Pedro J. Marín

Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises.

Abstract Wilson, JM, Marin, PJ, Rhea, MR, Wilson, SMC, Loenneke, JP, and Anderson, JC. Concurrent training: A meta-analysis examining interference of aerobic and resistance exercise. J Strength Cond Res 26(8): 2293–2307, 2012—The primary objective of this investigation was to identify which components of endurance training (e.g., modality, duration, frequency) are detrimental to resistance training outcomes. A meta-analysis of 21 studies was performed with a total of 422 effect sizes (ESs). Criteria for the study included were (a) compare strength training alone to strength plus endurance training (concurrent) or to compare combinations of concurrent training; (b) the outcome measures include at least one measure of strength, power, or hypertrophy; and (c) the data necessary to calculate ESs must be included or available. The mean ES for hypertrophy for strength training was 1.23; for endurance training, it was 0.27; and for concurrent training, it was 0.85, with strength and concurrent training being significantly greater than endurance training only. The mean ES for strength development for strength training was 1.76; for endurance training, it was 0.78; and for concurrent training, it was 1.44. Strength and concurrent training was significantly greater than endurance training. The mean ES for power development for strength training only was 0.91; for endurance training, it was 0.11; and for concurrent training, it was 0.55. Significant differences were found between all the 3 groups. For moderator variables, resistance training concurrently with running, but not cycling, resulted in significant decrements in both hypertrophy and strength. Correlational analysis identified significant negative relationships between frequency (−0.26 to −0.35) and duration (−0.29 to −0.75) of endurance training for hypertrophy, strength, and power. Significant relationships (p < 0.05) between ES for decreased body fat and % maximal heart rate (r = −0.60) were also found. Our results indicate that interference effects of endurance training are a factor of the modality, frequency, and duration of the endurance training selected.

Effects of Vibration Training on Muscle Strength: A Meta-Analysis

Marín, PJ and Rhea, MR. Effects of vibration training on muscle strength: A meta-analysis. J Strength Cond Res 24(2): 548-556, 2010-The purpose of this meta-analysis was to attempt to gain a clear picture of the magnitude of strength improvements expected after acute and chronic vibration training and to identify specific factors that influence the treatment effects. Studies employing a strength training intervention and containing data necessary to calculate effect size (ES) were included in the analysis. A total of 31 studies met the inclusion criterion. Analysis of ES demonstrated that the type of vibration platform employed is a moderator of the treatment effect of vibration on strength development. Differences were noted in both acute and chronic changes in muscle strength when vertical vibration platforms are compared with oscillating platforms. Vertical platforms elicit a significantly larger treatment effect for chronic adaptations (ES = 1.24) compared with oscillating platforms (ES = −0.13). However, oscillating platforms elicit a greater treatment effect for acute effects (ES = 0.24) compared with vertical platforms (ES = −0.07). The data also show that gender, training status, and exercise protocol are moderators of the response to vibration exercise for strength development (vertical platforms). Based on the overall analysis, it is apparent that vibration exercise can be effective at eliciting chronic muscle strength adaptations. The vibration exercise can be used by exercise professionals to enhance muscular strength.

Meta-analysis of postactivation potentiation and power: effects of conditioning activity, volume, gender, rest periods, and training status.

