Acute Bout Of Resistance Training Research Articles

Comparison of concentric and eccentric resistance training in terms of changes in the muscle contractile properties

The habitual use of resistance exercises involving concentric and eccentric contractions can increase muscle strength, speed and endurance. However, current knowledge has limited potential to fully understand the application of such resistance training and the muscle changes that occur to differentiate these two types of training. The aim of this study was to compare the effects of concentric contraction (CON) and eccentric contraction (ECC) during an acute bout of resistance training on the hamstring contractile properties. A group of 20 female recreational athletes were divided into two equal groups, CON training and ECC training. The contractile properties of the muscles on both sides of the body were assessed using tensiomyography (TMG): biceps femoris (BF) and semitendinosus (ST). The muscles were assessed twice, before and after 10 maximal repetitions of either concentric or eccentric isotonic contractions. The results indicate a greater change in TMG parameters with ECC training, with p < 0.001 (Td and Tc). An acute bout of resistance training induces changes in the muscle hamstrings contractile properties in both CON and ECC training. Eccentric training causes greater changes than concentric training, shortening contraction time (Td, Tc), increase radial displacement velocity (Vrd) and affecting changes in muscle belly displacement (Dm), so may be more effective in training.

Time Course Changes In Size And Echo Intensity Of The Bicep Brachii Following Resistance Training

Following resistance training, muscles swell due to a combination of damage and an increased demand for oxygen and substrates. Cross-Sectional Area (CSA), thickness, and echo intensity (EI) are measurements have been used to monitor muscle damage and recovery. Due to the variety in responses to resistance training, this study looks at muscle recovery over time while taking into consideration the differences between males and females. PURPOSE: The purpose of this study is to examine the time course changes in muscle size and EI of the biceps bracii following an acute bout of resistance training and determine the potential differences in response between males and females. METHODS: Twenty Males (71.00 ± 2.07 cm, 74.11 ± 9.37 kg, Age 19.85 ± 0.41) and 20 females (63.35 ± 2.99 cm, 60.62 ± 8.92 kg, Age 20.00 ± 0.72). Panoramic ultrasound images were taken on the largest circumference of the bicep bracii and used to determine CSA, Muscle thickness and EI. Day 1: Participants performed four sets to failure at 70% on a bicep curl machine with a 90 second rest between sets. Ultrasounds were done pre and post exercise. Day 2 and 3: Ultrasounds only. RESULTS: LINK Excel.Sheet.12 "D:\\Ultrasound 2020\\abstract data.xlsx" "Sheet1!R2C16:R11C20" \a \f 4 \hMales and females had similar responses over time (P = 0.17-0.96) for each variable. Post exercise values for CSA, thickness, and EI *(p < 0.001) where all large but returned to baseline values by 24 hrs. Males had large muscle size ^(p < 0.001), but not difference in EI (p = 0.769). CONCLUSION: Immediately following resistance training, muscle size and EI are significantly larger for both males and females and returns to baseline in 24 hrs. Males and females exhibit similar patterns; however, males have larger muscle size and but similar EI values.

Acute Changes In Muscle Size Of The Vastus Medialis Oblique Following Resistance Training

Resistance training causes a temporary swelling of the muscle that leads to an increase in muscle size. This phenomenon has been studied in the literature, but there is a need for more research studies that compare the acute muscle changes due to fatigue between males and females. PURPOSE: To observe the changes in the cross-sectional area (CSA) of the vastus medialis oblique muscle after resistance training to fatigue and to compare these acute responses between males and females. METHODS: Twenty Males (71.00 ± 2.07 cm, 74.11 ± 9.37 kg, Age 19.85 ± 0.41) and 20 females (63.35 ± 2.99 cm, 60.62 ± 8.92 kg, Age 20.00 ± 0.72). Day one served as a familiarization and was to determine a one repetition max leg extension. Day two Panoramic ultrasound images were taken on the largest circumference of the vastus medialis oblique before and after the participant performed four sets of leg extension to failure at 70% max. Images where then analyzed to measure CSA. A time and sex were compared using a repeated measures ANOVA. RESULTS: The mean and standard deviation of the pre-areas for males and females were 22.97 ± 4.49 vs 14.36 ± 3.22 cm2 respectively, while the post-areas for males and females were 24.47 ± 5.66 vs 15.70 ± 3.51 cm2 respectively. There was no interaction effect (F = 0.04, p = 0.74), males had an overall a larger CSA (F = 41.5, p < 0.001) and the post measurement was larger than the pre for both groups (F = 36.56, p < 0.001). CONCLUSION: Males overall had larger muscle size but both responded similarly with an increase in CSA following an acute bout of resistance training to fatigue.

