Increased Neuromuscular Activity, Force Output, and Resistance Exercise Volume When Using 5-Minute Compared with 2-Minute Rest Intervals Between the Sets.

ABSTRACT: McMahon, G, Best, N, Coulter, T, and Erskine, RM. Increased neuromuscular activation, force output and resistance exercise volume when using 5-minute compared with 2-minute rest intervals between the sets. J Strength Cond Res XX(X): 000-000, 2024-Longer rest intervals between resistance exercise (RE) sets may promote greater muscle hypertrophy and strength gains over time by facilitating the completion of greater training volume and intensity. However, little is known about the acute neuromuscular responses to RE sets incorporating longer vs. shorter rest intervals. Using a within-subject, crossover design, 8 healthy, young subjects completed 2 separate acute bouts of 4 sets of 8 × 3-s maximal isometric contractions using either a 2-minute (REST-2) or 5-minute (REST-5) rest interval between sets. Peak torque (PT) and electromyography (EMG) were measured pre and 5 minutes postexercise. Peak torque and mean torque (MT), EMG, mean, and median frequencies were measured during each set, whereas blood lactate (BLa), heart rate (HR), and rating of perceived exertion (RPE) were measured following each set. Peak torque and MT were lower (p < 0.05) in sets 3 and 4, and sets 2-4 in REST-2 compared with REST-5, respectively. Electromyography and BL were lower and higher, respectively, in REST-2 vs. REST-5. There was no main effect of condition on HR or RPE. Pre-to-post exercise reductions in PT (-17 ± 9% vs. -4 ± 7%) and EMG (-29 ± 14% vs. -10 ± 7%) were greater (p < 0.001) in REST-2 vs. REST-5. Total exercise volume was less in REST-2 vs. REST-5 (9,748 ± 2296 N·m-1 vs. 11,212 ± 2513 N·m-1, p < 0.001). These results suggest that incorporating 5-minute between-set rest intervals into a resistance exercise session facilitates improved neuromuscular function, increased exercise volume, and less metabolic stress compared with 2-minute rest intervals. Thus, 5-minute rest intervals may be more efficacious for promoting muscle hypertrophy and strength gains in a chronic resistance training program.

No Effect of Interset Palm Cooling on Acute Bench Press Performance, Neuromuscular or Metabolic Responses, Following Moderate-Intensity Resistance Exercise.

ABSTRACT: McMahon, G. No effect of interset palm cooling on acute bench press performance, neuromuscular or metabolic responses, following moderate-intensity resistance exercise. J Strength Cond Res 38(7): 1213-1220, 2024-Despite the growing literature in high-intensity exercise regarding palm cooling, the acute effects of palm cooling on exercise performance indices, neuromuscular and metabolic responses, have not been described during moderate-intensity resistance exercise. Nine (age, 22 ± 1 year; mass, 80.8 ± 16.2 kg; height, 1.80 ± 0.11 m) healthy, male (n = 7) and female (n = 2) resistance-trained subjects performed 4 sets of bench press to failure at 60% 1 repetition maximum with 3-minute passive recovery. Subjects were randomly allocated to either the cooling (COL; 2 minutes of cooling at 10 °C) or the control (passive rest; CON) condition separated by 1 week between the conditions. Exercise performance (volume load, repetitions, barbell velocity), muscle activation, blood lactate, and rate of perceived exertion were assessed. Despite changes across the variables during the resistance exercise sessions, there were no statistical differences (p > 0.05) in any of the performance, neuromuscular or physiological responses, between the 2 experimental conditions, despite palm temperature being significantly (p < 0.001) reduced in the cooling condition compared with control throughout. Therefore, based on the results of this study, palm cooling does not enhance acute moderate-intensity resistance exercise.

Joint angle-specific neuromuscular time course of recovery after isometric resistance exercise at shorter and longer muscle lengths.

