Unilateral Exercise Research Articles

Resistance exercise volume affects myofibrillar protein synthesis and anabolic signalling molecule phosphorylation in young men.

We aimed to determine if any mechanistic differences exist between a single set (1SET) and multiple sets (i.e. 3 sets; 3SET) of resistance exercise by utilizing a primed constant infusion of [ring-13C6]phenylalanine to determine myofibrillar protein synthesis (MPS) and Western blot analysis to examine anabolic signalling molecule phosphorylation following an acute bout of resistance exercise. Eight resistance-trained men (24+/-5 years, BMI=25+/-4 kg m2) were randomly assigned to perform unilateral leg extension exercise at 70% concentric one repetition maximum (1RM) until volitional fatigue for 1SET or 3SET. Biopsies from the vastus lateralis were taken in the fasted state (Fast) and fed state (Fed; 20 g of whey protein isolate) at rest, 5 h Fed, 24 h Fast and 29 h Fed post-exercise. Fed-state MPS was transiently elevated above rest at 5 h for 1SET (2.3-fold) and returned to resting levels by 29 h post-exercise. However, the exercise induced increase in MPS following 3SET was superior in amplitude and duration as compared to 1SET at both 5 h (3.1-fold above rest) and 29 h post-exercise (2.3-fold above rest). Phosphorylation of 70 kDa S6 protein kinase (p70S6K) demonstrated a coordinated increase with MPS at 5 h and 29 h post-exercise such that the extent of p70S6K phosphorylation was related to the MPS response (r=0.338, P=0.033). Phosphorylation of 90 kDa ribosomal S6 protein kinase (p90RSK) and ribosomal protein S6 (rps6) was similar for 1SET and 3SET at 24 h Fast and 29 h Fed, respectively. However, 3SET induced a greater activation of eukaryotic translation initiation factor 2B (eIF2B) and rpS6 at 5 h Fed. These data suggest that 3SET of resistance exercise is more anabolic than 1SET and may lead to greater increases in myofibrillar protein accretion over time.

Low-Load High Volume Resistance Exercise Stimulates Muscle Protein Synthesis More Than High-Load Low Volume Resistance Exercise in Young Men

BackgroundWe aimed to determine the effect of resistance exercise intensity (% 1 repetition maximum—1RM) and volume on muscle protein synthesis, anabolic signaling, and myogenic gene expression.Methodology/Principal FindingsFifteen men (21±1 years; BMI = 24.1±0.8 kg/m2) performed 4 sets of unilateral leg extension exercise at different exercise loads and/or volumes: 90% of repetition maximum (1RM) until volitional failure (90FAIL), 30% 1RM work-matched to 90%FAIL (30WM), or 30% 1RM performed until volitional failure (30FAIL). Infusion of [ring-13C6] phenylalanine with biopsies was used to measure rates of mixed (MIX), myofibrillar (MYO), and sarcoplasmic (SARC) protein synthesis at rest, and 4 h and 24 h after exercise. Exercise at 30WM induced a significant increase above rest in MIX (121%) and MYO (87%) protein synthesis at 4 h post-exercise and but at 24 h in the MIX only. The increase in the rate of protein synthesis in MIX and MYO at 4 h post-exercise with 90FAIL and 30FAIL was greater than 30WM, with no difference between these conditions; however, MYO remained elevated (199%) above rest at 24 h only in 30FAIL. There was a significant increase in AktSer473 at 24h in all conditions (P = 0.023) and mTORSer2448 phosphorylation at 4 h post-exercise (P = 0.025). Phosporylation of Erk1/2Tyr202/204, p70S6KThr389, and 4E-BP1Thr37/46 increased significantly (P<0.05) only in the 30FAIL condition at 4 h post-exercise, whereas, 4E-BP1Thr37/46 phosphorylation was greater 24 h after exercise than at rest in both 90FAIL (237%) and 30FAIL (312%) conditions. Pax7 mRNA expression increased at 24 h post-exercise (P = 0.02) regardless of condition. The mRNA expression of MyoD and myogenin were consistently elevated in the 30FAIL condition.Conclusions/SignificanceThese results suggest that low-load high volume resistance exercise is more effective in inducing acute muscle anabolism than high-load low volume or work matched resistance exercise modes.

