The effects of acute garlic supplementation on the fibrinolytic and vasoreactive response to exercise.

BACKGROUND: The purpose of this project was to examine the effects of acute garlic supplementation on fibrinolysis and vasoreactivity both at rest and following maximal exercise. METHODS: Eighteen healthy trained males (20.9 ± 2.2 years, 178 ± 7.7 cm, 75.5 ± 9.6 kg, VO2max = 59.8 ± 6.7 ml • kg(-1) • min(-1)) performed a graded treadmill test to volitional exhaustion. Blood samples were taken at rest, within two minutes post-exercise, and one hour post-exercise. Eleven of the subjects also had a brachial vasoreactivity test performed immediately after the blood sample to assess flow-mediated dilation (FMD) of the brachial artery. Participants were randomly assigned to ingest either 900 mg of powdered garlic or a placebo three hours before the exercise session. The supplement was distributed in a double-blind, crossover fashion. Participants repeated the protocol with the other treatment after a 14-day washout period. Paired t-tests were used to compare VO2max between the two trials. A two-factor (treatment and time) repeated measures analysis of variance (ANOVA) was used to assess changes in FMD, tPA activity, tPA antigen, and PAI-1 activity. A priori statistical significance was set at P <0.05. RESULTS: VO2max was greater for the garlic treatment trial vs. placebo (Placebo = 59.8 ± 6.7 ml • kg(-1) • min(-1); Garlic = 61.4 ± 6.6 ml • kg(-1) • min(-1)). There was no main effect for treatment and no treatment x time interaction for FMD or any fibrinolytic variables examined. CONCLUSION: Acute garlic supplementation does not alter vasoreactivity, fibrinolytic potential or the fibrinolytic response to exercise in young healthy trained males. Acute garlic supplementation does, however, cause a small but statistically significant increase in VO2max. It remains unclear if this increase in VO2max is of functional importance.

ERK1/2 inhibition prevents contraction-induced increase in plasma membrane FAT/CD36 content and FA uptake in rodent muscle.

AIM: The purpose of this experiment was to investigate the role of extracellular signal-regulated kinase 1/2 (ERK1/2) signalling in the contraction-induced increase in muscle FA uptake. METHODS: Male Wistar rats (n = 41) were randomly assigned to either a resting or stimulated group. Within each group, animals were randomly assigned to receive PD-98059, an inhibitor of MAP/ERK kinase 1/2 (MEK1/2), a kinase upstream of ERK1/2 and perfused with 550 microM palmitate, [(14)C]palmitate, 7 mM glucose, and no insulin. In the stimulated group, electrical stimulation (ES) of supramaximal trains of 100 ms was delivered every 2 s for 20 min. RESULTS: ERK1/2 phosphorylation was increased by 50% (P < 0.05) during ES but the contraction-induced increase was prevented by the addition of PD-98059. Glucose uptake increased by 3.6-fold (P < 0.05) from rest to ES in muscle perfused without PD-98059 and was not affected by the addition of PD-98059 either at rest (P > 0.05) or during ES (P > 0.05). For a matched palmitate delivery, ES increased palmitate uptake by 35% (P < 0.05). PD-98059 had no effect on palmitate uptake at rest but completely abolished the increase in palmitate uptake during ES. Plasma membrane FAT/CD36 protein content was increased by 38% during ES (P < 0.05) but the contraction-induced increase was prevented by the addition of PD-98059. AMPK activity was increased by ES (P < 0.05) but was unaffected by PD-98059. CONCLUSION: These results show for the first time that the increase in FA uptake and in plasma membrane FAT/CD36 protein content is mediated, at least in part, by the ERK1/2 signalling pathway during muscle contraction.

Knee osteoarthritis and high-heeled shoes.

BACKGROUND: Little is known about the effects of walking in high heels on joints in the legs. Since osteoarthritis of the knee is twice as common in women as in men, we investigated torques (forces applied about the leg joints) of women who wore high-heeled shoes. METHODS: We studied 20 healthy women who were comfortable wearing high-heeled shoes. The women walked with their own high-heeled shoes and barefoot. Data were plotted and qualitatively compared; major peak values for high-heeled and barefoot walking were statistically compared. Bonferroni adjustment was made for multiple comparisons. FINDINGS: Measurement showed increased force across the patellofemoral joint and a greater compressive force on the medial compartment of the knee (average 23% greater forces) during walking in high heels than barefoot. INTERPRETATION: The altered forces at the knee caused by walking in high heels may predispose to degenerative changes in the joint.

