Albuterol helps resistance exercise attenuate unloading-induced knee extensor losses

INTRODUCTION: While resistance exercise (REX) attenuates knee extensor (KE) mass and strength deficits during short-term unloading, additional treatments concurrently administered with REX are required to reduce the greater losses seen with longer periods of unloading. METHODS: To determine whether albuterol helps REX attenuate unloading-induced KE losses, two groups of subjects strength trained their left thigh three times per week, and otherwise refrained from ambulatory and weight-bearing activity for 40 d while receiving a capsule dosing treatment (albuterol, placebo) with no crossover. A third group served as unloaded controls (CTRL). On days 0, 20, and 40, the following data were collected from the nonweight-bearing (left) thigh: cross-sectional area (CSA); integrated electromyography (IEMG); and concentric and eccentric KE strength measures. Thigh CSA was estimated using anthropometric methodology. IEMG was used to provide root mean square (RMS) values from submaximal (100 nm) and maximal isometric contractions. Concentric and eccentric strength were measured from eight-repetition unilateral leg press sets. RESULTS: Repeated-measures mixed-factorial 3 x 3 ANCOVAs with day 0 values as a covariate showed group by time interactions for concentric and eccentric total work (CTW, ETW). Tukey's post hoc test showed REX-albuterol evoked significant (p < 0.05) day 40 CTW and ETW gains vs. within-group day 0 and within-time REX-placebo and CTRL values. By days 20 and 40, CTRL subjects incurred significant decrements. CONCLUSIONS: Albuterol augmented the effects of REX to increase CTW and ETW. Research identifying possible mechanisms responsible for such changes, as well as the safety of REX-albuterol administration in other models, is warranted.     

Effects of exercise mode on muscle glycogen restorage during repeated days of exercise

The purpose of this study was to examine differences in muscle glycogen storage during three successive days of running or cycling. In a crossover design, seven male subjects performed two 3-d trials of either running (trial R) or cycling (trial C) for 60 min at 75% VO2max. Biopsy samples were obtained before and after each day's exercise from the gastrocnemius (trial R) or vastus lateralis (trial C) muscle. Diets in the 2 d preceding and during each trial contained 5 g carbohydrate.kg-1.d-1 and 14,475 +/- 402 kJ.d-1. Mean pre-exercise glycogen content (mmol.kg-1 wet wt.) was significantly reduced in both trials on day 3 (103.4 +/- 6.0) when compared to day 1 and day 2 (119.9 +/- 6.8 and 116.4 +/- 5.7, respectively). Day 1 glycogen reduction was significantly greater in trial C (P less than 0.03), and glycogen restorage was greater (P less than 0.02) only in trial C between the 1st and 2nd d. On day 3, spectrophotometric analysis of PAS strains showed that pre-exercise glycogen content in either muscle group was significantly (P less than 0.01) less in Type I as compared to Type II fibers. This difference in fiber glycogen storage did not appear to be attributable to muscle damage as negligible leukocyte infiltration and low blood CK levels were obtained. No difference between modes were observed for CK values throughout the trials. These data suggest that the depressed glycogen storage before the 3rd d of exercise was due to the moderate carbohydrate intake.     

Effects of strength exercise on the knee and ankle proprioception of individuals with knee osteoarthritis

This study aims to investigate the effects of 8-week strength exercise on knee and ankle proprioception of individuals with knee osteoarthritis (KOA). Forty participants were randomly divided into control and strength exercise groups. Strength exercise group underwent squat training of three times a week for 8 weeks, while control group received an education programme. Threshold for detection of passive movement of knee and ankle joint was tested using an electrically driven movable frame. Between- and within-group differences were evaluated through repeated-measurement analysis of variance. After intervention, passive motion sense in knee flexion of participants in strength exercise group significantly improved (p = 0.033, 95% confidence interval of mean difference: 0.019–1.478) with significant difference between groups. No significant differences of passive motion senses were found in knee extension and ankle between strength exercise and control groups. Eight-week squat training significantly improves the motion sense of knee flexion in patients with KOA.     