Resistance training at longer muscle lengths induces greater muscle hypertrophy and different neuromuscular functional adaptations than training at shorter muscle lengths. However, the acute time course of recovery of neuromuscular characteristics after resistance exercise at shorter and longer muscle lengths in the quadriceps has never been described. Eight healthy young participants (4 M, 4 F) were randomly assigned to perform four sets of eight maximal isometric contractions at shorter (SL; 50° knee flexion) or longer (LL; 90° knee flexion) muscle lengths in a crossover fashion. During exercise, peak torque (PT), muscle activity [electromyogram (EMG)], and internal muscle forces were assessed. PT and EMG at shorter (PT50, EMG50) and longer (PT90, EMG90) muscle lengths, creatine kinase (CK), and muscle soreness were measured at baseline, immediately after exercise (Post), after 24 h (24 h), and after 48 h (48 h). During exercise, EMG (P = 0.002) and internal muscle forces (P = 0.017) were greater in LL than in SL. During recovery, there was a main effect of exercise angle, with PT50 (P = 0.002), PT90 (P = 0.016), and EMG50 (P = 0.002) all significantly reduced to a greater degree in LL compared with SL. CK and muscle soreness increased after resistance exercise, but there were no differences between SL and LL. The present results suggest that if the preceding isometric resistance exercise is performed at longer muscle lengths, function and muscle activity at shorter and longer muscle lengths are inhibited to a larger degree in the subsequent recovery period. This information can be used by practitioners to manipulate exercise prescription.NEW & NOTEWORTHY Despite the established long-term benefits of training at longer muscle lengths for muscle size and strength, acutely performing resistance exercise at longer muscle lengths may require a longer time course of neuromuscular recovery compared with performing resistance exercises at shorter muscle lengths. Furthermore, there appear to be different joint angle-specific recovery profiles, depending on the muscle length of the preceding exercise.

The Effects of Palm Cooling on Physiological and Metabolic Responses, Exercise Performance, and Total Volume During High-Intensity Bench Press Exercise in Resistance-Trained Men.

ABSTRACT: McMahon, G, and Kennedy, R. The effects of palm cooling on physiological and metabolic responses, exercise performance, and total volume during high-intensity bench press exercise in resistance-trained men. J Strength Cond Res 37(11): 2122-2129, 2023-Previous research suggests that cooling distal to the working agonist muscles during the interset rest periods of high-intensity resistance exercise may facilitate improved performance by means of improving metabolic conditions of contractile machinery. However, these studies have not directly measured indicators of metabolic conditions. Therefore, the aim of this study was to compare 2 palm-cooling conditions with a thermoneutral condition during high-intensity resistance exercise and subsequent effects on physiological and metabolic responses and exercise performance. Eleven healthy, resistance-trained, young men (20-36 years old) performed 4 sets of bench press exercise to exhaustion at 80% 1 repetition maximum each separated by 3 minutes of passive recovery. Palm cooling (10° C [TEN] or 15° C [FTN]) or thermoneutral (28° C [CON]) condition was applied for 60 seconds during the recovery interval of each set in a randomized, double-blind fashion, with 4 days recovery between the experimental conditions. There were no differences ( p > 0.05) in volume load between the experimental conditions across all sets. Mean repetition velocity and force of the bench press declined significantly following set 1 in all conditions ( p < 0.05), but there were no differences between the conditions. Lactate, heart rate, and rating of perceived exertion systematically increased from sets 1 to 4; however, there were no significant differences ( p > 0.05) between any of the conditions. Palm cooling at either 10 or 15° C had no observable effects on physiological and metabolic responses during exercise, nor has it any effect on bench press performance or volume load compared with a thermoneutral condition. Therefore, cooling cannot be currently recommended as an ergogenic strategy to enhance acute bench press performance or mitigate fatigue during high-intensity resistance training.

No Effect of Interset Palm Cooling on Acute Bench Press Performance, Electromyography Amplitude, or Spectral Frequencies in Resistance-Trained Men.

