Marco Machado

Effect of varying rest intervals between sets of assistance exercises on creatine kinase and lactate dehydrogenase responses.

Machado, M, Koch, AJ, Willardson, JM, Pereira, LS, Cardoso, IM, Motta, MKS, Pereira, R, and Monteiro, AN. Effect of varying rest intervals between sets of assistance exercises on creatine kinase and lactate dehydrogenase responses. J Strength Cond Res 25(5): 1339-1345, 2011-To examine the effects of different rest intervals between sets on serum creatine kinase (CK) and lactate dehydrogenase (LDH) activity, 10 men (age = 25.6 ± 2.2 years, height = 173.1 ± 7.1 cm, and body mass = 75.9 ± 10.0 kg) participated in a randomized within-subject design that involved 4 resistance exercise sessions. Each session consisted of 4 sets of 10 repetitions with 10 repetition maximum loads for the chest press, pullover, biceps curl, triceps extension, leg extension, and prone leg curl. The sessions differed only in the length of the rest interval between sets and exercises, specifically: 60, 90, 120, 180 seconds. Serum CK and LDH were significantly (p < 0.05) elevated 24-72 hours after each session, with no significant differences between rest intervals (p = 0.94 and p = 0.99, respectively). The mechanical stress imposed by the 4 resistance exercise sessions invoked similar damage to the muscle fibers independent of the rest interval between sets. These data indicate that the accumulated volume of work is the primary determinant of muscle damage in trained subjects who are accustomed to resistance exercise with short rest intervals.

Short recovery augments magnitude of muscle damage in high responders.

PURPOSE To examine serum creatine kinase (CK) activity after resistance exercise bouts with different rest intervals between sets and exercises in high responding (HR) and normal responding (NR) subjects. METHODS During each resistance exercise bout, three sets with 10-repetition maximum (10RM) loads were completed for the chest press, cable pulldown, biceps curl, triceps extension, leg extension, and prone leg curl. Each bout differed in the length of the rest interval between sets and exercises, specifically either 1 or 3 min. After blood analysis, subjects were separated into NR or HR on the basis of the peak serum CK activity being in the 90th percentile. RESULTS The volume completed (load x sets x repetitions) was significantly greater for the 3-min bout versus the 1-min bout, with no significant differences between the HR and the NR groups. For the NR group, serum CK was significantly elevated from 24 to 72 h after each bout, with no significant differences between bouts. Conversely, for the HR group, the 1-min bout resulted in serum CK activity levels that were approximately 70% greater than the 3-min bout at the 48- and 72-h time points. CONCLUSIONS The key finding from the current study was that the HR group experienced significantly greater CK responses when using shorter rest intervals between sets. Conversely, for the NR group, CK responses were not significantly different between bouts. These findings may have implications for resistance exercise prescription in that some individuals might be less tolerant of shorter rest intervals between sets with greater skeletal muscle microtrauma.

Carbohydrate mouth rinse enhances time to exhaustion during treadmill exercise

Mouth rinsing with a CHO solution has been suggested to improve short (<1 h) endurance performance through central effect. We examined the effects of mouth rinsing with a CHO solution on running time to exhaustion on a treadmill. Six well‐trained subjects ran to exhaustion at 85% VO2max, on three separate occasions. Subjects received either an 8% CHO solution or a placebo (PLA) every 15 min to mouth rinse (MR) or a 6% CHO solution to ingest (ING). Treatments were assigned in a randomized, counterbalanced fashion, with the mouth‐rinsing treatments double‐blinded. Blood samples were taken to assess glucose (Glu) and lactate (Lac), as well as the perceived exertion (RPE). Gas exchange and heart rate (HR) were collected during all trials. Subjects ran longer (P = 0·038) in both the MR (2583 ± 686 s) and ING (2625 ± 804 s) trials, compared to PLA (1935 ± 809 s), covering a greater distance (MR 9685 ± 3511·62 m; ING 9855 ± 4118·62; PLA 7295 ± 3727 m). RER was significantly higher in both ING and MR versus PLA. No difference among trials was observed for other metabolic or cardiovascular variables (VO2, Lac, Glu, HR), nor for RPE. Endurance capacity, based on time to exhaustion on a treadmill, was improved when either mouth rinsing or ingesting a CHO solution, compared to PLA.

