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Understanding the skeletal effects of resistance exercise involves delineating the spatially heterogeneous response of bone to load distributions from different muscle contractions. Bone mineral density (BMD) analyses may obscure these patterns by averaging data from tissues with variable mechanoresponse. To assess the proximal femoral response to resistance exercise, we acquired pretraining and posttraining quantitative computed tomography (QCT) images in 22 subjects (25-55 years, 9 males, 13 females) performing two resistance exercises for 16 weeks. One group (SQDL, n = 7) performed 4 sets each of squats and deadlifts, a second group (ABADD, n = 8) performed 4 sets each of standing hip abductions and adductions, and a third group (COMBO, n = 7) performed two sets each of squat/deadlift and abduction/adduction exercise. Subjects exercised three times weekly, and the load was adjusted each session to maximum effort. We used voxel-based morphometry (VBM) to visualize BMD distributions. Hip strength computations used finite element modeling (FEM) with stance and fall loading conditions. We used QCT analysis for cortical and trabecular BMD, and cortical tissue volume. For muscle size and density, we analyzed the cross-sectional area (CSA) and mean Hounsfield unit (HU) in the hip extensor, flexor, abductor, and adductor muscle groups. Whereas SQDL increased vertebral BMD, femoral neck cortical BMD and volume, and stance hip strength, ABADD increased trochanteric cortical volume. The COMBO group showed no changes in any parameter. VBM showed different effects of ABADD and SQDL exercise, with the former causing focal changes of trochanteric cortical bone, and the latter showing diffuse changes in the femoral neck and head. ABADD exercise increased adductor CSA and HU, whereas SQDL exercise increased the hip extensor CSA and HU. In conclusion, we observed different proximal femoral bone and muscle tissue responses to SQDL and ABADD exercise. This study supports VBM and volumetric QCT (vQCT) to quantify the spatially heterogeneous effects of types of muscle contractions on bone.

In 1981, the US military adopted body fat standards to promote physical readiness and prevent obesity. Separate circumference-based equations were developed for women and men. Both predictive equations were known to underestimate % BF. However, it was not known how well these abdominal circumference-based methods tracked changes in %BF. This study examined the validity of the circumference-based %BF equations for assessing changes in %BF in young adult recruits during Army Basic Combat Training (BCT). Dual-energy X-ray absorptiometry (DXA) and circumference-based measures of %BF were obtained in women (n = 481) and men (n = 926) at the start (pre-BCT) and end (post-BCT) of 8 weeks of BCT. Repeated-measure ANOVAs were used to assess differences between DXA and circumference pre-BCT and for the change during BCT. Pre-BCT, circumferences underestimated %BF relative to DXA, with mean errors of −6.0% ± 4.4% for women and −6.0% ± 3.5% for men (both p < 0.01), and no difference between sexes was observed (p = 0.77). DXA detected a −4.0% ± 2.4% and −3.3% ± 2.8% change in %BF for women and men in response to BCT, respectively (both p < 0.01), whereas circumference estimates of %BF indicated a 0.0% ± 3.3% (p = 0.86) change in women and a −2.2% ± 3.3% (p < 0.01) change in men (sex difference by technique p < 0.01). In conclusion, circumference-based measures underestimated %BF at the start of BCT in both sexes as compared to DXA. Circumference measures underestimated changes in %BF during BCT in men and did not detect changes in women. These findings suggest that circumference-based %BF metrics may not be an appropriate tool to track changes in body composition during short duration training. [ABSTRACT FROM AUTHOR]