Is there Evidence for the Suggestion that Fatigue Accumulates Following Resistance Exercise?

It has been suggested that improper post-exercise recovery or improper sequence of training may result in an 'accumulation' of fatigue. Despite this suggestion, there is a lack of clarity regarding which physiological mechanisms may be proposed to contribute to fatigue accumulation. The present paper explores the time course of the changes in various fatigue-related measures in order to understand how they may accumulate or lessen over time following an exercise bout or in the context of an exercise program. Regarding peripheral fatigue, the depletion of energy substrates and accumulation of metabolic byproducts has been demonstrated to occur following an acute bout of resistance training; however, peripheral accumulation and depletion appear unlikely candidates to accumulate over time. A number of mechanisms may contribute to the development of central fatigue, postulating the need for prolonged periods of recovery; however, a time course is difficult to determine and is dependent on which measurement is examined. In addition, it has not been demonstrated that central fatigue measures accumulate over time. A potential candidate that may be interpreted as accumulated fatigue is muscle damage, which shares similar characteristics (i.e., prolonged strength loss). Due to the delayed appearance of muscle damage, it may be interpreted as accumulated fatigue. Overall, evidence for the presence of fatigue accumulation with resistance training is equivocal, making it difficult to draw the conclusion that fatigue accumulates. Considerable work remains as to whether fatigue can accumulate over time. Future studies are warranted to elucidate potential mechanisms underlying the concept of fatigue accumulation.

Executive Function Improves Following Acute Exercise in Adults with Down Syndrome.

The influence of exercise on brain function is an important topic, especially in persons with intellectual deficits. The aim of this study is to determine the effect of an acute bout of resistance training (RT) compared to assisted cycle therapy (ACT) and no training (NT) in adults with DS on cognitive function. Fourteen participants attended four sessions: a baseline assessment, an assisted cycling therapy (ACT) session, a resistance training (RT) session, and a session of no training (NT). In the RT session, the leg press, chest press, seated row, leg curl, shoulder press, and latissimus pulldown were performed. The ACT session consisted of 30 min of cycling and in NT session consisted of 20 min of board games. Inhibition was measured by the Erikson flanker task and cognitive planning was measured by the Tower of London test and both were administered prior to (pretest) and after each intervention (posttest). Our results showed that inhibition time improved more following RT and ACT than NT. There was also a significant difference between ACT and NT. For cognitive planning, improvements were seen following ACT and NT. In conclusion, an acute session of ACT demonstrated a significant trend towards improvements in executive functions in adults with DS which we interpreted using a model of neural changes and the cognitive stimulation hypothesis.

The Effects Of An Acute Bout Of Resistance Training On College-aged Male 24hr Rmr

It has been demonstrated that increasing caloric expenditure through exercise participation is one mechanism by which to modify caloric balance in favor of weight loss. While chronic resistance training (RT) has been demonstrated to elevate resting metabolic rate (RMR) due to increased lean mass, there has been less research on the acute effects of a single bout of resistance training on RMR. PURPOSE: To determine the effects of an acute bout of resistance training on the 24 h RMR of college-aged males. METHODS: Ten healthy men aged 18-24yr performed 8 exercises (2 sets, 10 repetitions, 2 min recovery, 70% 1RM & 8RM) following ACSM Guidelines for RT. Subjects reported for testing following a 12 h fast and engaged in 7, 30 min RMR measurements over the next 24 h. Subjects completed both an experimental (RT) and control (no exercise) day separated by 1 week. RESULTS: RMR (kcal) data was analyzed using a 1 way ANOVA with repeated measures on 2 factors (group and time). Statistical analysis revealed that there was no significant main effect for group (2179.58± 44.82 kcal vs. 2143.16 ± 44.82 kcal; F = .330, p = .567) or group x time interaction (F =.592, p =.736, Table 1). There was a significant main effect for time (F = 5.126, p < .001, Table 2). CONCLUSION: We conclude that an acute bout of RT, following ACSM guidelines, did not significantly impact RMR in RT males 24 hrs post-exercise.Table 1: Mean 24-hour RMR Values by GroupTable 2: Mean RMR Values across Measurements

The acute effect of Quercetin on muscle performance following a single resistance training session.