ABSTRACT: McMahon, G, Kennedy, R, and Burden, A. No effect of interset palm cooling on acute bench press performance, electromyography amplitude or spectral frequencies in resistance-trained men. J Strength Cond Res 37(3): 555-563, 2023-Previous research has suggested that cooling distal to the working agonist muscles during the interset rest periods of high-intensity resistance exercise may facilitate improved performance through increased agonist activation. However, these studies have used inappropriate electromyography (EMG) normalization techniques. Therefore, the aim of this study was to compare 2 palm-cooling conditions with a thermoneutral condition during high-intensity resistance exercise and subsequent effects on exercise performance, EMG amplitude, and spectral frequencies using appropriate normalization methodologies. Eleven healthy, resistance-trained, young men (20-36 years old) performed 4 sets of bench press exercise to exhaustion at 80% 1RM each separated by 3 minutes of passive recovery. Palm-cooling (10° C [TEN] or 15° C [FTN]) or thermoneutral (28° C [CON]) conditions were applied for 60 seconds during the recovery interval of each set in a randomized, double-blind fashion, with 4 days of recovery between experimental conditions. Palm temperature was significantly lower (p < 0.05) in the TEN and FTN conditions compared with CON. Number of repetitions and mean power in the bench press declined significantly after each set in all conditions (p < 0.05). There were no significant differences (p > 0.05) in any bench press performance or EMG-related variables between any of the conditions. Palm cooling at either 10 or 15° C had no effects on bench press performance compared with a thermoneutral condition, with no observable effects on neuromuscular responses during exercise. Therefore, cooling is not currently recommended as an ergogenic strategy to enhance acute bench press performance during high-intensity resistance training.

Exercise, type 1 diabetes mellitus and blood glucose: The implications of exercise timing.

The scientific literature shows that exercise has many benefits for individuals with type 1 diabetes. Yet, several barriers to exercise in this population exist, such as post-exercise hypoglycaemia or hyperglycaemia. Several studies suggest that the timing of exercise may be an important factor in preventing exercise-induced hypoglycaemia or hyperglycaemia. However, there is a paucity of evidence solely focused on summarising findings regarding exercise timing and the impact it has on glucose metabolism in type 1 diabetes. This report suggests that resistance or high-intensity interval exercise/training (often known as HIIT) may be best commenced at the time of day when an individual is most likely to experience a hypoglycaemic event (i.e., afternoon/evening) due to the superior blood glucose stability resistance and HIIT exercise provides. Continuous aerobic-based exercise is advised to be performed in the morning due to circadian elevations in blood glucose at this time, thereby providing added protection against a hypoglycaemic episode. Ultimately, the evidence concerning exercise timing and glycaemic control remains at an embryonic stage. Carefully designed investigations of this nexus are required, which could be harnessed to determine the most effective, and possibly safest, time to exercise for those with type 1 diabetes.

No Strain, No Gain? The Role of Strain and Load Magnitude in Human Tendon Responses and Adaptation to Loading.

ABSTRACT: McMahon, G. No strain, no gain? The role of strain and load magnitude in human tendon responses and adaptation to loading. J Strength Cond Res 36(10): 2950-2956, 2022-Transmission of force and energy storage and release are affected by the mechanical properties and morphology of tendons. Therefore, understanding the modulation of mechanical properties through training is key as part of optimizing athletic task performance and rehabilitation. In vivo human tendon adaptation to exercise occurs in a nongraded manner, that is, there seems to be a threshold to which a tendon responds and adapts to mechanical stimuli, whereas below this threshold, minimal or no adaptation is observed. However, this remains controversial as such findings have not always been universal. Modulation of strain magnitude (change in tendon length relative to its original length) or loading intensity (e.g., % 1 repetition maximum or % maximal voluntary contraction) therefore may play a fundamental role in enhancing tendon adaptation. This review outlines the key evidence of these phenomena through direct comparative studies of higher vs. lower strain/load magnitude and indirect noncomparative studies and also explores some of the potential mechanobiological underpinnings of these adaptations. Furthermore, this review outlines practical considerations for exercise prescription using a strain magnitude-based approach and why previous non-strain magnitude-based approaches may have been a confounding factor in load magnitude studies investigating tendon adaptation.

Running Performance Is Correlated With Creatine Kinase Levels and Muscle Soreness During an Olympic Games in Hockey.