Order effects of high-intensity intermittent and strength exercise on lipoprotein profile

Purpose

To compare the effects of the order of concurrent exercise (endurance plus strength or strength plus endurance) on lipoprotein profiles in men.

Methods

After the evaluation of maximum strength (one repetition maximum—1RM) in the half-squat and of aerobic fitness (maximal velocity in treadmill incremental test), 11 physically active male subjects underwent two randomized sessions composed of four sets of half-squat strength exercises until exhaustion (at 80 % of 1RM) and a 5-km run high-intensity intermittent exercise (1:1 min at V _max), performed in different orders: (1) strength plus run (S-A) and inverse order, and run plus strength (A-S). Blood samples were collected before and immediately after the first exercise (Post-1) and after the second exercise (Post-2) in the intra-session sequence. Serum was analyzed for total cholesterol (TC) and its ratio, HDL-c and LDL-c, and triacylglycerol (TAG).

Results

There were effects of condition for TC, LDL-c, and TC/HDL, with greater values in the AS than SA (p < 0.001 for all). For the delta analysis, there was an interaction effect for TAG, with greater delta-1 S-A than delta-1 A-S (p = 0.035), and higher delta-1 S-A than delta-2 S-A (p = 0.001); for LDL-c, with higher delta-1 S-A values than delta-2 S-A (p = 0.010); and for TC, with higher delta-1 S-A values than delta-2 S-A (p = 0.038).

Conclusion

We conclude that there are no differences between the order of acute high-intensity intermittent run plus strength exercises regarding modulation of the lipoprotein profile in healthy, physically active men.

     

The effects of a prolonged running exercise on strength characteristics

The aim of this study was to examine concentric, isometric, and eccentric strength reductions in the quadriceps muscle following a prolonged running exercise. Before and after a 2 h run (28.4+/-1.4 km) peak torque (PT) of the knee extensors at angular velocities of -120, -90, -60, 0, 60, 120, 180, 240 degrees x s(-1) using an isokinetic dynamometer, electromyographic (EMG) activity of the vastus lateralis (VL) and vastus medialis (VM) muscles and height of a counter movement jump were recorded in twelve well-trained triathletes. Counter movement jump performances decreased by 10% and PT values were all significantly lower (p < 0.01) at each angular velocity following the run. The torque loss was significantly (p < 0.01) greater under eccentric contractions (from 18 to 21%) than under concentric ones (from 11 to 14%). EMG activity (RMS) was lower in both VL and VM muscles after the 2 h run but no difference existed in RMS losses between concentric and eccentric contractions. The present results demonstrate that 1) a prolonged running exercise more greatly affects eccentric force production in the quadriceps muscle, and 2) this specificity seems to be due to an impairment of the muscular contractile mechanism rather than a modification to the neural input.     

Interaction between angiotensin converting enzyme insertion/deletion genotype and exercise training on knee extensor strength in older individuals

Prior data in young individuals suggest that the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism interacts with exercise to affect athletic performance, but the direction of the genotype effect depends on the outcome assessed (endurance vs. strength). The purpose of this study was to determine whether the ACE I/D genotype influences physical function responses to exercise training in older individuals. Physical function (muscle strength, walking distance, and self-reported disability) was measured before and after an 18-month randomized, controlled exercise trial in 213 older (>or= 60 yrs), obese (BMI >or= 28 kg/m2) men and women. Exercise training consisted of walking and light weight lifting for one hour 3 times/wk. At baseline, there were no associations between ACE I/D genotype and measures of physical function. Following exercise training, individuals with the DD genotype showed greater gains in knee extensor strength compared to II individuals. There was a significant (p = 0.014) interaction between ACE I/D genotype and exercise treatment on percent change in knee strength. In addition, there was a trend towards a greater improvement in physical disability score in DD genotypes (p = 0.13), but changes in 6-minute walk distance were not different between genotype groups. Thus, changes in muscle strength with exercise training in older individuals may be dependent on ACE I/D genotype.     

