Andrew C. Fry

The purpose of this study was to examine the mechanomyographic (MMGRMS) and electromyographic (EMGRMS) amplitude vs. force relationships of the vastus lateralis (VL) for aerobically-trained (AT), resistance-trained (RT), and sedentary individuals (SED). Five RT (mean ± SD age = 23 ± 3 yrs; body mass = 101 ± 37 kg; height = 176 ± 8 cm), 5 AT (32 ± 5 yrs; 67 ± 4 kg; 176 ± 2 cm), and 5 SED (23 ± 4 yrs; 93 ± 32 kg; 180 ± 5 cm) men volunteered to perform two 6-s isometric ramp muscle actions from 5% to 100% of their maximal voluntary contraction (MVC) while MMG (m·s⁻²) and EMG (μV) signals were recorded from the VL muscle. Thigh skinfold measurements and Bergstrom muscle biopsies were taken from the VL. The muscle samples were analyzed for myosin heavy chain (MHC) isoform content. Simple linear regression models were fit to the natural log-transformed EMGRMS and MMGRMS vs. force relationships. The slope (b term) and the antilog of the Y-intercept (a term) were calculated for each relationship. For %MHC, the AT group had a greater percentage of type I fibers than the RT and SED groups (p ≤0.05). The RT group had a greater percentage of type IIa fibers than the AT group (p ≤0.05), and the SED group had a greater percentage of type IIx fibers than the AT and RT groups (p ≤0.05). For both the log-transformed EMGRMS and MMGRMS vs. force relationships, the mean a term for the AT group was higher than the RT and SED groups (p ≤0.05). For the log-transformed MMGRMS vs. force relationships, however, the b term for the AT group was lower than the RT and SED groups (p ≤0.05). There were no differences (p >0.05) among the b terms of the AT, RT, and SED groups for the log-transformed EMGRMS vs. force relationships. In addition, the mean skinfold for the SED group was higher than the AT group (p ≤0.05) (AT = 8.7 ± 2.2mm, RT = 15.4 ± 7.6mm, and SED = 25.4 ± 9.2mm). The group-related differences among the a terms for both the log-transformed EMGRMS and MMGRMS patterns might be best explained by the group differences in skinfold thickness. However, the fact that the AT group had a lower mean b term for the log-transformed MMGRMS vs. force relationships may suggest that the differences in motor control strategies between individuals with predominantly type I vs. type II fibers in the vastus lateralis could be detectible with the MMG signal, but not EMG. The lower b term for the AT group suggested that the MMG-force relationship may have been sensitive to the earlier achievement of rate coding, whereas the RT and SED groups relied more on motor unit recruitment to reach higher force levels. The b terms from the EMGRMS vs. force relationships were unable to differentiate among the groups. The log-transformed MMGRMS, but not EMGRMS, vs. force relationships may be useful as non-invasive measurements to determine the onset of rate coding, which may differ among muscles that are predominantly type I vs. type II fiber types. Therefore, the MMG signal may offer an attractive, simple technique for examining changes in the motor control strategies that govern incremental isometric force production.

Ollowing 4 weeks of weight training (phase I), subjects performed weight training concurrently with high-volume conditioning drills (phase II). Phase III consisted of 15 spring football practice sessions executed over a 30-day period. Performance and hormonal changes were assessed prior to phase I, and following phases I, II, and III. Maximal strength was significantly increased (p > 0.05) for all strength tests during phase I. Squat and power clean values decreased following phase II (p > 0.05), with all values returning to baseline upon completion of phase III. Sprinting speed significantly worsened during phase I (p > 0.05), but then returned to baseline during phase III. Vertical jump and agility improved during phase I (p > 0.05), with vertical jump remaining unchanged for the duration of the study and agility returning to baseline following phase II. Testosterone levels decreased during phase II (p > 0.05) prior to returning to baseline levels during phase III. Cortisol and the testosterone/cortisol ratio remained unchanged during the course of the investigation. Even though overtraining did not occur in the current investigation, a significant maladaptation in performance did occur subsequent to phase II. For this particular athletic population, a strength and conditioning program utilizing a reduced training volume-load may prove more effective for improving performance in the future. Address correspondence to Dr. Andrew C. Fry, afry@memphis.edu. © 2007 National Strength and Conditioning Association...

Previous research on overtraining due to excessive use of maximal resistance exercise loads [100% 1 repetition maximum (1 RM)] indicates that peripheral muscle maladaptation contributes to overtraining-induced performance decrements. This study examined the cellular and molecular responses of skeletal muscle to performance decrements due to high-relative-intensity (%1 RM) resistance exercise overtraining. Weight-trained men were divided into overtrained (OT, n = 8) and control (Con, n = 8) groups. The OT group performed 10 × 1 at 100% 1 RM daily for 2 wk, whereas the Con group performed normal training 2 days/wk. Muscle biopsies from the vastus lateralis muscle, voluntary static and dynamic muscle performances, and nocturnal urinary epinephrine were assessed before (pre) and after (post) overtraining. Overtraining occurred as indicated by a decrease in 1-RM strength for the OT group (mean ± SE; OT pre = 159.3 ± 10.1 kg, OT post = 151.4 ± 9.9 kg, Con pre = 146.0 ± 12.9 kg, Con post = 144.9 ± 13.3 kg), as well as a 36.3% decrease in mean power at 100% 1-RM loads. Normal training could be resumed only after 2–8 wk of training cessation. Muscle β₂-adrenergic receptor (β₂-AR; fmol/mg protein) density significantly decreased by 37.0% for the OT group and was unchanged for the Con group (−1.8%). Nocturnal urinary epinephrine for the OT group increased by 49%, although this was not significant (effect size = 0.42). The ratio of nocturnal urinary epinephrine to β₂-AR density suggested a decreased β₂-AR sensitivity for the OT group (2.4-fold increase). Overtraining occurred based on decreased muscular force and power. Desensitization of the β₂-AR system suggests that this may be an important contributor to performance decrements due to excessive use of maximal resistance exercise loads.