Abstract Wilson, JM, Duncan, NM, Marin, PJ, Brown, LE, Loenneke, JP, Wilson, SMC, Jo, E, Lowery, RP, and Ugrinowitsch, C. Meta-analysis of postactivation potentiation and power: Effects of conditioning activity, volume, gender, rest periods, and training status. J Strength Cond Res 27(3): 854–859, 2013—There is no clear agreement regarding the ideal combination of factors needed to optimize postactivation potentiation (PAP) after a conditioning activity. Therefore, a meta-analysis was conducted to evaluate the effects of training status, volume, rest period length, conditioning activity, and gender on power augmentation due to PAP. A total of 141 effect sizes (ESs) for muscular power were obtained from a total of 32 primary studies, which met our criteria of investigating the effects of a heavy preconditioning activity on power in randomized human trials. The mean overall ES for muscle power was 0.38 after a conditioning activity (p < 0.05). Significant differences were found between moderate intensity (60–84%) 1.06 and heavy intensity (>85%) 0.31 (p < 0.05). There were overall significant differences found between single sets 0.24 and multiple sets 0.66 (p < 0.05). Rest periods of 7–10 minutes (0.7) after a conditioning activity resulted in greater ES than 3–7 minutes (0.54), which was greater than rest periods of >10 minutes (0.02) (p < 0.05). Significant differences were found between untrained 0.14 and athletes 0.81 and between trained 0.29 and athletes. The primary findings of this study were that a conditioning activity augmented power output, and these effects increased with training experience, but did not differ significantly between genders. Moreover, potentiation was optimal after multiple (vs. single) sets, performed at moderate intensities, and using moderate rest periods lengths (7–10 minutes).

Effects of Vibration Training on Muscle Power: A Meta-Analysis

Marín, PJ and Rhea, MR. Effects of vibration training on muscle power: a meta-analysis. J Strength Cond Res 24(3): 871-878, 2010-The purpose of this meta-analysis was to attempt to gain a clear picture of the magnitude of adaptations in muscular power expected after acute and chronic training, as well as identify specific factors that influence the treatment effects. Studies using a power training intervention and containing data necessary to calculate effect size (ES) were included in the analysis a total of 30 studies. Effect size demonstrated that the type of vibration platform used is a moderator of the treatment effect of vibration on power development is the type of vibration platform employed. Differences were noted in both acute and chronic changes in power when vertical vibration platforms were compared with oscillating platforms. Vertical platforms elicit a significantly larger treatment effect for chronic adaptations (ES = 0.99) as compared with oscillating platforms (ES = 0.36). The data also show that age is a moderator of the response to vibration exercise for power. On the basis of the overall analysis, it is apparent that vibration exercise can be effective at eliciting chronic power adaptations. Exercise professionals can include vibration exercise as a means of fostering power improvements.

Neuromuscular Activity During Whole-Body Vibration of Different Amplitudes and Footwear Conditions: Implications for Prescription of Vibratory Stimulation

Marín, PJ, Bunker, D, Rhea, MR, and Ayllón, FN. Neuromuscular activity during whole-body vibration of different amplitudes and footwear conditions: implications for prescription of vibratory stimulation. J Strength Cond Res 23(8): 2311-2316, 2009-This study investigated the magnitude of whole-body vibration (WBV) at 30 Hz induced in surface electromyography root-mean-square (EMGrms) signals of different amplitudes and footwear conditions of unloaded isometric half squat (100o). For this purpose, 10 healthy and active males (age 28.7 ± 4.6 yr; height 180 ± 5.9 cm; and weight 90 ± 13.4 kg) volunteered to participate in this study. Subjects were exposed to the WBV treatment using a vibration platform (FreeMotion Fitness iTonic). The subjects were exposed randomly to 4 different treatments of WBV: with shoes 2 mm amplitude, without shoes 2 mm, with shoes 4 mm, and without shoes 4 mm. The EMGrms signals were recorded from the vastus lateralis and the gastrocnemius medialis muscle during the different conditions. The WBV treatments resulted in a significantly higher (p ≤ 0.05) EMGrms compared with unloaded isometric half squat (without WBV). The WBV treatment that induced the highest EMGrms signals of the vastus lateralis was during the amplitude of 4 mm without shoes (+62.7%; p < 0.01), whereas 4 mm with shoes induced the highest EMGrms signals of the gastrocnemius medialis (+142.7%; p < 0.01). These data suggest that wearing shoes does alter the neuromuscular response to WBV stimuli, and exercise professionals should consider such differences when using WBV to target neuromuscular activation of such muscle groups. In this study, the magnitude of the WBV effect was clearly higher with the amplitude 4 mm versus 2 mm for the vastus lateralis muscle and gastrocnemius medialis muscle. The vastus lateralis showed the greatest activity without shoes and at amplitude of 4 mm. The maximal activation for the gastrocnemius medialis was measured with shoes at 4 mm.