Immediate effects of different ankle pushoff instructions during walking exercise on hip kinematics and kinetics in individuals with total hip arthroplasty

Residual hip impairments, such as decreased hip muscle moment and power during walking, have been reported in patients with total hip arthroplasty (THA). Meanwhile, greater ankle power has also been reported in these patients. We investigated the interaction between hip and ankle joints during walking to determine the effects of different ankle pushoff instructions on hip biomechanics in patients with THA. Twenty-four women (age, 60.8±5.5 years) were randomly assigned to walking exercise groups with either decreased pushoff or increased pushoff. Patients in the decreased pushoff group and increased pushoff group were given the instructions "push less with your foot when you walk" and "push more with your foot when you walk," respectively. Exercises lasted approximately 10-15 min. A series of gait-related parameters were analyzed during pre-exercise, exercise, and post-exercise session. In the decreased ankle pushoff group, hip flexor power absorption and hip/ankle power ratio were higher during post-exercise than during pre-exercise. An increase in hip power from -9.8% to 32.1% was identified. The effect of increase in the hip power by the decreasing ankle pushoff was higher in the patients with greater ankle pushoff in their natural gaits. The patients in the increased ankle pushoff group showed decreased hip flexion angle and hip muscle moment and power after the walking exercise, although ankle pushoff was not increased. Walking exercise with decreased ankle pushoff may help improve the distribution of muscle power between hip flexors and ankle plantarflexors during walking in patients with THA.     

Acute effects of static and dynamic stretching on leg flexor and extensor isokinetic strength in elite women athletes

The aim of this study was to explore the effects of static and dynamic stretching of the leg flexors and extensors on concentric and eccentric peak torque (PT) and electromyography (EMG) amplitude of the leg extensors and flexors in women athletes. Ten elite women athletes completed the following intervention protocol in a randomized order on separate days: (a) non‐stretching (control), (b) static stretching, and (c) dynamic stretching. Stretched muscles were the quadriceps and hamstring muscles. Before and after the stretching or control intervention, concentric and eccentric isokinetic PT and EMG activity of the leg extensors and flexors were measured at 60 and 180°/s. Concentric and eccentric quadriceps and hamstring muscle strength at both test speeds displayed a significant decrease following static stretching (P<0.01–0.001). In contrast, a significant increase was observed after dynamic stretching for these strength parameters (P<0.05–0.001). Parallel to this, normalized EMG amplitude parameters exhibited significant decreases following static (P<0.05–0.001) and significant increases following dynamic stretching (P<0.05–0.001) during quadriceps and hamstring muscle actions at both concentric and eccentric testing modes. Our findings suggest that dynamic stretching, as opposed to static or no stretching, may be an effective technique for enhancing muscle performance during the pre‐competition warm‐up routine in elite women athletes.     

The effects of ankle compliance and flexibility on ankle sprains

PURPOSE: The goal of this study was to examine the influence of changes in subtalar joint flexibility and compliance on ankle sprain occurrence. METHODS: Muscle model driven simulations of 10 subjects performing the landing phase of a side-shuffle movement were performed. The passive flexibility or compliance of the subtalar joint was varied, and each subject-specific simulation was exposed to a set of perturbed floor conditions. RESULTS: Increases in flexibility and compliance both led to an increase in the occurrence of excessive supination, while changes in flexibility had a greater influence. Changes in flexibility or compliance caused only small changes in the occurrence of excessive supination torques. CONCLUSION: These results suggest that increased mechanical laxity does not directly cause an increase in sprain occurrence during side-shuffle movements.     