PURPOSE: To compare the global positioning system- and accelerometry-derived running demands, creatine kinase (CK), and self-reported wellness during an Olympic Games in international hockey. METHODS: Data were collected across 5 games during the 2016 Rio Olympic Games. Global positioning system units (10 Hz) were used to assess the running demands, accelerations, and decelerations of outfield players in a men's hockey squad with matches 2 to 5 compared with match 1. CK was used as a marker of muscle damage, and self-reported psychometric questionnaires were used to assess wellness, with each of the 5 matches compared with precompetition assessments. RESULTS: There were significant increases (P < .05) in either, or both, absolute and relative total distance, player load, high-speed running distance, sprint distance, and accelerations and decelerations, compared with baseline. There was a significant decrease (P < .05) in maximal velocity by match 5. CK significantly increased from match 1 to 5 and displayed significant correlations with total distance (r = .55) and player load (r = .41). Muscle soreness correlated with total distance and player load, with other wellness markers unchanged compared with baseline. CONCLUSIONS: International hockey athletes may maintain or increase running activities over the course of an Olympic tournament; however, this may be impacted by situational (match score/outcome) and environmental (ambient temperature) factors. Despite CK and muscle soreness displaying relationships with running variables, further work is needed to establish their individual value in monitoring international hockey athletes.

Ingestion of Carbohydrate Prior to and during Maximal, Sprint Interval Cycling Has No Ergogenic Effect: A Randomized, Double-Blind, Placebo Controlled, Crossover Study.

Carbohydrate (CHO) ingestion may improve intermittent sprint performance in repeated sprint efforts ≤15 s. Yet, evidence for its efficacy on sprint interval durations ~30 s is lacking. The purpose of this study was to investigate the effects of CHO ingestion on maximal sprint interval exercise. Fifteen (n = 15) recreational athletes (13/2 males/females, age 22 ± 2 years; height 176 ± 11 cm; mass 76.8 ± 11.3 kg) volunteered for this randomised, double-blind, placebo-controlled, crossover design. Participants completed two experimental trials (performed 10-days apart) involving the ingestion of an 8% CHO solution or a flavour and appearance-matched placebo (PLA) solution (5 mL/kg/bw), immediately before exercise, and preceding the second interval of four × 30 s bouts of repeated maximal sprint efforts (separated by 3.5 min of passive recovery). Peak and mean power (W) output progressively decreased during the repeated sprints (main effect of time, p < 0.0001), but there were no differences between CHO and PLA during any of the sprints (p > 0.05 for condition main effect and condition × time interaction). Physiological responses (blood lactate, heart rate, oxygen consumption, respiratory exchange ratio and RPE) were also unaltered by CHO ingestion. In conclusion, CHO ingestion does not enhance performance or modulate physiological responses during intermittent maximal, sprint cycling.

Monitoring Wellness, Training Load, and Running Performance During a Major International Female Field Hockey Tournament.

McGuinness, McMahon, G, A, Malone, S, Kenna, D, Passmore, D, and Collins, K. Monitoring wellness, training load, and running performance during a major international female field hockey tournament. J Strength Cond Res 34(8): 2312-2320, 2020-The current observational study quantified players' activity profiles during a major international female field hockey tournament and determined whether an association exists between well-being measures and running performance within elite female hockey players. Elite female field hockey players (23 ± 3 years; 162.6 ± 13 cm; and 66 ± 6 kg) participated in the study. Participants running performance was monitored using global positioning system technology (S5; Catapult Innovations, Scoresby, Victoria, Australia), with daily well-being questionnaires used to quantify player responses during the tournament. Thresholds for the magnitude of the observed change for each variable were determined using the Hopkins Spreadsheets for analysis of controlled trials. Relative distance (m·min) was likely lower when compared with game 1 in game 7. Relative high speed (m·min >16 km·h) was likely lower in games 5, 6, and 7 when compared with game 1. Subjective load was very likely higher in game 2 and very likely lower in game 3 when compared with game 1. Mood and sleep quality were likely lower in game 1 when compared with game 4 and game 7. Muscle soreness was likely higher when compared with game 1 in game 7. During the tournament, it was observed that a decrease in players' daily well-being was accompanied by changes in running performance. Furthermore, changes to players' muscle soreness and sleep quality result in decreased players' high-speed running performance during match-play. Therefore, to prevent the observed effects, coaches should adopt strategies to enhance sleep quality and incorporate specific recovery modalities to reduce musculoskeletal soreness.

Changes in Player Activity Profiles After the 2015 FIH Rule Changes in Elite Women's Hockey.

