Laurie Wideman

Effects of acute aerobic and anaerobic exercise on blood markers of oxidative stress

The purpose of this study was to compare oxidative modification of blood proteins, lipids, DNA, and glutathione in the 24 hours following aerobic and anaerobic exercise using similar muscle groups. Ten cross-trained men (24.3 ± 3.8 years, [mean ± SEM]) performed in random order 30 minutes of continuous cycling at 70% of VO2max and intermittent dumbbell squatting at 70% of 1 repetition maximum (1RM), separated by 1–2 weeks, in a crossover design. Blood samples taken before, and immediately, 1, 6, and 24 hours postexercise were analyzed for plasma protein carbonyls (PC), plasma malondialdehyde (MDA), and whole-blood total (TGSH), oxidized (GSSG), and reduced (GSH) glutathione. Blood samples taken before and 24 hours postexercise were analyzed for serum 8-hydroxy-29-deoxyguanosine (8-OHdG). PC values were greater at 6 and 24 hours postexercise compared with pre-exercise for squatting, with greater PC values at 24 hours postexercise for squatting compared with cycling (0.634 ± 0.053 vs. 0.359 ± 0.018 nM·mg protein-1). There was no significant interaction or main effects for MDA or 8-OHdG. GSSG experienced a shortlived increase and GSH a transient decrease immediately following both exercise modes. These data suggest that 30 minutes of aerobic and anaerobic exercise performed by young, cross-trained men (a) can increase certain biomarkers of oxidative stress in blood, (b) differentially affect oxidative stress biomarkers, and (c) result in a different magnitude of oxidation based on the macromolecule studied. Practical applications: While protein and glutathione oxidation was increased following acute exercise as performed in this study, future research may investigate methods of reducing macromolecule oxidation, possibly through the use of antioxidant therapy.

Growth hormone release during acute and chronic aerobic and resistance exercise: recent findings.

AbstractExercise is a potent physiological stimulus for growth hormone (GH) secretion, and both aerobic and resistance exercise result in significant, acute increases in GH secretion. Contrary to previous suggestions that exercise-induced GH release requires that a ’threshold’ intensity be attained, recent research from our laboratory has shown that regardless of age or gender, there is a linear relationship between the magnitude of the acute increase in GH release and exercise intensity. The magnitude of GH release is greater in young women than in young men and is reduced by 4-7-fold in older individuals compared with younger individuals. Following the increase in GH secretion associated with a bout of aerobic exercise, GH release transiently decreases. As a result, 24-hour integrated GH concentrations are not usually elevated by a single bout of exercise. However, repeated bouts of aerobic exercise within a 24-hour period result in increased 24-hour integrated GH concentrations.Because the GH response to acute resistance exercise is dependent on the work-rest interval and the load and frequency of the resistance exercise used, the ability to equate intensity across different resistance exercise protocols is desirable. This has proved to be a difficult task. Problems with maintaining patent intravenous catheters have resulted in a lack of studies investigating alterations in acute and 24-hour GH pulsatile secretion in response to resistance exercise. However, research using varied resistance protocols and sampling techniques has reported acute increases in GH release similar to those observed with aerobic exercise.In young women, chronic aerobic training at an intensity greater than the lactate threshold resulted in a 2-fold increase in 24-hour GH release. The time line of adaptation and the mechanism(s) by which this training effect occurs are still elusive. Unfortunately, there are few studies investigating the effects of chronic resistance training on 24-hour GH release.The decrease in GH secretion observed in individuals who are older or have obesity is associated with many deleterious health effects, although a cause and effect relationship has not been established. While exercise interventions may not restore GH secretion to levels observed in young, healthy individuals, exercise is a robust stimulus of GH secretion. The combination of exercise and administration of oral GH secret agogues may result in greater GH secretion than exercise alone in individuals who are older or have obesity. Whether such interventions would result in favourable clinical outcomes remains to be established.

