Effects of short-term resistance training on motor unit properties and neuromuscular function in young and old men

Aging is accompanied by decreases in neuromuscular functioning that can lead to decreased mobility and quality of life in older adults. The purpose of this study was two-fold: 1) To investigate the age-related differences in maximum motor unit firing rates and motor unit action potential size. 2) To examine the effects of short-term resistance training on motor unit properties and neuromuscular function in young and old men. Twenty-five young (range: 18-30) and twenty-three older adults (range: 55-88 yrs) volunteered to participate in this study and were randomly assigned to either a training or control group. The training groups performed 3 sessions of unilateral resistance training per week for 4 weeks, while the control group only performed the testing. Testing was performed for the trained and untrained leg before (PRE), after 2 weeks (MID), and after 4 weeks (POST) of training. Motor unit properties including maximum motor unit firing rates (MaxFR), motor unit action potential size (MUAP-size), and recruitment threshold (RT) were obtained through the use of decomposing surface electromyography. Linear regression was used for the MaxFR and RT as well as the MUAP-size relationship in order to obtain slope coefficients (MaxFRSLOPE and MUAP-sizeSLOPE, respectfully). In addition, strength, peak velocity (PV), rate of velocity development (RVD), and rate of muscle activation (RER) were measured during each testing visit. Older adults exhibited a decreased MUAP-sizeSLOPE at PRE compared to younger adults, but MaxFRSLOPE was similar between groups. MaxFRSLOPE increased at MID and POST, while MUAP-sizeSLOPE increased at POST in both groups with no age-related differences being demonstrated for either. Older adults exhibited an attenuated response to the training as young training group demonstrated larger gains after 2 and 4 weeks of resistance training. While RVD (unloaded knee extension) for the trained leg remained unchanged, it increased for the untrained leg in both, the young and old training group. These findings provide preliminary evidence of aging- and training-related alterations in MU morphology Also, new information was provided that may contribute to understanding the functional implications for cross-education

Evaluation of a Position-specific Task in Ncaa Division I Linemen

It is the responsibility of the strength and conditioning professional to implement quality training programs and properly evaluate each athlete's physical performance. It is essential that strength and conditioning professionals have access to an evaluative tool that provides a practical, position-specific assessment of playing ability in collegiate linemen. The purpose of this study was two-fold: To compare the performance of a position-specific task on the MAXX Football Sled Device (MFSD) between NCAA Division I offensive and defensive linemen. Also, to investigate any associations among selected strength and power variables with performance on the MFSD in NCAA Division I offensive and defensive linemen. Twenty-six NCAA Division I offensive (n=12) and defensive linemen (n=14) (age 20.11 1.49yrs) performed ten "fire-and-drive" repetitions on the MFSD. Upon an auditory signal rendered from the MFSD, subjects exploded in to the breast plate region of the dummy as forcefully and rapidly as possible. After each repetition subjects reset themselves in a three point stance. Timing between repetitions was an automatically randomized duration of 6 to 10 sec. The MFSD measured average force (AVGF) across the ten trials and movement time (MT), the time from the auditory signal to initial contact on the dummy, for each of the ten repetitions. Secondary data including 1 RM of the squat, bench press, and power clean, along with vertical jump, 10 yd. sprint, 40 yd. sprint, and body fat percentage were gathered from the team's strength and conditioning staff. Defensive linemen were found to produce significantly lower movement times when compared to offensive linemen (p = 0.032). There were no significant relationships found between the dependent variables gathered from the MFSD and any independent variables. Test-retest reliability demonstrated strong reliability with the device for both AVGF (ICC = .813; SEM = 93.4) and MT (ICC = .828; SEM = .022). Results of this study indicate that defensive linemen accelerate out of the three point stance quicker than offensive linemen. Further exploration for the purpose of finding exercises that correlate with a position-specific task in these athletes is warranted.School of Teaching and Curriculum Leadershi