Creatine Kinase Activity Weakly Correlates to Volume Completed Following Upper Body Resistance Exercise

In the current study, we examined the relationship between serum creatine kinase (CK) activity following upper body resistance exercise with a 1- or 3-min rest between sets. Twenty men performed two sessions, each consisting of four sets with a 10-repetition maximum load. The results demonstrated significantly greater volume for the 3-min condition (M = 4,156 kg, SD = 867, for 3 min; vs. M = 3,503 kg, SD = 759, for 1 min; p < .001), with no significant differences in delta CK activity between conditions (p = .574). Nevertheless, there was a weak correlation between the delta CK activity and total volume of exercise completed (r = .55 with a 1-min rest, and r =.45 with a 3-min rest). Therefore, the volume following upper body resistance exercise correlates weakly with serum CK levels, irrespective of rest interval length between sets.

Short intervals between sets and individuality of muscle damage response.

Abstract Machado, M, Pereira, R, and Willardson, JM. Short intervals between sets and individuality of muscle damage response. J Strength Cond Res 26(11): 2946–2952, 2012—This study examined creatine kinase (CK) activity after resistance exercise sessions in subjects classified as high (HiR), medium (MeR), or low responders (LoR). Two resistance exercise sessions were performed that each involved 4 sets of the biceps curl at 85% of a 1 repetition maximum (1RM) and either 1- or 3-minute rest intervals between sets. High responders and MeR demonstrated significantly greater CK activity after the 1-minute session vs. the 3-minute session. Therefore, the HiR and MeR subjects exhibited less tolerance to resting 1 minute between sets, whereas the CK activity was not significantly different between rest intervals for the LoR subjects. The application of these findings indicates the need to vary the length of the rest interval between sets with the understanding that individuals exhibit varying recuperative abilities and some might be less tolerant of shorter rest intervals between sets.

Effect of a Single Dose of Caffeine Supplementation and Intermittent-interval Exercise on Muscle Damage Markers in Soccer Players

This study examined the effect of caffeine supplementation on the white cell count and muscle damage marker responses to intermittent-interval exercise as performed by soccer players. Subjects (n = 20) completed a placebo-controlled double-blind test protocol. Forty-five minutes before exercise, participants ingested 4.5 mg·kg−1 body mass of caffeine (EXP) or placebo (CONT). Blood samples were collected before and after exercise to measure hematological parameters, serum creatine kinase (CK), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AP) and γ-glutamyl transferase (γ-GT) activity. To compare differences among all variables, 2 (time) × 2 (group) repeated measures ANOVA (with Tukeys post hoc tests) was conducted. Exercise caused leukocytosis (38.5% and 36.1%in EXP and CONT, respectively), lymphocytosis (42.1%and 44.9%; p 0.05). Also, serum CK and LDH activity were enhanced by exercise in both groups (p

Caffeine Supplementation and muscle damage in soccer players

The aim of this work was to evaluate the effect of caffeine supplementation and intermittent exercise on the muscle injury markers in soccer players. 15 male professional soccer players completed a placebo controlled double blind test protocol. 45 minutes before exercise, participants ingested 5.5 mg.kg-1 body mass of caffeine (EXP, n=8) or placebo (CONT, n=7). The exercise was 12 sets of 10 sprints (20 m each) with 10 sec recovery time between sprints and 2 min between sets. Blood samples were collected before (PRE) and 48h after exercise (POST). Serum activity of CK, LDH, AST, and ALT were quantified. Serum enzyme activity was enhanced by exercise in both groups, without a synergistic effect of caffeine. The findings suggest muscle injury markers concentration increases after physical activities, but caffeine supplementation (as used in this study) has no influence upon muscle cellular integrity.