Arterial stiffening following eccentric exercise-induced muscle damage

Acute inflammatory responses are linked to a transient increase in risk of a cardiovascular event, and this risk may be mediated by a concomitant reduction in vascular function. Humans experience an acute inflammatory response as a consequence of infection, injury, or muscle damage. We measured macrovascular function before and after eccentric exercise to determine whether muscle damage from unaccustomed exercise has an unfavorable effect on the large elastic arteries. A total of 27 healthy sedentary or recreationally active men (age 18-38 years) participated in either bilateral leg press eccentric exercise or unilateral elbow flexor eccentric exercise. Postexercise muscle damage was confirmed by significant reductions in isometric strength and increases in muscle soreness (P < 0.05). Carotid-femoral pulse-wave velocity was significantly elevated 48 h after leg exercise (808 ± 31 vs. 785 ± 30 cm/s; P < 0.05) and arm exercise (790 ± 28 vs. 755 ± 24 cm/s; P < 0.05). There were no changes in mean arterial pressure. C-reactive protein was elevated after leg exercise but not after arm exercise. The increase in carotid-femoral pulse wave velocity 48 h after arm exercise was associated with muscle strength (r = -0.47; P < 0.05) and creatine kinase concentrations (r = 0.70; P < 0.01). We concluded that eccentric exercise in both small and large muscle mass translates to transient, unfavorable changes in central macrovascular function and that the increase in central arterial stiffness after small muscle eccentric exercise is associated with indicators of muscle damage.

Muscle Deoxygenation during Sustained and Intermittent Isometric Exercise in Hypoxia

It is reported that the rate of locomotor muscle fatigue development during intermittent isometric exercise in hypoxia is accelerated compared with normoxia. In contrast, when sustained isometric contractions are used, some studies do not show any effect of hypoxia on fatigue development. Increased intramuscular pressure during sustained isometric exercise causes substantial and sustained ischemia, even in normoxia. Therefore, we hypothesized that the difference in muscle deoxygenation between normoxia and hypoxia would be small during sustained exercise compared with intermittent exercise and that this may contribute to the inconsistent findings. Subjects performed sustained and intermittent isometric, unilateral, and submaximal knee-extension exercises (60% maximal voluntary contraction to exhaustion) while breathing normoxic (inspired O2 fraction = 0.21) or hypoxic gas mixtures (inspired O2 fraction = 0.10-0.12). Muscle oxygenation (deoxyhemoglobin/myoglobin and tissue oxygenation index) using near-infrared spectroscopy and surface EMG were measured from the left vastus lateralis. During intermittent isometric exercise in hypoxia, increases in deoxyhemoglobin/myoglobin and reductions of tissue oxygenation index were larger (P < 0.05) than those in normoxia. The rate of rise in integrated EMG during intermittent exercise was accelerated (P < 0.05) in hypoxia. In contrast, there were no significant differences in changes in near-infrared spectroscopy variables and integrated EMG during sustained isometric exercise between normoxia and hypoxia. These results suggest that muscle deoxygenation is exaggerated during intermittent isometric exercise in hypoxia compared with normoxia, whereas during sustained isometric exercise, the extent of muscle deoxygenation is the same between normoxia and hypoxia. The different extent of muscle deoxygenation during sustained and intermittent isometric exercise in normoxia and hypoxia could affect muscle fatigability, which results from the varied rate of accumulation of metabolites.

