Todd A Trappe

CSU Mentor, Long Beach, California, United States

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Publications (123)315.35 Total impact

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    ABSTRACT: Evidence suggests that myofibers from endurance trained skeletal muscle display unique contractile parameters. However, the underlying mechanisms remain unclear. To further elucidate the influence of endurance training on myofiber contractile function, we examined factors that may impact myofilament interactions (i. e., water content, concentration of specific protein fractions, actin and myosin content) or directly modulate myosin heavy chain (MHC) function (i. e., myosin light chain (MLC) composition) in muscle biopsy samples from highly-trained competitive (RUN) and recreational (REC) runners. Muscle water content was lower (P<0.05) in RUN (73±1%) compared to REC (75±1%) and total muscle and myofibrillar protein concentration was higher (P<0.05) in RUN, which may indicate differences in myofilament spacing. Content of the primary contractile proteins, myosin (0.99±0.08 and 1.01±0.07 AU) and actin (1.33±0.09 and 1.27±0.09 AU) in addition to the myosin to actin ratio (0.75±0.04 and 0.80±0.06 AU) was not different between REC and RUN, respectively, when expressed relative to the amount of myofibrillar protein. At the single-fiber level, slow-twitch MHC I myofibers from RUN contained less (P<0.05) MLC 1 and greater (P<0.05) amounts of MLC 3 than REC, while MLC composition was similar in fast-twitch MHC IIa myofibers between REC and RUN. These data suggest that the distinctive myofiber contractile profile in highly-trained runners may be partially explained by differences in the content of the primary contractile proteins and provides unique insight into the modulation of contractile function with extreme loading -patterns.
    International Journal of Sports Medicine 11/2013; · 2.27 Impact Factor
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    ABSTRACT: Studies of real and simulated microgravity exposure show the lower limb muscles atrophy to the greatest extent, with the calf muscles being most affected and most difficult to target with exercise countermeasures. This ground-based study examined the metabolic involvement of the thigh and calf muscles during two cycle exercise protocols (moderate and high intensity) central to the exercise countermeasures program on the International Space Station. Intramuscular glycogen and triglyceride levels were quantified in the vastus lateralis and soleus muscles before and after a moderate (current ISS prescription: 45 min at 55% VO(2max), 131 +/- 12 W) and high (proposed ISS prescription: 8 x 30-s intervals at 150% VO(2max), 459 +/- 34 W) intensity cycle exercise bout in nine individuals. During moderate intensity cycling, glycogen was significantly reduced in the vastus lateralis (114 +/- 27 mmol x kg(-1) dry weight) and remained unchanged in the soleus. High intensity cycling significantly reduced glycogen in both muscles, but the vastus lateralis (151 +/- 25 mmol x kg(-1) dry weight) used significantly more (-160%) than the soleus (59 +/- 11 mmol x kg(-1) dry weight). Intramuscular triglycerides were unchanged in both muscles at both intensities. These findings, coupled with other ground-based studies, provide strong support for high intensity cycling being a more appropriate component of the ISS prescription for upper and lower leg skeletal muscle health and cardiorespiratory fitness, although additional exercise paradigms that target the calf are warranted. These muscle-specific findings should be considered when designing exercise strategies for combating conditions of sarcopenia and muscle wasting on Earth.
    Aviation Space and Environmental Medicine 08/2013; 84(8):789-96. · 0.78 Impact Factor
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    ABSTRACT: Exercise and nutritional interventions have been examined independently as countermeasures to offset the loss of skeletal muscle mass with unloading, yet a protocol to completely preserve the soleus has not been identified. Little is known regarding the combined effect of exercise and nutrition on factors regulating skeletal muscle growth. The purpose of this investigation was to evaluate the influence of amino acid (AA) infusion on myogenic (MRF-4, MyoD, and Myogenin), proteolytic (MuRF-1, Atrogin-1, FOXO3A, Calpain-1, Calpain-2, Caspase-3, Cathepsin L1), and cytokine (IL-6, IL-8, and IL-15) mRNA transcripts in two skeletal muscles that respond distinctly to microgravity unloading. Muscle biopsies were obtained from the vastus lateralis (VL) and soleus of eight male subjects prior to and after 4 h of AA infusion for analysis of mRNA expression. All subjects performed a standardized exercise bout (45-min treadmill run) 24 h prior to the AA infusion. In the VL, proteolytic factors MuRF-1 and FOXO3A were reduced (44 +/- 9 and 28 +/- 6%, respectively) in response toAA infusion. In the soleus, mRNA transcripts of myogenic factor MRF-4 (91 +/- 36%) and cytokines IL-6, IL-8, and IL-15 were elevated while the proteolytic marker FOXO3A mRNA was reduced by 19 +/- 9%. These data suggest that the expression of genes related to skeletal muscle remodeling is altered during acute AA infusion 24 h post-exercise. It appears that increased amino acid availability in concert with exercise may create an intramuscular environment favorable for the prevention of muscle atrophy associated with unloading, which may be particularly beneficial for the soleus.
