Barefoot Running Reduces the Submaximal Oxygen Cost in Female Distance Runners

Berrones, AJ, Kurti, SP, Kilsdonk, KM, Cortez, DJ, Melo, FF, and Whitehurst, M. Barefoot running reduces the submaximal oxygen cost in female distance runners. J Strength Cond Res 30(8): 2348-2353, 2016-Being a competitive distance runner is, in part, attributable to a high V[Combining Dot Above]O2max. However, running economy (RE) is a more robust indicator of distance running performance among endurance athletes of similar V[Combining Dot Above]O2max levels. The purpose of this study was to examine the influence of unshod (barefoot) vs. shod (wearing shoes) running on RE (expressed as ml·kg·min) during three 5-minute submaximal running trials representing 65, 75, and 85% of V[Combining Dot Above]O2max. Other physiologic and perceptual variables such as respiratory exchange ratio, lactate, heart rate, and ratings of perceived exertion were also chosen as dependent variables. We measured V[Combining Dot Above]O2max in 14 recreationally active trained distance female runners (age = 27.6 ± 1.6 years; height = 163.3 ± 1.7 cm; weight = 57.8 ± 1.9 kg) who were completely inexperienced with unshod running. After initial testing, each subject was randomized to either unshod or shod for days 2 and 3. We analyzed the data with a 2-way (condition by intensity) repeated-measures analysis of variance. Submaximal oxygen consumption was significantly reduced at 85% of V[Combining Dot Above]O2max (p = 0.018), indicating an improvement in RE, but not during the 65% or 75% trials (p > 0.05, both). No other dependent measure was different between unshod and shod conditions. Our results indicate that the immediate improvement to RE while barefoot occurs at a relatively high fraction of maximal oxygen consumption. For the recreational or competitive distance runner, training or competing while barefoot may be a useful strategy to improve endurance performance.

Association of calprotectin with leukocyte chemotactic and inflammatory mediators following acute aerobic exercise

The objective of this study was to examine whether acute aerobic exercise-mediated calprotectin in plasma would be associated with monocyte chemotactic protein-1 (MCP-1), myeloperoxidase (MPO), and interleukin-6 (IL-6) in healthy individuals. Eleven healthy participants, aged 18 to 30 years, were recruited to perform a 30-min bout of aerobic exercise at 75% maximal oxygen uptake. Acute aerobic exercise elicited a significant elevation across time in plasma calprotectin, MCP-1, MPO, and IL-6. Body mass index (BMI) was positively correlated with calprotectin area-under-the-curve with "respect to increase" (AUCi) and IL-6 AUCi. Furthermore, calprotectin AUCi was positively correlated with IL-6 AUCi and MPO AUCi, even after controlling for BMI. Although MPO AUCi was positively correlated with IL-6 AUCi, this relationship no longer existed after controlling for BMI. These results suggest that acute aerobic exercise could mediate innate immune response associated with calprotectin and its related leukocyte chemotactic and inflammatory mediators, especially in individuals with elevated BMI.

Attenuated fibroblast growth factor 21 response to acute aerobic exercise in obese individuals

BACKGROUND AND AIM

Fibroblast growth factor 21 (FGF21) is positively associated with body mass index, potentially as a compensatory mechanism to mediate obesity related metabolic and inflammatory insult due to chronic low-grade elevations of the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α). Therefore, FGF21 response in obese subjects and the associations with increased pro-inflammatory cytokines, insulin resistance, and energy utilization warrants investigation.

METHODS AND RESULTS

Twenty four untrained subjects (12 obese and 12 normal-weight) performed 30 min of continuous submaximal aerobic exercise. Following exercise, obese subjects exhibited a blunted FGF21 response to exercise compared to normal-weight subjects as indicated by area-under-the-curves "with respect to increase" (AUCi) analyses (p = 0.005). Furthermore, while exercise-induced plasma FGF21 was not associated with any inflammatory cytokine (IL-6 and TNF-α) response, FGF21 AUCi was positively correlated with glucose AUCi (r = 0.495, p = 0.014), total relative energy expenditure (r = 0.562, p = 0.004), and relative maximal oxygen consumption (VO2max; r = 0.646, p = 0.001) in all subjects.

CONCLUSION

Impaired cardiorespiratory fitness may influence the sensitivity of FGF21 response to acute exercise in obese individuals, potentially contributing to the attenuated metabolic response (e.g., glucose) and total exercise energy expenditure. Therefore, exercise training aimed at improving cardiorespiratory fitness and/or body composition may augment cardioprotective properties against obesity-associated CVD through enhanced FGF21 flux.