Spiering, BA, Clark, BC, Schoenfeld, BJ, Foulis, SA, and Pasiakos, SM. Maximizing strength: the stimuli and mediators of strength gains and their application to training and rehabilitation. J Strength Cond Res 37(4): 919–929, 2023—Traditional heavy resistance exercise (RE) training increases maximal strength, a valuable adaptation in many situations. That stated, some populations seek new opportunities for pushing the upper limits of strength gains (e.g., athletes and military personnel). Alternatively, other populations strive to increase or maintain strength but cannot perform heavy RE (e.g., during at-home exercise, during deployment, or after injury or illness). Therefore, the purpose of this narrative review is to (a) identify the known stimuli that trigger gains in strength; (b) identify the known factors that mediate the long-term effectiveness of these stimuli; (c) discuss (and in some cases, speculate on) potential opportunities for maximizing strength gains beyond current limits; and (d) discuss practical applications for increasing or maintaining strength when traditional heavy RE cannot be performed. First, by conceptually deconstructing traditional heavy RE, we identify that strength gains are stimulated through a sequence of events, namely: giving maximal mental effort, leading to maximal neural activation of muscle to produce forceful contractions, involving lifting and lowering movements, training through a full range of motion, and (potentially) inducing muscular metabolic stress. Second, we identify factors that mediate the long-term effectiveness of these RE stimuli, namely: optimizing the dose of RE within a session, beginning each set of RE in a minimally fatigued state, optimizing recovery between training sessions, and (potentially) periodizing the training stimulus over time. Equipped with these insights, we identify potential opportunities for further maximizing strength gains. Finally, we identify opportunities for increasing or maintaining strength when traditional heavy RE cannot be performed. [ABSTRACT FROM AUTHOR]

Swim sprints are a central component of water polo competitions; however, a paucity of data describes the effect of repeated swim sprints on game-like performances. Therefore, the purpose of this study was to investigate the effect of repeated swim sprints on water polo throwing velocity and accuracy. Eleven female community college water polo players (age: 18.91 [+ or -] 1.04 years, height: 165.91 [+ or -] 4.69 cm, and mass: 70.22 [+ or -] 15.36 kg) performed 2 conditions: control and sprint. The control condition consisted of 10 shots at the 5-m line, each with a 35-second rest period and aimed at a specific target on the goal. The sprint condition also had the same 10 shots but included a sprint between each throwing attempt. The sprints consisted of 'head-down' swimming from the 2-m line to half court, then 'head-up' swimming from half court to the 5-m line where the ball was shot and aimed at a specific target on the goal. Analysis was performed on ball velocity and accuracy between conditions. Ball velocity in the control condition (26.01 [+ or -] 3.13 mph) was significantly (p < 0.05) greater than the sprint condition (25.08 [+ or -] 2.76 mph); however, there was no significant difference in accuracy (shots made; Control: 3.00 [+ or -] 1.67; Sprint: 2.45 [+ or -] 1.03). These results indicate that ball velocity decreases in female collegiate water polo players after repeated swim sprints when compared with a control condition, yet accuracy is unaffected. Therefore, coaches should incorporate 'game-like' conditions during practice that include repeated sprints-while focusing on maintaining high velocity to promote goal scoring. KEY WORDS speed, pool, shoulder, women

The purpose of the current investigation was to identify any existing relationships between off-ice performance measures and on-ice performance quantified by speed and acceleration. Twenty-seven women (age 19 [+ or -] 1 year; body mass (59.5 [+ or -] 6.8 kg; height 164.6 [+ or -] 6.35 cm; body fat 23.2 [+ or -] 3.9%) who were collegiate synchronized figure skaters volunteered for the investigation. To examine the relationship between off-ice performance and on-ice speed and acceleration, collegiate synchronized skaters were evaluated on various performance tests over a 1-week period. Off-ice tests completed were peak torque for hip abduction and adduction, 40-yard sprint, vertical jump height, 30-second slide board stride count, and a 1-RM (repetition maximum) squat. On-ice tests included a timed single lap sprint, 4.5-minute (duration of long program) lap count, and an approximately 16.5-m (18-yard blue line to blue line) timed acceleration. Significance was set at P [less than or equal to] 0.05. This study showed 3 primary findings: (a) slide board stride count was the single best predictor for both single lap on-ice speed and acceleration accounting for 53.5% (adjusted [R.sup.2] value) of the variance in the single lap test and 42.5% (adjusted [R.sup.2] value) of the variance in acceleration times; (b) vertical jump height test was the second best predictor for both the single lap test and on-ice acceleration accounting for 36.6% and 39.9% (adjusted [R.sup.2] values) of the variance in times recorded, respectively; and (c) the best combined predictors for the single lap speed test were slide board stride count and 40-yard dash ([R.sup.2] = 0.675), whereas the best combined predictors for on-ice acceleration were slide board stride count and vertical jump height test ([R.sup.2] = 0.571). Conditioning for synchronized skaters to enhance performance of on-the-ice speed and acceleration should include slide board training implementation of plyometric and linear speed training while developing and maintaining 1-RM strength to support power capabilities. KEY WORDS sport science, speed, power, winter sports, athletic performance