    Aviation Space and Environmental Medicine 07/2013; 84(7):669-74. · 0.78 Impact Factor
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    ABSTRACT: Introduction: We examined if epinephrine in the local anesthetic to help control incision-related bleeding interferes with molecular measurements obtained with the Duchenne-Bergström percutaneous needle biopsy technique for sampling human skeletal muscle. Methods: Three groups received 2.5-3.0ml of 1%-lidocaine in 2 injections: 1) 0.5-1.0ml superficially that varied among the groups: i) -Epi: intra- and subcutaneous without epinephrine; ii) +Epi-Fascia: intra- and subcutaneous with epinephrine, avoiding the fascia; iii) +Epi+Fascia: intra- and subcutaneous with epinephrine, directing a small amount (~0.2ml) into the fascia area; and 2) ~2.0ml without epinephrine into the fascia area for all subjects. A muscle biopsy was obtained 5-10min later for IL-6 and MuRF-1 mRNA levels. Results: IL-6 mRNA levels were low in -Epi and +Epi-Fascia, but ~300 fold higher in +Epi+Fascia. MuRF-1 mRNA levels were similar among groups. Conclusion: Lidocaine with epinephrine can confound intramuscular measurements from needle biopsies, but this can be avoided with a careful injection approach. © 2013 Wiley Periodicals, Inc.
    Muscle & Nerve 04/2013; · 2.31 Impact Factor
  • Todd A Trappe, Sophia Z Liu
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    ABSTRACT: It has been ~40 years since the discovery that prostaglandins are produced by exercising skeletal muscle, and since the discovery that inhibition of prostaglandin synthesis is the mechanism of action of what are now known as cyclooxygenase (COX)-inhibiting drugs. Since that time, it has been established that prostaglandins are made during and after aerobic and resistance exercise and have a potent paracrine/autocrine effect on muscle metabolism. Consequently, it has also been determined that orally consumed doses of COX-inhibitors can profoundly influence muscle prostaglandin synthesis, muscle protein metabolism, and numerous other cellular processes that regulate muscle adaptations to exercise loading. Although data from acute human exercise studies, as well as animal and cell culture data would predict regular consumption of a COX-inhibitor during exercise training would dampen the typical muscle adaptations, the chronic data do not support this conjecture. From the studies in young and older individuals lasting from 1.5-4 months, no interfering effects of COX-inhibitors on muscle adaptations to resistance exercise training have been noted. In fact, in older individuals a substantial enhancement of muscle mass and strength has been observed. The collective findings of the prostaglandin/COX pathway regulation of skeletal muscle responses and adaptations to exercise are compelling. Considering the discoveries in other areas of COX regulation of health and disease there is certainly an interesting future of investigation in this re-emerging area, especially as it pertains to older individuals and the condition of sarcopenia, as well as exercise training and performance of individuals of all ages.
    Journal of Applied Physiology 03/2013; · 3.48 Impact Factor
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    ABSTRACT: Cyclooxygenase (COX) inhibiting drugs augment muscle mass and strength improvements during resistance exercise based treatment of sarcopenia in older individuals. Initial evidence suggests a potential mechanism of COX inhibitor blunted prostaglandin (PG) E2 stimulation of interleukin (IL)-6 and the ubiquitin ligase MuRF-1, reducing their inhibition on muscle growth. The purpose of this investigation was to determine if PGE2 stimulates IL-6 and MuRF-1 transcription in skeletal muscle. Muscle biopsies were obtained from 10 young individuals and incubated ex vivo with PGE2 or control and analyzed for IL-6 and MuRF-1 mRNA levels. PGE2 upregulated (P<0.05) expression of both IL-6 (195%) and MuRF-1 (51%). A significant relationship was found between IL-6 and MuRF-1 expression after incubation with PGE2 (r=0.77, P<0.05), suggesting regulation through a common pathway. PGE2 induces IL-6 and MuRF-1 transcription in human skeletal muscle, providing a mechanistic link between COX inhibiting drugs, PGE2, and the regulation of muscle mass.
