Family Eating Behavior and Child Eating Patterns Differences Between Children With and Without Siblings.

OBJECTIVE: To examine the differences in family eating behaviors and child eating patterns in children with siblings (nonsingletons) and without siblings (singletons). METHODS: Cross-sectional analysis of mother-child dyads of 5-7-year-old children, (nonsingletons with a 2-to-4-year-old sibling) was conducted. Anthropometrics were measured. Mothers completed questionnaires and a child dietary log. Healthy Eating Index 2010 (HEI) score was calculated. Linear regression models adjusting for child age, child sex, maternal body mass index, and hours-away-from-home were conducted, with a revised P < .021. RESULTS: Sixty-eight mother-child dyads (27 singletons, 41 nonsingletons) participated. Singletons exhibited less healthy family eating behaviors (ß = -4.98, SE = 1.88, P = .003), and lower total HEI scores than did nonsingletons (average: ß = -8.91, SE =2.40, P = .001). On average, singletons had lower scores in 3 HEI components compared with nonsingletons (P < .021 for all). CONCLUSION: In this sample, singleton children exhibited less healthy eating behaviors. Additional investigation into parent-level differences is warranted.

Difference in Objectively Measured Physical Activity and Obesity in Children With and Without Siblings.

Background/Context: Children without siblings (singletons) have higher rates of obesity than do children with siblings (nonsingletons). Higher moderate to vigorous physical activity (PA) and less sedentary behavior (SB) are associated with lower childhood obesity. PURPOSE: To examine the difference in PA and SB between singleton and nonsingleton children. METHODS: Mothers of children ages 5.0-7.9 years old who were singletons or nonsingletons with a sibling between the ages of 2.0 and 4.9 years old were recruited. Height, weight, and waist circumference of the 5.0- to 7.9-year-old children were measured, and age and sex percentiles were calculated. Accelerometry measured SB and PA, including light PA, moderate to vigorous PA, and counts per minute. RESULTS: Fifty-six mother-child dyads (23 singletons and 33 nonsingletons) with an average child age of 5.7 (0.7) years participated. More singletons were classified as overweight or obese than were nonsingletons (49% vs 17%, P = .04). In adjusted linear models, singletons had less light PA per day (ß = -38.1, SE = 19.2, P = .001) and more SB (ß = 38.0, SE = 16.5, P = .02) than did nonsingletons, with no difference in moderate to vigorous PA or counts per minute. CONCLUSION: In this sample, singletons had higher obesity and lower light PA than did nonsingleton children. Investigation into differences in singleton/nonsingleton families, including family health behaviors, may help assess sibling influence in early behavior development.

Montmorency tart cherry protects against age-related bone loss in female C57BL/6 mice and demonstrates some anabolic effects.

PURPOSE: Age-related bone loss is a consequence of endocrine and immune changes that disrupt bone remodeling. Functional foods (e.g., tart cherries) with antioxidant, anti-inflammatory and prebiotic activity can potentially counter this age-related phenomenon. The aim of this study was to determine if Montmorency tart cherry protects against early age-related bone loss and the culpable alterations in bone metabolism. METHODS: Female, 5-month-old, C57BL/6 mice were assigned to baseline or treatment groups: AIN-93M diet supplemented with 0, 1, 5, or 10% tart cherry for 90 days. Bone mineral density (BMD) and trabecular and cortical bone microarchitecture were assessed. Treatment effects on bone metabolism and regulators of bone formation, resorption and mineralization were determined. RESULTS: Mice consuming the 5% and 10% doses had higher vertebral and tibial BMD (p < 0.05) compared to controls. The age-related decrease in trabecular bone volume (BV/TV) of the distal femur was prevented with these doses. Vertebral trabecular BV/TV and cortical bone thickness of the femur mid-diaphysis were greater (p < 0.05) in the groups receiving the 5% and 10% cherry than the control diet. Notably, these improvements were significantly greater than the baseline controls, consistent with an anabolic response. Although no differences in systemic biomarkers of bone formation or resorption were detected at 90 days, local increases in Phex and decreases in Ppar-γ suggest a bone environment that supports increased mineralization. CONCLUSIONS: These findings demonstrate that cherry supplementation (5% and 10%) improves BMD and some indices of trabecular and cortical bone microarchitecture; these effects are likely attributed to increased bone mineralization.