Exacerbated heat strain during consecutive days of repeated exercise sessions in heat

ObjectivesAn exercise session in a hot environment may increase thermal strain during subsequent exercise sessions on the same and consecutive days. Therefore, this study was conducted to determine lasting physiological strain from moderate-high intensity, intermittent exercise in heat on subsequent exercise.DesignRepeated measures laboratory study.MethodsSeventeen healthy, recreationally active men (age: 22 ± 3 y, maximal oxygen consumption: 54.6 ± 5.3 mL kg⁻¹ min⁻¹) underwent two intermittent moderate-high intensity aerobic exercise sessions separated by 2 h of rest one day, followed by one session 24 h later in a 40 °C, 40% relative humidity environment. Heart rate, rectal temperature, heat stress perception, and environmental symptoms were assessed.Results100%, 35%, and 71% of participants completed the full exercise protocol during the first exercise session, second exercise session, and the following day, respectively. Exercising heart rate and rectal temperature were greater during the second exercise session (189 ± 11 bpm, 38.80 ± 0.47 °C) than the first identical exercise session (180 ± 17 bpm, p = 0.004; 38.41 ± 0.52 °C, p = 0.001), respectively. Immediate post-exercise heart rate, rectal temperature, thirst, thermal sensation, fatigue, and perceived exertion were similar among exercise sessions despite a shorter exercise duration during the second exercise session (93 ± 27 min, p = 0.001) and the following day (113 ± 12 min, p = 0.032) than the first exercise session (120 ± 0 min).ConclusionsModerate-high-intensity intermittent exercise in the heat resulted in greater heat strain during a second exercise session the same day, and exercise the subsequent day.     

A comparison of drop jump training methods: effects on leg extensor strength qualities and jumping performance.

The purpose of this study was to determine the effects of two drop jump (DJ) training methods on the strength qualities of the leg extensors and vertical jumping performance. Thirty-five males were allocated to either a control group or one of two training groups, required to perform 72-90 DJ per week for 6 weeks: DJ for maximum rebound height (DJ-H) or DJ for maximum height and minimum ground contact time (DJ-H/t). The subjects were tested before and after the training on leg extensor function for maximum strength and speed-strength under concentric and stretch-shortening cycle muscular actions, and on vertical jumps from a standing position and a run-up. ANOVA with repeated measures showed that a 20% gain in reactive strength (RS) for the DJ-H/t group was significantly greater (p < 0.05) than the other groups, however, this did not transfer to vertical jumping performance. The DJ-H group did not achieve a significant training effect. It was concluded that DJ-H/t method was effective for the development of RS, but training with DJ-H was not intense and/or specific enough to stimulate gains in strength qualities of the leg extensors or jumping performance.     

Effects of prior strength exercise on the heart rate oxygen uptake relationship during submaximal exercise.

Fourteen young males (mean age 26.7 yrs) were tested to determine if there was an alteration, in the heart rate-oxygen uptake relationship during submaximal cycle ergometer exercise following isokinetic strength training activity as has been documented following high intensity endurance activity. Results indicated that there was a significant increase rate without a concomitant increase in heart oxygen uptake during the first five minutes of submaximal cycle riding at 73% VO2max after heavy strength leg exercise, angular velocity of 30 degrees/second, when compared to no prior exercise. This alteration in the heart rate-oxygen uptake relation is not apparent by 20 minutes of the same submaximal exercise despite higher lactate values and greater ratings of perceived exertion. For individuals using heart rate as a guide to exercise intensity, the elevated heart rate at five minutes of submaximal exercise following heavy strength leg exercise does not exceed the 20 minute value which is an accurate reflection of energy cost and intensity.     