    Prostaglandins Leukotrienes and Essential Fatty Acids 03/2013; · 2.73 Impact Factor
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    ABSTRACT: Twelve weeks of resistance training (3d/wk) combined with daily consumption of the cyclooxygenase-inhibiting drugs acetaminophen (4.0g/d; n=11, 64±1y) or ibuprofen (1.2g/d; n=13, 64±1y) unexpectedly promoted muscle mass and strength gains 25-50% above placebo (n=12, 67±2y). To investigate the mechanism of this adaptation, muscle biopsies obtained before and ~72h following the last training bout were analyzed for mRNA levels of prostaglandin (PG)/COX pathway enzymes and receptors (arachidonic acid synthesis: cPLA(2) and sPLA(2); PGF(2α) synthesis: PGF(2α) synthase and PGE(2) to PGF(2α) reductase; PGE(2) synthesis: PGE(2) synthase-1, -2, and -3; PGF(2α) receptor and PGE(2) receptor-4), cytokines and myokines involved in skeletal muscle adaptation (TNF-α, IL-1β, IL-6, IL-8, IL-10), and regulators of muscle growth (myogenin, MRF4, myostatin) and atrophy (FOXO3A, atrogin-1, MuRF-1, IKKβ). Training increased (P<0.05) cPLA(2), PGF(2α) synthase, PGE(2) to PGF(2α) reductase, PGE(2) receptor-4, TNF-α, IL-1β, IL-8, and IKKβ. However, the PGF(2α) receptor was up-regulated (P<0.05) only in the drug groups and the placebo group up-regulation (P<0.05) of IL-6, IL-10, and MuRF-1 was eliminated in both drug groups. These results highlight prostaglandin and myokine involvement in the adaptive response to exercise in older individuals and suggest two mechanisms underlying the enhanced muscle mass gains in the drug groups: 1) The drug-induced PGF(2α) receptor up-regulation helped offset the drug suppression of PGF(2α)-stimulated protein synthesis after each exercise bout, and enhanced skeletal muscle sensitivity to this stimulation. 2) The drug-induced suppression of intramuscular PGE(2) production increased net muscle protein balance after each exercise bout through a reduction in PGE(2)-induced IL-6 and MuRF-1, both promoters of muscle loss.
    AJP Regulatory Integrative and Comparative Physiology 12/2012; · 3.28 Impact Factor
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    ABSTRACT: We examined whole body aerobic capacity and myocellular markers of oxidative metabolism in lifelong endurance athletes (n=9, 81±1 y, 68±3 kg, BMI=23±1 kg/m(2)) and age-matched, healthy, untrained men (n=6; 82±1 y, 77±5 kg, BMI=26±1 kg/m(2)). The endurance athletes were cross-country skiers, including a former Olympic champion and several national/regional champions, with a history of aerobic exercise and participation in endurance events throughout their lives. Each subject performed a maximal cycle test to assess aerobic capacity (VO(2)max). Subjects had a resting vastus lateralis muscle biopsy to assess oxidative enzymes (citrate synthase and βHAD) and molecular (mRNA) targets associated with mitochondrial biogenesis (PGC-1α and Tfam). The octogenarian athletes had a higher (P<0.05) absolute (2.6±0.1 vs. 1.6±0.1 L•min(-1)) and relative (38±1 vs. 21±1 ml•kg(-1)•min(-1)) VO(2)max, ventilation (79±3 vs. 64±7 L•min(-1)), heart rate (160±5 vs. 146±8 b•min(-1)), and final workload (182±4 vs. 131±14 watts). Skeletal muscle oxidative enzymes were 54% (citrate synthase) and 42% (βHAD) higher (P<0.05) in the octogenarian athletes. Likewise, basal PGC-1α and Tfam mRNA were 135% and 80% greater (P<0.05) in the octogenarian athletes. To our knowledge, the VO(2)max of the lifelong endurance athletes is the highest recorded in humans >80 y of age and comparable to non-endurance trained men 40 years younger. The superior cardiovascular and skeletal muscle health profile of the octogenarian athletes provides a large functional reserve above the aerobic frailty threshold and is associated with lower risk for disability and mortality.
