Autophagy is stimulated by acute high intensity interval exercise in human skeletal muscle and electrical pulse stimulation in C2C12 myotubes in vitro

Purpose: 1) To compare the effects of an acute bout of HIIT exercise (treadmill running) on autophagy to MICT exercise in human skeletal muscle 3 hours post exercise, and 2) to test an in vitro model of muscle contraction-induced autophagy using electrical pulse stimulation in C2C12 myotubes. Methods: Study 1: Ten recreationally active males and females completed a bout of high intensity interval training (HIIT) exercise and moderate intensity continuous exercise (MICT) exercise in a fasted state. Muscle biopsies from the vastus lateralis were taken pre and 3 hours post-exercise. Muscle tissue was analyzed for protein expression of markers of autophagy (LC3I, LC3II) and autophagy signaling (p38MAPK). Study 2: C2C12 myoblasts were differentiated into myotubes and underwent 8 hours of low-frequency electrical pulse stimulation (EPS) and starvation (St) and EPS+St conditions with and without bafilomycin A1 (Baf) or non-treatment control conditions (Con). Cells were harvested immediately following EPS and analyzed for protein expression of markers of autophagy (LC3I, LC3II, and p62). Results: Study 1: No differences were detected for LC3I, LC3II, and p38MAPK at the 3h time point vs. pre-exercise in both HIIT and MICT conditions. The LC3II:LC3I ratio increased 3-h post exercise in the HIIT (162.4, SE: 45.9%), which was significantly higher than the 3h timepoint in the MICT (48.8, SE: 9.4%; p\u3c0.05) Study 2: LC3II (324.4, SE: 29.8%) LC3II:I (258.2, SE: 323.3%), and p62 (437.8, SE: 9.7%) were significantly higher in EPS+Baf conditions compared to control (100%, SE: 9.3, 8.8, 22.6%, respectively) and EPS alone (127.7, SE: 24.3%; 95.5, SE: 13.2%, 251.2, SE: 33.2%) . p62 protein expression was also higher in EPS compared to Con and in St+Baf (320.9, SE: 65.9%) compared Con and St (91, SE: 20.3%). There were no differences between EPS and St alone vs. combined EPS+St conditions in LC3I, LC3II, LC3II:I or p62. Conclusions: HIIT stimulates autophagy in a distinct fashion compared to MICT. Additionally, EPS may serve as an in vitro model for muscle contraction-induced autophagy in C2C12 myotubes in fed and fasted conditions. s

The Effects of Elevation Gain on the Pack Hike Test: Implications for Interagency Hotshot Crews

It is unknown if administering a graded load carriage task, which more closely mirrors the occupational circumstances wildland firefighters are exposed to, improves the validity of the Pack Hike Test and its’ ability to differentiate between the fitness profiles amongst Interagency Hotshots (IHC) and type 2 crews. PURPOSE: The aim of the current study was to examine the performance differences and HR responses between IHC and type 2 crews when completing a maximal effort graded load carriage task. METHODS: This study compared performance outcome measures amongst two classes of hand crews, Type 1 (IHC; n=12) and Type 2 (T2C; n=7). All participants engaged in one maximal effort hike test, which covered 1.3 miles with a 16.5% grade while carrying a 45 lb. load carriage system. Additionally, participants were instructed to complete the hike at a maximal pace and were given no feedback or motivation during the execution of the test. Immediately following the termination of the test, participants were instructed to perform a supine 1-minute recovery period. Participants wore Polar H10 monitors in order to collect the following variables: Pace (min/mile), HR recovery (bpm), HR average (bpm) and HR max (bpm). RESULTS: There were no significant differences between groups for any of the performance or HR response variables (p\u3e.05). Compared to T2C, IHC pace (-2.07 min/mile) as well as HR recovery (+3.00 bpm) values trended towards increased performance. Additionally, a tendency emerged for IHC members to sustain higher physiological stress, as indicated by greater relative HR average (+8.18 bpm) and HR max (+8.51 bpm) values. CONCLUSION: IHC, compared to T2C, showed a slight positive trend in their ability to sustain maximal work rates for a longer duration, thus resulting in improved hiking performance. A maximal effort graded load carriage test may provide a better understanding of occupational fitness amongst wildland firefighters

Autophagy and Aging: Maintaining the Proteome through Exercise and Caloric Restriction

