (140 contractions in 14 days) of resistive exercise is an effective countermeasure against immobilization-induced atrophy of the quadriceps femoris but is only partially effective for the triceps surae.

The effect of menthol application to the skin on sweating rate response during exercise in swimmers and controls

We tested the hypothesis that menthol application would reduce the magnitude and initiation of sweating via excitation of cold-sensitive afferent pathways and concurrently via a cross-inhibition of heat loss pathways in acclimatized (swimmers, SW) and non acclimatized (control, CON) subjects in cool water. It was expected this effect to be exaggerated in SW subjects. Eight SW and eight CON subjects cycled at 60% of their VO(2)max, as long as to reach 38 degrees C in rectal temperature (Tre), without or with (4.6 g per 100 ml of water) all-body application of menthol sediment. Heart rate (HR), Tre, sweating rate (SwR), the proximal-distal skin temperature gradient (TSk(f-f)), and oxygen consumption (VO(2)) were measured continuously. VO(2) and HR were similar between groups and conditions. Menthol increased TSk(f-f), Tre threshold for SwR [+0.32 (0.01) degrees C] and Tre gain, while menthol reduced exercise time by 8.1 (4.1) min. SW group showed higher changes in Tre threshold for SwR [+0.50 (0.01) degrees C for SW vs. +0.13 (0.03) degrees C for CON], higher Tre gain, lower time for Tre increase and shorter exercise time [-10.7 (7) min for SW vs. -4.9 (4) min for CON] in menthol condition. Upon exercise initiation, previously applied menthol on the skin seems to induce vasoconstriction, results in a delayed sweating, which in turn affects the rectal temperature. Acclimatized subjects showed higher delay in SwR and earlier rise in Tre, which most probably is due to the inter-group differences in cold receptors activity.

BOLD Response During Spatial Working Memory in Youth With Heavy Prenatal Alcohol Exposure

Prenatal alcohol exposure has been consistently linked to neurocognitive deficits and structural brain abnormalities in affected individuals. Structural brain abnormalities observed in regions supporting spatial working memory (SWM) may contribute to observed deficits in visuospatial functioning in youth with fetal alcohol spectrum disorders (FASDs). We used functional magnetic resonance imaging (fMRI) to assess the blood oxygen level dependent (BOLD) response in alcohol-exposed individuals during a SWM task. There were 22 young subjects (aged 10-18 years) with documented histories of heavy prenatal alcohol exposure (ALC, n = 10), and age- and sex-matched controls (CON, n = 12). Subjects performed a SWM task during fMRI that alternated between 2-back location matching (SWM) and simple attention (vigilance) conditions. Groups did not differ on task accuracy or reaction time to the SWM condition, although CON subjects had faster reaction times during the vigilance condition (617 millisecond vs. 684 millisecond, p = 0.03). Both groups showed similar overall patterns of activation to the SWM condition in expected regions encompassing bilateral dorsolateral prefrontal lobes and parietal areas. However, ALC subjects showed greater BOLD response to the demands of the SWM relative to the vigilance condition in frontal, insular, superior, and middle temporal, occipital, and subcortical regions. CON youth evidenced less increased brain activation to the SWM relative to the vigilance task in these areas (p < 0.05, clusters > 1,664 microl). These differences remained significant after including Full Scale IQ as a covariate. Similar qualitative results were obtained after subjects taking stimulant medication were excluded from the analysis. In the context of equivalent performance to a SWM task, the current results suggest that widespread increases in BOLD response in youth with FASDs could either indicate decreased efficiency of relevant brain networks, or serve as a compensatory mechanism for deficiency at neural and/or cognitive levels. In context of existing fMRI evidence of heightened prefrontal activation in response to verbal working memory and inhibition demands, the present findings may indicate that frontal structures are taxed to a greater degree during cognitive demands in individuals with FASDs.