Bench v2 Optimization

The client is a furniture production company located in Woodstock, GA. One of their products is a bench used for café style settings in a major United States bank chain. The client defined their requirements with a prioritized list of wants, needs, and problems that they encouraged us to accomplish. The number one item on their list is that the benches are heavy and awkward to turn, flip over, and otherwise manufacture and maneuver, a potential safety hazard for workers. After reviewing several options for improving the company’s manufacturing process, Finite Element Analysis [FEA] was determined as the team’s highest impact method for assisting the company. FEA tests a product without costly machinery or numerous sample products, “[allowing] the removal of the indefiniteness before the manufacturing and making the decisions related to manufacturing in a more healthy and economical manner” (Koç, et al., 2011). The AutoCAD model of the bench was acquired from the client. Slight alterations were then made to the model to make it capable of undergoing stress testing, including drilling holes and adding bolts and screws. Then, eight alternate models were made, ranging from using plywood instead of Birch wood to less supports and larger holes in the interior. Stress was applied in three evolving ways as the team strived for a realistic method: one point force in the center, two point forces on top of the interior support, and two pressures applied to a 144 square inch square. One important note is that “the intention of performing FEA is not to eliminate the real tests but rather to reduce the time for a product to pass through the process” (Rundgren and Wörmke, 2011). Using Safety Factor as the primary metric for determining if a model is viable, the team came to the conclusion that either the baseline model or the baseline interior replaced with Plywood were the most viable options

Influence of Sport Specialization on Athletic Performance and Injury Risk in Collegiate Swimmers

To assess the effect of swimming specialization on performance and injury risk in collegiate swimmers, thirty collegiate swimmers (20.1 ± 0.9 years [18.5 – 22.3 years]) were asked to complete an anonymous survey to provide information regarding their sports participation history, success in swimming, and the occurrence and quantity of swimming-related injuries. Specialization status was determined by the swimmer claiming they had specialized and by the number of months (≥ 8 months) they participated in swimming each year. Correlation analysis revealed several significant (p \u3c 0.05) relationships between all determinants of specialization, swimming success, and swimming injuries. Stepwise regression analysis revealed that the age which an athlete specialized was the best predictor of the occurrence of a swimming- related injury (R2 = 0.34, p = 0.004) and the number of injuries sustained (R2 = 0.25, p = 0.019). Years of competitive swimming experience was the best predictor (p \u3c 0.008) of performance in the freestyle stroke at 50-yards (R2 = 0.47), 100-yards (R2 = 0.53), and 500-yards (R2 = 0.43), the back stroke at 200-yards (R2 = 0.41), and the 100-yard butterfly (R2 = 0.55). The age in which the athlete specialized in swimming was the best predictor of the 200-yard individual medley (R2 = 0.30, p = 0.037). Our data suggests that swimming specialization may be beneficial for success in select swimming events but is not as important as years of competitive experience and may also lead to a greater number of swimming-related injuries

Agreement Between 3 Physical Activity Monitors for Estimating Step Count

PURPOSE: The ActiGraph GT3X, ActiGraph GT9X, and ActivPAL 4 are accelerometry devices used to measure human physical activity for both research and clinical data. The accelerometer selection is important to yield the most accurate data. This study tests the association and agreement between estimated step counts measured by these accelerometry devices. METHODS: Two males and five females participated (Age: 19.6±3.0 years, BMI: 23.2±6.0 kg/m2). Three accelerometers were worn simultaneously for at least 19 hours. Two ActiGraphs (GT3X and GT9X) were worn on the waist and one ActivPAL monitor was affixed to the right thigh. Step count data from the 3 devices were compared using ANOVA test and were associated using Pearson correlation test. Agreement was determined by calculating the correlation between the difference in step count between 2 devices and the average of the step counts from the 2 devices. RESULTS: Average step count recorded from the GT3X (5644± 2410.3), GT9X (5229.2± 2088.1), and ActivPAL 4 (5836.4± 2641.6) appear to be similar (p=0.924). Strong correlations were found in step count between GT3X and GT9X (r= 0.978, p= 0.001), GT3X and ActivPAL 4 (r=0.995, p=0.001), and GT9X and ActivPAL 4 (r= 0.968, p=0.001). Step count data was in agreement between GT3X and GT9X (r= 0.479, p= 0.316), GT3X and ActivPAL 4 (r= -0.463, p= 0.355), GT9X and ActivPAL 4 (r= -0.568, p= 0.183) were also found. CONCLUSION: These findings suggest that for estimating step count, the three devices may be used interchangeably

The effect of chronic quercetin supplementation on bone health in postmenopausal women: A double-blind placebo-controlled investigation