Accumulation of dysfunctional and damaged cellular proteins and organelles occursduring aging, resulting in a disruption of cellular homeostasis and progressive degen-eration and increases the risk of cell death. Moderating the accrual of these defunctcomponents is likely a key in the promotion of longevity. While exercise is knownto promote healthy aging and mitigate age‐related pathologies, the molecular under-pinnings of this phenomenon remain largely unclear. However, recent evidencessuggest that exercise modulates the proteome. Similarly, caloric restriction (CR), aknown promoter of lifespan, is understood to augment intracellular protein quality.Autophagy is an evolutionary conserved recycling pathway responsible for thedegradation, then turnover of cellular proteins and organelles. This housekeepingsystem has been reliably linked to the aging process. Moreover, autophagic activitydeclines during aging. The target of rapamycin complex 1 (TORC1), a central kinaseinvolved in protein translation, is a negative regulator of autophagy, and inhibitionof TORC1 enhances lifespan. Inhibition of TORC1 may reduce the production ofcellular proteins which may otherwise contribute to the deleterious accumulationobserved in aging. TORC1 may also exert its effects in an autophagy‐dependentmanner. Exercise and CR result in a concomitant downregulation of TORC1 activityand upregulation of autophagy in a number of tissues. Moreover, exercise‐inducedTORC1 and autophagy signaling share common pathways with that of CR. There-fore, the longevity effects of exercise and CR may stem from the maintenance ofthe proteome by balancing the synthesis and recycling of intracellular proteins andthus may represent practical means to promote longevity

The Prevalence of Physical Inactivity and Low Back Pain in Sedentary Office Employees: A Survey Analysis

Low back pain (LBP) is an increasingly common chronic condition and self-perceived disability that full-time sedentary employees are at risk of being exposed to. Sedentary employees are paid workers who fulfill all or most of their occupational duties seated. Currently, there is very little research available that discusses how physical inactivity affects LBP in sedentary office employees. PURPOSE: The purpose of this study is to: (1) determine the prevalence of LBP pain among sedentary office employees, (2) identify the number of sedentary employees who meet the current physical activity guidelines outlined by the American College of Sports Medicine (ACSM) and mirroring Physical Activity Guidelines for Americans, and (3) to determine the prevalence of LBP amongst physical activity habits in the surveyed population. METHODS: One hundred sixty-four participants completed the 36-question survey. Survey questions assessed past injuries, working history, chair type, exercise history and training frequency, sedentary habits, and pain prevalence and management. RESULTS: The survey found 73.7% of participants experience some level of LBP when seated at work. Additionally, 32.3% of participants were inactive, 57.9% of participants were insufficiently active, 7.9% of participants were active and 1.8% of participants were highly active in accordance with the Physical Activity Guidelines for Americans. Sixty-six participants reported engaging in resistance training with 63.6% reporting LBP. Ninety-five participants reported engaging in aerobic activity with 75.7% reporting LBP. Eighty-nine participants reported engaging in core training with 70.7% reporting LBP. CONCLUSION: The majority of sedentary office employees reported LBP. Additionally, only ~10% of survey respondents met or exceeded ACSM’s Physical Activity Guidelines and LBP was still prevalent in most participants despite their engagement in physical activity

A Comparison of Muscle Activation Among the Front Squat, Overhead Squat, Back Extension and Plank

International Journal of Exercise Science 13(1): 714-722, 2020. The purpose of this study was to compare the muscle activation of the scapula, leg, and trunk among the front squat (FS), overhead squat (OHS), back extension (BE) and plank (PL). Seven recreationally trained men (age: 28 ± 3.6 years, body mass: 92 ± 26.1 kg, height: 175 ± 5.3 cm, 3-RM front squat test: 125 ± 49.8 kg, 3-RM overhead squat test: 91 ± 15.5 kg) participated in this within-subject crossover design. Two isometric exercises (plank and Biering-Sorenson back extension) were also included for trunk musculature comparisons. Neuromuscular activitation of the vastus lateralis (VL), biceps femoris (BF), thoracic region of erector spinae (ES), middle trapezius (MT), rectus abdominis (RA), external oblique (EO), serratus anterior (SA), and anterior deltoid (AD). The neuromuscular activity of the FS and OHS were analyzed using a 2 X 3 (squat variation X intensity) repeated measures analysis of variance (ANOVA). Effects were further analyzed by Bonferroni corrected paired t-tests. Results showed that AD activity was significantly greater (p \u3c .05) during the FS compared to OHS at 65 and 95% of the 3-RM, while MT activity was significantly greater (p \u3c .05) during the OHS than the FS at 80 and 95% of the 3-RM. ES activity was significantly greater (p\u3c .05) during both the FS and OHS compared to the BE, but PL elicited significantly greater EO and RA activity than both the FS and OHS. These findings reveal that the FS and OHS can help facilitate the activation of muscles supporting the shoulder complex, scapula and lower back