Influence of supplementation with branched-chain amino acids in combination with resistance exercise on p70S6 kinase phosphorylation in resting and exercising human skeletal muscle

Skeletal muscle growth is thought to be regulated by the mammalian target of rapamycin (mTOR) pathway, which can be activated by resistance exercise and branched-chain amino acids (BCAA). The major aim of the present study was to distinguish between the influence of resistance exercise and BCAA on key enzymes considered to be involved in the regulation of protein synthesis, including p70(S6) kinase (p70(S6k)). Nine healthy subjects (four men and five women) performed unilateral resistance exercise on two occasions separated by 1 month. Subjects were randomly supplied either a mixture of BCAA or flavoured water. Muscle biopsies were taken from both resting and exercising muscle before, after and 1 h after exercise. Phosphorylation of Akt was unaltered by either resistance exercise and/or BCAA supplementation whereas mTOR phosphorylation was enhanced (P<0.05) to a similar extent in both exercising and resting muscle following exercise in the absence (70-90%) and presence of BCAA supplementation (80-130%). Phosphorylation of p70(S6k) was unaffected by resistance exercise alone; however, BCAA intake increased (P<0.05) this phosphorylation in both legs following exercise. In resting muscle, a 5- and 16-fold increase in p70(S6k) was observed immediately after and 1 h after exercise, respectively, as compared to 11- and 30-fold increases in the exercising muscle. Phosphorylation of eukaryotic elongation factor 2 was attenuated 1 h after exercise (P<0.05) in both resting (10-40%) and exercising muscle (30-50%) under both conditions. The present findings indicate that resistance exercise and BCAA exert both separate and combined effects on the p70(S6k) phosphorylation in an Akt-independent manner.

The Effects of Disinhibitory Transcutaneous Electrical Nerve Stimulation on Contralateral Quadriceps Activation in Osteoarthritic Patients

Bilateral quadriceps activation failure has been reported following unilateral knee injuries, suggesting that muscle inhibition may be modulated by central nervous system processes. Transcutaneous electrical nerve stimulation (TENS) applied to the injured knee has been reported to disinhibit ipsilateral quadriceps of patients with tibiofemoral osteoarthritis (TFOA), yet no data exists regarding how the contralateral or uninjured quadriceps are affected. PURPOSE: To determine the effects of disinhibitory TENS and therapeutic exercise applied to the injured knee on the uninjured quadriceps central activation ratio (CAR). METHODS: Thirty-six participants with TFOA were stratified by Kellgren-Lawrence Score and baseline CAR, and randomized into 3 groups (control: 5M, 7F; 58.3 ± 11.8yrs, 28.6± 5.6 BMI,), placebo TENS (4M, 8F; 60.3 ± 12.9yrs, 29.5±9.8 BMI) and TENS groups (6 M,6F; 61 ± 10.9yrs, 28.6± 4.8 BMI). The involved leg was determined as the knee that had the most radiographic evidence of TFOA. All groups participated in 12 supervised, unilateral lower extremity exercise sessions over 4 weeks. TENS and placebo TENS groups wore the intervention on the injured leg during all exercise sessions and for at least 8 hours daily for 4 weeks. Quadriceps CAR was tested on the uninvolved quadriceps prior to the intervention and at 2 and 4 weeks following baseline. A 3x3 repeated measures ANOVA was used to detect differences in CAR and standardized effect sizes calculated to assess effect magnitude. RESULTS: No significant differences were found in CAR score between groups at baseline (TENS 86±10, placebo 84±15, control 84±12), 2 weeks (93±4, 84±13, 86±11) or 4 weeks (94±.07, 82±16, 81±17), yet strong to moderate effect sizes were found at 2 weeks (d =.92; 95% confidence interval.05, 1.73) and 4 weeks (.58; -.26, 1.37) in the TENS group. Weak effect sizes were calculated for both the placebo (0; -.8, 8: -.13; -.93,.68) and the control group (.17; -.63,.97: -.2; -1,.61) at 2 and 4 weeks, respectively. CONCLUSION: Although there were no statistically significant differences between groups in the uninvolved leg following 4 weeks of disinhibitory TENS treatment, effect sizes were strong, suggesting a clinically significant increase in uninvolved quadriceps CAR.

