Trabecular bone microarchitecture in female collegiate gymnasts.

UNLABELLED: Using high-resolution magnetic resonance imaging, we observed more developed trabecular bone microarchitecture in the proximal tibia of female collegiate gymnasts vs. matched controls. This suggests that high-load physical activity may have a positive effect on the trabecular microarchitecture in weight-bearing bone. INTRODUCTION: Participation in physical activities that overload the skeleton, such as artistic gymnastics, is associated with increased areal bone mineral density (aBMD); however, the status of trabecular microarchitecture in the weight-bearing bone of gymnasts is unknown. METHODS: Eight female collegiate artistic gymnasts and eight controls matched for age, height, body mass, gender and race were recruited for the study. Apparent trabecular bone volume to total volume (appBV/TV), trabecular number (appTb.N), thickness (appTb.Th) and trabecular separation (appTb.Sp) were determined using high resolution magnetic resonance imaging. Areal bone mineral density, bone mineral content (BMC) and bone area in the proximal tibia were determined using dual-energy X-ray absorptiometry. Group differences were determined using t-tests. The magnitude of group differences was expressed using Cohen's d (d). RESULTS: Gymnasts had higher appBV/TV (13.6%, d = 1.22) and appTb.N (8.4%, d = 1.45), and lower appTb.Sp (13.7%, d = 1.33) than controls (p < 0.05). Gymnasts had higher aBMD and BMC in the proximal tibia, although the differences were smaller in magnitude (d = 0.75 and 0.74, respectively) and not statistically significant (p > 0.05). CONCLUSION: The findings suggest that high-load physical activity, such as performed during gymnastics training, may enhance the trabecular microarchitecture of weight-bearing bone.

Spasticity may defend skeletal muscle size and composition after incomplete spinal cord injury.

DESIGN: Cross-sectional. OBJECTIVES: (1) To determine the effects of the level of spinal cord injury (SCI) on skeletal muscle, intramuscular fat (IMF) cross-sectional areas (CSAs) and relative IMF; (2) to determine the relation, if any, of spasticity to each of these variables after incomplete SCI. SETTINGS: In-patient study at the Shepherd Center, Atlanta, GA, USA. METHODS: Thirteen individuals with incomplete SCI were classified according to their level of injury into a high level of injury group (HLI, C5-C7, n=8) and a low level of injury group (LLI, T12-L2, n=5). Spasticity was determined for thigh muscles using a modified Ashworth scale at 6 weeks post-injury. T1-weighted magnetic resonance (MR) images were taken 6 weeks post-injury to measure thigh skeletal muscle and IMF CSAs. RESULTS: Spasticity was significantly evident in the HLI group compared to the LLI group (P=0.023). Six weeks post-injury, muscle CSA was 103+/-18 cm(2) in the HLI group and 80+/-20 cm(2) in the LLI group (P=0.042). Relative IMF was 3.6+/-2.0% in HLI and 7.5+/-4.0% in LLI (P=0.021). Additionally, spasticity accounted for 54% of the variability in muscle CSA for all subjects (r (2)=0.54, P=0.006). CONCLUSIONS: Spasticity may be an important factor in defending skeletal muscle size and indirectly preventing IMF accumulation early after incomplete SCI.

Skeletal muscle atrophy and increased intramuscular fat after incomplete spinal cord injury.