    Journal of Applied Physiology 10/2012; · 3.48 Impact Factor
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    ABSTRACT: To examine potential age-specific adaptations in skeletal muscle size and myofiber contractile physiology in response to aerobic exercise, seven young (YM; 20±1 yr) and six older (OM; 74±3 yr) men performed 12-weeks of cycle-ergometer training. Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of isolated slow (MHC I) and fast (MHC IIa) myofibers. Aerobic capacity was higher (P<0.05) after training in both YM (16±2%) and OM (13±3%). Quadriceps muscle volume, determined via MRI, was 5±1 and 6±1% greater (P<0.05) after training for YM and OM, respectively, which was associated with an increase in MHC I myofiber cross-sectional area (CSA). MHC I peak power was higher (P<0.05) after training for both YM and OM while MHC IIa peak power was increased (P<0.05) with training in OM only. MHC I and MHC IIa myofiber peak and normalized (P(0)/CSA) force were preserved with training in OM while MHC I P(0)/CSA and MHC IIa peak force were lower (P<0.05) after training in YM. These data suggest relative improvements in muscle size and aerobic capacity are similar between young and older men while adaptations in myofiber contractile function showed improvement in OM. Training-related increases in MHC I and MHC IIa peak power reveal that skeletal muscle of OM is responsive to aerobic training and further support the use of aerobic exercise for improving cardiovascular and skeletal muscle health in older individuals.
    Journal of Applied Physiology 09/2012; · 3.48 Impact Factor
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    ABSTRACT: The aim of this project was to develop a method to assess fiber type specific protein content across the continuum of human skeletal muscle fibers. Individual vastus lateralis muscle fibers (n = 264) were clipped into two portions: one for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) fiber typing and one for Western blot protein identification. Following fiber type determination, fiber segments were combined into fiber type specific pools (∼20 fibers/pool) and measured for total protein quantity, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), citrate synthase (CS), and total p38 content. GAPDH content was 64, 54, 160, and 138% more abundant in myosin heavy chain (MHC) I/IIa, MHC IIa, MHC IIa/IIx, and MHC IIx fibers, respectively, when compared with MHC I. Inversely, CS content was 528, 472, 242, and 47% more abundant in MHC I, MHC I/IIa, MHC IIa, and MHC IIa/IIx fibers, respectively, when compared with MHC IIx. Total p38 content was 87% greater in MHC IIa versus MHC I fibers. These data and this approach establish a reliable method for human skeletal muscle fiber type specific protein analysis. Initial results show that particular proteins exist in a hierarchal fashion throughout the continuum of human skeletal muscle fiber types, further highlighting the necessity of fiber type specific analysis.
    Analytical Biochemistry 03/2012; 425(2):175-82. · 2.58 Impact Factor
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    ABSTRACT: This investigation examined the effects of acute resistance exercise (RE), progressive resistance training (PRT), and age on the human skeletal muscle Transcriptome. Two cohorts of young and old adults [study A: 24 yr, 84 yr (n = 28); study B: 25 yr, 78 yr (n = 36)] were studied. Vastus lateralis biopsies were obtained pre- and 4 h post-RE in conjunction with the 1st and 36th (last) training session as part of a 12-wk PRT program in study A, whereas biopsies were obtained in the basal untrained state in study B. Additionally, the muscle fiber type specific (MHC I and MHC IIa) Transcriptome response to RE was examined in a subset of young and old women from study A. Transcriptome profiling was performed using HG U133 Plus 2.0 Arrays. The main findings were 1) there were 661 genes affected by RE during the 1st and 36th training bout that correlated with gains in muscle size and strength with PRT (termed the Transcriptome signature of resistance exercise adaptations); 2) the RE gene response was most pronounced in fast-twitch (MHC IIa) muscle fibers and provided additional insight into the skeletal muscle biology affected by RE; 3) skeletal muscle of young adults is more responsive to RE at the gene level compared with old adults and age also affected basal level skeletal muscle gene expression. These skeletal muscle Transcriptome findings provide further insight into the molecular basis of sarcopenia and the impact of resistance exercise at the mixed muscle and fiber type specific level.