Recovery from an American football game has had limited study. The purpose of this study was to examine markers of skeletal muscle tissue damage and circulating anabolic and catabolic hormones to gain insight into the recovery process from Friday until Monday, when a new practice week begins. Twenty-eight National Collegiate Athletic Association Division I football players gave consent to participate in the investigation in the ninth game of the season. Sixteen players started the game and played the entire game (PL), and 12 others did not play and were on the bench during the game (DNP). Each player had fasted blood samples obtained at the same time of day between 1000 and 1200 hours the day before the game (Friday; T1), 18-20 hours after the game (Sunday; T2), and then 42-44 hours after the game (Monday; T3). Blood samples were analyzed for concentrations of creatine kinase (CK), lactate dehydrogenase (LDH), myoglobin, testosterone, and cortisol. The PL players showed significantly (p [less than or equal to] 0.05) increased concentrations of CK (T2 > T1 and T3), myoglobin (T2 > T1 and T3), and LDH (T2 > T1). In contrast, DNP players showed significant differences in cortisol (T3 < T1 and T2) and testosterone:cortisol (T3 > T1). Few changes were observed in testosterone and cortisol changes, indicating stability of the anabolic/catabolic hormones. In conclusion, these data indicate that participation in a college football game late in the season results in some degree of tissue damage but with minimal hormonal responses, which seem to have stabilized at resting concentrations without predominance of cortisol's catabolic presence. As previously noted in the literature, some type of 'contact adaptation' to the season may have occurred with regard to tissue damage responses. However, by the ninth game of a season, players do carry soft tissue damage levels above resting ranges into subsequent games, indicating that recovery should be monitored, with coaches being careful with scheduling scrimmage and full-contact drills. How such data implicate overuse injuries remains unclear, considering that hormonal status in this study was highly stable, with catabolic influences minimized by the high level of athlete conditioning. These data again support that high-level conditioning can stabilize anabolic and catabolic hormonal signals and limit acute soft tissue injury, making cerebral concussion (acute and chronic) and traumatic injury the biggest threats to a student-athlete's health and well-being during an American football game. Key Words competition, contact sports, collision injury, endocrine, performance, recovery, skeletal muscle

The purpose of this investigation was to examine the influence of upper-body static stretching and dynamic stretching on upper-body muscular performance. Eleven healthy men, who were National Collegiate Athletic Association Division I track and field athletes (age, 19.6 [+ or -] 1.7 years; body mass, 93.7 [+ or -] 13.8 kg; height, 183.6 [+ or -] 4.6 cm; bench press 1 repetition maximum [1RM], 106.2 [+ or -] 23.0 kg), participated in this study. Over 4 sessions, subjects participated in 4 different stretching protocols (i.e., no stretching, static stretching, dynamic stretching, and combined static and dynamic stretching) in a balanced randomized order followed by 4 tests: 30% of 1 RM bench throw, isometric bench press, overhead medicine ball throw, and lateral medicine ball throw. Depending on the exercise, test peak power (Pmax), peak force (Fmax), peak acceleration (Amax), peak velocity (Vmax), and peak displacement (Dmax) were measured. There were no differences among stretch trials for Pmax, Fmax, Amax, Vmax, or Dmax for the bench throw or for Fmax for the isometric bench press. For the overhead medicine ball throw, there were no differences among stretch trials for Vmax or Dmax. For the lateral medicine ball throw, there was no difference in Vmax among stretch trials; however, Dmax was significantly larger (p [less than or equal to] 0.05) for the static and dynamic condition compared to the static-only condition. In general, there was no short-term effect of stretching on upper-body muscular performance in young adult male athletes, regardless of stretch mode, potentially due to the amount of rest used after stretching before the performances. Since throwing performance was largely unaffected by static or dynamic upperbody stretching, athletes competing in the field events could perform upper-body stretching, if enough time were allowed before the performance. However, prior studies on lower-body musculature have demonstrated dramatic negative effects on speed and power. Therefore, it is recommended that a dynamic warm-up be used for the entire warm-up. KEY WORDS power, force; static stretch, dynamic stretch, throwing