To examine the effect of acute quercetin (Q) ingestion on neuromuscular function, biomarkers of muscle damage, and rate of perceived exertion (RPE) in response to an acute bout of resistance training. 10 young men (22.1 ± 1.8 years, 24.1 ± 3.1 BMI) participated in a randomized, double-blind, crossover study. Subjects consumed Q (1g/day) or placebo (PLA) 3h prior to a resistance training session which consisted of 3 sets of 8 repetitions at 80% of the one repetition maximum (1RM) completed bilaterally for eight different resistance exercises. Electromyographic (EMG) signals were recorded from the knee extensor muscles during maximal isometric (MVIC) and isokinetic voluntary contractions, and during an isometric fatiguing test. Mechanical and EMG signals, biomarkers of cell damage, and RPE score were measured PRE, immediately POST, and 24h (blood indices only) following the resistance exercise. After a single dose of Q, the torque-velocity curve of knee extensors was enhanced and after the resistance exercise, subjects showed a lower MVIC reduction (Q: 0.91 ± 6.10%, PLA: 8.66 ± 5.08%) with a greater rate of torque development (+ 10.6%, p < 0.005) and neuromuscular efficiency ratio (+ 28.2%, p < 0.005). Total volume of the resistance exercises was significantly greater in Q (1691.10 ± 376.71 kgrep) compared to PLA (1663.65 ± 378.85 kgrep) (p < 0.05) with a comparable RPE score. No significant differences were found in blood marker between treatments. The acute ingestion of Q may enhance the neuromuscular performance during and after a resistance training session.

Autonomic modulation in resistance-trained individuals after acute resistance exercise.

The effects of different types of acute bouts of resistance exercise on autonomic modulation in individuals that are resistance-trained compared to untrained individuals are unknown. Seventeen untrained and 17 resistance-trained participants were assessed for autonomic modulation after various acute resistance exercise bouts. Electrocardiogram readings were collected at rest and 25 min after a control period, whole-, lower-, or upper-body acute bouts of resistance exercise. Heart rate variability and heart rate complexity were used to assess autonomic modulation. Participants were similar for age, height, weight and measures of body composition (p>0.05) and were different for measures of maximal strength (p<0.05). There were no differences (p>0.05) in autonomic modulation at rest between groups. Significant decreases (p<0.05) in parasympathetic modulation after the acute bouts of resistance exercise were noted. Sample entropy was not affected in the untrained group, but was significantly decreased after whole- (-17.5%) and upper-body exercise (-13.5%) in the resistance training group. The changes in sample entropy after lower-body resistance exercise were not significant (-15.7%; p=0.06). These data suggest that resistance exercise training further attenuates the parasympathetic responses to an acute bout of resistance training regardless of the modality compared to the untrained state.

Muscle Strength Recovery Following Acute Bout of Resistance Training: Role of Dehydroepiandrosterone Sulfate

Lifelong overexpression of heat shock protein (HSP) 72 in skeletal muscle is known to protect against age-related oxidative stress and muscle damage. This study aimed to ascertain whether exhaustive exercise-induced damage can be prevented by lifelong overexpression of HSP72. Transgenic mice that were heterozygous for a porcine HSP70.2 gene ([+]HSP72) and transgene-negative littermate controls ([-]HSP72) were subjected to an exhaustive exercise protocol. Mice were divided into four groups, including control, HSP72, exhaustive exercise and HSP72 exhaustive exercise groups. Eighty-two min after completion of the exhaustive exercise, animals were sacrificed and different tissues, including brain, heart, liver, lung, kidney and muscle were isolated. Then the levels of HSP72, matrix metalloproteinase (an indicator for inflammatory myopathies), pathological observations and p-P-38 MAP kinase (p-P-38) expressions were determined in all tissues. When exhaustive exercise group or HSP72 exhaustive exercise group underwent an exhaustive exercise test, the latency values (the mean duration of exhaustive exercise onset) for the occurrence of exhaustive exercise was found to be different significantly (82 ± 3 and 110 ± 3 min, respectively). HSP72 exhaustive exercise group underwent a exhaustive exercise test, and had a longer exercise time. Furthermore HSP72 exhaustive exercise group showed significantly increased matrix metalloproteinase levels and p-P-38 expression, whereas morphological damage was significantly decreased compared to exhaustive exercise group. The results suggest that the improvement of inflammation and damage induced by exhaustive exercise in HSP72 overexpressing transgenic mice may be associated with p-P-38 expression.