Branched-Chain Amino Acid Ingestion Can Ameliorate Soreness from Eccentric Exercise

The purpose of this study was to examine the role of branched-chain amino acid (BCAA) supplementation during recovery from intense eccentric exercise. Twenty-four non-weight-trained males were assigned to one of two groups: one group (supplementary, SUP) ingested BCAA beverages (n = 12); the second group (placebo, PLA) ingested artificially flavored water (n = 12). Diet was controlled throughout the testing period to match habitual intake. The eccentric exercise protocol consisted of 12 x 10 repetitions of unilateral eccentric knee extension exercise at 120% concentric one repetition maximum. On the day of the exercise, supplements were consumed 30 min before exercise, 1.5 h after exercise, between lunch and dinner, and before bed. On the following 2 d, four supplements were consumed between meals. Muscle soreness, muscle function, and putative blood markers of muscle damage were assessed before and after (1, 8, 24, 48, and 72 h) exercise. Muscle function decreased after the eccentric exercise (P < 0.0001), but the degree of force loss was unaffected by BCAA ingestion (51% +/- 3% with SUP vs -48% +/- 7% with PLA). A decrease in flexed muscle soreness was observed in SUP compared with PLA at 48 h (21 +/- 3 mm vs 32 +/- 3 mm, P = 0.02) and 72 h (17 +/- 3 mm vs 27 +/- 4 mm, P = 0.038). Flexed muscle soreness, expressed as area under the curve, was lower in SUP than in PLA (P = 0.024). BCAA supplementation may attenuate muscle soreness, but it does not ameliorate eccentric exercise-induced decrements in muscle function or increases in reputed blood markers of muscle damage, when consumed before exercise and for 3 d after an eccentric exercise bout.

Evaluation of Bone Markers during Unilateral Lower Limb Suspension and Blood Flow Restricted Exercise

Evaluation of Bone Markers during Unilateral Lower Limb Suspension and Blood Flow Restricted Exercise

Lower Extremity Muscle Activation During Baseball Pitching

The purpose of this study was to investigate muscle activation levels of select lower extremity muscles during the pitching motion. Bilateral surface electromyography data on 5 lower extremity muscles (biceps femoris, rectus femoris, gluteus maximus, vastus medialis, and gastrocnemius) were collected on 11 highly skilled baseball pitchers and compared with individual maximal voluntary isometric contraction (MVIC) data. The pitching motion was divided into 4 distinct phases: phase 1, initiation of pitching motion to maximum stride leg knee height; phase 2, maximum stride leg knee height to stride foot contact (SFC); phase 3, SFC to ball release; and phase 4, ball release to 0.5 seconds after ball release (follow-through). Results indicated that trail leg musculature elicited moderate to high activity levels during phases 2 and 3 (38-172% of MVIC). Muscle activity levels of the stride leg were moderate to high during phases 2-4 (23-170% of MVIC). These data indicate a high demand for lower extremity strength and endurance. Specifically, coaches should incorporate unilateral and bilateral lower extremity exercises for strength improvement or maintenance and to facilitate dynamic stabilization of the lower extremities during the pitching motion.

Single Limb Exercise: Pilot Study of Physiological and Functional Responses to Forced Use of the Hemiparetic Lower Extremity

Purpose: Stroke-related deficits can impede both functional performance and walking tolerance. Individuals with hemiparesis rely on the stronger limb during exercise and functional tasks. The single limb exercise (SLE) intervention was a unique training protocol that focused only on the hemiparetic limb. Our objective was to determine the effect of the SLE intervention on cardiorespiratory fitness parameters. Methods: Twelve participants (5 male) with a mean age of 60.6 ± 14.5 years and 69.1 ± 82.2 months post stroke participated in the training intervention. All participants performed SLE using the hemiparetic leg three times a week for 4 weeks. The nonhemiparetic limb served as the control limb and did not engage in SLE. Peak oxygen uptake (VO2 peak) and oxygen uptake (VO2) were measured at baseline and post intervention in all 12 participants. At pre and post intervention, gait velocity was assessed in a subset of participants (n = 7) using the 10-m fast-walk test. Results: After the 4-week SLE training intervention, significant improvements were found for VO2 during submaximal work effort (P = .009) and gait velocity (n = 7) (P = .001). Peak oxygen uptake did not increase (P = .41) after the training intervention. Conclusion: These data suggest that SLE training was an effective method for improving oxygen uptake and reducing energy expenditure during submaximal effort. Unilateral exercise focused on the hemiparetic leg may be an effective intervention strategy to consider for stroke rehabilitation.

