In addition to skeletal muscle dysfunction, cancer cachexia is a systemic disease involving remodeling of nonmuscle organs such as adipose and liver. Impairment of mitochondrial function is ...associated with multiple chronic diseases. The tissue-specific control of mitochondrial function in cancer cachexia is not well defined. This study determined mitochondrial respiratory capacity and coupling control of skeletal muscle, white adipose tissue (WAT), and liver in colon-26 (C26) tumor-induced cachexia. Tissues were collected from PBS-injected weight-stable mice, C26 weight-stable mice and C26 mice with moderate (10% weight loss) and severe cachexia (20% weight loss). The respiratory control ratio (RCR) an index of oxidative phosphorylation (OXPHOS) coupling efficiency was low in WAT during the induction of cachexia because of high nonphosphorylating LEAK respiration. Liver RCR was low in C26 weight-stable and moderately cachexic mice because of reduced OXPHOS. Liver RCR was further reduced with severe cachexia, where Ant2 but not Ucp2 expression was increased. Ant2 was inversely correlated with RCR in the liver (
= -0.547,
< 0.01). Liver cardiolipin increased in moderate and severe cachexia, suggesting this early event may also contribute to mitochondrial uncoupling. Impaired skeletal muscle mitochondrial respiration occurred predominantly in severe cachexia, at complex I. These findings suggest that mitochondrial function is subject to tissue-specific control during cancer cachexia, whereby remodeling in WAT and liver arise early and may contribute to altered energy balance, followed by impaired skeletal muscle respiration. We highlight an under-recognized role of liver and WAT mitochondrial function in cancer cachexia and suggest mitochondrial function of multiple tissues to be therapeutic targets.
Obesity may attenuate the expression of brain-derived neurotrophic factor (BDNF), thereby increasing the risk of cognitive dysfunction. High-intensity interval exercise (HIIE) has been shown to be as ...or more effective than continuous moderate-intensity exercise (CME) in promoting the expression of BDNF in normal-weight individuals. Therefore, the primary purpose of this study was to examine whether or not acute HIIE could be utilized as a practical model to explore the BDNF response in obese versus normal-weight subjects when compared to acute CME. The potential relationship of exercise-induced BDNF with blood lactate and cortisol was also examined. Twelve male subjects (six obese and six normal-weight) participated in a counterbalanced and caloric equated experiment: HIIE (30 min, 4 intervals of 4 min at 80%–90% of VO2max with 3 min of active recovery at 50–60% VO2max) and CME (38 min at 50%–60% VO2max). Blood samples were collected prior to, immediately following exercise, and 1 h into recovery for measurements of serum BDNF, blood lactate, and plasma cortisol. Our results showed that the BDNF response to acute HIIE was greater than CME in obese subjects when compared to normal-weight subjects. Similarly, although acute HIIE induced greater blood lactate and plasma cortisol levels than CME, obese subjects produced less blood lactate, but no difference in cortisol than normal-weight subjects. These findings suggest that acute HIIE may be a more effective protocol to upregulate BDNF expression in an obese population, independent of increased lactate and cortisol levels.
Impact statement
High-intensity interval exercise (HIIE) has been shown to be a time-efficient exercise strategy that provides similar or superior physiological benefits as traditional continuous moderate-intensity exercise (CME). Our previous study demonstrated an equivalent elevation on the BDNF response in both obese and normal-weight individuals following 30 min of acute CME. To discover a time-efficient exercise strategy to improve brain health in an obese population, the present study found that obese individuals elicit a greater level of BDNF following acute HIIE versus CME than normal-weight individuals. These findings indicate that acute HIIE may be an effective strategy to upregulate BDNF expression in obese individuals.
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.
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.
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).
These findings indicate a moderate dose of caffeine may be sufficient for enhancing strength performance in resistance-trained women.
Graham, PL, Zoeller, RF, Jacobs, PL, and Whitehurst, MA. Effect of cadence on time trial performance in recreational female cyclists. J Strength Cond Res 32(6): 1739-1744, 2018-The impact of pedaling ...cadence on cycling performance remains unresolved especially in female cyclists. The purpose of this study was to determine the effect of cadence on time trial (TT) performance in recreational female cyclists. Ten recreational female cyclists volunteered to participate in this study. Subjects performed 3 exercise sessions: 1 to assess peak oxygen uptake (VCombining Dot AboveO2peak) and 2 TTs. Cadence was randomly ordered and fixed for each TT (60 or 100 rpm), whereas power output (PO) was freely adjusted by the participant, as tolerated. Time trial time, heart rate (HR), blood lactate, PO, VCombining Dot AboveO2, and ratings of perceived exertion were measured throughout the TTs. The major finding of this study was the significantly faster (p = 0.001) TT time during the 60-rpm condition (34:23 ± 4:21) vs. the 100-rpm condition (37:34 ± 5:53). Also the 60-rpm TT resulted in significant differences for HR (155.9 ± 3.97 vs. 161.2 ± 5.20 b·min, p = 0.04), gross efficiency, (21.1 ± 0.37 vs. 17.7 ± 0.85%, p < 0.001), and PO (147 ± 7.06 vs. 129 ± 10.62 W, p = 0.003). Thus, a slower cycling cadence was associated with greater mechanical efficiency and PO, resulting in significantly better performance in a TT. These results suggest that recreational female cyclists may benefit from adopting a low cadence during an 8-km TT.
Abstract 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 30 min 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 (VO2max ) (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.
Abstract 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 30 years, were recruited. PBMCs were cultured for 24 h with 10 ng/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.