Intensity of acute exercise does not affect serum leptin concentrations in young men

Purpose: We examined the effects of exercise intensity on serum leptin levels. Methods: Seven men (age = 27.0 yr; height = 178.3 cm; weight = 82.2 kg) were tested on a control (C) day and on 5 exercise days (EX). Subjects exercised (30 min) at the following intensities: 25% and 75% of the difference between the lactate threshold (LT) and rest (0.25 LT, 0.75 LT), at LT, and at 25% and 75% of the difference between LT and peakOV2? (1.25 LT, 1.75 LT). Results: Kcal expended during the exercise bouts ranged from 150 ± 11 kcal (0.25 LT) to 529 ± 45 kcal (1.75 LT), whereas exercise + 3.5 h recovery kcal ranged from 310 ± 14 kcal (0.25 LT) to 722 ± 51 kcal (1.75 LT). Leptin area under the curve (AUC) (Q 10-min samples) for all six conditions (C + 5 Ex) was calculated for baseline (0700–0900 h) and for exercise + recovery (0900–1300 h). Leptin AUC for baseline ranged from 243 ± 33 to 291 ± 56 ng~mL-1 X min; for exercise + recovery results ranged from 424 ± 56 to 542 ± 99 ng~mL-1 X min. No differences were observed among conditions within either the baseline or exercise + recovery time frames. Regression analysis confirmed positive relationships between serum leptin concentrations and percentage body fat (r = 0.94) and fat mass (r = 0.93, P < 0.01). Conclusion: We conclude that 30 min of acute exercise, at varying intensity of exercise and caloric expenditure, does not affect serum leptin concentrations during exercise or for the first 3.5 hours of recovery in healthy young men.

The validity of regulating blood lactate concentration during running by ratings of perceived exertion

We examined whether ratings of perceived exertion (RPE) observed during an incremental (response) protocol could be used to produce target blood [HLa] of 2.5 mM and 4.0 mM during a 30-min treadmill run at a constant RPE. RPE (15.3, 17.6, 19.1), oxygen uptake (VO2) (3.31, 3.96, 4.00 l.min-1), velocity (V) (198, 218, 223 m.min-1), and heart rate (HR) (179, 185, 190 bpm) at blood [HLa] of 2.5 mM and 4.0 mM, and peak were determined for nine subjects (5 males, 4 females) during incremental exercise. Subjects then completed two 30-min runs at the RPE corresponding to blood [HLa] of 2.5 mM (RPE 2.5 mM) and 4.0 mM (RPE 4.0 mM) measured during the incremental protocol. For both 30-min runs, VO2 was not different from VO2 corresponding to either 2.5 or 4.0 mM blood [HLa] during the incremental test. During the 30-min run at RPE 2.5 mM: (a) only during minutes 25-30 was the blood [HLa] significantly different than 2.5 mM (3.2 +/- 0.6 mM, P < 0.05), (b) for the first 20 min HR was significantly lower than the HR at 2.5 mM during the incremental protocol, and (c) V did not differ from V at 2.5 mM during the incremental protocol. During the 30-min run at RPE 4.0 mM: (a) blood [HLa] was not significantly different from 4.0 mM, (b) HR at every time point was significantly lower than HR 4.0 mM during the incremental protocol, and (c) V was decreased over time by an average of 24.6 m.min-1 (P < 0.05). Because RPE from the response protocol was able to produce a blood [HLa] close to the criterion value during each 30-min run, we conclude that RPE is a valid tool for prescribing exercise intensities corresponding to blood [HLa] of 2.5 mM and 4.0 mM.

Effects of Tai Chi Chuan on Insulin and Cytokine Levels in a Randomized Controlled Pilot Study on Breast Cancer Survivors

BACKGROUND Tai Chi Chuan (TCC) is an integrative medicine mind-body practice with a physical activity component that has positive effects on aerobic capacity, muscular strength, and quality of life among cancer survivors, similar to the effects elicited by other modes of moderate-intensity exercise. Inflammatory cytokines and insulin and insulin-related signaling molecules may contribute to weight gain and affect cancer recurrence rates and survival; exercise can curb cancer- and treatment-related weight gain, increase survival, and reduce levels of insulin and inflammatory cytokines. Despite knowing the beneficial effects of conventional exercise interventions on these mediators, little is known about the physiologic effects of TCC on these pathways in breast cancer survivors. METHODS We assessed the effects of a 12-week, moderately intense, TCC intervention (n = 9) compared with a non-physical activity control (n = 10) consisting of psychosocial support therapy (PST), on levels of insulin, insulin-like growth factor (IGF)-1, insulin growth factor-like binding protein (IGFBP)-1, IGFBP-3, and cytokines interleukin (IL)-6, IL-2, and interferon (IFN)-γ in breast cancer survivors. RESULTS Levels of insulin are significantly different in TCC and PST groups; levels remained stable in the TCC group but increased in the PST control group (P = .099). Bivariate analysis revealed novel and significant correlations (all r > 0.45, all P ≤ .05) of both decreased fat mass and increased fat-free mass with increased IL-6 and decreased IL-2 levels. CONCLUSIONS This pilot study shows that TCC may be associated with maintenance of insulin levels and changes in cytokine levels that may be important for maintenance of lean body mass in breast cancer survivors.