Dried Plum Polyphenolic Extract Combined with Vitamin K and Potassium Restores Trabecular and Cortical Bone in Osteopenic Model of Postmenopausal Bone Loss.

Dried plum has unique anabolic effects on bone, but the responsible bioactive components have remained unclear. This study investigated components of dried plum with potential osteoprotective activity utilizing aged, osteopenic Sprague Dawley rats fed diets supplemented with a crude polyphenol extract, potassium, vitamin K or their combination. Whole body and femoral bone mineral density were restored with the polyphenol and combination treatments to a similar extent as the dried fruit. The combination treatment reversed trabecular bone loss in the spine and cortical bone in the femur mid-diaphysis in a similar manner. Biomarkers of bone resorption were reduced by the polyphenol and combination treatments. The polyphenol extract accounted for most of the anabolic effect of dried plum on bone. This study is the first to show the bioactive components in dried plum responsible for restoring bone in vivo.

Select polyphenolic fractions from dried plum enhance osteoblast activity through BMP-2 signaling.

Dried plum supplementation has been shown to enhance bone formation while suppressing bone resorption. Evidence from previous studies has demonstrated that these responses can be attributed in part to the fruit's polyphenolic compounds. The purpose of this study was to identify the most bioactive polyphenolic fractions of dried plum with a focus on their osteogenic activity and to investigate their mechanisms of action under normal and inflammatory conditions. Utilizing chromatographic techniques, six fractions of polyphenolic compounds were prepared from a crude extract of dried plum. Initial screening assays revealed that two fractions (DP-FrA and DP-FrB) had the greatest osteogenic potential. Subsequent experiments using primary bone-marrow-derived osteoblast cultures demonstrated these two fractions enhanced extracellular alkaline phosphatase (ALP), an indicator of osteoblast activity, and mineralized nodule formation under normal conditions. Both fractions enhanced bone morphogenetic protein (BMP) signaling, as indicated by increased Bmp2 and Runx2 gene expression and protein levels of phosphorylated Smad1/5. DP-FrB was most effective at up-regulating Tak1 and Smad1, as well as protein levels of phospho-p38. Under inflammatory conditions, TNF-α suppressed ALP and tended to decrease nodule formation (P=.0674). This response coincided with suppressed gene expression of Bmp2 and the up-regulation of Smad6, an inhibitor of BMP signaling. DP-FrA and DP-FrB partially normalized these responses. Our results show that certain fractions of polyphenolic compounds in dried plum up-regulate osteoblast activity by enhancing BMP signaling, and when this pathway is inhibited by TNF-α, the osteogenic response is attenuated.

Osteoclast Differentiation is Downregulated by Select Polyphenolic Fractions from Dried Plum via Suppression of MAPKs and Nfatc1 in Mouse C57BL/6 Primary Bone Marrow Cells.