STUDY DESIGN: Cross-sectional and longitudinal design. OBJECTIVES: (1) To quantify skeletal muscle cross-sectional area (CSA) after correcting for intramuscular fat (IMF) in thigh muscle groups 6 weeks after incomplete spinal cord injury (SCI), (2) to monitor the changes in muscle CSA and IMF after 3 months from the initial measurement. SETTING: Academic institution Athens, GA, USA. METHODS: Six incomplete SCI patients (28+/-4 years, 178+/-5 cm and 78+/-6 kg, mean+/-SE, C7 to L3, American Spinal Injury Association B or C) were tested at 5+/-1 weeks and 3 months after the initial measurement. T1-weighted magnetic resonance images were taken of both thighs. Six able-bodied (AB) controls were matched in age, sex, height and weight (29+/-4 years, four male and two female subjects, 179+/-5 cm and 77+/-6 kg). RESULTS: At 6 weeks post-injury, muscle CSA was 82+/-4 cm(2) in incomplete SCI and 123+/-21 cm(2) in AB controls (P=0.04). IMF CSA was 5.2+/-1.3 and 2.3+/-0.6 cm(2) in incomplete SCI and AB controls, respectively (P=0.03). Relative IMF was three-fold higher (P=0.03) in the SCI group versus AB controls (5.8+/-1.4 versus 2.0+/-0.6%). After 3 months, IMF increased 26% in the SCI group compared to the initial measurement (P=0.02). CONCLUSIONS: Skeletal muscle atrophy is associated with greater IMF accumulation in SCI group 6 weeks post-injury compared to AB controls. Moreover, IMF continues to increase over time in incomplete SCI.

Electrical stimulation-evoked resistance exercise therapy improves arterial health after chronic spinal cord injury.

STUDY DESIGN: Repeated measures training intervention. OBJECTIVES: To evaluate the effects of neuromuscular electrical stimulation (NMES)-induced resistance exercise therapy on lower extremity arterial health in individuals with chronic, complete spinal cord injury (SCI). We define "arterial health" using three surrogate markers: (a) resting diameter, (b) flow-mediated dilation (FMD), and (c) arterial range. SETTING: Department of Kinesiology, University of Georgia, USA. METHODS: We assessed five 36+/-5-year-old male individuals with chronic, complete SCI before, during, and after 18 weeks of training. The quadriceps femoris muscle group of both legs were trained twice a week with 4 x 10 repetitions of unilateral, dynamic knee extensions. The health of the posterior tibial artery was assessed using a B-mode ultrasound unit equipped with a high-resolution video capture device. Proximal occlusion was used to evoke ischemia for 5 min and then for 10 min. FMD was calculated using the peak diameter change (above rest) following 5 min occlusion. Arterial range was calculated using minimum (during occlusion) and maximum diameters (post 10 min occlusion). Hierarchical linear modeling accounted for the nested (repeated measures) experimental design. RESULTS: FMD improved from 0.08+/-0.11 mm (2.7%) to 0.18+/-0.15 mm (6.6%) (P=0.004), and arterial range improved from 0.36+/-0.28 to 0.94+/-0.40 mm (P=0.001), after 18 weeks of training. Resting diameter did not significantly change. CONCLUSIONS: Home-based, self-administered NMES resistance exercise therapy consisting of 80 contractions/week improved FMD and arterial range. This provides evidence that resistance exercise therapy can improve arterial health after SCI, which may reduce the risk of future cardiovascular disease.

Electrically stimulated resistance training in SCI individuals increases muscle fatigue resistance but not femoral artery size or blood flow.

STUDY DESIGN: Longitudinal. OBJECTIVES: The purpose of this study was to evaluate the effect of lower extremity resistance training on quadriceps fatigability, femoral artery diameter, and femoral artery blood flow. SETTING: Academic Institution. METHODS: Five male chronic spinal cord injury (SCI) individuals (American Spinal Injury Association (ASIA): A complete; C5-T10; 36+/-5 years old) completed 18 weeks of home-based neuromuscular electrical stimulation (NMES) resistance training. Subjects trained the quadriceps muscle group twice a week with four sets of 10 dynamic knee extensions against resistance while in a seated position. All measurements were made before training and after 8, 12, and 18 weeks of training. Ultrasound was used to measure femoral artery diameter and blood flow. Blood flow was measured before and after 5 and 10 min of distal cuff occlusion, and during a 4-min isometric electrical stimulation fatigue protocol. RESULTS: Training resulted in significant increases in weight lifted and muscle mass, as well as a 60% reduction in muscle fatigue (P = 0.001). However, femoral arterial diameter did not increase. The range was 0.44+/-0.03 to 0.46+/-0.05 cm over the four time points (P = 0.70). Resting, reactive hyperemic, and exercise blood flow did not appear to change with training. CONCLUSION: NMES resistance training improved muscle size and fatigue despite an absence of response in the supplying vasculature. These results suggest that the decreases in arterial caliber and blood flow seen with SCI are not tightly linked to muscle mass and fatigue resistance. In addition, muscle fatigue in SCI patients can be improved without increases in arterial diameter or blood flow capacity.