Effects of Maximal Static Apnea on Antioxidant Defenses in Trained Free Divers

To investigate the effects of maximal static apnea on plasma antioxidant status, oxidative stress, and antioxidant enzyme activities in trained free divers. Blood was taken from apnea-trained (Tr) and control (Con) subjects at baseline (B) and after one (A1), three (A3), and five (A5) apneas. Trolox equivalent antioxidant capacity (TEAC), ferric reducing ability of plasma (FRAP), uric acid, and bilirubin assays assessed plasma antioxidant status and malondialdehyde (MDA) quantified the oxidative stress response. The activities of erythrocyte antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were determined at baseline and after the fifth apnea. TEAC was significantly higher in divers versus controls after A1 (P < 0.05). A group effect of SOD activity indicated higher activity throughout the protocol in Tr (mean +/- SD; Con, 43.2 +/- 10.1 U.g Hb; Tr, 50.1 +/- 7.3 U.g Hb; P = 0.04). With no other group differences, the groups' data were combined. Apnea significantly increased SOD (B, 44.1 +/- 11.1 U.g Hb; A5, 48.1 +/- 7.5 U.g Hb; P < 0.05) and GPx activity (B, 60.5 +/- 14.9 U.g Hb; A5, 70.1 +/- 16.0 U.g Hb; P = 0.02); however, CAT activity decreased (B, 5.25 +/- 0.59 U.mg Hb; A5, 5.00 +/- 0.53 U.mg Hb; P = 0.03). MDA was unaffected by apnea (P = 0.32). Trained free divers have increased SOD activity during apnea; however, there is little difference in their antioxidant and oxidative stress responses compared with controls. In both groups, acute changes in antioxidant enzyme activities suggest that they may protect from excessive antioxidant depletion and oxidative stress during apnea.

Supine LBNP Exercise Maintains Exercise Capacity in Male Twins during 30-d Bed Rest

Exercise capacity is reduced after both short- and long-duration exposures to microgravity. Previously, we have documented that supine treadmill exercise within lower-body negative pressure (LBNP(ex)) maintains upright exercise responses in men after 5 and 15 d of bed rest, as a simulation of microgravity. The purpose of this study was to determine whether LBNP(ex) would protect against loss of upright exercise capacity (VO2peak) and sprint performance during a longer-duration bed rest. Eight sets of male twins participated in 30 d of bed rest. Within each twin pair, one was randomly assigned to a control group (CON) who performed no exercise, and the other was assigned to an exercise group (EX) that performed a 40-min interval (40-80% pre-bed rest VO2peak) LBNP(ex) (55 +/- 4 mm Hg) protocol, plus 5 min of resting LBNP, 6 d.wk(-1). LBNP produced footward force equivalent to 1.0-1.2 body weight. Before and after bed rest, subjects completed an upright graded exercise test to volitional fatigue and a sprint test of 30.5 m. After bed rest, VO2peak was decreased significantly in the CON subjects (-23 +/- 4%, P < 0.01) but was maintained in the EX subjects (-3 +/- 3%). Sprint time was increased in the CON subjects (24 +/- 8%, P < 0.05) but was maintained in the EX group (8 +/- 2%). This exercise countermeasure protocol may help prevent microgravity-induced deconditioning during long-duration space flight.

Vascular abnormalities in primary amyloidosis

Primary amyloidosis (AL) is a systemic disease; however, there is limited information regarding the presence and character of vascular abnormalities. Validated ultrasound techniques were used to prospectively determine carotid artery intimal-medial thickness (IMT) and brachial artery flow-mediated dilatation (FMD) in 59 consecutive AL patients and 17 age-similar, healthy, asymptomatic volunteers (CON). Carotid IMT was increased in AL when compared with CON (0.07 +/- 0.02 vs. 0.04 +/- 0.01 mm, P < 0.01). Similarly, brachial artery FMD was significantly lower in AL when compared with CON subjects (3 +/- 7 vs. 12 +/- 8%, P < 0.01). Multivariable analysis revealed that AL was associated with larger IMT and lower FMD after controlling for several confounding variables. However, within AL cases, there was not a significant association of cardiac vs. non-cardiac involvement with IMT or FMD (P = 0.1 and 0.2, respectively). AL is associated with abnormal vascular morphology and endothelial dysfunction. Vascular abnormalities do not appear to be related to echocardiographic evidence of cardiac involvement.