Whey protein isolate attenuates strength decline after eccentrically-induced muscle damage in healthy individuals

BackgroundWe examined the effects of short-term consumption of whey protein isolate on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals.MethodsSeventeen untrained male participants (23 ± 5 yr, 180 ± 6 cm, 80 ± 11 kg) were randomly separated into two supplement groups: i) whey protein isolate (WPH; n = 9); or ii) carbohydrate (CHO; n = 8). Participants consumed 1.5 g/kg.bw/day supplement (~30 g consumed immediately, and then once with breakfast, lunch, in the afternoon and after the evening meal) for a period of 14 days following a unilateral eccentric contraction-based resistance exercise session, consisting of 4 sets of 10 repetitions at 120% of maximum voluntary contraction on the leg press, leg extension and leg flexion exercise machine. Plasma creatine kinase and lactate dehydrogenase (LDH) levels were assessed as blood markers of muscle damage. Muscle strength was examined by voluntary isokinetic knee extension using a Cybex dynamometer. Data were analyzed using repeated measures ANOVA with an alpha of 0.05.ResultsIsometric knee extension strength was significantly higher following WPH supplementation 3 (P < 0.05) and 7 (P < 0.01) days into recovery from exercise-induced muscle damage compared to CHO supplementation. In addition, strong tendencies for higher isokinetic forces (extension and flexion) were observed during the recovery period following WPH supplementation, with knee extension strength being significantly greater (P < 0.05) after 7 days recovery. Plasma LDH levels tended to be lower (P = 0.06) in the WPH supplemented group during recovery.ConclusionsThe major finding of this investigation was that whey protein isolate supplementation attenuated the impairment in isometric and isokinetic muscle forces during recovery from exercise-induced muscle injury.

Endocrine Response Patterns to Acute Unilateral and Bilateral Resistance Exercise in Men

Rehabilitation programs and research experiments use single-arm protocols in which the contralateral arm is not functional or used as a control limb. This study was interested in determining the hormonal signal impacts of such one- versus two-arm exercise responses that might have an impact on adaptational changes with training. The purpose was to examine the acute hormonal responses to a unilateral and a bilateral upper-body resistance exercise (RE) protocol. A balanced randomized treatment intervention with series time frame for blood collections before and after exercise was used as the basic experimental design. Ten recreationally resistance trained men (18-25 years, 20.4 +/- 1.2 years, 175.6 +/- 4.5 cm, 81.7 +/- 9.3 kg) gave informed consent to participate in the investigation. Each subject performed unilateral (dominant arm only) and bilateral upper-body RE protocol separated by 1 week in a balanced randomized fashion. The RE protocol consisted of 3 sets of 10 repetitions of 5 different dumbbell upper-body exercises at 80% of 1-repetition maximum, and blood samples were obtained before and 5, 15, and 30 minutes immediately postexercise (IP). Blood was obtained and analyzed for lactate, immunoreactive growth hormone (iGH), cortisol (C), total testosterone (T), and insulin concentrations. Total volume of work also was determined for the 2 exercise sessions. Total volume of work performed during the unilateral protocol was 52.1% of that for the bilateral protocol. Both RE protocols elicited a significant (p < or = 0.05) increase in lactate and iGH, but the increase for the bilateral condition was significantly greater. Cortisol decreased significantly during recovery for the unilateral condition. Testosterone was not affected by either protocol. Insulin was significantly increased at IP and 5 minutes postexercise for both conditions.These results indicate that the hormonal responses to dominant-arm unilateral RE is blunted compared to that for bilateral RE. This differential endocrine response is likely a result of the difference in volume between the protocols. It is important to pay attention to the amount of muscle mass utilized in a resistance exercise protocol to optimize endocrine signaling.