Technical variability of the GT3X accelerometer

To analyze the intra- and inter-instrument reliability of the ActiGraph GT3X accelerometer using a vibration table on each orthogonal axis and at five frequencies of motion. Ten GT3X units were subjected to a specific vibration using a motorized vibration table along the vertical, horizontal right-left and horizontal front-back axis, and at 1.1, 2.1, 3.1, 4.1 and 10.2 Hz. The 5 min data for each frequency were analyzed separately for frequency, axis effects, and inter- and intra-instrument variability. We found overall high intra-and inter-instrument reliability for the GT3X accelerometer at frequencies between 2.1 and 4.1 Hz. For frequencies ranging between 2.1 and 4.1 Hz, the intra-instrument coefficient of variation was ≤2.5%. The inter-instrument coefficient of variation ranged widely along axes and frequencies, with the lowest values (≤9%) corresponding to 2.1-4.1 Hz. The intra-class correlation coefficient for activity counts across frequencies and for all axes was 0.97. Overall, our findings support the use of the GT3X accelerometer as an accurate tool to estimate free-living physical activity, at least within those frequencies that are common to most types of human daily activities.

Randomized placebo-controlled phase II trial of autologous mesenchymal stem cells in multiple sclerosis.

Objective Uncontrolled studies of mesenchymal stem cells (MSCs) in multiple sclerosis suggested some beneficial effect. In this randomized, double-blind, placebo-controlled, crossover phase II study we investigated their safety and efficacy in relapsing-remitting multiple sclerosis patients. Efficacy was evaluated in terms of cumulative number of gadolinium-enhancing lesions (GEL) on magnetic resonance imaging (MRI) at 6 months and at the end of the study. Methods Patients unresponsive to conventional therapy, defined by at least 1 relapse and/or GEL on MRI scan in past 12 months, disease duration 2 to 10 years and Expanded Disability Status Scale (EDSS) 3.0–6.5 were randomized to receive IV 1–2×106 bone-marrow-derived-MSCs/Kg or placebo. After 6 months, the treatment was reversed and patients were followed-up for another 6 months. Secondary endpoints were clinical outcomes (relapses and disability by EDSS and MS Functional Composite), and several brain MRI and optical coherence tomography measures. Immunological tests were explored to assess the immunomodulatory effects. Results At baseline 9 patients were randomized to receive MSCs (n = 5) or placebo (n = 4). One patient on placebo withdrew after having 3 relapses in the first 5 months. We did not identify any serious adverse events. At 6 months, patients treated with MSCs had a trend to lower mean cumulative number of GEL (3.1, 95% CI = 1.1–8.8 vs 12.3, 95% CI = 4.4–34.5, p = 0.064), and at the end of study to reduced mean GEL (−2.8±5.9 vs 3±5.4, p = 0.075). No significant treatment differences were detected in the secondary endpoints. We observed a non-significant decrease of the frequency of Th1 (CD4+ IFN-γ+) cells in blood of MSCs treated patients. Conclusion Bone-marrow-MSCs are safe and may reduce inflammatory MRI parameters supporting their immunomodulatory properties. ClinicalTrials.gov NCT01228266

Balancing with Vibration: A Prelude for “Drift and Act” Balance Control

Stick balancing at the fingertip is a powerful paradigm for the study of the control of human balance. Here we show that the mean stick balancing time is increased by about two-fold when a subject stands on a vibrating platform that produces vertical vibrations at the fingertip (0.001 m, 15–50 Hz). High speed motion capture measurements in three dimensions demonstrate that vibration does not shorten the neural latency for stick balancing or change the distribution of the changes in speed made by the fingertip during stick balancing, but does decrease the amplitude of the fluctuations in the relative positions of the fingertip and the tip of the stick in the horizontal plane, A(x,y). The findings are interpreted in terms of a time-delayed “drift and act” control mechanism in which controlling movements are made only when controlled variables exceed a threshold, i.e. the stick survival time measures the time to cross a threshold. The amplitude of the oscillations produced by this mechanism can be decreased by parametric excitation. It is shown that a plot of the logarithm of the vibration-induced increase in stick balancing skill, a measure of the mean first passage time, versus the standard deviation of the A(x,y) fluctuations, a measure of the distance to the threshold, is linear as expected for the times to cross a threshold in a stochastic dynamical system. These observations suggest that the balanced state represents a complex time–dependent state which is situated in a basin of attraction that is of the same order of size. The fact that vibration amplitude can benefit balance control raises the possibility of minimizing risk of falling through appropriate changes in the design of footwear and roughness of the walking surfaces.