Nutritional Formula Improved Immune Profiles of Seniors Living in Nursing Homes

To assess whether an experimental nutritional formula (EXP) supports immune function in seniors living in long-term care facilities. Prospective, randomized, double-blind, controlled trial conducted September 2002 through January 2003. North central Florida nursing homes. Subjects aged 65 and older (n = 157). Subjects received 240 mL/d of EXP or standard liquid nutrition (CON) for 4 weeks before and 6 weeks after an influenza vaccination. Influenza vaccine antibody responses, immunophenotyping, lymphocyte activation, cytokines, and clinical measures (fever, number of prescribed antibiotics). Ninety-two subjects (n = 40, CON; n = 52, EXP) completed the study. Geometric mean antibody titers were similar between groups, yet the percentage of subjects with H1N1 antibody titers greater than 100 postvaccination was higher in the EXP group than in the CON group (43% vs 23%, P=.047). Similar trends were found for the percentage of subjects (intent to treat) with fourfold increases against the B/Hong Kong component (64% vs 46%, P = .09) or with H3N2 antibody titers of 40 or more (97% vs 89%, P=.06). EXP subjects had higher levels of influenza-activated lymphocytes (CD69+ and CD25+). Cytokine production after mitogen activation was lower in EXP than CON subjects (interleukin (IL)-6: 20+/-3 vs 29+/-3 ng/mL, P = .045; IL-10: 310+/-60 vs 603+/-140 pg/mL, P = .06). Fewer EXP subjects were treated for fever (5% vs 16%, P = .02) or prescribed antibiotics (7 vs 11 new antibiotics/100 days of study, P = .06). Seniors consuming the EXP formula demonstrated enhanced immune function, indicated by increased influenza vaccine response and lymphocyte activation, less fever, and fewer newly prescribed antibiotics than those consuming a standard ready-to-drink nutritional supplement.

Assessment of muscle shortening and static posture in children with persistent asthma

Asthmatic patients experience an increase in airway resistance that overburdens both respiratory and non-respiratory muscles. The objective of the present study was to determine whether children with persistent asthma present muscle shortening and postural changes. The 60 boys evaluated, aged 7-12 (pubertal ages up to Tanner stage G2) were divided into three age- and BMI-matched groups of equal number: CON (no history of asthma or allergy); MPA (mild persistent asthma); SPA (severe persistent asthma). Pulmonary function, muscle shortening and static posture were evaluated. The SPA group presented higher protraction of the head and shoulder compared with the CON group [9.5 (6.0-12.0) degrees vs 5.5 (0.0-12.0) degrees, P < 0.05; 0.89 (0.80-0.94) anterior/posterior ratio vs 0.94 (0.87-1.1) anterior/posterior ratio, P < 0.01)]. Severe asthmatic patients also presented shortening of arm flexor and posterior muscle of the thigh compared with the CON group [18.0 (10.0-24.0) degrees vs 12.0 (6.0-16.0) degrees, P < 0.05; and 16.5 (10.0-38.5) cm vs 8.0 (0.0-21.0) cm, respectively, P < 0.05]. Chest expansion at axillar and xiphoid levels were limited in SPA subjects compared with CON subjects [3.7 (1.5-6.5) cm vs 5.5 (2.0-8.0) cm and 4.7 (1.5-6.5) vs 6.0 (3.5-8.0) cm, respectively, P < 0.01]. SPA subjects also presented a higher incidence of lumbar spine straightening compared with CON and MPA subjects. Moderate asthmatic subjects presented intermediate values compared with severe and control subjects in five out nine evaluated outcomes. Our data suggest that severe asthmatic children present postural adaptations and muscle shortening that seem to be related to disease severity.