Biomechanical gait alterations independent of speed in the healthy elderly: evidence for specific limiting impairments.

OBJECTIVES: It is not known whether changes in the biomechanics of elderly gait are related to aging per se, or to reduced walking speed in this population. The goals of the present study were to identify specific biomechanical changes, independent of speed, that might impair gait performance in healthy older people by identifying age-associated changes in the biomechanics of gait, and to determine which of these changes persist at increased walking speed. DESIGN: Stereophotogrammetric and force platform data were collected. Differences in peak joint motion (kinematic) and joint moment and power (kinetic) values between healthy young and elderly subjects at comfortable and increased walking speed were measured. SETTING: A gait laboratory. SUBJECTS: Thirty-one healthy elderly (age 65 to 84 years) and 31 healthy young adult subjects (age 18 to 36 years), all without known neurologic, musculoskeletal, cardiac, or pulmonary problems. MAIN OUTCOME MEASURES: All major peak kinematic and kinetic variables during the gait cycle. RESULTS: Several kinematic and kinetic differences between young and elderly adults were found that did not persist when walking speed was increased. Differences that persisted at both comfortable and fast walking speeds were reduced peak hip extension, increased anterior pelvic tilt, and reduced ankle plantarflexion and ankle power generation. CONCLUSION: Gait performance in the elderly may be limited by both subtle hip flexion contracture and ankle plantarflexor concentric weakness. Results of the current study should motivate future experimental trials of specific hip flexor stretching and ankle plantarflexor concentric strengthening exercises to preserve and potentially improve walking performance in the elderly.

Gender differences in joint biomechanics during walking: normative study in young adults.

The effect of gender on specific joint biomechanics during gait has been largely unexplored. Given the perceived, subjective, and temporal differences in walking between genders, we hypothesized that quantitative analysis would reveal specific gender differences in joint biomechanics as well. Sagittal kinematic (joint motion) and kinetic (joint torque and power) data from the lower limbs during walking were collected and analyzed in 99 young adult subjects (49 females), aged 20 to 40 years, using an optoelectronic motion analysis and force platform system. Kinetic data were normalized for both height and weight. Female and male data were compared graphically and statistically to assess differences in all major peak joint kinematic and kinetic values. Females had significantly greater hip flexion and less knee extension before initial contact, greater knee flexion moment in pre-swing, and greater peak mechanical joint power absorption at the knee in pre-swing (P < 0.0019 for each parameter). Other differences were noted (P < 0.05) that were not statistically significant when accounting for multiple comparisons. These gender differences may provide new insights into walking dynamics and may be important for both clinical and research studies in motivating the development of separate biomechanical reference databases for males and females.

Comparison of methods for evaluating exercise-induced changes in thromboxane B2 and beta-thromboglobulin.

This study compared the effects of exercise or TXB2 and beta-TG when evaluated by four methods: 1) not adjusted; 2) adjusted for plasma volume changes (PV); 3) standardized per 10(5) platelets (PC); 4) or both PC and PV (PC-PV). Blood was collected from 16 men (41.3 +/- 8.1 yr) at rest after 30 min of exercise (IPE) and after 30 min recovery. Resting TXB2 and beta-TG concentrations were 62.0 +/- 6.2 pg.mL-1 and 129.8 +/- 12.5 ng.mL-1, respectively. When expressed on a per 10(5) platelet basis, resting PCTXB2 was 23.8 +/- 2.8 pg.mL-1.10(5-1) platelets and PC beta-TG was 50.77 +/- 6.0 ng.mL-1. 10(5-1) platelets. At IPE, TXB2 decreased 20.5% and beta-TG increased 13.6%. Thirty minutes after exercise TXB2 was 4.2% lower than resting values, whereas beta-TG was 26% higher. TXB2, beta-TG, PVTXB2, and PV beta-TG were not significantly altered by exercise. The only significant changes in TXB2 occurred at IPE when values were adjusted for changes in platelet count. At IPE, PCTXB2, and PC-PVTXB2 decreased 32.8% and 33.6%, respectively (P < 0.05). Similarly, beta-TG were not altered significantly by exercise except when the samples taken after 30 min of recovery were adjusted for changes in platelet count. At 30 min post-exercise PC beta-TG and PC-PV beta-TG were 21.2% and 28.4% greater (P < 0.05) than the resting beta-TG values. These data suggest that methods used to adjust concentrations of platelet derived substances for changes owing to exercise may influence conclusions about the effect of exercise on platelet function. Thus, it is imperative that researchers consider the purpose for which they are collecting TXB2 and beta-TG, as well as other constituents derived from blood cells, before they determine which methods of analysis to use.