Effect of itonic Whole-body Vibration on Delayed-onset Muscle Soreness Among Untrained Individuals

Rhea, MR, Bunker, D, Marín, PJ, and Lunt, K. Effect of iTonic whole-body vibration on delayed-onset muscle soreness among untrained individuals. J Strength Cond Res 23(6): 1677-1682, 2009-Attempts to reduce or eliminate delayed-onset of muscle soreness are important as this condition is painful and debilitating. The purpose of this study was to examine the effectiveness of whole-body vibration (WBV) massage and stretching exercises at reducing perceived pain among untrained men. Sixteen adult men (age, 36.6 ± 2.1 yr) volunteered to perform a strenuous exercise session consisting of resistance training and repeated sprints. Subjects were randomly assigned to 1 of 2 recovery groups: a group performing WBV stretching sessions or a stretching group performing static stretching without vibration. Both groups performed similar stretches, twice per day for 3 days after the workout. The vibration group performed their stretches on the iTonic platform (frequency, 35 Hz; amplitude, 2 mm). Perceived pain was measured at 12, 24, 48, and 72 hours postworkout. Statistical analyses identified a significantly lower level of reported perceived pain at all postworkout measurement times among the WBV group (p < 0.05). No difference existed at the preworkout measurement time. The degree of attenuation of pain ranged from 22-61%. These data suggest that incorporating WBV as a recovery/regeneration tool may be effective for reducing the pain of muscle soreness and tightness after strenuous training.

Concurrent training in elite male runners: the influence of strength versus muscular endurance training on performance outcomes.

Abstract Sedano, S, Marín, PJ, Cuadrado, G, and Redondo, JC. Concurrent training in elite male runners: The influence of strength versus muscular endurance training on performance outcomes. J Strength Cond Res 27(9): 2433–2443, 2013—Much recent attention has been given to the compatibility of combined aerobic and anaerobic training modalities. However, few of these studies have reported data related to well-trained runners, which is a potential limitation. Therefore, because of the limited evidence available for this population, the main aim was to determine which mode of concurrent strength-endurance training might be the most effective at improving running performance in highly trained runners. Eighteen well-trained male runners (age 23.7± 1.2 years) with a maximal oxygen consumption (V[Combining Dot Above]O2max) more than 65 ml·kg−1·min−1 were randomly assigned into 1 of the 3 groups: Endurance-only Group (n = 6), who continued their usual training, which included general strength training with Thera-band latex-free exercise bands and endurance training; Strength Group (SG; n = 6) who performed combined resistance and plyometric exercises and endurance training; Endurance-SG (ESG; n = 6) who performed endurance-strength training with loads of 40% and endurance training. The study comprised 12 weeks of training in which runners trained 8 times a week (6 endurance and 2 strength sessions) and 5 weeks of detraining. The subjects were tested on 3 different occasions (countermovement jump height, hopping test average height, 1 repetition maximum, running economy (RE), V[Combining Dot Above]O2max, maximal heart rate [HRmax], peak velocity (PV), rating of perceived exertion, and 3-km time trial were measured). Findings revealed significant time × group interaction effects for almost all tests (p < 0.05). We can conclude that concurrent training for both SG and ESG groups led to improved maximal strength, RE, and PV with no significant effects on the V[Combining Dot Above]O2 kinetics pattern. The SG group also seems to show improvements in 3-km time trial tests.