Multilateral Versus Unilateral Exercises of Universal Criminal Jurisdiction

This Article draws a distinction between two types of exercise of universal criminal jurisdiction with a view to demonstrating that one of them is deeply detrimental to domestic IHL enforcement mechanisms, and especially zeroes in on contemporay unilateral exercises of universal criminal jurisdiction, arguing that their unilateral character deprives domestic enforcement procedures of their legitimacy and efficacy. It begins by distinguishing between unilateral and multilateral uses of criminal universal jurisdiction. It then explains why unilateral exercises of universal jurisdiction and the absence of conventional basis do not, per se, stir any problems of legality. Its last part shows that unilateral exercises of universal jurisdiction, while not generating any problem of legality, fuel problems of legitimacy because of the discourse that generally accompanies such proceedings as well as the impossibility to relate such exercises to the consent of the State of nationality of the accused or that where the crime was committed. On this occasion, it is shown that the perceived illegitimacy of unilateral exercises of jurisdiction can prove harmful to the legitimacy and efficacy of domestic IHL enforcement procedures as a whole.

Resistance exercise‐induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men

We aimed to determine whether exercise-induced elevations in systemic concentration of testosterone, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) enhanced post-exercise myofibrillar protein synthesis (MPS) and phosphorylation of signalling proteins important in regulating mRNA translation. Eight young men (20 +/- 1.1 years, BMI = 26 +/- 3.5 kg m(-2)) completed two exercise protocols designed to maintain basal hormone concentrations (low hormone, LH) or elicit increases in endogenous hormones (high hormone, HH). In the LH protocol, participants performed a bout of unilateral resistance exercise with the elbow flexors. The HH protocol consisted of the same elbow flexor exercise with the contralateral arm followed immediately by high-volume leg resistance exercise. Participants consumed 25 g of protein after arm exercise to maximize MPS. Muscle biopsies and blood samples were taken as appropriate. There were no changes in serum testosterone, GH or IGF-1 after the LH protocol, whereas there were marked elevations after HH (testosterone, P < 0.001; GH, P < 0.001; IGF-1, P < 0.05). Exercise stimulated a rise in MPS in the biceps brachii (rest = 0.040 +/- 0.007, LH = 0.071 +/- 0.008, HH = 0.064 +/- 0.014% h(-1); P < 0.05) with no effect of elevated hormones (P = 0.72). Phosphorylation of the 70 kDa S6 protein kinase (p70S6K) also increased post-exercise (P < 0.05) with no differences between conditions. We conclude that the transient increases in endogenous purportedly anabolic hormones do not enhance fed-state anabolic signalling or MPS following resistance exercise. Local mechanisms are likely to be of predominant importance for the post-exercise increase in MPS.

Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men

This study was designed to compare the acute response of mixed muscle protein synthesis (MPS) to rapidly (i.e., whey hydrolysate and soy) and slowly (i.e., micellar casein) digested proteins both at rest and after resistance exercise. Three groups of healthy young men (n = 6 per group) performed a bout of unilateral leg resistance exercise followed by the consumption of a drink containing an equivalent content of essential amino acids (10 g) as either whey hydrolysate, micellar casein, or soy protein isolate. Mixed MPS was determined by a primed constant infusion of l-[ring-(13)C(6)]phenylalanine. Ingestion of whey protein resulted in a larger increase in blood essential amino acid, branched-chain amino acid, and leucine concentrations than either casein or soy (P < 0.05). Mixed MPS at rest (determined in the nonexercised leg) was higher with ingestion of faster proteins (whey = 0.091 +/- 0.015, soy = 0.078 +/- 0.014, casein = 0.047 +/- 0.008%/h); MPS after consumption of whey was approximately 93% greater than casein (P < 0.01) and approximately 18% greater than soy (P = 0.067). A similar result was observed after exercise (whey > soy > casein); MPS following whey consumption was approximately 122% greater than casein (P < 0.01) and 31% greater than soy (P < 0.05). MPS was also greater with soy consumption at rest (64%) and following resistance exercise (69%) compared with casein (both P < 0.01). We conclude that the feeding-induced simulation of MPS in young men is greater after whey hydrolysate or soy protein consumption than casein both at rest and after resistance exercise; moreover, despite both being fast proteins, whey hydrolysate stimulated MPS to a greater degree than soy after resistance exercise. These differences may be related to how quickly the proteins are digested (i.e., fast vs. slow) or possibly to small differences in leucine content of each protein.