Pituitary-adrenal and pituitary-thyroid hormone responses during exercise-cold exposure after 7 days of exhaustive exercise

BACKGROUND: After several days of exhaustive exercise in mild-warm environments, cutaneous vasoconstrictor responses to cold exposure are less effective in conserving body heat than in the rested condition. Hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes hormones could mediate this response since they may affect vasoconstriction. The effects of exertional fatigue on pituitary-adrenal hormones and thyroid hormone responses to exercise-cold stress are unknown. HYPOTHESIS: We hypothesized that 7 consecutive days of exercise would decrease adrenocorticotropin (ACTH) and cortisol, while elevating thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) and that these hormones would be related to a blunted vasoconstrictor response to cold. METHODS: Nine male volunteers walked, completely wetted, for up to 6 h in 5 degrees C air, when rested (day 0, control) and after 7 consecutive days (day 7) of exhaustive exercise (4 h each day of mixed aerobic and anaerobic activities in thermoneutral conditions). Blood was sampled on day 0 and day 7 at baseline (0700 hours), and before and immediately after cold exposure. RESULTS: At 0700 hours, ACTH and cortisol were elevated (p < 0.05) after 7 d of exercise, compared with control conditions. Following exercise-cold exposure, cortisol, T3, and T4 increased (p < 0.05) similarly on both day 0 and day 7. ACTH and TSH did not increase as a result of exercise-cold exposure on either day. CONCLUSIONS: These data indicate that 7 d of exercise elevates basal (0700 hours) pituitary-adrenal stress hormones (ACTH, cortisol). However, 7 d of exercise did not modify adrenal or thyroid hormone responses, relative to the day 0 cold exposure, suggesting that they are not responsible for the blunted vasoconstriction during exercise-cold exposure following 7 consecutive days of exercise.     

The effects of water-based strength exercise on quality of life in young women

Background

Exercise improves quality of life (QoL). However, little is known concerning the effects of different volumes of strength exercise on QoL. The aims of this study are to: (1) evaluate the effects of water-based strength exercise on QoL of healthy young women and (2) compare the effects of different volumes of water-based strength exercises on QoL of healthy young women.

Methods

Sixty-six participants were randomly allocated into four groups with different volumes of exercise. The participants performed water-based strength exercises for 20 weeks, two times a week, supervised by trained physiologists.

Results

A significant improvement was found in overall QoL (F = 5.96; p = 0.018) and in physical (F = 22.01; p < 0.001), psychological (F = 8.408; p = 0.006) and environment domains (F = 8.34; p = 0.006). In addition, a significant decrease of depressive symptoms was found (F = 22.32; p < 0.001). No difference was found between groups in any domain of QoL or depressive symptoms.

Conclusion

Water-based strength exercise improves specific domains of QoL and decreases depressive symptoms of young healthy women. Different volumes of exercise promote similar effects on QoL and depressive symptoms.

     

Effects of eccentric exercise on trunk extensor torque and lumbar paraspinal EMG

PURPOSE: Little is known about the effects of eccentric contractions on the function of the lumbar paraspinal muscles. The purpose of this study was to determine the effects of a single bout of eccentric contractions using the trunk extensor muscles on torque and lumbar paraspinal electromyographic (EMG) parameters. METHODS: Twenty healthy men between the ages of 18 and 49 yr participated in the study. Subjects performed a single bout of 50 maximal voluntary concentric (N = 10) or eccentric (N = 10) trunk extension movements while surface EMG signals were recorded from the multifidus and iliocostalis lumborum muscles. A series of isometric contractions were performed both before the exercise protocol and at five additional time points over the following 7 d. RESULTS: During the exercise protocol, peak torque decreased 30% and 24% in the eccentric and concentric groups, respectively, whereas no change occurred in EMG root-mean-square (RMS). There were no group differences in peak torque generation at any of the postexercise protocol time points. Compared with the preexercise protocol values, multifidus EMG was elevated 27% immediately post and 15 min post in the eccentric group. Similarly, compared with the concentric group, multifidus EMG in the eccentric group was increased 34%, 40%, and 25% immediately post, 15 min post, and 1 d after the exercise protocol, respectively. CONCLUSION: Eccentric contractions using the trunk extensor muscles result in higher levels of multifidus EMG activity to produce a given level of torque. This reduction in neuromuscular efficiency persisted for one day with recovery to baseline levels by the third day. Contrary to studies using other muscle groups, no sustained alteration in muscle function was observed.     