Head sway response to optic flow: Effect of age is more important than the presence of unilateral vestibular hypofunction

The purpose of this study was to examine how older adults with vestibular impairment use sensory feedback for postural control. Nine older adult subjects with unilateral vestibular hypofunction (UVH, mean age 69 y) and 14 older (mean age 70 y) and 8 young adult controls (CON, mean age 28 y) viewed full-field optic flow scenes while standing on a fixed or sway-referenced support surface. The subjects with UVH had 100% caloric asymmetry. Optic flow consisted of sinusoidal anterior-posterior movement of the visual surround at three frequencies and three amplitudes of stimulation. The anterior-posterior head sway was measured. The number of head sway responses that were coupled to the optic flow and magnitude of head sway during optic flow relative to during quiet stance on fixed floor was quantified. The number of trials in which the head sway response was significantly coupled to the optic flow was significantly greater in the Older UVH and Older CON subjects compared with the Young CON subjects. Furthermore, the magnitude of head sway was two to three times greater in Older UVH and CON compared with Young CON subjects. There was no difference in coupling or magnitude of head sway between Older UVH and Older CON subjects. The amplitude of sway was also dependent on the amount of surface support, stimulus frequency, and stimulus amplitude. Older adults with unilateral vestibular hypofunction who are able to effectively compensate show no difference in postural responses elicited by optic flow compared with age-matched controls.

E-selectin S128R polymorphism and severe coronary artery disease in Arabs

BackgroundThe E-selectin p. S128R (g. A561C) polymorphism has been associated with the presence of angiographic coronary artery disease (CAD) in some populations, but no data is currently available on its association with CAD in Arabs.MethodsIn the present study, we determined the potential relevance of the E-selectin S128R polymorphism for severe CAD and its associated risk factors among Arabs. We genotyped Saudi Arabs for this polymorphism by PCR, followed by restriction enzyme digestion.ResultsThe polymorphism was determined in 556 angiographically confirmed severe CAD patients and 237 control subjects with no CAD as established angiographically (CON). Frequencies of the S/S, S/R and R/R genotypes were found as 81.1%, 16.6% and 2.3% in CAD patients and 87.8%, 11.8%, and 0.4% in CON subjects, respectively. The frequency of the mutant 128R allele was higher among CAD patients compared to CON group (11% vs. 6%; odds ratio = 1.76; 95% CI 1.14 – 2.72; p = .007), thus indicating a significant association of the 128R allele with CAD among our population. However, the stepwise logistic regression for the 128R allele and different CAD risk factors showed no significant association.ConclusionAmong the Saudi population, The E-selectin p. S128R (g. A561C) polymorphism was associated with angiographic CAD in Univariate analysis, but lost its association in multivariate analysis.

Kinetic Asymmetry In Female Runners With And Without Retrospective Tibial Stress Fractures

The tendency for a runner to become injured on a particular side is not well understood. It has been suggested that it may be due, in part, to asymmetry in their mechanics. PURPOSE The purposes of this study were (1) to compare the levels of kinetic asymmetry in runners who have previously sustained a tibial stress fracture (TSF) and those who have not (CON) and (2) to compare loading parameters between the involved and uninvolved sides of the TSF runners. It was hypothesized that the TSF group would be more asymmetric than the CON group and that they would exhibit greater loading on the involved side. METHODS Twenty-five CON and 24 TSF subjects were eligible for this study. CON subjects reported to have never sustained a running injury. TSF subjects were included if they had sustained one or more tibial stress fractures on a single side of their body. Subjects were asked to run along a 25 meter runway at a speed of 3.65 m/s (± 5%), striking a force platform (Bertec Corp., Worthington, OH) at its center. Data were sampled at 960 Hz. The speed was monitored with photoelectric cells placed 2.86 m apart. Five trials were collected for both the left and right sides. Any trials indicative of targeting were discarded. The same type of neutral running shoe was worn by each subject during data collection. Peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and instantaneous vertical loading rates, and peak shock were measured in each subject. Symmetry Index (SI) was used to quantify asymmetry: SI = (XL – XR)/0.5*(XL+ XR). A 1-tailed, independent t-test was used to compare SI values between the TSF and CON groups. A 1-tailed, dependent t-test was used to compare loading values between the involved and uninvolved sides of the TSF group. RESULTS SI values were not significantly different between the CON and TSF groups for any of the parameters. The peak vertical impact ground reaction force and peak shock were both significantly higher on the involved side in the TSF subjects (p = 0.04 and 0.02 respectively). CONCLUSIONS These results indicate that while CON and TSF subjects have similar levels of asymmetry, those in the TSF group may have elevated loading values, bilaterally, that predispose them to injury.