Background: Clinical and preclinical studies have shown that dietary supplementation with dried plum improves bone health. These osteoprotective effects are a result, in part, of the antiresorptive properties of the fruit, which appear to be mediated by its polyphenolic compounds. Objective: This study was designed to determine if certain fractions of the polyphenolic compounds in dried plums are responsible for the antiresorptive effects and whether they alter mitogen-activated protein kinase (MAPK) and calcium signaling, which are essential to osteoclast differentiation and activity, under normal and inflammatory conditions. Methods: Six polyphenolic fractions were derived from the total polyphenolic extract of dried plum based on solubility. Initial screening, with the use of the Raw 264.7 monocyte and macrophage cell line, showed that 3 fractions had the most marked capacity to downregulate osteoclast differentiation. This response was confirmed in 2 of the fractions by using primary bone marrow-derived cultures and in all subsequent experiments to determine how osteoclast differentiation and function were altered with a focus on these 2 fractions in primary cultures. Data were analyzed by using ANOVA followed by post hoc analyses. Results: Both of the polyphenol fractions decreased osteoclast differentiation and activity coincident with downregulating nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (Nfatc1), which is required for osteoclast differentiation. Calcium signaling, essential for the auto-amplification of Nfatc1, was suppressed by the polyphenolic fractions under normal conditions as indicated by suppressed mRNA expression of costimulatory receptors osteoclast-associated receptor (Oscar), signaling regulatory protein ß1 (Sirpb1), and triggering receptor expressed on myeloid cells 2 (Trem2). In contrast, in the presence of tumor necrosis factor α (TNF-α), only Sirpb1 was downregulated. In addition to calcium signaling, phosphorylation of extracellular signal-regulated kinase (Erk) and p38 MAPK, involved in the expression and activation of Nfatc1, was also suppressed by the polyphenolic fractions. Conclusion: These results show that certain types of polyphenolic compounds from dried plum downregulate calcium and MAPK signaling, resulting in suppression of Nfatc1 expression, which ultimately decreases osteoclast formation and activity.

Strain differences in the attenuation of bone accrual in a young growing mouse model of insulin resistance.

Skeletal fractures are considered a chronic complication of type 2 diabetes mellitus (T2DM), but the etiology of compromised bone quality that develops over time remains uncertain. This study investigated the concurrent alterations in metabolic and skeletal changes in two mouse strains, a responsive (C57BL/6) and a relatively resistant (C3H/HeJ) strain, to high-fat diet-induced glucose intolerance. Four-week-old male C57BL/6 and C3H/HeJ mice were randomized to a control (Con = 10 % kcal fat) or high-fat (HF = 60 % kcal fat) diet for 2, 8, or 16 weeks. Metabolic changes, including blood glucose, plasma insulin and leptin, and glucose tolerance were monitored over time in conjunction with alterations in bone structure and turn over. Elevated fasting glucose occurred in both the C57BL/6 and C3H/HeJ strains on the HF diet at 2 and 8 weeks, but only in the C57BL/6 strain at 16 weeks. Both strains on the HF diet demonstrated impaired glucose tolerance at each time point. The C57BL/6 mice on the HF diet exhibited lower whole-body bone mineral density (BMD) by 8 and 16 weeks, but the C3H/HeJ strain had no evidence of bone loss until 16 weeks. Analyses of bone microarchitecture revealed that trabecular bone accrual in the distal femur metaphysis was attenuated in the C57BL/6 mice on the HF diet at 8 and 16 weeks. In contrast, the C3H/HeJ mice were protected from the deleterious effects of the HF diet on trabecular bone. Alterations in gene expression from the femur revealed that several toll-like receptor (TLR)-4 targets (Atf4, Socs3, and Tlr4) were regulated by the HF diet in the C57BL/6 strain, but not in the C3H/HeJ strain. Structural changes observed only in the C57BL/6 mice were accompanied with a decrease in osteoblastogenesis after 8 and 16 weeks on the HF diet, suggesting a TLR-4-mediated mechanism in the suppression of bone formation. Both the C57BL/6 and C3H/HeJ mice demonstrated an increase in osteoclastogenesis after 8 weeks on the HF diet; however, bone turnover was decreased in the C57BL/6 with prolonged hyperglycemia. Further investigation is needed to understand how hyperglycemia and hyperinsulinemia suppress bone turnover in the context of T2DM and the role of TLR-4 in this response.

Mechanical scale and load cell underwater weighing: a comparison of simultaneous measurements and the reliability of methods.