Deteriorated geometric structure and strength of the midfemur in men with complete spinal cord injury.

Spinal cord injury (SCI) results in a dramatic loss of bone mineral and a marked increase in fracture incidence in the femur; however, its effect on the femur's geometric structure and strength is poorly studied. The primary purpose of the present study was to assess the geometric structure, composition, and strength of the midfemur in men with long-term (>2 years), complete SCI (C6-L1 level; n=7) relative to men without SCI (n=8). T1-weighted axial images of the thigh were collected on a GE 1.5-T magnetic resonance imager and geometric, structure, composition, and strength measurements of the midfemur and skeletal muscle volume of the midthigh were determined. Areal bone mineral density (aBMD), bone mineral content (BMC), and bone area of the midthird of the femur and arms were determined using dual-energy X-ray absorptiometry. There were no differences in age, height, weight, femur length, arm BMC, arm aBMD, or arm bone area between the SCI group and controls. While the volume of the midfemur was not different in the two groups, the medullary cavity had 53% more volume and was 21-25% wider in the SCI group (P<0.05). In contrast, the cortical wall in the SCI group had a 24% lower volume and was 27-47% thinner (P<0.05). The cortical wall was particularly thin in the posterior section of the bone. The SCI group also had lower BMC and aBMD in the midfemur (21% and 25%, respectively, P<0.05). Calculated cross-sectional moment of inertia (CSMI), section modulus (Z), and polar moment of inertia (J) were lower in the SCI group (13-19%, P<0.05). A higher ratio of cortical bone volume to muscle volume and BMC to muscle volume in the SCI group (P<0.05) suggests that there was a greater loss of muscle than cortical bone after SCI; however, muscle volume was strongly correlated with cortical bone volume and BMC in the SCI and control groups (r=0.71 to 0.90, P<0.05). Muscle volume was also moderately to strongly correlated with CSMI and Z in the anterior-posterior direction and J. Muscle volume was weakly correlated or not correlated with bone strength measures in the control group (P>0.05). These findings suggest that after SCI, the midfemur erodes on the endosteal surface, resulting in a decreased resistance to bending and torsion. Although midthigh muscle volume appears to decline to a greater degree than midfemur cortical bone volume and BMC, their relationships remain strong.

Intramuscular fat and glucose tolerance after spinal cord injury--a cross-sectional study.

STUDY DESIGN: Survey. OBJECTIVE: Determine intramuscular fat (IMF) in affected skeletal muscle after complete spinal cord injury using a novel analysis method and determine the correlation of IMF to plasma glucose or plasma insulin during an oral glucose tolerance test. SETTING: General community of Athens, GA, USA. METHODS: A total of 12 nonexercise-trained complete spinal cord injured (SCI) persons (10 males and two females 40+/-12 years old (mean+/-SD), range 26-71 years, and 8+/-5 years post SCI) and nine nonexercise-trained nondisabled (ND) controls 29+/-9 years old, range 23-51 years, matched for height, weight, and BMI, had T(1) magnetic resonance images of their thighs taken and underwent an oral glucose tolerance test (OGTT) after giving consent. RESULTS: Average skeletal muscle cross-sectional area (CSA) (mean+/-SD) was 58.6+/-21.6 cm(2) in spinal cord subjects and 94.1+/-32.5 cm(2) in ND subjects. Average IMF CSA was 14.5+/-6.0 cm(2) in spinal cord subjects and 4.7+/-2.5 cm(2) in nondisabled subjects, resulting in an almost four-fold difference in IMF percentage of 17.3+/-4.4% in spinal cord subjects and 4.6+/-2.6% in nondisabled subjects. The 60, 90 and 120 min plasma glucose or plasma insulin were higher in the SCI group. IMF (absolute and %) was related to the 90 or 120 min plasma glucose or plasma insulin (r(2)=0.71-0.40). CONCLUSIONS: IMF is a good predictor of plasma glucose during an OGTT and may be a contributing factor to the onset of impaired glucose tolerance and type II diabetes, especially in SCI. In addition, reports of skeletal muscle CSA should be corrected for IMF.