Effects Of Supine Lower Body Negative Pressure Exercise On Sprint And Balance In Women And Men After 30 Days Of Bedrest In 6 Degree Head Down Tilt

INTRODUCTION Muscle mass and bone density decrease during exposure to microgravity and neuromotor function is impaired. Exercise protocols must be developed that minimize these losses during prolonged spaceflight. PURPOSE We hypothesized supine treadmill exercise against lower body negative pressure (LBNP) would prevent losses of sprint and balance ability in subjects exposed to prolonged microgravity, simulated by 6-degree head down bed rest (BR). METHODS Fifteen sets of identical twins (female, n = 7; male, n = 8) completed a 30-day BR study. They were tested pre- and post-BR for sprint time and walk back over 30.5m, one foot rail balance with eyes closed (EC) (up to 30 sec), rail walk balance down a 4.9m beam with eyes open (EO). Each twin was randomly assigned to: 1) an experimental group that ran on a vertically oriented treadmill 40 minutes, 6 days per week against −55 ± 4mmHg LBNP (EXP) or 2) a control group that did no exercise (CON). Rail walk performance was determined by averaging percent distance traveled divided by total time. Pre- and post-BR results were compared using repeated measures ANOVA, and are reported as mean±SD. RESULTS The male CON group had significantly shorter (p<0.05) left foot balance times EC POST 7.5 ± 7.5 s versus PRE 23.6 ± 11.9 s. Rail walk (EO) was significantly less (p<0.05) POST 8.8 ± 3.2%d/t versus PRE 10.2 ± 3.6%d/t with no differences between any other groups. Female CON subjects had significantly slower sprint times after bed rest (Pre: 6.1±04; Post: 8.7±1.4 sec). All other groups maintained sprint times pre- and post-BR. Walk back times were significantly slower in all groups after bed rest (Pre: 23.2±1.8; Post: 26.8±4.6sec). Left foot balance (EO) was significantly less (p<0.05) POST 27.04±5.2s versus PRE 30±0 s. CONCLUSION The results suggest exercise in LBNP may maintain sprint times in female subjects and some balance parameters after 30 days of bedrest in 6 degree head-down tilt. Supported by NASA grant#NAG9-1425 & NIH grant M01 RR00827 to the UCSD GCRC

Effects Of Supine Lower Body Negative Pressure Exercise On Sprint And Balance In Women And Men After 30 Days Of Bedrest In 6 Degree Head Down Tilt