Currently, there is limited research investigating the effects of quercetin on bone turnover and density. Therefore, this study aimed to examine the efficacy of 90-day quercetin supplementation on bone turnover, inflammation, body composition, and physical function in postmenopausal women. Thirty-four healthy postmenopausal women (59.2 ± 7.0 yrs, 80.7 ± 15.6 kg, 29.8 ± 6.1 kg⸱m2) participated in the double-blind placebo-controlled investigation. Participants were randomly assigned to one of two groups: 500 mg of Q or 500 mg of fiber (placebo; PLB). Data collected during the pre-and post-supplementation assessments included: bone turnover (osteocalcin, P1NP, CTX), inflammation markers (IL-6, TNF-alpha, CRP), body composition, dominant handgrip strength, and timed up and go test. Independent samples t-tests were used for between-group comparisons of baseline values and the percent change for each dependent variable. A significant difference in percent change for osteocalcin (Q: 20.5±25.7; PLB: 1.3±17.2; p=0.016; d=0.89), P1NP (Q: 28.9 (6.0–57.3); PLB: 4.6 (-7.6 – 8.5); p=0.030; d=0.64), and CTX (Q: 39.0 (-10.0 – 84.6); PLB: -7.74 (-28.9 – 18.5); p=0.023; d=0.91) was found between Q and PLB, with greater increases in Q. Changes in the inflammation markers IL-6 (Q: -17.6±24.1; PLB: 2.90±31.1; p=0.045; d=0.73) and TNF-alpha (Q: -4.9± (-15.3 – [-3.2]); PLB: 1.9 (-7.8 – 4.0); p=0.021; d=0.90) between the two groups were significant. No significant changes were found between groups for CRP, body composition, and physical function (p\u3e0.05). The data suggest that Q may improve bone health status in postmenopausal women through its ability to decrease pro-inflammatory mediators and increase turnover markers

The Effect of Quercetin on Bone Turnover Markers, Inflammatory Markers, and Bone Mineral Density in Postmenopausal Women: A Double-Blind Placebo-Controlled Investigation

Maintaining optimal bone health prevents major bone disorders (e.g., osteoporosis) and prolongs longevity. Quercetin is a plant-based flavonoid that is suggested to have anti-inflammatory effects and may improve bone health. PURPOSE: To investigate the effects of quercetin supplementation over 90-days on prominent bone turnover markers (BTMs), inflammatory markers, bone mineral density (BMD), body composition, and physical functioning in postmenopausal women. METHODS: Thirty-three healthy, nonosteoporotic, postmenopausal women (59.2±7.0 years) participated in a double-blind, placebo-controlled investigation. Participants were randomized into one of two supplement groups: 1) 500 mg of quercetin (QUE) once daily or 2) 500 mg of methylcellulose (placebo; PLB) once daily. Pre- and post-testing visits included assessments of BTMs (i.e., osteocalcin [OC], procollagen type-I N-terminal propeptide [PINP], and type-I collagen cross-linked C-terminal telopeptide [CTX]), inflammatory markers (i.e., interleukin [IL]-6, tumor necrosis factor-alpha [TNF-a], and C-reactive protein [CRP]), BMD measurements, body composition measurements (i.e., body fat percentage), and physical function. RESULTS: The QUE group increased OC (p=0.016; d=0.89), PINP (p=0.030; d=0.64), and CTX (p=0.023; d=0.91) levels and decreased IL-6 (p=0.045; d=0.73) and TNF-a (p=0.021; d=0.90) levels compared to PLB. CRP (p=0.448; d=0.34), BMD, body composition, and physical function remained unchanged. CONCLUSION: The results indicate that QUE may maintain optimal bone health by mediating bone formation and decreasing pro-inflammatory cytokines

Sex Differences in Plantar Flexor Strength and Contractile Properties after Isometric and Dynamic Fatigue