MRI evaluation of topical heat and static stretching as therapeutic modalities for the treatment of eccentric exercise-induced muscle damage.

The aim of this study was to monitor the effects of topical heat and/or static stretch treatments on the recovery of muscle damage by eccentric exercise. For this purpose, 32 untrained male subjects performed intense eccentric knee extension exercise, followed by 2 weeks of treatment (heat, stretch, heat plus stretch) or no treatment (control, n=8/group). Isometric strength testing, pain ratings, and multi-echo magnetic resonance imaging of the thigh were performed before and at 2, 3, 4, 8, and 15 days following the exercise. Increased T2 relaxation time, muscle swelling, pain ratings, and strength loss confirmed significant muscle damage during the post-exercise period. Pain ratings and muscle volume recovered to baseline by 15 days, although muscle strength remained lower [77 (4) vs. 95 (3) kg pre-exercise, mean (SE)] and T2 values higher [32.2 (0.8) vs. 28.6 (0.2) ms pre-exercise]. Our results indicate that heat and/or static stretching does not consistently reduce soreness, swelling or muscle damage. The practical implication of our findings is that clinicians should be aware that prescribing heat and/or static stretching following intense eccentric or unaccustomed exercise will not enhance the recovery of damaged muscles.

The effect of a repeat bout of exercise on muscle injury in persons with spinal cord injury.

Following an initial bout of damaging exercise, a successive bout of similar exercise typically results in less injury, known as the "protective effect". Unloading due to spinal cord injury (SCI) increases the susceptibility to contraction-induced muscle injury. We tested the hypothesis that two bouts of isometric actions would evoke the same damage in the quadriceps femoris (QF) of patients with SCI. Six male subjects [32 (5) years old, 182 (9) cm, 81 (21) kg, injury level C6-T7, 6 (2) years post-injury, mean (SD)] were tested at two time points (Time1, Time2), separated by 8 weeks. Magnetic resonance images were taken of the QF prior to, immediately after, and 3 days after electromyostimulation (EMS) that evoked isometric knee extension. EMS (50 Hz) consisted of five sets of ten contractions (2 s on/6 s off, 1 min b/t sets) followed by three sets of ten contractions (1 s on/1 s off, 30 s b/t sets). Relative cross-sectional area of stimulated and injured skeletal muscle was obtained by quantifying pixels with an elevated T2. Relative area of stimulated QF was the same for both time points [92 (6)% and 89 (7)%] as was torque loss (approximately 55%). Three days post-EMS, the relative area of stimulated QF injured was not different between time points [30 (14)% vs 29 (17)%, P>0.05]. These results indicate an absence of a protective effective for repeat exercise bouts separated by 8 weeks in SCI patients using EMS.

Effects of testosterone replacement therapy on skeletal muscle after spinal cord injury.