McMahon, GE and Kennedy, RA. Changes in player activity profiles after the 2015 FIH rule changes in elite women's hockey. J Strength Cond Res 33(11): 3114-3122, 2019-The aim of this study was to compare the player activity profiles of elite international women's hockey players before (2014) and after (2015) the 2015 the International Hockey Federation (FIH) match rule changes at team and positional levels. The match activity profiles (n = 400) of 19 female hockey players (age 23 ± 4 years, mass 63.6 ± 5.5 kg, VO2max 57 ± 6 ml·kg·min in 2014, 58 ± 6 ml·kg·min in 2015) were recorded during competitive international matches in 2014 (match n = 12) and 2015 (match n = 13) using 10-Hz global positioning system units. The practical utility of an effect was only classified as substantial when there was a >75% likelihood that the ±90% confidence interval of the effect size (ES) was equal to or greater than the small (ES ± 0.2) reference value. Mean match time decreased by over 2 minutes from 71.72 ± 1.38 to 69.40 ± 4.72 minutes. There were increases at the team level in relative substitutions (SUB), relative distance (RD), high-speed running (HSR: 3.08-5.27 m·s), and surges (S), with a fall in low-speed running (LSR: 0-3.05 m·s) between 2014 and 2015. There were no changes in the between-position differences observed from 2014 to 2015. Within positions, there were relative increases in RD for all positions, HSR and S for midfield, and in SUB and S in forwards. The 2015 FIH rule changes seem to have increased the general intensity of international women's hockey. However, the different facets of physical performance did not change uniformly across team positions. Therefore, specific modifications to conditioning practices for each position may be warranted to more accurately reflect match demands.

Circulating Tumor Necrosis Factor Alpha May Modulate the Short-Term Detraining Induced Muscle Mass Loss Following Prolonged Resistance Training.

INTRODUCTION: Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine that has been shown to modulate muscle mass, and is responsive to exercise training. The effects of resistance training (RT) followed by a short period of detraining on muscle size, architecture and function in combination with circulating TNFα levels have not been previously investigated in a young, healthy population. METHODS: Sixteen participants (8 males and 8 females) were randomly assigned to a training group (TRA; age 20 ± 3 years, mass 76 ± 7 kg), whilst fourteen participants (7 males and 7 females) age 22 ± 2 years, mass 77 ± 6 kg were assigned to a control group (CON). Measures of vastus lateralis (VL) muscle size (normalized physiological cross-sectional area allometrically scaled to body mass; npCSA), architecture (fascicle length; LF, pennation angle Pθ), strength (knee extensor maximal voluntary contraction; KE MVC), specific force, subcutaneous fat (SF) and circulating TNFα were assessed at baseline (BL), post 8 weeks RT (PT), and at two (DT1) and four (DT2) weeks of detraining. RESULTS: Pooled BL TNFα was 0.87 ± 0.28 pg/mL with no differences between groups. BL TNFα tended to be correlated with npCSA (p = 0.055) and KEMVC (p = 0.085) but not specific force (p = 0.671) or SF (p = 0.995). There were significant (p < 0.05) increases in npCSA compared to BL and CON in TRA at PT, DT1, and DT2, despite significant (p < 0.05) decreases in npCSA compared to PT at DT1 and DT2. There were significant (p < 0.05) increases in LF, Pθ and KE MVC at PT but only LF and torque at DT1. There were no significant (p > 0.05) changes in SF, specific force or TNFα at any time points. There was a significant correlation (p = 0.022, r = 0.57) between the relative changes in TNFα and npCSA at DT2 compared to PT. DISCUSSION: Neither RT nor a period of short term detraining altered the quality of muscle (i.e., specific force) despite changes in morphology and function. TNFα does not appear to have any impact on RT-induced gains in muscle size or function, however, TNFα may play a role in inflammatory-status mediated muscle mass loss during subsequent detraining in healthy adults.

Gender associated muscle-tendon adaptations to resistance training.