Purpose: To determine sex differences in strength and contractile properties after isometric and dynamic fatiguing exercise of the plantar flexors. Methods: Recreationally active males (n=13, age=22.4±2.2 yrs) and females (n=15, age=20.9±2.4 yrs) performed a maximal isometric (2 min) and isotonic (120 reps at 30% peak torque) fatigue task on 2 separate visits. Before and after each fatigue task, participants performed a 3 sec maximal voluntary isometric contraction (MVIC) with tibial nerve stimulation being delivered during and immediately after the MVIC. Peak torque (PT; highest 250 ms) was obtained during the voluntary phase of the MVIC. Peak twitch torque (TTQ), rate of torque development (RTD; Δtorque/Δtime), and half relaxation time (HRT; time for TTQto decrease from peak to 50%) were calculated from the resting twitch after the MVIC. Voluntary activation (VA%; ability of the muscle to be fully activated) was calculated using a corrected interpolated twitch formula. Three-way (condition × sex × time) repeated measures ANOVAs were used for analysis. Results: Regardless of sex or condition, TTQ(-23.1%), RTD (-12.6%), HRT (+22.9%) were changed after fatigue (p\u3c0.05), while VA% remained unchanged (p\u3e0.05). Regardless of condition, PT was more reduced in males (-22.5%) compared to females (-19.2%)(p=0.017). Conclusions: Our findings indicate that the fatigue-induced decrease in strength was greater in males than females. While our findings do not identify the contributing physiological mechanism(s), changes at the peripheral level may be responsible

Effects of plyometric- and cycle-based high-intensity interval training on body composition, aerobic capacity, and muscle function in young females: a field-based group fitness assessment

High-intensity interval training (HIIT) is an effective alternative to moderate intensity continuous training for improvements in body composition and aerobic capacity; however, there is little work comparing different modalities of HIIT. The purpose of this study was to compare the effects of plyometric- (PLYO) and cycle-oriented (CYC) HIIT on body composition, aerobic capacity, and skeletal muscle size, quality, and function in recreationally trained females. Young (21.7 ± 3.1 yrs), recreationally active females were quasi-randomized (1:1 ratio) to 8 weeks of twice weekly PLYO (n = 15) or CYC (n = 15) HIIT. Body composition (four-compartment model), VO2peak, countermovement jump performance, muscle size, and echo intensity (muscle quality), as well as strength and power of the knee extensors and plantar flexors were measured before and after training. Both groups showed a similar decrease in body fat percentage (p \u3c 0.001; = 0.409) and echo intensity (p \u3c 0.001; = 0.558), and an increase in fat-free mass (p \u3c 0.001; = 0.367) and VO2peak (p = 0.001; = 0.318). Muscle size was unaffected (p \u3e 0.05), whereas peak torque was reduced similarly in both groups (p = 0.017; = 0.188) and rapid torque capacity was diminished only for the knee extensors after CYC (p = 0.022; d = −0.67). These results suggest that PLYO and CYC HIIT are similarly effective for improving body composition, aerobic capacity, and muscle quality, whereas muscle function may express moderate decrements in recreationally active females. ClinicalTrials.gov (NCT05821504

Identifying an indoor air exposure limit for formaldehyde considering both irritation and cancer hazards

Formaldehyde is a well-studied chemical and effects from inhalation exposures have been extensively characterized in numerous controlled studies with human volunteers, including asthmatics and other sensitive individuals, which provide a rich database on exposure concentrations that can reliably produce the symptoms of sensory irritation. Although individuals can differ in their sensitivity to odor and eye irritation, the majority of authoritative reviews of the formaldehyde literature have concluded that an air concentration of 0.3 ppm will provide protection from eye irritation for virtually everyone. A weight of evidence-based formaldehyde exposure limit of 0.1 ppm (100 ppb) is recommended as an indoor air level for all individuals for odor detection and sensory irritation. It has recently been suggested by the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the US Environmental Protection Agency (US EPA) that formaldehyde is causally associated with nasopharyngeal cancer (NPC) and leukemia. This has led US EPA to conclude that irritation is not the most sensitive toxic endpoint and that carcinogenicity should dictate how to establish exposure limits for formaldehyde. In this review, a number of lines of reasoning and substantial scientific evidence are described and discussed, which leads to a conclusion that neither point of contact nor systemic effects of any type, including NPC or leukemia, are causally associated with exposure to formaldehyde. This conclusion supports the view that the equivocal epidemiology studies that suggest otherwise are almost certainly flawed by identified or yet to be unidentified confounding variables. Thus, this assessment concludes that a formaldehyde indoor air limit of 0.1 ppm should protect even particularly susceptible individuals from both irritation effects and any potential cancer hazard