Assessment of the Aerosport TEEM 100 portable metabolic measurement system.

The present study evaluated the utility of a portable metabolic measurement system, the Aerosport TEEM 100. A total of 505 data points [242 from incremental (INC) and 263 from constant load (CL) exercise] were collected on 12 subjects (age = 25 +/- 4 yr), by placing the Aerosport TEEM 100 medium flow pneumotach and mouthpiece in-line with a validated system, the Rayfield system. When VO2 values were separated into categories (< 1.5, 1.5-2.0, 2.0-2.5, 2.5-3.0, > 3.0 l.min-1), there was a small but statistically significant difference between the two metabolic measurement systems for VO2, VCO2, VE, RER, %ECO2, and %EO2 during both INC and CL exercise and measurement error for VO2 ranged between 2% and 11%. Correlations for VO2 values during INC and CL exercise between the two systems were r = 0.95 (SEest +/- 0.18 l.min-1) and r = 0.96 (SEest +/- 0.29 l.min-1), respectively. Correlations for RER were r = 0.82 (SEest +/- 0.08) and r = 0.47 (SEest +/- 0.11), for INC and CL, respectively. Results from the present investigation indicate that the Aerosport TEEM 100 has utility for the assessment of VO2, but the estimation of carbohydrate and fat utilization from RER should be used with caution.

Body composition by DEXA in older adults: accuracy and influence of scan mode.

Dual energy x-ray absorptiometry (DEXA) measures bone mineral content (BMC), bone mineral density (BMD), fat-free mass (FFM), and provides estimates of percent body fat. Changes in scan mode geometry (pencil beam vs array) may impact these measures and body composition estimates using multi-compartment models. Forty-one adults, ages 59-79 yr, were scanned in each mode and also underwent hydrostatic weighing and measurement of total body water (tritiated water dilution). The effect of scan mode on measurement of DEXA BMC, BMD, FFM, and percent body fat (DEXA %Fat) was examined. The effect of scan mode on percentage body fat determined by a 4-compartment body composition model (4 Comp %Fat) and comparison of DEXA %Fat and 4 Comp %Fat were also examined. BMC and DEXA %Fat were greater (1.3% and 3.9%, respectively, P < 0.01), and BMD and FFM were lower (1.1% and 1.9%, respectively, P < 0.01) with the array scan mode. The 4 Comp %Fat was significantly greater (0.2%) when the array scan mode measurements of total body bone mineral were used; however, these differences were physiologically inconsequential. Comparison between DEXA %Fat and 4 Comp %Fat measures revealed a total error of +/-5.0% in the older adults examined. These results indicate significant scan mode differences in total body BMC, BMD, FFM, and DEXA %Fat measurements and demonstrate the importance of using a single DEXA scan mode for clinical investigation, particularly with longitudinal studies. For all investigations with DEXA, the scan mode should be reported. Furthermore, the error associated with using DEXA alone to estimate percent fat in an older population suggests that this technique is unacceptable in a research setting.

Effect of exercise training on loss of bone mineral density during lactation.