Both load cell and mechanical scale-based hydrostatic weighing (HW) systems are used for the measurement of underwater weight. However, there has been no direct comparison of the 2 methods. The purpose of the current investigation was to simultaneously compare a load cell and mechanical scale for use in HW. Twenty-seven men and women (mean ± SD, age: 22 ± 2 years) participated in the 2-day investigation. Each subject completed 2 HW assessments 24 hours apart. Single-day comparisons of all trials for both days revealed no significant difference between the mechanical scale and the load cell (mean difference < 0.016 kg, p > 0.05). True underwater weight values were not significantly different between methods for either days (mean difference < 0.014 kg, p > 0.05) and accounted for a mean difference in percent fat (%FAT) of <0.108%. The 95% limits of agreement indicated a maximum difference between methods of 0.53% FAT. Both methods produced similar reliability SEM values (mechanical SEM < 0.72%FAT, load cell SEM < 0.75%FAT). In conclusion, there was no difference between mechanical scale and load cell measurements of underwater weights and the added precision of the load cell only marginally (<0.16%FAT) improved day-to-day reliability. Either a mechanical scale or load cell can be used for HW with similar accuracy and reliability in young adults with a body mass index of 18.7-34.4 (5-25%FAT).

Reproducibility and validity of bioimpedance spectroscopy for tracking changes in total body water: implications for repeated measurements.

Bioimpedance spectroscopy (BIS) has been used to track changes in total body water (TBW). Accurate TBW estimations can be influenced by both methodological and biological factors. One methodological variation that contributes to BIS TBW errors is the electrode placement. The purpose of the present study was to compare the reproducibility and validity of fixed-distance electrode placements (5 cm) with the standard single-site electrode placements. Twenty-nine subjects (fifteen men and fourteen women) participated in the reproducibility study, while sixty-nine subjects (thirty-three men and thirty-six women) participated in the validity study. The reproducibility study included two measurements that were taken 24 h apart, while the validity study consisted of a 12-week exercise intervention with measurements taken at weeks 1 and 12. TBW was estimated using BIS and 2H techniques. Reproducibility results indicated that fixed-distance electrodes reduced the day-to-day standard error of the measurement in men (from 1·13 to 0·81 litres) but not in women (0·47 litres). sem values were lower for women than for men, suggesting that BIS TBW estimates are sex dependent. Validity results produced similar accurate findings (mean difference < 0·21 litres). However, fixed-distance electrodes improved delta TBW errors (mean difference improvements>0·04 litres in men, women, and men and women combined). When tracking changes in TBW, fixed-distance electrodes may reduce reproducibility errors and allow for smaller changes to be detected. However, the reduction of reproducibility errors may be greater for men than for women. Therefore, reproducibility calculations should be based on the sex of the sample population.

Validity of electromyographic fatigue threshold as a noninvasive method for tracking changes in ventilatory threshold in college-aged men.

The submaximal electromyographic fatigue threshold test (EMG(FT)) has been shown to be highly correlated to ventilatory threshold (VT) as determined from maximal graded exercise tests (GXTs). Recently, a prediction equation was developed using the EMG(FT) value to predict VT. The aim of this study, therefore, was to determine if this new equation could accurately track changes in VT after high-intensity interval training (HIIT). Eighteen recreationally trained men (mean +/- SD; age 22.4 +/- 3.2 years) performed a GXT to determine maximal oxygen consumption rate (V(O2)peak) and VT using breath-by-breath spirometry. Participants also completed a discontinuous incremental cycle ergometer test to determine their EMGFT value. A total of four 2-minute work bouts were completed to obtain 15-second averages of the electromyographic amplitude. The resulting slopes from each successive work bout were used to calculate EMG(FT). The EMG(FT) value from each participant was used to estimate VT from the recently developed equation. All participants trained 3 days a week for 6 weeks. Training consisted of 5 sets of 2-minute work bouts with 1 minute of rest in between. Repeated-measures analysis of variance indicated no significant difference between actual and predicted VT values after 3 weeks of training. However, there was a significant difference between the actual and predicted VT values after 6 weeks of training. These findings suggest that the EMG(FT) may be useful when tracking changes in VT after 3 weeks of HIIT in recreationally trained individuals. However, the use of EMG(FT) to predict VT does not seem to be valid for tracking changes after 6 weeks of HIIT. At this time, it is not recommended that EMG(FT) be used to predict and track changes in VT.