Previous research has shown that L-carnitine L-tartrate (LCLT) supplementation beneficially affects markers of hypoxic stress following resistance exercise. However, the mechanism of this response is unclear. Therefore, the primary purpose of this study was to determine the effects of LCLT supplementation on muscle tissue oxygenation during and after multiple sets of squat exercise. Nine healthy, previously resistancetrained men (25.2 [+ or -] 6 years, 91.2 [+ or -]10.2 kg, 180.2 [+ or -] 6.3 cm) ingested LCLT (equivalent to 2g L-Carnitine/day) or an identical placebo for 23 days using a randomized, balanced, crossover, double-blind, placebo-controlled, repeated-measures study design. On day 21, forearm muscle oxygenation was measured during and after an upper arm occlusion protocol using near infrared spectroscopy (NIRS), which measures the balance of oxygen delivery in relation to oxygen consumption. On day 22, subjects performed 5 sets of 15 to 20 repetitions of squat exercise with corresponding measures of thigh muscle oxygenation, via NIRS, and serial blood draws. Compared to the placebo trial, muscle oxygenation was reduced in the LCLT trial during upper arm occlusion and following each set of resistance exercise. Despite reduced oxygenation, plasma malondealdehyde, a marker of membrane damage, was attenuated during the LCLT trial. There were no differences between trials in the vasoactive substance prostacyclin. In conclusion, because oxygen delivery was occluded during the forearm protocol, it is proposed that enhanced oxygen consumption mediated the reduced muscle oxygenation during the LCLT trial. Enhanced oxygen consumption would explain why hypoxic stress was attenuated with LCLT supplementation. KEY WORDS ergogenic aids, metabolic stress, performance, recovery, supplements

L-carnitine L-tartrate (LCLT) supplementation beneficially affects markers of postexercise metabolic stress and muscle damage. However, to date, no study has determined the dose response of LCLT to elicit such responses. Therefore, the purpose of this study was to determine the effects of different doses of LCLT on criterion variables previously shown to be responsive to LCLT supplementation. Eight healthy men (22 [+ or -] 3 y, 174 [+ or -] 5 cm, 83.0 [+ or -] 15.3 kg) were supplemented with 0 g, 1 g, and 2 g of LCLT for 3 weeks and then performed a bout of resistance exercise (5 sets of 15-20 repetition maximum with a 2-min rest between sets) with associated blood draws. This procedure was performed in a balanced, randomized, repeated measures design. Serum carnitine concentrations increased (p [less than or equal to] 0.05) following the 1 g and 2 g doses, with the 2-g dose providing the highest carnitine concentrations. The 1 and 2-g doses reduced postexercise serum hypoxanthine, serum xanthine oxidase, serum myoglobin, and perceived muscle soreness. In conclusion, both the 1- and 2-g doses were effective in mediating various markers of metabolic stress and of muscle soreness. Use of LCLT appears to attenuate metabolic stress and the hypoxic chain of events leading to muscle damage after exercise. KEY WORDS. ergogenic aids, metabolic stress, performance, recovery, sports supplements, strength training