PURPOSE During lactation, women transfer approximately 200 mg of calcium per day to breast milk. For 6 months, this is equivalent to 3%-9% of bone mineral density (BMD) loss at trabecular-rich sites. Bone mass usually returns to prepregnancy levels with cessation of lactation but not in all women. Therefore, the purpose of this study was to determine whether exercise slows bone loss from 4 to 20 wk postpartum (PP). METHODS At 4 wk PP, women were randomized to either an exercise group [EG, n = 10, weight bearing aerobic exercise (3 d·wk(-1), 45 min·d(-1)) and 3 d·wk(-1) of resistance exercise] or a control group (CG, n = 10, no exercise) for 16 wk. Body composition and BMD were measured by dual-energy x-ray absorptiometry at the lumbar spine (LS), hip, and total body. Maximal strength and predicted maximal oxygen consumption (VO2max) were determined by 1-repetition maximum and submaximal treadmill test, respectively. Repeated-measures ANOVA was used to test for time and time by group differences. RESULTS EG lost significantly less LS BMD than CG (-4.8 ± 0.6% vs -7.0 ± 0.3%, P < 0.01). There were no significant differences in total body and hip BMD. Both groups lost fat mass (EG = -2.9 ± 0.7 kg, CG = -1.8 ± 0.4 kg); however, EG lost less lean body mass (-0.7 ± 0.3 vs -1.6 ± 0.3 kg, P = 0.05). Maximal strength increased by 34% to 221% for all exercises in EG, whereas CG changed -5.7% to 12%. Predicted VO2max increased in both groups (EG = 11.4 ± 2.0, CG = 6.9 ± 1.7%). CONCLUSIONS These results suggest that resistance and aerobic exercise may slow bone loss during lactation.

Collagen Gene Variants Previously Associated With Anterior Cruciate Ligament Injury Risk Are Also Associated With Joint Laxity

Background: Genetic association studies demonstrate a relationship between several collagen gene variants and anterior cruciate ligament (ACL) injury, yet the mechanism of these relationships is still unclear. Joint laxity is a heritable trait; increased magnitudes of anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) have been consistently associated with a greater risk of ACL injury. Joint laxity may constitute an important intermediate phenotype for the genetic association with ACL injury that can be measured clinically. Hypothesis: To determine if genetic variants within the COL1A1, COL5A1, and COL12A1 genes, previously associated with ACL injury, were also associated with greater magnitudes of AKL, GR, and GJL. Study Design: Descriptive laboratory study. Methods: Blood samples and measures of AKL, GR, and GJL were obtained from 124 (50 male, 74 female) healthy, recreationally active subjects. Genomic DNA was extracted from the blood samples and genotyped for single-nucleotide polymorphisms previously examined relative to ACL injury. Univariate analyses of variance compared the magnitude of each laxity variable across the 3 genotypes for each single-nucleotide polymorphism in both sex-combined and sex-specific models. Results: Specific genotypes were associated with greater GR in all subjects. Some genotypes were associated with greater magnitudes of GR, AKL, and GJL in females only. Conclusions: Gene variants previously associated with ACL injury risk were in large part also associated with joint laxity. Sex-specific genetic associations with joint laxity were consistent with those previously reported for ACL injury. Clinical Relevance: These data provide insight into potential pathways through which genotypic variants in collagen genes have the potential to alter ligament structure and behavior and, thus, ACL injury risk.

Accuracy of calendar-based methods for assigning menstrual cycle phase in women.

Background: Sex steroid hormone fluctuations during the menstrual cycle are considered a risk factor for noncontact anterior cruciate ligament injuries. Objective: To determine whether self-reported menstrual history data can be used to accurately categorize menstrual cycle events using calendar-based counting methods. Study Design: Descriptive laboratory study. Methods: Seventy-three women completed a menstrual history questionnaire and submitted to blood sampling for the first 6 days of menses and 8 to 10 days after a positive ovulation test over 2 consecutive months. Frequency counts determined whether appropriate criterion hormone (progesterone) levels were achieved at predefined calendar days. Results: For the criterion of progesterone >2 ng/mL, 18% and 59% of women attained it when counting forward 10 to 14 days after the onset of menses and counting back 12 to 14 days from the end of the cycle, respectively. Most women (76%) attained the criterion for ovulation 1 to 3 days after a positive urinary ovulation test. Regardless of the counting method employed, the criterion of progesterone >4.5 ng/mL for identifying midluteal phase was attained in 67% of cases. Serial blood sampling for 3 to 5 days after the positive urinary ovulation test captured 68% to 81% of the hormone values indicative of ovulation and 58% to 75% indicative of the luteal phase. Conclusion: These data suggest that self-reported menstrual history and calendar-based counting methods should not be used alone if accurate identification of ovulation is essential. A urinary ovulation test and serial blood samples for verification of progesterone postovulation enhance the proper identification of menstrual cycle events. Clinical Relevance: Given the cost of serial blood sampling on numerous days, the use of urinary ovulation kits and strategically selected serial blood sampling could significantly reduce participant burden and provide cost-effective measures for clinical studies related to anterior cruciate ligament injury epidemiology.