STUDY DESIGN: Randomized control. OBJECTIVE: To examine the effects of testosterone replacement therapy (TRT) on skeletal muscle 11 weeks after complete SCI. SETTING: Athens, Georgia USA. METHODS: Soleus (SOL), gastrocnemius (GA), tibialis anterior (TA), vastus lateralis (VL) and triceps brachii (TRI) muscles were taken from twelve young male Charles River rats 11 weeks after complete SCI (T-9 transection, n=8) or sham surgery (n=4). Rats received either TRT (two 5 cm capsules, n=4) or empty capsules (n=8) implanted at surgery. Muscle samples were sectioned and fibers analyzed qualitatively for myosin ATPase and quantitatively for succinate dehydrogenase (SDH), alpha-glycerol-phosphate dehydrogenase (GPDH) and actomyosin ATPase (qATPase) activities using standard techniques. RESULTS: SCI decreased average fiber size (49+/-4%) in affected muscles and the percentage of slow fibers in SOL (93+/-3% to 17+/-2%). In addition, there was a decrease in SDH and an increase in GPDH and qATPase activities across the four hind-limb muscles of the SCI animals. Fiber size in the TRI was increased (31+/-2%) by SCI while enzyme activities were not altered. Average fiber size across the four hind limb muscles was decreased by only 30% in TRT SCI animals and their SOL contained 39+/-2% slow fibers. TRT also attenuated changes in enzyme activities. There was no effect of TRT on the TRI relative to SCI. CONCLUSIONS: TRT was effective in attenuating alterations in myofibrillar proteins during 11 weeks of SCI in affected skelatal muscles. SPONSORSHIP: Supported by a grant from The National Institutes of Health (HD-33738) and HD-37645 to KV, and HD-39676 to GAD.

Variable frequency trains enhance torque independent of stimulation amplitude.

AIM: Variable frequency trains have been reported to enhance force of fatigued human skeletal muscle. More rapid calcium turnover and/or enhanced stiffness may be responsible for the augmented torque-time integral during surface stimulation at moderate amplitude. In contrast, it has recently been suggested that variable frequency train enhancement occurs only at low forces as a result of preferential stimulation of fast fibres and/or altered motor unit recruitment. If correct, this would limit the practical benefit of variable frequency trains. Accordingly, we tested the hypothesis that torque augmentation by variable frequency trains in fatigued skeletal muscle was independent of stimulation amplitude. METHODS: The m. quadriceps femoris of six males was stimulated with constant frequency trains (six 200-micros square waves separated by 70 ms) or variable frequency trains (first interpulse interval 5 ms) at an amplitude that initially evoked approximately 25 or approximately 50% of maximal voluntary isometric torque. RESULTS: After 180 constant frequency trains (50% duty cycle), isometric peak torque decreased approximately 63%. In fatigued muscle, variable frequency trains enhanced the torque-time integral by approximately 23% over that for constant frequency trains and this effect was independent of stimulation amplitude. This was due to greater peak torque and less slowing of rise time. CONCLUSION: These responses show that the torque-time integral can be enhanced at both moderate and high stimulation amplitudes. As such, it is suggested that neither recruitment nor preferential activation of fast muscle is responsible for the "catch-like" property that can be demonstrated in fatigued human skeletal muscle.

Blood flow response in individuals with incomplete spinal cord injuries.

STUDY DESIGN: Cross sectional comparison, control group. OBJECTIVE: To determine if incomplete spinal cord injured patients (SCI) have an abnormal blood flow response to cuff ischemia compared to able-bodied individuals (AB). SETTING: Academic institution. METHODS: Blood flow in five chronic incomplete SCI patients (C4-C5) and 17 able bodied individuals was measured in the common femoral artery using quantitative Doppler ultrasound (GE LogiQ 400CL) at rest and after distal thigh cuff occlusion of 2, 4 and 10 min to investigate whether blood flow or vascular control were different in SCI's and AB. RESULTS: Blood flow and the diameter of the common femoral artery at rest were similar in incomplete SCI and AB. Peak flow after 10 min of cuff ischemia (the highest found) was also comparable between incomplete SCI and AB. The half-time for recovery of blood flow to baseline after 2, 4 or 10 min of ischemia was 50% longer for incomplete SCI compared to the AB (P = 0.023). In addition, peak blood flow after 2 and 4 min of ischemia relative to the maximum, 10 min value (2/10 and 4/10 ratios) was lower in incomplete SCI compared to AB (0.65 +/- 0.06 vs 0.76 +/- 0.15, P = 0.029 and 0.75 +/- 0.10 vs 0.89 +/- 0.11, P = 0.014, respectively). CONCLUSION: This study demonstrated that incomplete spinal cord injured patients have impaired vascular control seen as a slower return to resting flow after cuff ischemia and reduced sensitivity to ischemia relative to maximum flow. However, incomplete SCI patients did not demonstrate impaired flow capacity as seen in complete SCI patients suggesting that smaller cardiovascular abnormalities are seen with incomplete versus complete SCI injury. Impaired vascular control may serve to limit exercise capacity and may contribute to increased cardiovascular disease. Impaired circulation could contribute to impaired muscle function and poor cardiovascular health in incomplete SCI's, although these findings need to be replicated in a study with more subjects.