Low-calorie energy drink improves physiological response to exercise in previously sedentary men: a placebo-controlled efficacy and safety study.

Energy drink use has grown despite limited research to support efficacy or safety and amid concerns when combined with exercise. The purpose of this study was to assess the effects of 10 weeks of once-daily energy drink consumption or energy drink consumption with exercise on measures of body composition, cardiorespiratory fitness, strength, mood, and safety in previously sedentary males. Thirty-eight males were randomly assigned to energy drink + exercise (EX-A), energy drink (NEX-A), placebo + exercise (EX-B), or placebo (NEX-B). All participants consumed 1 drink per day for 10 weeks; EX-A and EX-B participated in 10 weeks of resistance and endurance exercise. Testing was performed before (PRE) and after (POST) the 10-week intervention. No significant (p > 0.05) changes were observed for body composition, fitness, or strength in NEX-A; however, significantly greater decreases in fat mass and percentage body fat and increases in VO2peak were observed in EX-A versus EX-B. Ventilatory threshold (VT), minute ventilation, VO2 at VT, and power output at VT improved significantly PRE to POST in EX-A but not in EX-B or nonexercising groups. Clinical markers for hepatic, renal, cardiovascular, and immune function, as determined by PRE and POST blood work revealed no adverse effects in response to the energy drink. Mood was not affected by energy drink use. Absent energy restriction or other dietary controls, chronic ingestion of a once-daily low-calorie energy drink appears ineffective at improving body composition, cardiorespiratory fitness, or strength in sedentary males. However, when combined with exercise, preworkout energy drink consumption may significantly improve some physiological adaptations to combined aerobic and resistance training.

The effects of four weeks of creatine supplementation and high-intensity interval training on cardiorespiratory fitness: a randomized controlled trial.

BACKGROUND: High-intensity interval training has been shown to be a time-efficient way to induce physiological adaptations similar to those of traditional endurance training. Creatine supplementation may enhance high-intensity interval training, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of high-intensity interval training (HIIT) and creatine supplementation on cardiorespiratory fitness and endurance performance (maximal oxygen consumption (VO2PEAK), time-to-exhaustion (VO2PEAKTTE), ventilatory threshold (VT), and total work done (TWD)) in college-aged men. METHODS: Forty-three recreationally active men completed a graded exercise test to determine VO2PEAK, VO2PEAKTTE, and VT. In addition, participants completed a time to exhaustion (TTE) ride at 110% of the maximum workload reached during the graded exercise test to determine TWD (TTE (sec) x W = J). Following testing, participants were randomly assigned to one of three groups: creatine (creatine citrate) (Cr; n = 16), placebo (PL; n = 17), or control (n = 10) groups. The Cr and PL groups completed four weeks of HIIT prior to post-testing. RESULTS: Significant improvements in VO2PEAK and VO2PEAKTTE occurred in both training groups. Only the Cr group significantly improved VT (16% vs. 10% improvement in PL). No changes occurred in TWD in any group. CONCLUSION: In conclusion, HIIT is an effective and time-efficient way to improve maximal endurance performance. The addition of Cr improved VT, but did not increase TWD. Therefore, 10 g of Cr per day for five days per week for four weeks does not seem to further augment maximal oxygen consumption, greater than HIIT alone; however, Cr supplementation may improve submaximal exercise performance.

Effects of four weeks of high-intensity interval training and creatine supplementation on critical power and anaerobic working capacity in college-aged men.