This investigation determined the influence of acute and chronic resistance exercise on responses of growth hormone (GH) molecular variants in women. Seventy-four healthy young women (23 [+ or -] 3 yr, 167 [+ or -] 7 cm, 63.8 - 9.3 kg, 26.3 [+ or -] 4.0% body fat) performed an acute bout of resistance exercise (6 sets of 10 repetition maximum squat). Blood samples were obtained pre- and post-exercise. Resulting plasma was fractionated by molecular mass (fraction A, >60 kDa; fraction B, 30-60 kDa; and fraction C, hormones; isoforms; somatotrophs; strength training

The purpose of this study was to examine changes in body composition (BC) and physical performance tests (PT) resulting from a competitive season in soccer. Twenty-five male collegiate players (age = 19.9 [+ or -] 1.3 years; height = 177.6 [+ or -] 6.4 cm; body mass = 77.6 [+ or -] 8.6 kg, and percentage body fat = 12.8 [+ or -] 5.2%) were tested before (PRE) and after (POST) the 2003-2004 National Collegiate Athletic Association season. The following tests were performed: BC (anthropometric and dual energy x-ray absorptiometry measurements), vertical jump (VJ), 9.1-m (9 m) and 36.5-m (36 m) sprint, lower-body power (LP), total body power (TP), and cardiorespiratory endurance ([Vo.sub.2]max). Training was divided into soccer-specific training: field warm-up drills, practices, games, and additional conditioning sessions. A daily, unplanned, nonlinear periodization model was used to assign session volume and intensity for strength sessions (total repetitions [less than or equal to] 96 and workload was [greater than or equal to] 80% of 1 repetition maximum). For the entire team, body mass significantly increased by 1.5 [+ or -] 0.4 kg from PRE to POST due to a significant increase in total lean tissue (0.9 [+ or -] 0.2 kg). Regionally, lean tissue mass significantly increased in the legs (0.4 [+ or -] 0.0 kg) and trunk (0.3 [+ or -] 0.1 kg). Physical performance variables were very similar for the entire team at PRE and POST; VJ (cm) = 61.9 [+ or -] 7.1 PRE vs. 63.3 [+ or -] 8.0 POST, 9.1-m (s) = 1.7 [+ or -] 0.1 PRE and POST, 36.5-m (s) = 5.0 [+ or -] 0.2 PRE and POST, predicted [Vo.sub.2]max (ml x kg x [min.sup.-1] = 59.8 [+ or -] 3.3 PRE vs. 60.9 [+ or -] 3.4 POST. The only significant improvements across the season were for TP (17.3%) and for LP (10.7%). In conclusion, soccer athletes who begin a season with a high level of fitness can maintain, and in some cases improve, body composition and physical performance from before to after a competitive season. A correct combination of soccer-specific practices and strength and conditioning programs can maintain and develop physical performance, allowing a soccer athlete to perform optimally throughout pre-, in-, and postseason play. KEY WORDS. starters, nonstarters, DEXA, conditioning, strength training

Resistance exercise intensity is commonly prescribed as a percent of 1 repetition maximum (1RM). However, the relationship between percent 1RM and the number of repetitions allowed remains poorly studied, especially using free weight exercises. The purpose of this study was to determine the maximal number of repetitions that trained (T) and untrained (UT) men can perform during free weight exercises at various percentages of 1RM. Eight T and 8 UT men were tested for 1RM strength. Then, subjects performed 1 set to failure at 60, 80, and 90% of 1RM in the back squat, bench press, and arm curl in a randomized, balanced design. There was a significant (p < 0.05) intensity x exercise interaction. More repetitions were performed during the back squat than the bench press or arm curl at 60% 1RM for T and UT. At 80 and 90% 1RM, there were significant differences between the back squat and other exercises; however, differences were much less pronounced. No differences in number of repetitions performed at a given exercise intensity were noted between T and UT (except during bench press at 90% 1RM). In conclusion, the number of repetitions performed at a given percent of 1RM is influenced by the amount of muscle mass used during the exercise, as more repetitions can be performed during the back squat than either the bench press or arm curl. Training status of the individual has a minimal impact on the number of repetitions performed at relative exercise intensity. KEY WORDS. weight training, percentage loading, intensity, exercise prescription