    Journal of Applied Physiology 02/2012; 112(10):1625-36. · 3.48 Impact Factor
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    ABSTRACT: Human skeletal muscle contains pure myosin heavy chain (MHC) fiber types (I, IIa, and IIx) along with hybrid fibers expressing multiple MHC isoforms (I/IIa, IIa/IIx, and I/IIa/IIx). Although hybrid fibers represent a common component of human muscle, little research exists on their relative MHC protein distribution or single fiber functional profiles. Purpose: Quantify the proportion of co-expressed MHC isoforms in hybrid fibers and determine its influence on single muscle fiber function. Methods: Human muscle fibers (n=68) were isolated from vastus lateralis biopsies, analyzed for single fiber physiology (size, strength, speed, power), typed electrophoretically, digitally imaged, and identified as one of three hybrid fiber types [MHC I/IIa (n=47), MHC IIa/IIx (n=20), and MHC I/IIa/IIx (n=1)]. Two researchers independently quantified (in duplicate) the proportion of MHC isoforms expressed in these fibers via densitometry. Results: Significant correlations in densitometry measures existed between observations from the same researcher (r≥0.995) and different researchers (r=0.998, ICC=0.997), indicating strong test-retest and inter-rater reliability. Proportions of MHC IIa isoform expressed in I/IIa and IIa/IIx hybrid fibers ranged between 7-94% and 28-83% of total MHC protein, respectively. MHC IIa isoform percentage positively correlated with strength (Po, R2=0.40), speed (Vo, R2=0.78), and normalized power (R2=0.76) in MHC I/IIa fibers. No significant correlations were observed between MHC isoform proportions and IIa/IIx hybrid fiber function. Conclusion: These initial results indicate hybrid fibers exist on a morphological and functional continuum. More research is needed to elucidate the physiological significance of hybrid muscle fibers in humans and their adaptability with changes in physical activity patterns. Supported by grants from the National Institutes of Health (AG038576) and the National Aeronautics and Space Administration (NNJ06HF59G).
    ACSM Annual Meeting, San Francisco, CA; 01/2012
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    ABSTRACT: Nine to 12 weeks of resistance exercise training in young individuals induces quadriceps muscle (∼6%) and region-specific patellar tendon (4-6%) hypertrophy. However, 12 weeks of resistance exercise training (∼1 h total exercise time) in older individuals (60-78 years) induces quadriceps muscle hypertrophy (9%) without impacting patellar tendon size. The current study examined if a different loading paradigm using cycle exercise would promote patellar tendon hypertrophy or alter the internal tendon properties, measured with magnetic resonance imaging signal intensity, in older individuals. Nine women (70 ± 2 years) completed 12 weeks of aerobic upright cycle exercise training (∼28 h total exercise time). Aerobic exercise training increased (P < 0.05) quadriceps muscle size (11 ± 2%) and VO(2max) (30 ± 9%). Mean patellar tendon cross-sectional area (CSA) (2 ± 1%) and signal intensity (-1 ± 2%) were unchanged (P > 0.05) over the 12 weeks of training. Region-specific CSA was unchanged (P > 0.05) at the proximal (-1 ± 3%) and mid regions (2 ± 2%) of the tendon but tended (P = 0.069) to increase at the distal region (5 ± 3%). Region-specific signal intensity differed along the tendon but was unchanged (P > 0.05) with training. Although more studies are needed, exercise-induced patellar tendon hypertrophy, compared with skeletal muscle, appears to be attenuated in older individuals, while the loading pattern associated with aerobic exercise seems to have more impact than resistance exercise in promoting patellar tendon hypertrophy.
    Scandinavian Journal of Medicine and Science in Sports 10/2011; · 3.21 Impact Factor
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    ABSTRACT: To assess myosin heavy chain (MHC) plasticity in aging skeletal muscle with aerobic exercise training, MHC composition was measured at the messenger RNA (mRNA) level and protein level in mixed-muscle homogenates and single myofibers. Muscle samples were obtained from eight nonexercising women (70 ± 2 years) before and after 12 weeks of training (20-45 minutes of cycle exercise per session at 60%-80% heart rate reserve, three to four sessions per week). Training elevated MHC I mRNA (p < .10) and protein (p < .05) in mixed-muscle (54% ± 4% to 61% ± 2%) and single myofibers (42% ± 4% to 52% ± 3%). The increase in MHC I protein was positively correlated (p < .05) with improvements in whole muscle power. Training resulted in a general downregulation of MHC IIa and IIx at the mRNA and protein levels. The training-induced increase in MHC I protein and mRNA demonstrates the maintenance of skeletal muscle plasticity with aging. Furthermore, these data suggest that a shift toward an oxidative MHC phenotype may be beneficial for metabolic and functional health in older individuals.