Muscle Strength Recovery Following Acute Bout of Resistance Training: Role of Dehydroepiandrosterone Sulfate

The purpose of this study was to investigate the effects of acute bout of moderate intensity resistance exercise on the recovery of maximal isometric muscle strength. Additionally, the association between muscle strength recovery and serum level of dehydroepiandrosterone sulfate (DHEA-S) was examined. Eighteen male hockey players were assigned into either high muscle strength (120.33±7.65 kg/w, HMS, n=9) or low muscle strength (71.66±3.57 kg/w, LMS, n=9) based on their maximal isometric strength of lower extremities. All subjects performed an acute bout of resistance training, consisting of 6 exercises. Three sets of 8 repetitions with 50% 1-RM intensity were performed for all exercises. Fasting blood samples were collected at pre-exercise, immediately after exercise, 48h and 72h after exercise for determining the serum DHEA-S and cortisol levels. Maximal isometric strength of upper and lower extremities was measured at 48h and 72h after acute bout of resistance exercise. No significant differences were detected in anthropometric measures between two groups. The serum DHEA-S level was significantly lower in HMS group at immediately and 48h after acute resistance exercise. However, there were no differences in serum cortisol levels at each time point between two groups. Maximal isometric muscle strength recovery was significantly faster in HMS group compared to LMS group. In addition, serum DHEA-S and muscle strength recovery showed markedly negative correlation. In conclusion, HMS group showed better recovery rate of muscle strength after acute bout of resistance exercise. This faster recovery could be associated with endogenous DHEA-S level, suggesting that endogenous DHEA-S might account for individual differences in training adaptation in response to resistance exercise.

Acute response of plasma markers of bone turnover to a single bout of resistance training or plyometrics

The time course of changes in plasma bone turnover markers following an acute bout of resistance training (RT) or plyometrics (PLY) has not been well characterized. This study is the first to compare the acute response of bone formation and resorption markers to a single bout of RT or PLY. Using a partially randomized, cross-over study design, 12 recreationally active men, aged 43 ± 5 yr, each completed four exercise trials: RT (Fed/Fasted) and PLY (Fed/Fasted). In addition to the RT and PLY trials, 5 of the original 12 participants also completed a fasted, no-exercise control trial to examine time-of-day variation. For each trial, blood was drawn immediately before exercise (PRE), immediately following exercise, and 15 min, 30 min, 1 h, 2 h, and 24 h following PRE for determination of plasma bone-specific alkaline phosphatase (BAP), osteocalcin (OC), tartrate-resistant acid phosphatase 5b (TRAP5b), COOH-terminal telopeptide of type I collagen (CTX), testosterone, parathyroid hormone, and cortisol. A one-factor repeated-measures ANOVA was performed for each trial to detect changes in bone markers during the 2 h following RT or PLY. TRAP5b transiently decreased during the 2 h following all exercise trials (main effect for time, P < 0.05), but returned to PRE concentrations 2 h postexercise. BAP, CTX, and OC remained unchanged, except for reductions in BAP and CTX following PLY-Fasted and PLY-Fed, respectively. During the control trial, BAP decreased, while TRAP5b, CTX, and OC remained unchanged. In general, plasma hormone concentrations decreased during the 2 h following PLY or RT, and cumulative decreases in TRAP5b during the 2 h following exercise were positively correlated with cumulative decreases in parathyroid hormone. The results of the present study suggest that the timing of the measurement of bone turnover markers relative to the last exercise bout is important for detection of exercise-associated changes in bone turnover markers, as the markers returned to preexercise values within 2 h of RT or PLY.