Delayed-onset muscle soreness induced by low-load blood flow-restricted exercise

We performed two experiments to describe the magnitude of delayed-onset muscle soreness (DOMS) associated with blood flow restriction (BFR) exercise and to determine the contribution of the concentric (CON) versus eccentric (ECC) actions of BFR exercise on DOMS. In experiment 1, nine subjects performed three sets of unilateral knee extension BFR exercise at 35% of maximal voluntary contraction (MVC) to failure with a thigh cuff inflated 30% above brachial systolic pressure. Subjects repeated the protocol with the contralateral limb without flow restriction. Resting soreness (0-10 scale) and algometry (pain-pressure threshold; PPT) were assessed before and 24, 48 and 96 h post-exercise. Additionally, MVC and vastus lateralis cross-sectional area (CSA) were measured as indices of exercise-induced muscle damage. At 24-h post-exercise, BFR exercise resulted in more soreness than exercise without BFR (2.8 +/- 0.3 vs 1.7 +/- 0.5) and greater reductions in PPT (15.2 +/- 1.7 vs. 20 +/- 2.3 N) and MVC (14.1 +/- 2.5% decrease vs. 1.5 +/- 4.5% decrease) (p <or= 0.05). In experiment 2, 15 different subjects performed three sets of unilateral BFR exercise at 35% MVC with one limb performing only the CON action and the contralateral performing the ECC action. The aforementioned indices of DOMS were assessed before exercise and 24, 48 and 96 h post-exercise. At 24 h post-exercise, CON BFR exercise resulted in more resting soreness than ECC BFR exercise (3.0 +/- 0.5 vs. 1.6 +/- 0.4), and a greater decrease in MVC (9.8 +/- 2.7% decrease vs. 3.4 +/- 2.5% decrease) (p <or= 0.05). These data suggest that knee extension BFR exercise induces mild DOMS and that BFR exercise elicits muscle damage under atypical conditions with low-tension concentric contractions.

Modification of Vascular Function after Handgrip Exercise Training in 73- to90-yr-Old Men

To examine the influence of a unilateral exercise training protocol on brachial artery reactivity (BAR) in 12 men (aged 81 +/- 5 yr). Brachial artery diameters and blood flow parameters were assessed, in both arms, using high-resolution ultrasonography, before and after 5 min of forearm occlusion, before and at the end of each week of a 4-wk training program. Training consisted of a unilateral handgrip training protocol (nondominant arm) at 60% of maximal voluntary handgrip strength, performed for 4 wk, 4 d x wk(-1), 20 min per session, and a cadence of one contraction per 4 s. After training, handgrip strength increased 6.2% (baseline = 32.4 +/- 7.0 kg vs week 4 = 34.4 +/- 6.7 kg) in the trained arm only but failed to reach statistical significance (P = 0.10). No statistical changes were observed for blood pressure or resting HR. In contrast, BAR increased 45% (Pre = 2.9% vs Post = 4.1%, P = 0.05) in the trained arm only. Improvements in BAR were observed after the second week of training, without significant changes in the main vasodilatory trigger, defined as the relevant shear stimulus after forearm occlusion (P > 0.05). These data indicate that a localized short-term exercise program results in significant improvements in vascular function in the trained arm of elderly men compared with the control arm. Furthermore, the findings indicate a statistically significant increase in BAR at the end of the second week of training, despite a similar trigger for dilation versus before training.