The critical power test provides 2 measures, critical power (CP) and anaerobic working capacity (AWC). In theory, the CP measurement represents the maximal power output that can be maintained without fatigue, and AWC is an estimate of work capacity associated with muscle energy reserves. High-intensity interval training (HIIT) has been shown to be an effective training method for improving endurance performance, including VO2PEAK. In addition, creatine (Cr) supplementation has been reported to improve AWC without training; however, it has shown no effect on CP. The purpose of this study was to examine the effects of 4 weeks of HIIT with Cr supplementation on CP and AWC. Forty-two recreationally active men volunteered to participate in this study. Participants were randomly assigned to 1 of 3 groups: Cr (n = 16), 10 g Cr + 10 g dextrose; placebo (PL, n = 16), 20 g dextrose; control (CON, n = 10), no treatment. Before and after supplementation, each participant performed a maximal oxygen consumption test VO2PEAK on a cycle ergometer to establish peak power output (PPO). Participants then completed a CP test involving 3 exercise bouts with the workloads set as a percentage of their PPO to determine CP and AWC. After a 2-week familiarization period of training and supplementing, PPO, CP, and AWC were remeasured before an additional 4 weeks of HIIT and supplementation were completed. Training consisted of 5 sets of 2-minute exercise bouts with 1 minute rest in between performed on the cycle ergometer, with intensities based on PPO. A significant improvement in CP was observed in the Cr group (6.72% +/- 2.54%), whereas PL showed no significant change (3.87% +/- 2.30%), and CON significantly decreased (6.27% +/- 2.38%). Furthermore, no changes in AWC were observed in any of the groups after treatment. The current findings suggest that Cr supplementation may enhance the effects of intense interval endurance training on endurance performance changes.

Total body water changes after an exercise intervention tracked using bioimpedance spectroscopy: a deuterium oxide comparison.

BACKGROUND & AIMS: Bioimpedance spectroscopy (BIS) for the estimation of total body water (TBW) has advantages over isotope dilution techniques, including cost, portability, and ease of use. The aim of the current study was to determine the validity of a BIS device (Imp SFB7) for tracking changes in overfat and obese individuals. METHODS: Sixty overfat and obese men and women (27+/-8 yr, 33.41+/-3.81%fat) participated in the study. TBW was estimated using BIS and deuterium oxide (D(2)O) before and after the ten-week intervention. RESULTS: Pre-and post-intervention BIS TBW estimations errors increased as body mass index (BMI), fat mass (FM), and fat-free mass (FFM) increased (p<0.05). Delta values were more accurate than pre- and post-TBW estimations (total error=1.45 L). Age significantly influenced pre- and post-TBW errors (p<0.05). Therefore, a regression equation was developed to correct for the pre- and post-BIS-estimated TBW errors: D(2)O TBW=11.478+0.743(BIS TBW)-2.429(Gender), (Men=1, Women=2). CONCLUSIONS: BIS can be considered an accurate tool for tracking changes in TBW regardless of variations in BMI, FM, FFM, or age in both overfat and obese men and women (BMI>24). Employing a BIS TBW equation is suggested over the development of resistivity coefficients based on BMI, FM, FFM or age.

Effects of beta-alanine supplementation and high-intensity interval training on endurance performance and body composition in men; a double-blind trial.

BACKGROUND: Intermittent bouts of high-intensity exercise result in diminished stores of energy substrates, followed by an accumulation of metabolites, promoting chronic physiological adaptations. In addition, beta-alanine has been accepted has an effective physiological hydrogen ion (H+) buffer. Concurrent high-intensity interval training (HIIT) and beta-alanine supplementation may result in greater adaptations than HIIT alone. The purpose of the current study was to evaluate the effects of combining beta-alanine supplementation with high-intensity interval training (HIIT) on endurance performance and aerobic metabolism in recreationally active college-aged men. METHODS: Forty-six men (Age: 22.2 +/- 2.7 yrs; Ht: 178.1 +/- 7.4 cm; Wt: 78.7 +/- 11.9; VO2peak: 3.3 +/- 0.59 l.min-1) were assessed for peak O2 utilization (VO2peak), time to fatigue (VO2TTE), ventilatory threshold (VT), and total work done at 110% of pre-training VO2peak (TWD). In a double-blind fashion, all subjects were randomly assigned into one either a placebo (PL - 16.5 g dextrose powder per packet; n = 18) or beta-alanine (BA - 1.5 g beta-alanine plus 15 g dextrose powder per packet; n = 18) group. All subjects supplemented four times per day (total of 6 g/day) for the first 21-days, followed by two times per day (3 g/day) for the subsequent 21 days, and engaged in a total of six weeks of HIIT training consisting of 5-6 bouts of a 2:1 minute cycling work to rest ratio. RESULTS: Significant improvements in VO2peak, VO2TTE, and TWD after three weeks of training were displayed (p < 0.05). Increases in VO2peak, VO2TTE, TWD and lean body mass were only significant for the BA group after the second three weeks of training. CONCLUSION: The use of HIIT to induce significant aerobic improvements is effective and efficient. Chronic BA supplementation may further enhance HIIT, improving endurance performance and lean body mass.