    The Journals of Gerontology Series A Biological Sciences and Medical Sciences 06/2011; 66(8):835-41. · 4.31 Impact Factor
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    ABSTRACT: Millions of older individuals consume acetaminophen or ibuprofen daily and these same individuals are encouraged to participate in resistance training. Several in vitro studies suggest that cyclooxygenase-inhibiting drugs can alter tendon metabolism and may influence adaptations to resistance training. Thirty-six individuals were randomly assigned to a placebo (67 ± 2 yr old), acetaminophen (64 ± 1 yr old; 4,000 mg/day), or ibuprofen (64 ± 1 yr old; 1,200 mg/day) group in a double-blind manner and completed 12 wk of knee extensor resistance training. Before and after training in vivo patellar tendon properties were assessed with MRI [cross-sectional area (CSA) and signal intensity] and ultrasonography of patellar tendon deformation coupled with force measurements to obtain stiffness, modulus, stress, and strain. Mean patellar tendon CSA was unchanged (P > 0.05) with training in the placebo group, and this response was not influenced with ibuprofen consumption. Mean tendon CSA increased with training in the acetaminophen group (3%, P < 0.05), primarily due to increases in the mid (7%, P < 0.05) and distal (8%, P < 0.05) tendon regions. Correspondingly, tendon signal intensity increased with training in the acetaminophen group at the mid (13%, P < 0.05) and distal (15%, P = 0.07) regions. When normalized to pretraining force levels, patellar tendon deformation and strain decreased 11% (P < 0.05) and stiffness, modulus, and stress were unchanged (P > 0.05) with training in the placebo group. These responses were generally uninfluenced by ibuprofen consumption. In the acetaminophen group, tendon deformation and strain increased 20% (P < 0.05) and stiffness (-17%, P < 0.05) and modulus (-20%, P < 0.05) decreased with training. These data suggest that 3 mo of knee extensor resistance training in older adults induces modest changes in the mechanical properties of the patellar tendon. Over-the-counter doses of acetaminophen, but not ibuprofen, have a strong influence on tendon mechanical and material property adaptations to resistance training. These findings add to a growing body of evidence that acetaminophen has profound effects on peripheral tissues in humans.
    Journal of Applied Physiology 05/2011; 111(2):508-15. · 3.48 Impact Factor
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    ABSTRACT: The goal of this investigation was to assess the influence of tracer selection on mixed muscle fractional synthesis rate (FSR) at rest and postexercise during amino acid infusion in multiple human skeletal muscles. Fractional synthesis rate was measured before and 24 hours after 45 minutes of running using simultaneous infusion of [(2)H(5)]-phenylalanine (Phe) and [(2)H(3)]-leucine (Leu) coupled with muscle biopsies from the vastus lateralis and soleus in aerobically trained men (n = 8; age, 26 ± 2 years). Mixed muscle protein FSR was analyzed by gas chromatography-mass spectrometry combined with a standard curve using the enriched muscle tissue fluid as the precursor pool. To control for potential analytical differences between tracers, all samples and standards for both tracers were matched for m + 0 abundance. Tracer selection did not influence resting FSR for the vastus lateralis or soleus (P > .05). Fractional synthesis rate measured 24 hours postexercise was higher (P < .05) compared with rate at rest and was similar between tracers for the vastus lateralis (Phe, 0.110% ± 0.010%·h(-1); Leu, 0.109% ± 0.005%·h(-1)) and soleus (Phe, 0.123% ± 0.008%·h(-1); Leu, 0.122% ± 0.005%·h(-1)). These data demonstrate that tracer selection does not influence the assessment of resting or postexercise FSR, thereby supporting the use of both [(2)H(5)]-phenylalanine and [(2)H(3)]-leucine for the measurement of FSR in exercise-based studies of human skeletal muscle.