Comparing Muscle Oxygenation and Maximal Blood Lactate Concentration in Middle-Distance Athletes: A Speed Reserve Ratio Analysis

Middle-distance running is a unique discipline that utilizes both aerobic and anaerobic abilities, resulting in a physiologically diverse athlete population. This diversity in athlete makeup underscores the necessity for precise physiological profiling methods to improve individualized training and race strategy approaches. While the Speed Reserve Ratio (SRR) has garnered attention as an accurate and effective tool in athlete profiling, skeletal muscle oxygenation (SmO2) and blood lactate also have shown potential in this field. However, the effectiveness of these biomarkers in middle-distance populations, especially in conjunction with SRR, is less understood. PURPOSE: This research aims to understand the relationships between SRR, changes in SmO2, and peak blood lactate concentrations in male middle-distance runners. By establishing correlations between these biomarkers, we aim to evaluate their potential to characterize an athlete\u27s aerobic and anaerobic capabilities, which could enhance personalized training and performance optimization. METHODS: Nine male middle-distance runners (age 22.89±2.62 years, weight 71.03±8.42 kg, height 172.03±9.24 cm) were evaluated in two distinct exercise tests. The initial test was a 50m sprint designed to determine max sprint speed (MSS). The subsequent test involved an incremental treadmill protocol that measured VO2 max, max aerobic speed (MAS), the change in SmO2 via a portable near-infrared spectroscopy (NIRS) device, and post-exercise peak blood lactate levels. Pearson correlation coefficients were used to analyze associations. RESULTS: Analysis revealed significant correlations between SRR and VO2max (r = -0.897, p = 0.009), SRR and changes in SmO2 (r = 0.698, p = 0.036), and between SmO2 and MSS (r = 0.756, p = 0.019). CONCLUSION: The correlations establish a strong link between SRR, VO2max, and SmO2 changes. The data suggests that measuring SmO2 can help predict a middle-distance runner’s aerobic and anaerobic capacities, emphasizing its potential as a pivotal biomarker for athlete profiling. Additionally, our findings bolster the SRR\u27s role as a tool for detailed physiological profiling, advocating for its application in athlete evaluation and tailored training recommendations

The Effect of a Moderately-low and High Carbohydrate Intake on Crossfit Performance

International Journal of Exercise Science 9(4): 460-470, 2016. CrossFit is a metabolically demanding strength and conditioning method which performance may benefit from a carbohydrate (CHO)-rich diet. This study investigated the effect of three consecutive days of high CHO intake on CrossFit performance and corresponding metabolically -related variables in strength trained individuals. Eighteen subjects with a CHO intake of \u3c6 g/kg/day were randomly assigned into a CHO (n = 9) or control (C) group (n =9) and underwent a 9-day training protocol. During days 1, 5, and 9, performance was measured as repetitions completed during a 12 minute CrossFit workout. Oxygen consumption (VO2), respiratory exchange ratio (RER), and blood lactate (BL) were also measured. Days 6-8, the CHO group increased CHO intake from \u3c6 g/kg/day to 6-8 g/kg/day; the C group maintained their current intake of \u3c6 g/kg/day. On days 6 and 7 both groups performed CrossFit workouts followed by a day of rest prior to day 9. There was a significant increase in repetitions completed in both groups in day 9 (vs. means score of day 1 + 5) (p = 0.002), but no differences between C and CHO groups (p = 0.111). However, the CHO group displayed a 15.2 repetition increase (+10.9%) in day 9, compared to 5.7 (+4.2%) by the C group. VO2, RER, and BL were not influenced by the experimental intervention. Our results suggest that the CrossFit-embraced practice of moderately-low CHO diets may be adequate in CHO during short periods of training, however, given the noted trend, extended training periods may be effected

Comparing Knee Kinetics and Muscular Activity between the Barbell Squat and Flywheel Squat in Recreationally Trained Females