The effects of phosphatidylserine supplementation on cognitive functioning prior and following an acute bout of resistance training in young males

Background Making quick decisions and reducing the amount of errors at the beginning of a competition are crucial to the success in team sports and individual events. Phosphatidylserine (PS) has been shown to reduce stress and increase performance in runners, cyclists and golfers. A randomized, double-blind, placebo-controlled, cross-over pilot study was performed to evaluate the effect of PS supplementation on cognitive function prior to and following an acute bout of resistance training in 18 males aged 18-30.

Resistance training improves the inflammatory response to an acute resistance exercise bout in healthy young adults

Ten non‐resistance trained subjects (8 men, 2 women, 21–28 y) participated in a 9 mo supervised resistance exercise training 3 times/wk. We examined the inflammatory response to: 1) an acute resistance exercise bout (ARET) and 2) a 9 mo resistance training program by comparing the responses at baseline (T0) and after 9 months (T9). The ARET consisted of 6 × 10 repetitions of squats (75% of 1RM) with 2 min rest between sets. Blood was drawn pre‐ exercise, immediately post, 15 and 60 min after the ARET. Plasma cytokines were measured at all time points both at T0 and at T9. Analysis of the acute effects at T0 indicated that the proinflammatory cytokines interleukin (IL)‐1β, IL‐8 and tumor necrosis factor (TNF)‐α increased to a lesser extent than the anti‐inflammatory cytokines IL‐1ra and IL‐10 after 60 min. These results suggest that in spite of the large inflammatory response induced by ARET, this is counterbalanced by the body's anti‐inflammatory response in healthy subjects. When T0 and T9 were compared, the area under the curve for TNF‐α was significantly lower after training (T0=105.9 vs. T9=62.9 p=0.029) and it almost reached significance for IL‐15 (T0=26.5 vs T9=38.0 p=0.07). TNF‐α responses were diminished with training at 15m (T0=63.9.5 pg/mL vs T9=60.4 pg/mL p=0.035) and 60 m. (T0=79.7 pg/mL vs T9=34.8 pg/mL p=0.025). These reductions in TNF‐α indicate that resistance training reduces the inflammatory response to an acute bout of resistance training [Supported by the National Dairy Council]

Blood Lipid Profile Response To An Acute Bout of Resistance Training

Obesity, a risk factor for diabetes mellitus, is a growing epidemic. It is well known that the blood lipid profile improves with endurance training and resistance training. Whether improvements occur in the lipid profile in response to one session of resistance training are unclear. PURPOSE: To determine the effect of an acute bout of resistance training on the blood lipid profile response in young adults. METHODS: Twenty healthy recreationally trained college students (13M, 7F; 20.1±1.3 yr; 82.0±24.4 kg; BMI 27.4±6.7, respectively) enrolled in a resistance training activity class volunteered for participation in this study. All participants were free of any illness or medication that might affect lipid profile. Workout modalities included resistance training machines and free weights. Fasting seated blood samples were taken immediately before (pre) and after (post) the class session and measured for total cholesterol (TC), high-density lipoproteins (HDL), low-density lipoproteins (LDL), triglycerides (TG) and TC/HDL ratio. Paired t-tests were used to compare the responses in the individual components of the pre-exercise and post-exercise lipid profile. RESULTS: Data are reported as mean ± SD. TC was reduced post-exercise vs. pre-exercise (139.2±34.8 vs. 145.2±39.4 mg·dl-1, p=0.02), as was LDL (88.0±29.0 vs. 96.7±42.2 mg·dl-1, p=0.04). There were no significant differences (p>0.05) between pre- and post- HDL, TG, and TC/HDL. CONCLUSION: From these data, participation in an acute bout of resistance training that was one hour in duration improved the TC and LDL components of the blood lipid profile. To better understand the longitudinal lipid profile response with resistance training across age, gender, and ethnicity, future research may involve measuring the lipid profile on a more frequent basis. Supported by a Grant from the TAMUK College of Education.