    Metabolism: clinical and experimental 05/2011; 60(5):689-97. · 3.10 Impact Factor
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    ABSTRACT: Evidence suggests that consumption of over-the-counter cyclooxygenase (COX) inhibitors may interfere with the positive effects that resistance exercise training has on reversing sarcopenia in older adults. This study examined the influence of acetaminophen or ibuprofen consumption on muscle mass and strength during 12 wk of knee extensor progressive resistance exercise training in older adults. Thirty-six individuals were randomly assigned to one of three groups and consumed the COX-inhibiting drugs in double-blind placebo-controlled fashion: placebo (67 ± 2 yr; n = 12), acetaminophen (64 ± 1 yr; n = 11; 4 g/day), and ibuprofen (64 ± 1 yr; n = 13; 1.2 g/day). Compliance with the resistance training program (100%) and drug consumption (via digital video observation, 94%), and resistance training intensity were similar (P > 0.05) for all three groups. Drug consumption unexpectedly increased muscle volume (acetaminophen: 109 ± 14 cm(3), 12.5%; ibuprofen: 84 ± 10 cm(3), 10.9%) and muscle strength (acetaminophen: 19 ± 2 kg; ibuprofen: 19 ± 2 kg) to a greater extent (P < 0.05) than placebo (muscle volume: 69 ± 12 cm(3), 8.6%; muscle strength: 15 ± 2 kg), when controlling for initial muscle size and strength. Follow-up analysis of muscle biopsies taken from the vastus lateralis before and after training showed muscle protein content, muscle water content, and myosin heavy chain distribution were not influenced (P > 0.05) by drug consumption. Similarly, muscle content of the two known enzymes potentially targeted by the drugs, COX-1 and -2, was not influenced (P > 0.05) by drug consumption, although resistance training did result in a drug-independent increase in COX-1 (32 ± 8%; P < 0.05). Drug consumption did not influence the size of the nonresistance-trained hamstring muscles (P > 0.05). Over-the-counter doses of acetaminophen or ibuprofen, when consumed in combination with resistance training, do not inhibit and appear to enhance muscle hypertrophy and strength gains in older adults. The present findings coupled with previous short-term exercise studies provide convincing evidence that the COX pathway(s) are involved in the regulation of muscle protein turnover and muscle mass in humans.
    AJP Regulatory Integrative and Comparative Physiology 03/2011; 300(3):R655-62. · 3.28 Impact Factor
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    ABSTRACT: We have recently shown that 12 weeks of progressive aerobic exercise training improves whole-muscle size and function in older women. The purpose of this investigation was to evaluate molecular markers that may be associated with muscle hypertrophy after aerobic training in aging skeletal muscle. Muscle biopsies were obtained before and after 12 weeks of aerobic exercise training on a cycle ergometer in nine older women (70 ± 2 years) to determine basal levels of messenger RNA and protein content of select myogenic, proteolytic, and mitochondrial factors. The training program increased (p < .05) aerobic capacity 30 ± 9%, whole-muscle cross-sectional area 11 ± 2%, and whole-muscle force production 29 ± 8%. Basal messenger RNA levels of FOXO3A, myostatin, HSP70, and MRF4 were lower (p < .05) after aerobic training. FOXO3A, FOXO3A phosphorylation, and HSP70 protein content were unaltered after training. Mitochondrial protein COX IV was elevated (p < .05) 33 ± 7% after aerobic training, whereas PGC-1α protein content was 20 ± 5% lower (p < .05). These data suggest that reductions in FOXO3A and myostatin messenger RNA are potentially associated with exercise-induced muscle hypertrophy. Additionally, it appears that mitochondrial biogenesis can occur with aerobic training in older women independent of increased PGC-1α protein. Aerobic exercise training alters molecular factors related to the regulation of skeletal muscle, which supports the beneficial role of aerobic training for improving muscle health in older women.
    The Journals of Gerontology Series A Biological Sciences and Medical Sciences 11/2010; 65(11):1201-7. · 4.31 Impact Factor
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    ABSTRACT: The purpose of this investigation was to assess mixed-muscle fractional synthesis rate (FSR) and the expression of genes involved in skeletal muscle remodeling after aerobic exercise in the fasted and fed states. Eight recreationally active males (25 ± 1 yr; Vo(2 max): 52 ± 2 ml·kg(-1)·min(-1)) performed 60-min of cycle ergometry at 72 ± 1% Vo(2 max) on two occasions in a counter-balanced design. Subjects ingested a noncaloric placebo (EX-FAST) or a beverage containing (per kg body wt): 5 kcal, 0.83 g carbohydrate, 0.37 g protein, and 0.03 g fat (EX-FED) immediately and 1 h after exercise. FSR was assessed at rest and following exercise with the use of a l-[ring (2)H(5)]-phenylalanine infusion combined with muscle biopsies at 2 and 6 h postexercise. mRNA expression was assessed at 2 and 6 h postexercise via real-time RT-PCR. FSR was higher (P < 0.05) after exercise in both EX-FAST (0.112 ± 0.010%·h(-1)) and EX-FED (0.129 ± 0.014%·h(-1)) compared with rest (0.071 ± 0.005%·h(-1)). Feeding attenuated the mRNA expression (P < 0.05) of proteolytic factors MuRF-1 (6 h) and calpain-2 (2 and 6 h) postexercise but did not alter FOXO3A, calpain-1, caspase3, or myostatin mRNA expression compared with EX-FAST. Myogenic regulatory factor (MRF4) mRNA was also attenuated (P < 0.05) at 2 and 6 h postexercise in EX-FED compared with EX-FAST. These data demonstrate that a nonexhaustive bout of aerobic exercise stimulates skeletal muscle FSR in the fasted state and that feeding does not measurably enhance FSR between 2 and 6 h after aerobic exercise. Additionally, postexercise nutrient intake attenuates the expression of factors involved in the ubiquitin-proteosome and Ca(2+)-dependent protein degradation pathways. These data provide insight into the role of feeding on muscle protein metabolism during recovery from aerobic exercise.