Previous literature has supported flywheel (FW) training with inducing muscular size and strength comparable to resistance training with free weights. However, it remains unclear how the biomechanical demands of these two training methods differ regarding reducing the risk of load-dependent injuries. PURPOSE: With the growing population of female astronauts, this study aimed to compare knee joint kinetics and muscle activation when squatting to full depth on the barbell back (BB) squat and a gravity-independent FW device utilizing technology to be deployed in future long-term space missions. METHODS: Twenty recreationally trained females (22.3 ± 2.7 yrs, 1.6 ± 0.1 m, 59.8 ± 6.8 kg) with at least two years of experience in BB squat training participated in this study. The first session involved one-repetition maximum (1RM) testing on the BB squat and familiarizing the participants with squatting on the FW device (YoYo ™ Multigym). In session two, the participants conducted: 1) one set of seven repetitions at 83% of their 1 RM in the BB and 2) one set of seven maximal repetitions on the FW training device using an inertial load of 0.100 kg ⋅ m2. The order of the exercises in session two was randomized. Three-dimensional motion capture, force platforms, and electromyography assessed knee joint moments and muscle activation on the participants\u27 dominant limb. Paired t-tests were conducted to compare these variables, with a significance set at p ≤ 0.05. RESULTS: Analysis revealed peak knee extensor moments were greater in the BB squat (BB: 2.14 ± 0.36 Nm/kg, p = 0.004; FW: 1.94 ± 0.06 Nm/kg). The BB squat elicited greater mean muscle activity over the set compared to FW squats in the following: (vastus lateralis: +5.68%, p = 0.015; bicep femoris: +4.63%, p \u3c 0.001; gluteus maximus: +4.67%, p = 0.024; gluteus medius: +2.75%, p = 0.011; gastrocnemius lateralis: +3.09%, p = 0.028; gastrocnemius medius: +2.48%, p = 0.024). However, FW squats attained greater tibialis anterior activity (+5.56%, p = 0.04). There was no significant difference in muscle activity observed in the rectus femoris and vastus medialis. CONCLUSION: Although FW training requires less mechanical demand on the knee extensors when squatting to similar depths, participants achieved greater muscular activation during the BB squat

Oregano (Origanum vulgare) Consumption Reduces Oxidative Stress and Markers of Muscle Damage after Combat Readiness Tests in Soldiers

Military activities often involve high-intensity exercise that can disrupt antioxidant capacity. We investigated the effects of oregano supplementation on muscle damage, oxidative stress, and plasma antioxidant markers of soldiers performing the army combat readiness test (ACRT). Twenty-four healthy male soldiers (age: 24 ± 3 years, height: 167 ± 14 cm, mass: 66 ± 3 kg) were randomized into a placebo group (n = 12) or an oregano supplementation group (n = 12). The participants consumed a capsule containing 500 mg Origanum vulgare immediately after completing the ACRT. Blood sampling was taken before exercise, immediately after exercise, and 60 and 120 min after oregano consumption. Plasma levels of creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant capacity (TAC), and glutathione peroxidase (GPX) were measured at the four time points. The time × group interactions were found for CK (p < 0.0001, d = 3.64), LDH (p < 0.0001, d = 1.64), MDA (p < 0.0001, d = 9.94), SOD (p < 0.0001, d = 1.88), TAC (p < 0.0001, d = 5.68) and GPX (p < 0.0001, d = 2.38). In all variables, the difference between placebo and oregano groups were significant at 60 (p < 0.0001) and 120 (p < 0.0001) minutes after ACRT test. The main effect of time was also significant for all the variables (p < 0.0001). Our results suggest that oregano supplementation has the potential to reduce muscle damage and increase oxidative capacity following ACRT. Supplementation with oregano may serve as a dietary strategy to increase preparedness and promote recovery in military recruits

Effect of Branched-Chain Amino Acid Supplementation on Recovery Following Acute Eccentric Exercise

This study investigated the effect of branched-chain amino acid (BCAA) supplementation on recovery from eccentric exercise. Twenty males ingested either a BCAA supplement or placebo (PLCB) prior to and following eccentric exercise. Creatine kinase (CK), vertical jump (VJ), maximal voluntary isometric contraction (MVIC), jump squat (JS) and perceived soreness were assessed. No significant (p \u3e 0.05) group by time interaction effects were observed for CK, soreness, MVIC, VJ, or JS. CK concentrations were elevated above baseline (p \u3c 0.001) in both groups at 4, 24, 48 and 72 hr, while CK was lower (p = 0.02) in the BCAA group at 48 hr compared to PLCB. Soreness increased significantly from baseline (p \u3c 0.01) in both groups at all time-points; however, BCAA supplemented individuals reported less soreness (p \u3c 0.01) at the 48 and 72 hr time-points. MVIC force output returned to baseline levels (p \u3e 0.05) at 24, 48 and 72 hr for BCAA individuals. No significant difference between groups (p \u3e 0.05) was detected for VJ or JS. BCAA supplementation may mitigate muscle soreness following muscle-damaging exercise. However, when consumed with a diet consisting of ~1.2 g/kg/day protein, the attenuation of muscular performance decrements or corresponding plasma CK levels are likely negligible