Post‐exercise ankle blood pressure and ankle to brachial index after heavy load bicycle exercise

The American Heart Association (AHA ) recommendations for diagnosing peripheral artery disease (PAD ) after exercise are a decrease >20% of ankle brachial index (ABI ) or >30 mm Hg of ankle systolic blood pressure (ASBP ) from resting values. We evaluated ABI and ASBP values during incremental maximal exercise in physically active and asymptomatic patients. Patients (n = 726) underwent incremental bicycle tests with pre‐ and post‐exercise recording of all four limbs arterial pressures simultaneously. Univariate and multivariate analyses were performed to define the correlation between post‐exercise ABI with various clinical factors, including age. Thereafter, the population was divided into groups of age: less than 40 (G < 40), from 40 to 44 (G40/44) from 45 to 49 (G45/49), from 50 to 54 (G50/54), from 55 to 59 (G55/59), from 60 to 64 (G60/64), and 65 and above (G ≥ 65) years. Results are mean ± SD . * is two‐tailed P  < .05 for ANOVA with Dunnett's post‐hoc test from G40. Changes from rest in ASBP were −3 ± 22 (G < 40), −2 ± 20 (G40/44), 4 ± 22* (G45/49), 10 ± 25* (G50/54), 18 ± 21* (G55/59), 23 ± 27* (G60/64), and 16 ± 22* (G ≥ 65) mm Hg. Decreases from rest in ABI were 32 ± 9 (G < 40), 33 ± 9 (G40/44), 29 ± 8 (G45/49), 27 ± 10* (G50/54), 24 ± 7* (G55/59), 22 ± 12* (G60/64), and 21 ± 12* (G ≥ 65) % of resting ABI . Maximal incremental exercise results in ABI and ASBP changes are mostly dependent on age. The AHA limits for post‐exercise ABI are inadequate following maximal incremental bicycle testing. Future studies detecting PAD in active patients should account for the effect of age.     

Psychological effects of music tempi during exercise

The purpose of this study was to investigate the effects of music tempi on music preference, intrinsic motivation, and flow during long-duration exercise (approximately 26 min). Subjects (n = 29) selected the music of a single artist then walked at 70 % of maximum heart rate reserve (maxHRR) on a treadmill under three experimental conditions (medium tempi, fast tempi, and mixed tempi) and a no-music control. A music preference item, the Intrinsic Motivation Inventory, and Flow State Scale-2 were completed after each trial. Data were analyzed using a mixed-model (Gender x Condition) ANOVA and MANOVA. The Gender x Condition interaction was nonsignificant in both analyses (p > 0.05). Contrary to expectations, higher preference scores were recorded for medium tempi than for mixed tempi (means: 7.8 +/- 1.3 vs. 7.1 +/- 1.1). The medium tempi music also yielded the highest levels of intrinsic motivation (p < 0.001). Pairwise comparisons showed that interest-enjoyment was higher for medium tempi when compared to mixed tempi, 95% CI = 1.80-8.48, p = 0.001, and that each of the music preference experimental conditions yielded higher scores than the no-music control. Also, pressure-tension was lower for medium tempi compared to fast tempi, 95% CI = -3.44-0.19, p = 0.022, and for both medium and mixed tempi compared to control (95% CI = -5.33-2.89, p = 0.000; 95% CI = -4.24 - 0.64, p = 0.004). A main effect was found for global flow (p = 0.000) with the highest mean score evident in the medium tempi condition (14.6 +/- 1.5). Follow-up comparisons indicated that the medium tempi condition yielded higher flow scores than the control, 95% CI = 1.25-3.60, p = 0.000, as did fast tempi, 95% CI = 0.89-3.14, p = 0.000, and mixed tempi, 95% CI = 1.36-3.76, p = 0.000. It was concluded that a medium tempi music program was the most appropriate for an exercise intensity of 70% maxHRR.