The effects of beta-alanine supplementation and high-intensity interval training on neuromuscular fatigue and muscle function.

The purpose of this study was to determine the effects of beta-alanine supplementation and high-intensity interval training (HIIT) on electromyographic fatigue threshold (EMG(FT)) and efficiency of electrical activity (EEA). A total of 46 men completed four, 2-min work bouts on a cycle ergometer. Using bipolar surface electrodes, the EMG amplitude was averaged and plotted over the 2-min. The resulting slopes were used to calculate EMG(FT) and EEA. Following initial testing, all participants were randomly assigned to either placebo (PL; n = 18), beta-alanine (BA; n = 18) or control groups (CON; n = 10). Following randomization, participants engaged in 6 weeks of HIIT training. Significant improvements in EMG(FT) and EEA resulted for both training groups. In conclusion, HIIT appeared to be the primary stimulus effecting EMG(FT) or EEA, suggesting adaptations from HIIT may be more influential than increasing skeletal muscle carnosine levels on delaying fatigue in recreationally active men.

The relationships among endurance performance measures as estimated from VO2PEAK, ventilatory threshold, and electromyographic fatigue threshold: a relationship design.

BACKGROUND: The use of surface electromyography has been accepted as a valid, non-invasive measure of neuromuscular fatigue. In particular, the electromyographic fatigue threshold test (EMG(FT)) is a reliable submaximal tool to identify the onset of fatigue. This study examined the metabolic relationship between VO(2PEAK), ventilatory threshold (VT), and the EMGFT, as well as compared the power output at VO(2PEAK), VT, and EMG(FT). METHODS: Thirty-eight college-aged males (mean +/- SD = 22.5 +/- 3.5 yrs) performed an incremental test to exhaustion on an electronically-braked cycle ergometer for the determination of VO(2PEAK) and VT. Each subject also performed a discontinuous incremental cycle ergometer test to determine their EMG(FT) value, determined from bipolar surface electrodes placed on the longitudinal axis of the vastus lateralis of the right thigh. Subjects completed a total of four, 2-minute work bouts (ranging from 75-325 W). Adequate rest was given between bouts to allow for subjects' heart rate to drop within 10 beats of their resting heart rate. The EMG amplitude was averaged over 10-second intervals and plotted over the 2-minute work bout. The resulting slopes from each successive work bout were used to calculate EMG(FT). RESULTS: Power outputs and VO2 values from each subject's incremental test to exhaustion were regressed. The linear equations were used to compute the VO2 value that corresponded to each fatigue threshold. Two separate one-way repeated measure ANOVAs indicated significant differences (p < 0.05) among metabolic parameters and power outputs. However, the mean metabolic values for VT (1.90 +/- 0.50 l.min-1) and EMG(FT)VO2(1.84 +/- 0.53 l.min-1) were not significantly different (p > 0.05) and were highly correlated (r = 0.750). Furthermore, the mean workload at VT was 130.7 +/- 37.8 W compared with 134.1 +/- 43.5 W at EMG(FT) (p > 0.05) with a strong correlation between the two variables (r = 0.766). CONCLUSION: Metabolic measurements, as well as the power outputs at VT and EMG(FT), were strongly correlated. The significant relationship between VT and EMG(FT) suggests that both procedures may reflect similar physiological factors associated with the onset of fatigue. As a result of these findings, the EMG(FT) test may provide an attractive alternative to estimating VT.