C1q-TNF-related protein-9 (CTRP9) increases endothelial nitric oxide synthase and reduces vasoconstrictors. There is limited information regarding exercise-mediated CTRP9 in obesity. The purpose of ...this study was to compare high-intensity interval exercise (HIIE) and continuous moderate-intensity exercise (CME) on the CTRP9 response and an indicator of endothelial function (FMD) in obese participants. Sixteen young male participants (9 obese and 7 normal-weight) participated in a counterbalanced and caloric equated experiment: HIIE (30 min, 4 intervals of 4 min at 80–90% of VO2 max with 3 min rest between intervals) and CME (38 min at 50–60% VO2 max). Serum CTRP9 and FMD were measured prior to, immediately following exercise, and 1 h and 2 h into recovery. CTRP9 was significantly increased immediately following acute HIIE and CME in both groups (p = 0.003). There was a greater CME-induced FMD response at 2 h into recovery in obese participants (p = 0.009). A positive correlation between CTRP9 and FMD percent change was observed in response to acute CME when combined with both obese and normal-weight participants (r = 0.589, p = 0.016). The novel results from this study provide a foundation for additional examination of the mechanisms of exercise-mediated CTRP9 on endothelial function in individuals with obesity.
Introduction: The purpose of this study was to investigate the efficacy of daily one-repetition maximum (1RM) training of the back squat on maximal strength. Material and methods: Three competitive ...lifters performed the squat for 37 consecutive days and are reported as individual cases. Participant 1 (P1) (body mass = 80.5 kg; age = 28 yrs.) and participant 3 (P3) (body mass = 108.8 kg; age = 34 yrs.) were powerlifters; participant 2 (P2) (body mass = 64.1 kg; age = 19 yrs.) was a weightlifter. Each participant had at least 5 years of training experience with the squat. During days 1-35, participants performed a 1RM squat followed by 5 volume sets of 3 repetitions at 85% or 2 repetitions at 90% of the daily 1RM. On day-36, participants performed only 1 set of 1 repetition at 85% of day-1 1RM; and a final 1RM was performed on day-37. Results: Absolute and percent changes for P1 from day-1 to day-37 were +5 kg/2.3%, and from day-1 to peak (greatest 1RM of the period) were +12.5 kg/5.8%. P2 experienced a 13.5 kg/10.8% increase in 1RM from both day-1 to day-37 and day-1 to peak. P3 demonstrated a 21.0 kg/9.5% increase from both day-1 to day-37 and day-1 to peak. All 3 participants exhibited significant (p < 0.05) correlations between time (days) and 1RM (P1: r = 0.65, P2: r = 0.78, P3: r = 0.48). Conclusions: Our findings suggest that daily 1RM training effectively produced robust changes in maximal strength in competitive strength athletes in a relatively short training period.
The purpose of this study was to examine the effects of different durations of static stretching on dynamic balance. Women (N = 28) were tested before and after 2 stretching interventions and a ...control condition on 3 separate days, at least 48 hours apart. The stretching sessions involved a cycle ergometer warm-up at 70 rpm and 70 W followed by passive stretching of the lower-body muscles. Each stretching position was held at a point of mild discomfort and repeated 3 times with 15 seconds between stretches. In the 2 stretching protocols, the positions were maintained for 15 or 45 seconds. The control condition involved the same cycle ergometer warm-up, with a 26-minute rest period between pre- and posttests. Balance was assessed using the Biodex Balance System. A 2-way repeated-measures analysis of variance was used with the effects of study condition (control, 15 seconds, 45 seconds) and time (pre-, postscores). Post hoc paired t-tests were used when appropriate to determine possible statistical significance between pre- and posttest scores. Analyses indicated no significant main effects for either study condition or time. However, there was a significant condition x time interaction (p < 0.05). Post hoc analyses indicated that the 15-second condition produced a significant improvement in the balance scores (p < 0.01), with no significant effects with the control condition or the 45-second treatment. The results of this study reveal that a stretching protocol of 45-second hold durations does not adversely affect balance when using the current stabilometry testing procedure. Furthermore, a stretching intervention with 15-second hold durations may improve balance performance by decreasing postural instability. Strength and conditioning professionals concerned with reported performance limitations associated with static stretching should consider applying shorter-duration stretching protocols when aiming to improve balance performance.
Reactive oxygen and nitrogen species-mediated cellular aging has been linked to diseases such as atherothrombosis and cancer. Although pentraxin 3 (PTX3) is associated with aging-related diseases via ...TLR4-dependent anti-inflammatory effects, its relationship with oxidative stress in aging remains to be elucidated. Exercise is proposed as the key intervention for health maintenance in the elderly. This study aimed to examine the association of PTX3 levels with changes in oxidative stress in both plasma and peripheral blood mononuclear cells (PBMCs), following aerobic training in elderly adults. Nine trained and five controls participated in an eight-week aerobic training protocol. Enzyme-linked immunosorbent assay (ELISA) and Western blot analyses were used to determine PTX3, toll-like receptor 4 (TLR4), and levels of oxidative stress biomarkers 3-nitrotyrosine (3NT), 4-hydroxynonenal (4-HNE), reduced glutathione (GSH), protein carbonyl (PC), reactive oxygen/ nitrogen species (ROS/RNS), trolox equivalent antioxidant capacity (TEAC) in plasma and/or PBMCs. Results showed a down-regulation of PTX3 expression in PBMCs following aerobic training, along with decreased PTX3/TLR4 ratios. Oxidative stress responses in PBMCs remained unchanged with the exercise protocol. Comparable levels of plasma PTX3 and oxidative stress biomarkers were observed in trained vs. control groups. No correlation was found between PTX3 and any oxidative stress biomarkers following training. These findings demonstrated the down-regulation of PTX3 and PTX3/TLR4 ratio, irrespective of oxidative stress response, in elderly adults following eight weeks of aerobic training.
PDF