The impact of acute aerobic exercise on chitinase 3-like protein 1 and intelectin-1 expression in obesity

Chitinase 3-like 1 (CHI3L1) and intelectin 1 (ITLN-1) recognize microbial N-acetylglucosamine polymer and galactofuranosyl carbohydrates, respectively. Both lectins are highly abundant in plasma and seem to play pro- and anti-inflammatory roles, respectively, in obesity and inflammatory-related illnesses. The aim of this study was to examine whether plasma levels of these lectins in obese subjects are useful for monitoring inflammatory conditions immediately influenced by acute aerobic exercise. Plasma interleukin-6, a pro-inflammatory cytokine, was also examined. Twenty-two (11 obese and 11 normal-weight) healthy subjects, ages 18-30 years, were recruited to perform a 30 min bout of acute aerobic exercise at 75% VO2max. We confirmed higher baseline levels of plasma CHI3L1, but lower ITLN-1, in obese subjects than in normal-weight subjects. The baseline levels of CHI3L1 were negatively correlated with cardiorespiratory fitness (relative VO2max). However, when controlled for BMI, the relationship between baseline level of CHI3L1 and relative VO2max was no longer observed. While acute aerobic exercise elicited an elevation in these parameters, we found a lower ITLN-1 response in obese subjects compared to normal-weight subjects. Our study clearly indicates that acute aerobic exercise elicits a pro-inflammatory response (e.g. CHI3L1) with a lower anti-inflammatory effect (e.g. ITLN-1) in obese individuals. Furthermore, these lectins could be predictors of outcome of exercise interventions in obesity-associated inflammation.

Acute aerobic exercise mediates G protein-coupled receptor kinase 2 expression in human PBMCs

AIMS

G protein-coupled receptor kinase 2 (GRK2), a cytosolic enzyme desensitizing G protein-couple receptors (e.g., β-adrenergic receptors [β-ARs]), is involved in regulation of hypertension, congestive heart failure, and inflammatory response. Since cellular GRK2 levels change quickly in response to exogenous/endogenous stimuli, this study examined whether GRK2 levels in human peripheral blood mononuclear cells (PBMCs) would increase during acute aerobic exercise and be associated with plasma IL-6 and cardiorespiratory fitness levels.

MAIN METHODS

Eighteen subjects (8 men and 10 women), ages 18 to 30 years, were recruited to perform a 30-minute bout of acute aerobic exercise at 75% VO2max.

KEY FINDINGS

Our results demonstrated that women exhibited significantly greater exercise-induced GRK2 expression in PBMCs compared to men. IL-6 modulation is independent of GRK2 expression. Furthermore, the percent change in GRK2 expression was negatively correlated with cardiorespiratory fitness levels (relative VO2max), but not plasma IL-6.

SIGNIFICANCE

Acute aerobic exercise induces a greater GRK2 expression in women than men, while increased cardiorespiratory fitness is associated with exercise-induced GRK2 expression in PBMCs. Gender could be a contributor to regulate this GRK2 responsiveness to acute aerobic exercise.

Brain-derived neurotrophic factor and substrate utilization following acute aerobic exercise in obese individuals

Brain-derived neurotrophic factor (BDNF) serves as a vital regulator of neuronal proliferation and survival, and has been shown to regulate energy homeostasis, glucose metabolism and body weight maintenance. Elevated concentrations of plasma BDNF have been associated with obesity and type 2 diabetes mellitus. Acute aerobic exercise transiently increases circulating BDNF, potentially correcting obesity-related metabolic impairment. The present study aimed to compare acute aerobic exercise elicited BDNF responses in obese and normal-weight subjects. Furthermore, we aimed to investigate whether acute exercise-induced plasma BDNF elevations would be associated with improved indices of insulin resistance, as well as substrate utilization [carbohydrate oxidation (CHOoxi) and fat oxidation (FAToxi)]. Twenty-two healthy, untrained subjects [11 obese (four men and seven women; age = 22.91 ± 4.44 years; body mass index = 35.72 ± 4.17 kg/m(2)) and 11 normal-weight (five men and six women; age = 23.27 ± 2.24 years; body mass index = 21.89 ± 1.63 kg/m(2))] performed 30 min of continuous submaximal aerobic exercise at 75% maximal oxygen consumption. Our analyses showed that the BDNF response to acute aerobic exercise was similar in obese and normal-weight subjects across time (time: P = 0.015; group: P = not significant) and was not associated with indices of IR. Although no differences in the rates of CHOoxi and FAToxi were found between both groups, total relative energy expenditure was significantly lower in obese subjects compared to normal-weight subjects (3.53 ± 0.25 versus 5.59 ± 0.85; P < 0.001). These findings suggest that acute exercise-elicited BDNF elevation may not be sufficient to modulate indices of IR or the utilization of either carbohydrates or fats in obese individuals.