Phenotypic adaptations in human muscle fibers 6 and 24 wk after spinal cord injury.

The effects of spinal cord injury (SCI) on the profile of sarco(endo) plasmic reticulum calcium-ATPase (SERCA) and myosin heavy chain (MHC) isoforms in individual vastus lateralis (VL) muscle fibers were determined. Biopsies from the VL were obtained from SCI subjects 6 and 24 wk postinjury (n = 6). Biopsies from nondisabled (ND) subjects were obtained at two time points 18 wk apart (n = 4). In ND subjects, the proportions of VL fibers containing MHC I, MHC IIa, and MHC IIx were 46 +/- 3, 53 +/- 3, and 1 +/- 1%, respectively. Most MHC I fibers contained SERCA2. Most MHC IIa fibers contained SERCA1. All MHC IIx fibers contained SERCA1 exclusively. SCI resulted in significant increases in fibers with MHC IIx (14 +/- 4% at 6 wk and 16 +/- 2% at 24 wk). In addition, SCI resulted in high proportions of MHC I and MHC IIa fibers with both SERCA isoforms (29% at 6 wk and 54% at 24 wk for MHC I fibers and 16% at 6 wk and 38% at 24 wk for MHC IIa fibers). Thus high proportions of VL fibers were mismatched for SERCA and MHC isoforms after SCI (19 +/- 3% at 6 wk and 36 +/- 9% at 24 wk) compared with only ~5% in ND subjects. These data suggest that, in the early time period following SCI, fast fiber isoforms of both SERCA and MHC are elevated disproportionately, resulting in fibers that are mismatched for SERCA and MHC isoforms. Thus the adaptations in SERCA and MHC isoforms appear to occur independently.

Creatine loading, resistance exercise performance, and muscle mechanics.

We tested the null hypothesis that creatine monohydrate loading (20 g per day for 7 days, n = 18) would not alter resistance exercise performance, isometric strength, or in vivo contractile properties of the quadriceps femoris muscle compared with loading with placebo (n = 13) in resistance-trained subjects. For the entire study group, the 1 repetition maximum (1RM) and 5-set performance (the number of repetitions) for unilateral, dynamic knee extension increased slightly (2% and 5%, respectively) after dietary supplementation, and these responses did not differ by condition. Maximal voluntary isometric torque and the rate of torque development did not change. During electromyostimulation, torque development and relaxation time were also unaffected. Our data suggest that creatine loading does not augment unilateral strength or multiset resistance exercise performance for knee extensions compared with placebo loading.

Biarticular and monoarticular muscle activation and injury in human quadriceps muscle.