Hemostatic Responses to Resistance Training in Patients With Coronary Artery Disease

This study was undertaken to evaluate changes in coagulation and fibrinolytic responses to an acute bout of resistance training in patients with coronary artery disease. Fourteen low-to-moderate risk men (mean age, 57.6 +/- 9 years; body mass index, 26.7 +/- 4.0 kg/m) with known coronary artery disease participated in this study. All subjects were recruited from the hospital's outpatient cardiac rehabilitation program and none were participating in a resistance training exercise program at the time. Using 8 different resistance training devices, each subject performed 1 set of 10 repetitions to volitional fatigue, resting 1 minute between sets. Blood samples (5 mL) were drawn preexercise, immediate postexercise, and 1 hour postexercise in the seated position. All values were corrected for plasma volume changes. Alterations in von Willebrand Factor antigen, tissue plasminogen activator antigen, and plasminogen activator inhibitor-1 activity were analyzed using repeated measures analysis of variance. Although von Willebrand Factor antigen remained unchanged from preexercise values, tissue plasminogen activator antigen and plasminogen activator inhibitor-1 activity increased and decreased, respectively, in the immediate postexercise recovery period. Moreover, the latter reduction persisted at 1 hour postexercise. An acute bout of resistance training improves fibrinolytic potential in men with coronary artery disease, without elevating thrombotic potential. These data support the safety of resistance training in this population when contemporary prescriptive guidelines are used.

EFFECTS OF DIFFERENT MACRONUTRIENT CONSUMPTION FOLLOWING A RESISTANCE-TRAINING SESSION ON FAT AND CARBOHYDRATE METABOLISM

The effect of consuming meals of different macronutrient content on substrate oxidation following resistance exercise was examined in 9 resistance-trained men (26.2 ±2.4 years). Subjects completed 3 resistance exercise bouts of 8 exercises and 1 warm-up set (50% of 10 repetition maximum [RM]), which were followed by 3 sets of 10 repetitions (72.7 ± 1.9% 10RM), with 60 seconds of rest between sets. Forty-five minutes after exercise, subjects consumed meals of high fat (HF, 37% carbohydrate, 18% protein, and 45% fat), high carbohydrate (HC, 79% carbohydrate, 20% protein, and 1% fat), or water (CON). Fat and carbohydrate oxidation were determined at 15-minute periods after meal consumption for 165 minutes. Blood was collected at preexercise (pre), premeal (0 minutes), and 15, 30, 45, 60, 90, 120, 150, and 180 minutes postmeal and was analyzed for insulin, glucose, triacylglycerols, and glycerol. There were no significant differences among the meal conditions for fat and carbohydrate oxidation. Insulin and glucose concentrations were significantly higher (p < 0.05) following HC at 15, 30, 45, 60, and 90 minutes compared to HF and CON. Triacyl-glycerol concentrations were significantly higher (p < 0.05) following HF at 90, 120, 150, and 180 minutes compared to HC and CON. Fat and carbohydrate oxidation were not affected by differences in macronutrient meal consumption after an acute bout of resistance training. Different macronutrient consumption does influence insulin, glucose, and triacylglycerol concentrations after resistance exercise.

THROMBOTIC AND FIBRINOLYTIC RESPONSES TO RESISTANCE TRAINING IN PATIENTS WITH CORONARY DISEASE.

Background: Previous studies in patients with cardiovascular disease have reported increased thrombotic and decreased fibrinolytic potentials, heightening the risk of thrombosis. Recent research has shown that many acute cardiac events occur during or following heavy muscular exertion, predominantly due to an occlusive thrombus. Although resistance training is widely recommended for persons with and without chronic disease, the acute coagulative responses to this form of exercise have not been evaluated in patients with coronary artery disease (CAD). The present study was designed to evaluate changes in thrombotic and fibrinolytic potentials following an acute bout of strength training in patients with CAD. METHOD: Ten men (mean ± SD age = 60.2 ± 9.1 years) with documented CAD, who had not previously engaged in a strength training regimen, were recruited from our outpatient (phase II and III) cardiac rehabilitation programs to participate. Each subject completed one set of 10 repetitions to volitional fatigue on eight separate resistance training devices. Blood samples (5cc) were drawn pre-exercise, postexercise, and 1-hour post-exercise in a seated position. All values were corrected for plasma volume changes. Alterations in tPA activity and antigen, PAI-1 activity, and Factor VIII antigen were analyzed using a one-way repeated ANOVA. RESULT: Mean ± SD thrombotic and fibrinolytic responses over time are shown in the table. Although Factor VIII antigen and tPA activity remained unchanged from pre-exercise values, tPA antigen and PAI-1 activity increased and decreased, respectively, in the immediate post-exercise recovery period. Moreover, the latter reduction persisted at 1-hour post-exercise. CONCLUSION: An acute bout of resistance training improves fibrinolytic potential in patients with CAD, without elevating thrombotic potential. These data support the safety of resistance training in this population when contemporary prescriptive guidelines are employed.Table: No Caption Available