INTRODUCTION Muscle mass and bone density decrease during exposure to microgravity and neuromotor function is impaired. Exercise protocols must be developed that minimize these losses during prolonged spaceflight. PURPOSE We hypothesized supine treadmill exercise against lower body negative pressure (LBNP) would prevent losses of sprint and balance ability in subjects exposed to prolonged microgravity, simulated by 6-degree head down bed rest (BR). METHODS Fifteen sets of identical twins (female, n = 7; male, n = 8) completed a 30-day BR study. They were tested pre- and post-BR for sprint time and walk back over 30.5m, one foot rail balance with eyes closed (EC) (up to 30 sec), rail walk balance down a 4.9m beam with eyes open (EO). Each twin was randomly assigned to: 1) an experimental group that ran on a vertically oriented treadmill 40 minutes, 6 days per week against −55 ± 4mmHg LBNP (EXP) or 2) a control group that did no exercise (CON). Rail walk performance was determined by averaging percent distance traveled divided by total time. Pre- and post-BR results were compared using repeated measures ANOVA, and are reported as mean±SD. RESULTS The male CON group had significantly shorter (p<0.05) left foot balance times EC POST 7.5 ± 7.5 s versus PRE 23.6 ± 11.9 s. Rail walk (EO) was significantly less (p<0.05) POST 8.8 ± 3.2%d/t versus PRE 10.2 ± 3.6%d/t with no differences between any other groups. Female CON subjects had significantly slower sprint times after bed rest (Pre: 6.1±04; Post: 8.7±1.4 sec). All other groups maintained sprint times pre- and post-BR. Walk back times were significantly slower in all groups after bed rest (Pre: 23.2±1.8; Post: 26.8±4.6sec). Left foot balance (EO) was significantly less (p<0.05) POST 27.04±5.2s versus PRE 30±0 s. CONCLUSION The results suggest exercise in LBNP may maintain sprint times in female subjects and some balance parameters after 30 days of bedrest in 6 degree head-down tilt. Supported by NASA grant#NAG9-1425 & NIH grant M01 RR00827 to the UCSD GCRC

Improved Physical Performance in Older Adults Undertaking a Short-Term Programme of High-Velocity Resistance Training

Background: The age-related loss of muscle power in older adults is greater than that of muscle strength and is associated with a decline in physical performance. Objective: To investigate the effects of a short-term high-velocity varied resistance training programme on physical performance in healthy community-dwelling adults aged 60–80 years. Methods: Subjects undertook exercise (EX; n = 15) or maintained customary activity (controls, CON; n = 10) for 8 weeks. The EX group trained 2 days/week using machine weights for three sets of eight repetitions at 35, 55, and 75% of their one-repetition maximum (the maximal weight that an individual can lift once with acceptable form) for seven upper- and lower-body exercises using explosive concentric movements. Results: Fourteen EX and 10 CON subjects completed the study. Dynamic muscle strength significantly increased (p = 0.001) in the EX group for all exercises (from 21.4 ± 9.6 to 82.0 ± 59.2%, mean ± SD) following training, as did knee extension power (p < 0.01). Significant improvement occurred for the EX group in the floor rise to standing (10.4 ± 11.5%, p = 0.004), usual 6-metre walk (6.6 ± 8.2%, p = 0.010), repeated chair rise (10.4 ± 15.6%, p = 0.013), and lift and reach (25.6 ± 12.1%, p = 0.002) performance tasks but not in the CON group. Conclusions: Progressive resistance training that incorporates rapid rate-of-force development movements may be safely undertaken in healthy older adults and results in significant gains in muscle strength, muscle power, and physical performance. Such improvements could prolong functional independence and improve the quality of life.

Discordant effects of a chronic physiological increase in plasma FFA on insulin signaling in healthy subjects with or without a family history of type 2 diabetes.