We hypothesized that activation of the quadriceps femoris muscle group during eccentric exercise is related to the increase in magnitude of several markers of muscle injury that developed during the next week. Fourteen male subjects performed six to eight sets of five to ten repetitions of single-leg eccentric-only seated knee extension exercise. Magnetic resonance (MR) images were collected before and immediately after exercise and on days 2-4 and 6 after eccentric exercise. Changes in maximal voluntary contraction (MVC), perceived soreness, muscle volume and muscle transverse relaxation of water protons (T2) were determined for the quadriceps femoris muscle group each day. Changes in muscle volume and T2 were determined every day for each muscle [vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)] of the quadriceps femoris group. Post-exercise T2 was greater than pre-exercise T2 (P < 0.05) for all muscles. The acute deltaT2 (Post-Pre) was similar (P>0.05) among VL, VM, VI, and RF [5.5 (0.3) ms], suggesting that the four muscles were equally activated during eccentric exercise. In the week after eccentric exercise, subjects experienced delayed-onset muscle soreness (DOMS) and all muscles demonstrated a delayed increase in T2 above pre-exercise values (P < 0.05), suggesting that muscle injury had occurred. For the quadriceps femoris muscle group, there was no correlation between acute deltaT2 and delayed (peak T2 during days 2, 3, 4, 6 minus pre-exercise T2) deltaT2 (r=0.04, P>0.05). Similar results were obtained when VL, VM, VI and RF were examined separately. Of the four muscles in quadriceps femoris, the biarticular RF experienced greater muscle injury [delayed deltaT2= 15.2 (2.0) ms] compared to the three monoarticular vasti muscles [delayed deltaT2 = 7.7 (1.3) ms; P< 0.05]. We propose that the disproportionate muscle injury to RF resulted from an ineffective transfer of torque from the knee to hip joint during seated eccentric knee extension exercise, thus causing RF to dissipate greater energy than normal. We conclude that in humans, muscle activation is not a unique determinant of muscle injury.

Nonsteroidal anti-inflammatory therapy after eccentric exercise in healthy older individuals.

BACKGROUND: Aging is associated with greater susceptibility to muscle injury and soreness after exercise. Although elderly persons regularly consume nonsteroidal anti-inflammatory drugs (NSAIDs), it is not clear that NSAIDs alleviate muscle dysfunction and/or inflammation following injurious exercise. METHODS: In this double-blind crossover study, 10 men and 5 women (aged 60 +/- 2 years, mean +/- SE) consumed naproxen sodium or placebo for 10 days after performing 64 unilateral eccentric (ECC) knee extensions using 75% of the ECC 1-repetition maximum. Strength was measured before, 3 days after, and 10 days after each bout. Injury and soreness were assessed using magnetic resonance images of m. quadriceps femoris (QF) and a visual analog scale. RESULTS: Three days after exercise, concentric strength loss was greater for placebo (-32 +/- 9%) than NSAID (-6 +/- 8%; p =.0064). Likewise, isometric strength declined less for NSAID than placebo (-12 +/- 7% vs -24 +/- 4%; p =.0213), and thigh soreness while rising from a chair was greater for placebo (p < or =.0393) than NSAID (43 +/- 7 mm vs 26 +/- 7 mm). QF cross-sectional area (cm(2)) showing elevated T(2) was 27% and 35% greater (p < or =.0096) for placebo on Days 3 and 10, respectively. CONCLUSIONS: Naproxen sodium attenuated muscle injury, strength loss, and soreness following ECC exercise in older individuals and may be beneficial during the early stages of increased physical activity.

Dietary creatine supplementation and muscular adaptation to resistive overload.

PURPOSE: This study examined the influence of dietary creatine (CR) supplementation upon mechanical and hypertrophic responses to a well-defined conditioning stimulus provided by electromyostimulation (EMS). METHODS: Eighteen resistance-trained subjects were assigned CR or a placebo (PL) in a randomized, double-blind fashion. After CR loading (20 g x d(-1) for 7 d), CR supplementation (5 g x d(-1)) or PL was continued for 8 wk. During supplementation, EMS (3--5 sets of 10 coupled eccentric and concentric actions) was applied to the left m. quadriceps femoris (QF) twice weekly while subjects continued voluntary resistance training of both lower limbs unsupervised. Cross-sectional area (CSA) of each QF was assessed with magnetic resonance imaging (MRI). Torque during EMS was analyzed to assess muscle loading and fatigue resistance. RESULTS: Maximal torque and the torque time integral increased markedly over training (P < or = 0.0001). These responses reflected activation of more muscle as EMS current was increased (about 16%), greater recovery between sets (P < or = 0.0423), and less fatigue during sets over training (P = 0.0002). CR did not influence these responses (P = 0.8093). In accord with these results, the increase in CSA for the stimulated QF (11%) was comparable for CR and PL (P = 0.2190). CSA in the nonstimulated QF increased 5% in CR (P = 0.0091) but did not change in PL. CONCLUSION: We conclude that CR supplementation did not augment the mechanical or hypertrophic response to a precisely measured conditioning stimulus that attenuated but did not ameliorate fatigue. We suggest that enhanced fatigue resistance may not explain the apparent ergogenic effect of CR during voluntary training.