The Effect of Muscle Damage on Strength and Fatigue Deficits

Many studies have reported prolonged force deficits after a bout of resistance training. However there is a dearth of information on the neuromuscular mechanisms underlying these deficits. This study examined whether an acute bout of resistance training had prolonged detrimental effects on muscle activation and excitation-contraction coupling. Two groups of 16 subjects each were tested before resistance exercise and at 1, 3, 5, and 7 days postexercise. A dynamic group was tested for concentric and eccentric 1 repetition maximum and 3-methylhistidine (3-MH). An isometric group was tested for maximal voluntary contraction, muscle inactivation, relative fatigue, and evoked twitch properties. Both groups experienced similar increases in pain, limb circumference, and decreased range of motion between 1 and 3 days postexercise. Decrements occurred with eccentric strength, maximal voluntary contraction, muscle inactivation, relative fatigue, twitch amplitude, and increases in 3-MH. Although muscle damage-induced characteristics (pain, swelling, range of motion, 3-MH) were not correlated with neuromuscular impairments (muscle activation, force output), disruption of excitation-contraction coupling may have contributed to decrements in fatigue.

The Effect of Muscle Damage on Strength and Fatigue Deficits

Many studies have reported prolonged force deficits after a bout of resistance training. However there is a dearth of information on the neuromuscular mechanisms underlying these deficits. This study examined whether an acute bout of resistance training had prolonged detrimental effects on muscle activation and excitation-contraction coupling. Two groups of 16 subjects each were tested before resistance exercise and at 1, 3, 5, and 7 days postexercise. A dvnamic group was tested for concentric and eccentric 1 repetition maximum and 3-methylhistidine (3-MH). An isometric group was tested for maximal voluntary contraction, muscle inactivation, relative fatigue, and evoked twitch properties. Both groups experienced similar increases in pain, limb circumference, and decreased range of motion between 1 and 3 days postexercise. Decrements occurred with eccentric strength, maximal voluntary contraction, muscle inactivation, relative fatigue, twitch amplitude, and increases in 3-MH. Although muscle damage-induced characteristics (pain, swelling, range of motion, 3-MH) were not correlated with neuromuscular impairments (muscle activation, force output), disruption of excitation-contraction coupling may have contributed to decrements in fatigue.

SERUM [IGF-1] RESPONSE TO RESISTANCE TRAINING IS SEX DEPENDENT

1296 Previously we presented evidence that both 3- and 6-months of 1-set and 3-set resistance training (RT) similarly and significantly increased the serum concentration of insulin-like growth factor-1 (IGF-1). Others have suggested that an acute bout of RT is accompanied by a small increase in serum [IGF-1] only in males, but it is unknown whether chronic RT has a sex dependent effect on serum [IGF-1]. In this study we compared serum [IGF-1] in females and males before and after 3-months RT. Female (n=9) and male (n=13) volunteers (age 39±6 yr) trained 3 d/wk and were randomized to either low volume (1-set per exercise) or high volume (3-sets per exercise) RT using 7 exercises of 8-12 reps to fatigue. Blood was drawn at training wk 0 and 13, and volunteers did not perform RT or other vigorous activity ≥24 h prior to sampling. IGF-1 was measured by radioimmunoassay. Males had significantly (p<0.05) increased serum [IGF-1] at RT wk 13, but females showed only a trend (p<0.08) toward increased serum [IGF-1] (Table). The 1-set compared to 3-set RT volume did not affect (p>0.05) the magnitude of increase in serum [IGF-1], for either sex. The magnitude of change in serum [IGF-1] was more than twice as great in the males compared to females (13% vs 31%, respectively). We conclude that 13 wk RT significantly increases resting, serum [IGF-1] in males, but not in females. This parallels prior observations of a blunted IGF-1 response to acute RT in females.Table