Muscle insulin resistance develops when plasma free fatty acids (FFAs) are acutely increased to supraphysiological levels (approximately 1,500-4,000 micromol/l). However, plasma FFA levels >1,000 micromol/l are rarely observed in humans under usual living conditions, and it is unknown whether insulin action may be impaired during a sustained but physiological FFA increase to levels seen in obesity and type 2 diabetes mellitus (T2DM) (approximately 600-800 micromol/l). It is also unclear whether normal glucose-tolerant subjects with a strong family history of T2DM (FH+) would respond to a low-dose lipid infusion as individuals without any family history of T2DM (CON). To examine these questions, we studied 7 FH+ and 10 CON subjects in whom we infused saline (SAL) or low-dose Liposyn (LIP) for 4 days. On day 4, a euglycemic insulin clamp with [3-3H]glucose and indirect calorimetry was performed to assess glucose turnover, combined with vastus lateralis muscle biopsies to examine insulin signaling. LIP increased plasma FFA approximately 1.5-fold, to levels seen in T2DM. Compared with CON, FH+ were markedly insulin resistant and had severely impaired insulin signaling in response to insulin stimulation. LIP in CON reduced insulin-stimulated glucose disposal (Rd) by 25%, insulin-stimulated insulin receptor tyrosine phosphorylation by 17%, phosphatidylinositol 3-kinase activity associated with insulin receptor substrate-1 by 20%, and insulin-stimulated glycogen synthase fractional velocity over baseline (44 vs. 15%; all P < 0.05). In contrast to CON, a physiological elevation in plasma FFA in FH+ led to no further deterioration in Rd or to any additional impairment of insulin signaling. In conclusion, a 4-day physiological increase in plasma FFA to levels seen in obesity and T2DM impairs insulin action/insulin signaling in CON but does not worsen insulin resistance in FH+. Whether this lack of additional deterioration in insulin signaling in FH+ is due to already well-established lipotoxicity, or to other molecular mechanisms related to insulin resistance that are nearly maximally expressed early in life, remains to be determined.

Muscle Fiber Characteristics and Performance Correlates of Male Olympic-Style Weightlifters

Biopsies from the vastus lateralis muscle of male weightlifters (WL; n = 6; X ± SE, age = 27.0 ± 2.1 years), and non-weight-trained men (CON; n = 7; age = 22.0 ± 2.0) were compared for fiber types, myosin heavy chain (MHC) and titin content, and fiber type-specific capillary density. Differences (p < 0.05) were observed for percent fiber types IIC (WL = 0.4 ± 0.2, CON = 2.4 ± 0.8); IIA (WL = 50.5 ± 3.2, CON = 26.9 ± 3.7); and IIB (WL = 1.7 ± 1.4, CON = 21.0 ± 5.3), as well as percent MHC IIa (WL = 65.3 ± 2.4, CON = 52.1 ± 4.2) and percent MHC IIb (WL = 0.9 ± 0.9, CON = 18.2 ± 6.1). All WL exhibited only the titin-1 isoform. Capillary density (caps·mm-2) for all fiber types combined was greater for the CON subjects (WL = 192.7 ± 17.3; CON = 262.9 ± 26.3), due primarily to a greater capillary density in the IIA fibers. Weightlifting performances and vertical jump power were correlated with type II fiber characteristics. These results suggest that successful weightlifting performance is not dependent on IIB fibers, and that weightlifters exhibit large percentages of type IIA muscle fibers and MHC IIa isoform content.

Two years of resistance training in older men and women: the effects of three years of detraining on the retention of dynamic strength.

Dynamic muscle strength (1-RM) and symptom-limited treadmill endurance were compared among three groups (5 M and 5 F per group) of older adults (mean age 72.5 yrs) who had either weight-trained continuously twice per week for 5 years (Tr), ceased to weight train after 2 years (Detr), or acted as controls throughout (Con). The Tr and Detr trained hard (progressing up to 3 sets at up to 80% of 1-RM) for 2 years; the Tr continued training for an additional 3 years at a maintenance level (2 to 3 sets at 60-70% 1-RM), whereas the Detr stopped training for those 3 years. The Con subjects did not train for the duration of the study but took part in identical testing procedures. After 2 years of resistance training, dynamic strength in the Tr and Detr groups increased significantly above baseline and Con values for all exercises, p < 0.0001. Following 3 years of maintenance level training, arm curl, leg press, and bench press 1-RM (sum of both limbs) in the Tr remained significantly above baseline values (21.6 kg = 17%; 15.7 kg = 82%; 8.3 kg = 34%, respectively). The 1-RM in Detr were 18.4 kg (14%), 5.3 kg (24%), and 1.4 kg (9%) above baseline for leg press, arm curl, and bench press after 5 years, whereas the Con declined over the 5-yr period by 18.4 kg (-9.7%), 4.4 kg (-19%), and 3.5 kg (-6%), respectively. There were nonsignificant improvements in treadmill performance in the Tr and Detr, and a decline in the Con after 2 years. Treadmill performance declined between Years 2 and 5 in all groups despite continued training (ns). We conclude that: (1) dynamic strength gains from 2 years of resistance training in older individuals are not entirely lost even after 3 years of detering; (2) these effects may be specific to the exercises performed in the training program; (3) adoption of maintenance-level moderate-intensity training significantly attenuates the decline in dynamic strength of previously trained muscles.