Combined effects of age and exercise on thromboxane B2 and platelet activation.

Nine healthy young (27.8 +/- 0.8 yr old, YM) and nine healthy older men (55.4 +/- 1.3 yr old, OM) ran on a treadmill at 70-75% of maximal O2 consumption for 30 min to determine the combined effects of age and acute exercise on plasma thromboxane B2 (TxB2) and beta-thromboglobulin (beta-TG). Blood samples (10 ml) were collected in tubes containing 0.5 ml of 4.5 mM EDTA, 30 mM acetylsalicylic acid, and 1 microM prostaglandin E1 after 15 min of rest, immediately after exercise, and at 30 min of recovery. Concentrations of TxB2 and beta-TG were determined by radioimmunoassay. Samples were adjusted for hemoconcentration and changes in platelet count not accounted for by plasma volume shifts. Data were analyzed with repeated-measures analysis of variance and Tukey's post hoc technique. Resting TxB2 was 53.3 +/- 9.6 and 79.0 +/- 18.2 pg/ml for the YM and OM, respectively. beta-TG at rest was 152.5 +/- 13.9 and 114.0 +/- 10.9 ng/ml for the YM and OM, respectively. No significant age group or exercise-induced differences for TxB2 or beta-TG were found immediately after exercise. TxB2 in the OM (101.7 +/- 16.4 pg/ml) 30 min after exercise was significantly (P = 0.05) higher than that in the YM (54.4 +/- 6.2 pg/ml). beta-TG values 30 min after exercise were not significantly different: 183.3 +/- 26.9 and 169.9 +/- 17.0 ng/ml in the OM and YM, respectively. These data suggest that OM may experience greater increases in TxB2 than YM 30 min after exercise and may be more predisposed to platelet activation.

Effect of exercise intensity on 6-keto-PGF1 alpha, TXB2, and 6-keto-PGF1 alpha/TXB2 ratios.

Six men (X = 27.3 yr) ran at 60%, 70% and 80% of maximal oxygen consumption on separate days for 30 minutes to determine exercise intensity effects on 6-keto-PGF1 alpha, TXB2, and 6-keto-PGF1 alpha/TXB2 ratios. At rest, 6-keto-PGF1 alpha was 384 +/- 68.3 pg/ml; TXB2 was 147 +/- 55.6 pg/ml; and the 6-keto-PGF1 alpha/TXB2 ratio was 4.63 +/- 1.3. After exercise at 60%, 70%, and 80% TXB2 increased to 523.2 +/- 117.5, 611.7 +/- 155.4*, and 643.8 +/- 121.7* pg/ml, respectively (*p less than .05). Post-exercise ratios tended to be inversely related to exercise intensity; however, no statistically significant differences were found between these values. These data suggest that exercise-induced increases in TXB2 may be related to intensity.

Effects of posture on upper and lower limb peripheral resistance following submaximal cycling.

The purpose of this study was to determine postural effects on upper and lower limb peripheral resistance (PR) after submaximal exercise. Twelve subjects (six men and six women) completed submaximal cycle ergometer tests (60% age-predicted maximum heart rate) in the supine and upright seated positions. Each test included 20 minutes of rest, 20 minutes of cycling, and 15 minutes of recovery. Stroke volume and heart rate were determined by impedance cardiography, and blood pressure was measured by auscultation during rest, immediately after exercise, and at minutes 1-5, 7.5, 10, 12.5, and 15 of recovery. Peripheral resistance was calculated from values of mean arterial pressure and cardiac output. No significant (p less than 0.05) postural differences in PR were noted during rest for either limb. Immediately after exercise, PR decreased (55% to 61%) from resting levels in both limbs, independent of posture. Recovery ankle PR values were significantly different between postures. Upright ankle PR returned to 92% of the resting level within four minutes of recovery, compared to 76% of the resting level after 15 minutes in the supine posture. Peripheral resistance values in the supine and upright arm were not affected by posture and demonstrated a gradual pattern of recovery similar to the supine ankle recovery response (85% to 88% of rest within 15 minutes). The accelerated recovery rate of PR after upright exercise may result from local vasoconstriction mediated by a central regulatory response to stimulation from gravitational pressure on lower body circulation.