    AJP Regulatory Integrative and Comparative Physiology 11/2010; 299(5):R1254-62. · 3.28 Impact Factor
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    ABSTRACT: Changes in skeletal muscle mass are controlled by mechanisms that dictate protein synthesis or degradation. The current human study explored whether changes in activation of the phosphoinositide 3-kinase (PI3K)-Akt1, p38, myostatin, and mRNA expression of markers of protein degradation and synthesis occur soon after withdrawal of weight bearing. Biopsies of the vastus lateralis muscle (VL) and soleus muscle (Sol) were obtained from eight healthy men before and following 3 days of unilateral lower limb suspension (ULLS). Akt1, Forkhead box class O (FOXO)-1A, FOXO-3A, p38, and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) phosphorylation and protein levels and myostatin protein level were analyzed by Western blot. Levels of mRNA of IGF1, FOXO-1A, FOXO-3A, atrogin-1, MuRF-1, caspase-3, calpain-2, calpain-3, 4E-BP1, and myostatin were measured using real-time PCR. The amounts of phosphorylated Akt1, FOXO-1A, FOXO-3A, and p38 were unaltered (P>0.05) after ULLS. Similarly, mRNA levels of IGF1, FOXO-1A, FOXO-3A, caspase-3, calpain-2, and calpain-3 showed no changes (P>0.05). The mRNA levels of atrogin-1 and MuRF-1, as well as the mRNA and protein phosphorylation of 4E-BP1, increased (P<0.05) in VL but not in Sol. Both muscles showed increased (P<0.05) myostatin mRNA and protein following ULLS. These results suggest that pathways other than PI3K-Akt stimulate atrogin-1 and MuRF-1 expression within 3 days of ULLS. Alternatively, transient changes in these pathways occurred in the early phase of ULLS. The increased myostatin mRNA and protein expression also indicate that multiple processes are involved in the early phase of muscle wasting. Further, the reported difference in gene expression pattern across muscles suggests that mechanisms regulating protein content in human skeletal muscle are influenced by phenotype and/or function.
    Journal of Applied Physiology 09/2010; 109(3):721-7. · 3.48 Impact Factor

Publication Stats

2k Citations
315.35 Total Impact Points

Institutions

  • 2012–2013
    • CSU Mentor
      Long Beach, California, United States
  • 1995–2013
    • Ball State University
      • Human Performance Laboratory
      Muncie, Indiana, United States
  • 2004–2010
    • Karolinska Institutet
      • • Institutionen för laboratoriemedicin
      • • Institutionen för fysiologi och farmakologi
      Solna, Stockholm, Sweden
  • 2009
    • University of Tours
      Tours, Centre, France
  • 2008
    • Mid Sweden University
      • Department of Health Sciences
      Härnösand, Vaesternorrland, Sweden
  • 2001–2007
    • University of Arkansas for Medical Sciences
      • • Department of Geriatrics
      • • Department of Physiology and Biophysics
      Little Rock, Arkansas, United States
    • University of Arkansas at Little Rock
      Little Rock, Arkansas, United States
    • Pennsylvania State University
      • Department of Kinesiology
      State College, PA, United States
  • 2002
    • University of California, Berkeley
      Berkeley, California, United States
    • Central Arkansas Veterans Healthcare System
      Washington, Washington, D.C., United States
  • 1998–2002
    • Medical College of Wisconsin
      • Cell Biology, Neurobiology and Anatomy
      Milwaukee, WI, United States
  • 1997–1999
    • Marquette University
      • Department of Biological Sciences
      Milwaukee, WI, United States