The impact of obesity on pentraxin 3 and inflammatory milieu to acute aerobic exercise

Pentraxin 3 (PTX3) has recently been linked to obesity-associated inflammation, serving as a cardioprotective modulator against cardiovascular disease (CVD). Aerobic exercise has been shown to enhance plasma PTX3 levels; however, the impact of obesity on PTX3 response to exercise remains unknown.

OBJECTIVE

Therefore, this study sought to examine whether obese subjects would have an attenuated plasma PTX3 response compared to normal-weight subjects following acute aerobic exercise. The relationship of plasma PTX3 with pro-inflammatory cytokines (IL-6 and TNF-α) was also examined.

METHODS

Twenty healthy subjects (10 obese [4 males and 6 females] and 10 normal-weight [4 males, 6 females]) performed 30min of continuous submaximal aerobic exercise.

RESULTS

At baseline, obese subjects exhibited approximately 40% lower plasma PTX3 and a 7-fold greater IL-6 concentration compared to normal-weight subjects. In response to exercise, no difference was observed in PTX3 or IL-6 as indicated by area-under-the-curve "with respect to increase" (AUCi) analyses. Furthermore, PTX3 AUCi was positively correlated with cardiorespiratory fitness levels (VO(2max)) (r=0.594, p=0.006), even after controlling for body mass index.

CONCLUSION

These findings suggest that in addition to obesity-associated complications, low cardiorespiratory fitness levels could impact exercise-induced PTX3 elevations, thereby potentially diminishing PTX3's effects of anti-inflammation and/or cardioprotection.

Brain-derived neurotrophic factor expression ex vivo in obesity

Obesity is associated with an increased risk in neurodegenerative diseases. To counteract the neuronal damage, the human body increases brain-derived neurotrophic factor (BDNF) expression, leading to neuronal survival and plasticity. Recently, peripheral blood mononuclear cells (PBMCs) have been found to release BDNF as a potential neuroprotective role of inflammation. Therefore, the purpose of this study was to examine whether lipopolysaccharide (LPS)-induced PBMC activation would lead to differences in BDNF and inflammatory responses between obese and non-obese subjects. Thirty-one subjects (14 obese and 17 non-obese), ages 18 to 30years, were recruited. PBMCs were cultured for 24h with 10ng/mL LPS. BDNF, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured in both plasma and cell culture supernatants. Our results did not illustrate any differences in plasma BDNF levels between obese and non-obese groups. However, obese subjects elicited a greater plasma IL-6 production, which was positively associated with plasma BDNF. Furthermore, LPS-induced PBMCs expressed significantly higher BDNF and IL-6 levels in obese subjects compared to the non-obese subjects. Finally, these BDNF levels were positively correlated with IL-6 response ex vivo. These findings suggest that under a high inflammatory state, PBMCs produce greater BDNF and IL-6 expression which may play a collaborative role to protect against neuronal damage associated with obesity.

Yoga Nidra relaxation increases heart rate variability and is unaffected by a prior bout of Hatha yoga

OBJECTIVE

The measurement of heart rate variability (HRV) is often applied as an index of autonomic nervous system (ANS) balance and, therefore, myocardial stability. Previous studies have suggested that relaxation or mind-body exercise can influence ANS balance positively as measured by HRV but may act via different mechanisms. No studies, to the authors' knowledge, have examined the acute response in HRV to interventions combining relaxation and mind-body exercise. The objective of this study was to compare the acute HRV responses to Yoga Nidra relaxation alone versus Yoga Nidra relaxation preceded by Hatha yoga.

DESIGN

This was a randomized counter-balanced trial.

SETTING

The trial was conducted in a university exercise physiology laboratory.

SUBJECTS

Subjects included 20 women and men (29.15±6.98 years of age, with a range of 18-47 years).

INTERVENTIONS

Participants completed a yoga plus relaxation (YR) session and a relaxation only (R) session.

RESULTS

The YR condition produced significant changes from baseline in heart rate (HR; beats per minute [bpm], p<0.001) and indices of HRV: R-R (ms, p<0.001), pNN50 (%, p=0.009), low frequency (LF; %, p=0.008) and high frequency (HF; %, p=0.035). The R condition produced significant changes from baseline in heart rate (bpm, p<0.001) as well as indices of HRV: R-R (ms, p<0.001), HF (ms(2), p=0.004), LF (%, p=0.005), HF (%, p=0.008) and LF:HF ratio (%, p=0.008). There were no significant differences between conditions at baseline nor for the changes from baseline for any of the variables.