Muscle fiber characteristics and performance correlates of male Olympic-style weightlifters.

Biopsies fro the vastus lateralis muscle of male weightlifters (WL; n=6; X +/- SE, age=27.0 +/- 2.1 years), and non-weight-trained men (CON; n=7; age=27.0 +/- 2.0 years) were compared for fiber types, myosin heavy chain (MHC) and titin content, and fiber type-specific capillary density. Differences (p<0.05) were observed for percent fiber types IIC (WL=0.4 +/- 0.2, CON=2.4 +/- 0.8); IIA (WL=50.5 +/- 3.2, CON=26.9 +/- 3.7); and IIB (WL=1.7 +/- 1.4, CON=21.0 +/- 5.3), as well as percent MHC IIa (WL=65.3 +/- 2.4, CON=52.1 +/- 4.2) and percent MHC IIB (WL=0.9 +/- 0.9; CON=18.2 +/- 6.1). All WL exhibited only the titin-1 isoform. Capillary density (caps.mm(-2)) for all fiber types combined was greater for the CON subjects (WL=192.7 +/- 17.3; CON=262.9 +/- 26.3), due primarily to a greater capillary density in the IIA fibers. Weightlifting performances and vertical jump power were correlated with type II fiber characteristics. These results suggest that successful weightlifting performance is not dependent on IIB fibers, and that weightlifters exhibit large percentages of type IIA muscle fibers and MHC IIa isoform content.

OBJECTIVE ASSESSMENT OF CONCUSSION IN COLLEGIATE FOOTBALL PLAYERS

Sports medicine clinicians are often faced with a dilemma when making return to play decisions following a sport-related concussion. Several methods of objective concussion assessment have been proposed in the literature, however, few have been validated in studies involving large sample sizes. This investigation involved a multi-institutional study of 3062 NCAA collegiate football players from 33 institutions. PURPOSE: To better understand the efficacy of objective tests for symptomatology, cognitive functioning and postural stability in players sustaining concussion (INJ), versus control subjects (CON); and to examine the role of recurrent concussion (concussion history) as a predisposition to further injury. METHODS: Pre-season baseline measures and a series of follow-up assessments were recorded on 63 INJ and 43 CON subjects. The following tests were conducted: Graded Symptom Checklist (GSC), Standardized Assessment of Concussion (SAC), Hopkins Verbal Learning Test (HVLT), Symbol Digit Modalities Test (SDMT), Stroop Color Word (SCW), Trail Making B Test (TRAIL-B), and the Balance Error Scoring System (BESS). RESULTS: Significant group by day interactions (P < .05) were revealed for GSC, SAC, and BESS, suggesting that INJ subjects scored significantly worse than CON subjects for the first two days following injury and gradually recovered to baseline. Other measures of cognitive functioning (HVLT, SDMT, SCW, TRAIL-B) did not reveal significant group by day interactions (p > .05). A significant association was revealed between concussion history and subsequent concussive injury (chi-squared analysis (3) = 33.52, p < .05). Of the injured players who reported 3 or more previous concussions, 13% sustained an injury during the season being studied. This was in contrast to those who had reported 2 previous injuries (11%), 1 previous injuries (5%), and no previous injuries (4%). CONCLUSIONS: These results suggest that athletes with a history of recurrent concussive injury (> 2) are likely predisposed to future injury. Graded symptom checklist, Standardized Assessment of Concussion, and Balance Error Scoring System appear to be useful tests for assessing concussion.