The purpose of this study was to determine if supplementation with a liquid multi-vitamin/mineral would improve anaerobic exercise performance. Fourteen resistance-trained men performed a 30-second cycle sprint and one set of squat exercise on 2 separate days before and following 8 weeks of supplementation with either a liquid multi-vitamin/mineral or a placebo. Heart rate, perceived exertion, blood lactate, peak and mean power, and rate of fatigue were determined for all tests. No differences were noted for any variable (P > 0.05). When controlling for presupplementation values, however, a decreased rate of fatigue was noted for both exercise tests following the multi-vitamin/mineral supplementation. These data suggest that in resistance trained men consuming a nutritionally sound diet, supplementation with a liquid multi-vitamin/mineral does not favorably impact most anaerobic exercise performances. Such supplementation, however, may result in a minor decreased rate of fatigue. It appears that, in terms of improved short duration anaerobic exercise performance, supplemental micronutrients may not be efficient ergogenic agents for well-trained individuals consuming an adequate diet.

The purpose of this study is to identify physical and performance variables that discriminate elite American junior-aged men weightlifters from nonelite performers. Using a cross-sectional design, multiple discriminant analysis was used to determine field tests identifying elite male junior weightlifters. Young men who were participants (n = 115) at the Junior National and Junior Olympics Weightlifting Championships volunteered as subjects (mean +/- SD age = 14.8 +/- 2.3 years). Elite weightlifters (n = 20) were identified as the top 17.5% of national-level competitors when weightlifting performances were adjusted for body mass using the Sinclair equation. All other weightlifters were classified as nonelite (n = 95). Test batteries were performed immediately upon completion of a national-level weightlifting competition. Variables measured included easily-administered field tests of physical dimensions and body composition, muscular strength and power, flexibility, and gross motor control. The resulting regression equations correctly classified 84.35% of the weightlifters as elite or nonelite. Five variables significantly contributed to the discriminant analysis (Wilks Lambda = 0.6637392, chi(2) = 44.880, df = 5, p < 0.0001, adjusted R(2) = 0.67). Body mass index accounted for 23.13% of the total variance, followed by vertical jump (22.78%), relative fat (18.09%), grip strength (14.43%), and torso angle during an overhead squat (0.92%). The use of these 5 easily administered field tests is potentially useful as a screening tool for elite American junior men weightlifters.

Thirty-six healthy men with varying degrees of physical training background performed maximal-effort isometric and isoinertial knee extensor actions, with relative loads equal to 40% and 70% of one-repetition maximum. Force, velocity, and power were derived from force and linear position transducers at 500 Hz. Biopsies were taken from the vastus lateralis and analyzed by SDS-PAGE for relative myosin heavy chain (MHC) content. Relative MHC IIx content was included in a regression model, and explained variance noted. Relative MHC I content was subsequently added to the regression model to determine what, if any, additional variance was explained beyond that of MHC IIx. Results indicated that no relationship (r = 0.0 to 0.1) exists between the relative expression of MHC isoforms from the vastus lateralis and isometric/isoinertial performance in a population with diverse training backgrounds. Lack of nervous system adaptations in the untrained subjects in the study possibly attenuates the significant relationship between MHC and in-vivo muscle performance previously established in trained populations.

This investigation estimated the amount of variance in voluntary in vivo muscle performance that can be explained by relative myosin heavy chain (MHC) isoform expression. The role of the relative expression of these proteins in relation to in vitro force and velocity performance is well understood, but the in vivo model is less clear. Twenty-two men and women (mean +/- SD age, 27 +/- 6 years) performed isometric knee extensor actions in which peak force and rate of force development (RFD) were measured. The results of regression analysis showed that the inclusion of MHC IIb explained a significant (19.9%, p < 0.05) amount of variance in relative peak force (adjusted for muscle mass) and 14.1% of the variance in the first half of the rise phase of the force-time curve (RFD(0-50%)) (p < 0.1). The addition of MHC I into this model explained a significant (p < 0.05) amount of variance above that accounted for by MHC IIb in RFD (45.4%), RFD(0-50%) (50.8%), and RFD(50-100%) (second half of the rise phase of the force-time curve) (37.4%). Since the percentage of MHC IIb is reduced rather quickly with training, these data suggest that peak force may also be affected quickly by training. The percentage of MHC I has a longer course for change with training; therefore, it may be inferred that the greatest changes in RFD variables will likely occur during a longer course.