The influence of muscle action on the acute growth hormone response to resistance exercise and short-term detraining.

The effects of resistance training with concentric or concentric-eccentric muscle actions on the acute hormonal response to a resistance exercise protocol was investigated. Thirty-two men completed a 19 week lower-body resistance training program (consisting of the leg press and leg extension exercises) in which they (1) performed concentric actions only (CON); (2) performed both concentric and eccentric actions (CON-ECC); (3) performed double concentric actions for each repetition (CON-CON); or (4) did not exercise. Following training each subject performed two exercise tests consisting of three sets of 30 isokinetic concentric (day 1) and eccentric (day 2) knee extensions separated by 48 h. The exercise tests were repeated following 4 weeks of detraining. Blood samples were obtained before and after each exercise test. Serum growth hormone (GH) was significantly (P< 0.05) greater for the concentric test in groups CON and CON-CON whereas GH was lower for the concentric test in CON-ECC compared with the eccentric test prior to detraining. Following detraining, GH was greater during the concentric test in CON-ECC than in the eccentric test, whereas no differences were observed between the concentric and eccentric tests in CON and CON-CON and the acute GH response to resistance exercise was attenuated. These data indicate that GH is sensitive to muscle action type with differential responses observed with resistance exercise after short-term detraining.

Metabolic enzymes and phenotypic expression among human locomotor muscles.

Percutaneous biopsies were taken from the right vastus lateralis (VL), tibialis anterior (TA), soleus (Sol), and lateral gastrocnemius (LG) muscles of eight recreationally active adult males. Approximately 60 fibers in each sample were analyzed for their type (I, IIa, or IIx), cross-sectional area (CSA), and succinic dehydrogenase (SDH), alpha glycerol phosphate dehydrogenase (GPDH) and calcium-activated actomyosin adenosine triphosphatase (qATPase) activities. This was done to test the hypothesis that metabolic enzyme activities are more reflective of the functional diversity among human locomotor muscles than fiber type composition. The results showed that enzymatic characteristics differed more or less than expected between muscles of the same or different fiber type. For example, the relative CSA occupied by fast fibers was only about 50% greater in the mixed (LG and VL) than in the slow (Sol and TA) muscles (57 vs. 38%). At the same time, average fiber SDH activity and fiber type specific SDH:qATPase*%CSA, both used as estimates of fatigue resistance, were greater in Sol and LG than in TA and VL. As a result, the two slow muscles and the two mixed muscles had different values, and a mixed muscle (LG) had higher values than a slow muscle (TA). The findings suggest that differences in enzymatic profile, more than fiber type composition, afford human locomotor muscles the capacity to perform their purportedly divergent functional tasks.

Muscle fiber type-specific myofibrillar Ca(2+) ATPase activity after spinal cord injury.

Biopsies of the vastus lateralis muscle were analyzed to determine if increased energy demand of contraction, as indirectly reflected by myofibrillar Ca(2+) adenosine triphosphate activity (qATPase), contributes to greater fatigue in affected muscle of spinal cord injured (SCI) patients. The qATPase activity showed a fiber-type effect, IIax + IIx > IIa > I. Average fiber qATPase and fiber specific qATPase activities were not different between SCI and able-bodied controls, nor did they change over time. We suggest greater fatigue in SCI subjects early after injury does not reflect increased energy demand of contraction.