CONCLUSIONS

These changes demonstrate a favorable shift in autonomic balance to the parasympathetic branch of the ANS for both conditions, and that Yoga Nidra relaxation produces favorable changes in measures of HRV whether alone or preceded by a bout of Hatha yoga.

High-Intensity Interval Training

High-intensity interval training (HIT) is characterized by intermittent periods of work and rest and may include work bouts lasting seconds to minutes. HIT has typically been applied to older, diseased, and at-risk populations using longer work intervals (2-4 minutes), whereas more recent definitions of HIT include work intervals of 30 to 60 s. Both traditional endurance training (TET) and HIT exert a peripheral affect increasing the capacity of muscle cells to oxidize substrate via signaling cascades that support the activation of transcription factors that orchestrate the coexpression of nuclear and mitochondrial genes, with HIT triggering these benefits following minutes of training. With 1 exception, reports of central adaptations (eg, increased stroke volume) have been based on longer work intervals (eg, 4 minutes). Recent investigations have tied HIT to increased lipolysis and enhanced insulin sensitivity. HIT favors the activation of oxidative as opposed to hypertrophic pathways. Although the length of the work interval may need to be adjusted to fit the needs and capacity of the participant, HIT should be considered as an alternative to TET for older adults with the expectation that it requires less time to execute, yet promotes peripheral and perhaps central adaptations.

Knee extensor function before and 1 year after simultaneous bilateral total knee arthroplasty: is there asymmetry between limbs?

One year after unilateral total knee arthroplasty (TKA), there is interlimb knee extensor function asymmetry. In the study reported here, we investigated whether there was knee extensor function "asymmetry" between limbs 1 year after simultaneous bilateral TKA. Fourteen patients volunteered to participate in this study before undergoing simultaneous bilateral TKA secondary to knee osteoarthritis. One year after surgery, 8 patients agreed to participate in follow-up testing. Torque production, work, and range of motion of knee extensors were assessed isokinetically at 1.047 radians . second(-1). Before surgery, there was no difference between limbs in peak torque, work, or range of motion during isokinetic testing. One year after surgery, this pattern persisted. The strength asymmetry evident in patients 1 year after unilateral TKA did not exist in patients who underwent simultaneous bilateral TKA. There is a symmetrical pattern between limbs for knee extensor function 1 year after the bilateral procedure.

A review of selected longitudinal studies on aging: past findings and future directions

A review of the 51 longitudinal aging studies currently in the National Institute on Aging Database of Longitudinal Studies was conducted to identify major information gaps and areas for future research. Database information, which included posted study summaries, study details from principal investigators or directors of these projects, and more than 300 recent publications based on the studies, were reviewed to identify significant findings of each study. This review summarizes the main findings and identifies the need for future work within six broad study topics: cognitive function, socioeconomic status, health and physical performance, morbidity and mortality predictors, healthcare costs, and genetics. The percentages of these 51 studies addressing the four most common topics are as follows: cognitive function (44%), health and physical performance (51%), socioeconomic factors (55%), and predictors of morbidity/mortality (63%). Important areas not addressed to any major degree were healthcare costs and genetics. Only two studies reported findings on genetics or epigenetics of human aging, and only a single study reported on associations between aging and financial costs, especially healthcare costs, which have been postulated to be important determinants of care and life quality. The results of this review, together with the specific directions proposed by other investigators with longitudinal study expertise, will inform the strategic planning of future long-term studies of aging.

Caffeine enhances upper body strength in resistance-trained women

Background

Research has indicated that low-to-moderate dosages of caffeine supplementation are ergogenic for sustained endurance efforts as well as high-intensity exercise. The effects of caffeine supplementation on strength-power performance are equivocal, with some studies indicating a benefit and others demonstrating no change in performance. The majority of research that has examined the effects of caffeine supplementation on strength-power performance has been carried out in both trained and untrained men. Therefore, the purpose of this study was to determine the acute effects of caffeine supplementation on strength and muscular endurance in resistance-trained women.

Methods

In a randomized manner, 15 women consumed caffeine (6 mg/kg) or placebo (PL) seven days apart. Sixty min following supplementation, participants performed a one-repetition maximum (1RM) barbell bench press test and repetitions to failure at 60% of 1RM. Heart rate (HR) and blood pressure (BP) were assessed at rest, 60 minutes post-consumption, and immediately following completion of repetitions to failure.