Muscle Protein Synthesis Is Not Augmented By Protein-carbohydrate Co-ingestion At Rest Or Following Resistance Exercise

PURPOSE: To determine whether increases in plasma insulin induced by carbohydrate ingestion would augment mixed muscle protein synthesis (MPS) when a bolus dose of whey protein, previously shown to be maximally effective for stimulation of MPS, is consumed at rest and following resistance exercise. METHODS: Nine male participants (23 ± 1.9 y, 24.2 ± 2.1 kg/m2; mean±SD) completed two trials in a double-blind randomized cross-over design. Trials consisted of unilateral knee extension exercise and the post-exercise consumption of a drink that contained 25g of whey protein (PRO) or 25g of whey protein plus 50g of maltodextrin (CHO). Participants completed 4 sets of unilateral resistance exercise performed at 80% maximal effort (8-12 repetitions to failure). RESULTS: There was a main effect for drink composition (CHO > PRO) for plasma glucose concentration (P < 0.05) and plasma insulin concentration (P < 0.05). The area under the glucose and insulin curves were 17.5 and 5 times greater (P < 0.05), respectively, for CHO than PRO. There was no difference in mixed MPS between CHO and PRO (P = 0.99) in the resting leg. Exercise increased mixed MPS by 36.8% and 36.2% in the PRO and CHO groups respectively, with no significant differences between the groups (P = 0.99). CONCLUSIONS: These data suggest that when a maximally effective bolus dose (25g) of protein is consumed, carbohydrate consumption, and the consequent increase in plasma insulin, does not further augment the synthesis of mixed muscle proteins at rest or following resistance exercise. These findings support the conclusion that insulin does not stimulate mixed MPS beyond protein ingestion, and the accompanying hyperaminoacidemia, alone. Supported by NSERC

Kinetics of Intramuscular Inorganic Phosphate During Low Intensity Exercise With Blood Flow Restriction

Under the same loading condition, dynamic exercise combined with blood flow restriction (BFR) causes more rapid reduction in muscle power (muscle fatigue) than without blood flow restriction. Furthermore, low-intensity resistance exercise combined with BFR causes as much muscle fatigue as that of high-intensity exercise. However, the mechanisms of such exercise induced muscle fatigue with BFR are unknown. Recent studies have suggested that the accumulation of inorganic phosphate (Pi), which accelerates under ischemic exercise, may also contribute to muscle fatigue. PURPOSE: To investigate the kinetics of intramuscular Pi concentration during resistance exercise with blood flow restriction. METHODS: Ten healthy young men (24.9Ã'±5.4 yrs, 174.4Ã'±7.1 cm, 71.1Ã'±10.0 kg) performed unilateral planter flexion exercise (30 reps Ã_ 1 set followed by 15 reps Ã_ 3 sets with 30-seconds rest between sets) in a supine position in phosphorus magnetic resonance spectroscopy (MRS system). Each subject underwent three exercise conditions; at low-intensity (20%1-RM) either with (L-BFR) or without (L-CON) blood flow restriction, and high-intensity exercise (HIGH; 70%1RM, 15 reps Ã_ 3 sets with 3 min rest between sets) without blood flow restriction. For L-BFR, proximal part of thigh in the exercising leg was pressurized at 220 mmHg with inflexible cuff (5cm wide). Change in intramuscular Pi was monitored continuously during the entire protocol. RESULTS: During exercise, Pi increased progressively and similarly for L-BFR and L-CON group. However, during the rest interval, the rate of decline (recovery rate) was slower in L-BFR such that the % change in Pi was significantly higher in L-BFR than L-CON before the initiation of following set. As a result, the % change in Pi at the end of 4th set was significantly higher in L-BFR than L-CON (L-BFR; 94.0Ã'±30.3 %, L-CON; 64.0Ã'±20.2 %). However, % change in Pi for HIGH was still significantly higher than L-BFR and L-CON. CONCLUSIONS: Low-intensity resistance exercise combined with blood flow restriction induced accumulation of Pi faster than control exercise mainly due to the delayed recovery during the rest periods.

Counterpoint: Estrogen and Sex do not Significantly Influence Post-Exercise Indexes of Muscle Damage, Inflammation, and Repair

Exercise-induced muscle damage (EIMD) occurs following strenuous, novel exercise and is assessed directly via tissue analysis and characterized indirectly by muscle dysfunction, inflammation, delayed onset muscle soreness, and increased levels of muscle proteins [e.g., creatine kinase (CK),