Creatine supplementation: effects on blood creatine kinase activity responses to resistance exercise and creatine kinase activity measurement

The purpose of this study was to determine the effects of creatine supplementation and exercise on the integrity of muscle fiber, as well as the effect of the supplementation on the creatine kinase (CK) assay measurement. Forty-nine sedentary individuals participated in a double-blind study and were divided into two groups: C (n=26) received 4x5-day packages of 0.6 g.kg-1 of body weight contained 50% of creatine + 50% of dextrose, and P (n=23) received packages containing only dextrose. On the first day the groups performed a 1RM test for bench press, seated row, leg extension, leg curl and leg press. On D7 they received the supplements. On the fourteenth day, they performed a training session of five exercises, each in three sets of ten repetitions at 75% of 1RM. Blood was collected before (D14) and after the exercise session (D15). Differing levels of blood creatine were tested to determine the influence on the assay measurements of CK. ANOVA and Tukeys post-hoc tests were used to compare groups and different times of study protocol (P<0.05). No changes were observed in CK activity of the groups from D0, D7 and D14. On D15 CK activity increases 140% (women) and 200% (men). There was no difference in CK activity between groups. Blood creatine levels up to 5mM produced no significant effect on CK assay results. CK activity increased after resistance exercise, while creatine supplementation produced no difference in the muscle cellular integrity nor compromised assay methodology.

Hormonal status, creatine kinase and soccer: a need for research

occer is a physically demanding sport in which muscular damage and trauma are frequent occurrences (1,2). These occurrences are especially true for those ath-letes involved in top-division clubs at national or international levels. Many factors may come into play when determining the degree of muscular damage that may oc-cur during a soccer match, such as intensity of physical participation, environmental conditions, skill level, prior level of rest, and aggressiveness of the teams involved in the match (2).It is well-established that a multitude of hormones influence the degree of protein turnover in the human body. These hormones are typically categorized as anabolic (promoting protein synthesis) or catabolic (promoting protein degradation) in terms of their influence on protein turnover. Cellular protein turnover status can influence the structural integrity of a muscle, and thus its potential for damage (i.e., less integrity → greater risk of damage) (3). The disposition of anabolic and catabolic hormones to influence protein turnover and, in turn, their influence on the structural status of skel -etal muscles, led us to speculate as to whether the basal hormonal status of an athlete before a soccer match would be a factor that potentially affects their muscle response to damage. To address this assumption, we conducted a preliminary study to examine the relationship between basal levels of anabolic-catabolic hormones and muscle dam -age, assessed by creatine kinase response following a 90-minute soccer match. The study of muscular damage following sport activity is critical because of the influence such damage has on the adaptation and training responses of athletes and their ability to perform and compete in subsequent sport events (1,3).Twelve healthy male soccer players were recruited to participate in this study. All of them signed a written informed consent form before starting the study. These players were all experienced sportsmen and had participated in top-division soccer for a num -ber of years (minimum 2 years as professionals). Their physical characteristics were as follows (mean ± SD): age = 26.3 ± 3.8 yrs., height = 177.8 ± 2.9 cm, and body mass = 75.5 ± 8.3 kg. Subjects rested and performed minimal physical activity in the 24 hours prior to the match. On the day of the match, basal, resting blood samples were collected from the subjects by venipuncture at 8 am in the morning, after a 12-hour fast. Collected blood samples were handled using standard clinical procedures to ensure they were viable for later hormonal-hematological analysis. The soccer match took place in the afternoon of the day of blood sampling, at around 5 pm. The average temperature during the match was 27

Exclusive glueball production in high-energy nucleus-nucleus collisions

The cross sections for the glueball candidates in quasireal photon-photon collisions and on central diffraction processes (i.e., double Pomeron exchange) in heavy-ion interactions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) are computed. The rates for these distinct production channels are compared, and they may be a fruitful approach to the investigation of glueballs.