Results

Repeated measures ANOVA indicated a significantly greater bench press maximum with caffeine (p ≤ 0.05) (52.9 ± 11.1 kg vs. 52.1 ± 11.7 kg) with no significant differences between conditions in 60% 1RM repetitions (p = 0.81). Systolic blood pressure was significantly greater post-exercise, with caffeine (p < 0.05) (116.8 ± 5.3 mmHg vs. 112.9 ± 4.9 mmHg).

Conclusions

These findings indicate a moderate dose of caffeine may be sufficient for enhancing strength performance in resistance-trained women.

Knee extensor and flexor torque characteristics before and after unilateral total knee arthroplasty

OBJECTIVE

The purpose of this study was to document torque characteristics and strength recovery of the knee extensors and flexors before and up to 1 yr after unilateral total knee arthroplasty. Our goal was to also document the responsiveness of isokinetic testing over repeated measures.

DESIGN

Thirteen individuals voluntarily participated in this study. Torque production of the knee extensors and flexors was assessed isokinetically at 1.047 and 3.142 radians/sec.

RESULTS

Regardless of time, the knee extensors and flexors on the involved side generated a range of 76 and 82% of the average peak torque produced by the uninvolved side at both 1.047 and 3.142 radians/sec, respectively. At 30 days after surgery, there was a "dip" in both knee extensor and flexor torque production. Responsiveness indices for the knee extensors and flexors ranged from 0.95 to 2.12 at 1.047 radians/sec. At 3.142 radians/sec, the responsiveness indices for the knee extensors and flexors ranged from 0.65 to 2.87.

CONCLUSION

One year after surgery, there continues to be knee extensor and flexor strength asymmetry between limbs. Moreover, within the first month after surgery, the knee extensors and flexors are at the weakest point compared with before, 60 days, and 1 yr after surgery. Isokinetic testing is a useful tool to document torque production before and in the early time after unilateral total knee arthroplasty.

The influence of body position on load range during isokinetic knee extension/flexion

rate of velocity development (RVD), load range (LR), and deceleration (DCC). The purpose of this study was to determine if differences in isokinetic knee extension/flexion LR exist between body positions. Ten subjects (4 males and 6 females, age 29.3 ± 5.4 yrs, ht 1.71 ± 0.10 m, wt 71.9 ± 12.9 kg) volunteered to participate in the seated vs. prone investigation and nine different subjects (4 males and 5 females, age 29.5 ± 6.9 yrs, ht 1.72 ± 0.09 m, wt 69.0 ± 13.8 kg) volunteered to participate in the seated vs. supine study. Each subject completed 3 maximal reciprocal concentric/concentric repetitions of dominant knee extension/flexion on a Biodex System 2 isokinetic dynamometer at 60, 120, 180, 240 and 360 deg·sec(-1) in the supine or prone and seated positions. Repeated measures ANOVA revealed that only seated flexion at 360 deg·sec(-1) (57.6 ± 1.7 degrees) elicited significantly (p < 0.05) greater LR than prone (49.2 ± 2.8 degrees). No significant differences in LR extension or flexion existed at any velocity between the supine vs. seated positions. ANOVA also demonstrated differences between seated vs. prone torque, work and power at most velocities while there was no difference between seated vs. supine. LR is the only phase of an isokinetic repetition where quantifiable resistance is maintained and this data appears to support that it may not be position-dependent but position may alter traditional performance variables. Key PointsLoad range is the constant velocity phase where torque is collected.Load range has an inverse relationship with velocity.Load range may not be position dependent for the knee extensors or flexors.

Early strength response of the knee extensors during eight weeks of resistive training after unilateral total knee arthroplasty

The purpose of this study was to document the early history of knee extensor torque production before and after total knee arthroplasty (TKA), explore the relationship between strength assessments, and describe an 8-week resistive-training protocol. Thirty-eight individuals (19 men, 19 women) with unilateral TKA volunteered to participate in this repeated-measures study. For this group, the mean age was 72.23 +/- 5.34 years; height was 168.00 +/- 8.57 cm; and weight was 79.42 +/- 14.57 kg. Torque production of the knee extensors was assessed isokinetically at 60 and 180 degrees .s(-1) before surgery, 30 days after unilateral TKA (+30), and 60 days after unilateral TKA (+60). Torque production was significantly different between limbs at both 60 and 180 degrees .s(-1) (p < 0.0125) before surgery. Torque production was lower at +30 compared with before surgery at both 60 and 180 degrees .s(-1) (p < 0.002). By +60, torque production was greater than at +30 at both 60 and 180 degrees .s(-1) (p < 0.002).