PURPOSE: To compare the relative changes in muscle-tendon complex (MTC) properties following high load resistance training (RT) in young males and females, and determine any link with circulating TGFß-1 and IGF-I levels. METHODS: Twenty-eight participants were assigned to a training group and subdivided by sex (T males [TM] aged 20±1 year, n = 8, T females [TF] aged 19±3 year, n = 8), whilst age-matched 6 males and 6 females were assigned to control groups (ConM/F). The training groups completed 8 weeks of resistance training (RT). MTC properties (Vastus Lateralis, VL) physiological cross-sectional area (pCSA), quadriceps torque, patella tendon stiffness [K], Young's modulus, volume, cross-sectional area, and length, circulating levels of TGFß-1 and IGF-I were assessed at baseline and post RT. RESULTS: Post RT, there was a significant increase in the mechanical and morphological properties of the MTC in both training groups, compared to ConM/F (p<0.001). However, there were no significant sex-specific changes in most MTC variables. There were however significant sex differences in changes in K, with females exhibiting greater changes than males at lower MVC (Maximal Voluntary Contraction) force levels (10% p = 0.030 & 20% MVC p = 0.032) and the opposite effect seen at higher force levels (90% p = 0.040 & 100% MVC p = 0.044). There were significant increases (p<0.05) in IGF-I in both TF and TM following training, with no change in TGFß-1. There were no gender differences (p>0.05) in IGF-I or TGFß-1. Interestingly, pooled population data showed that TGFß-1 correlated with K at baseline, with no correlations identified between IGF-I and MTC properties. CONCLUSIONS: Greater resting TGFß-1 levels are associated with superior tendon mechanical properties. RT can impact opposite ends of the patella tendon force-elongation relationship in each sex. Thus, different loading patterns may be needed to maximize resistance training adaptations in each sex.

Muscular adaptations and insulin-like growth factor-1 responses to resistance training are stretch-mediated.

INTRODUCTION: Modulation of muscle characteristics was attempted through altering muscle stretch during resistance training. We hypothesized that stretch would enhance muscle responses. METHODS: Participants trained for 8 weeks, loading the quadriceps in a shortened (SL, 0-50° knee flexion; n=10) or lengthened (LL, 40-90°; n=11) position, followed by 4 weeks of detraining. Controls (CON; n=10) were untrained. Quadriceps strength, vastus lateralis architecture, anatomical cross-sectional area (aCSA), and serum insulin-like growth factor-1 (IGF-1) were measured at weeks 0, 8, 10, and 12. RESULTS: Increases in fascicle length (29±4% vs. 14±4%), distal aCSA (53±12% vs. 18±8%), strength (26±6% vs. 7±3%), and IGF-1 (31±6% vs. 7±6%) were greater in LL compared with SL muscles (P<0.05). No changes occurred in CON. Detraining decrements in strength and aCSA were greater in SL than LL muscles (P<0.05). CONCLUSIONS: Enhanced muscle in vivo (and somewhat IGF-1) adaptations to resistance training are concurrent with muscle stretch, which warrants its inclusion within training.

Impact of range of motion during ecologically valid resistance training protocols on muscle size, subcutaneous fat, and strength.

The impact of using different resistance training (RT) kinematics, which therefore alters RT mechanics, and their subsequent effect on adaptations remain largely unreported. The aim of this study was to identify the differences to training at a longer (LR) compared with a shorter (SR) range of motion (ROM) and the time course of any changes during detraining. Recreationally active participants in LR (aged 19 ± 2.6 years; n = 8) and SR (aged 19 ± 3.4 years; n = 8) groups undertook 8 weeks of RT and 4 weeks of detraining. Muscle size, architecture, subcutaneous fat, and strength were measured at weeks 0, 8, 10, and 12 (repeated measures). A control group (aged 23 ± 2.4 years; n = 10) was also monitored during this period. Significant (p > 0.05) posttraining differences existed in strength (on average 4 ± 2 vs. 18 ± 2%), distal anatomical cross-sectional area (59 ± 15 vs. 16 ± 10%), fascicle length (23 ± 5 vs. 10 ± 2%), and subcutaneous fat (22 ± 8 vs. 5 ± 2%), with LR exhibiting greater adaptations than SR. Detraining resulted in significant (p > 0.05) deteriorations in all muscle parameters measured in both groups, with the SR group experiencing a more rapid relative loss of postexercise increases in strength than that experienced by the LR group (p > 0.05). Greater morphological and architectural RT adaptations in the LR (owing to higher mechanical stress) result in a more significant increase in strength compared with that of the SR. The practical implications for this body of work follow that LR should be observed in RT where increased muscle strength and size are the objective, because we demonstrate here that ROM should not be compromised for greater external loading.

The manipulation of strain, when stress is controlled, modulates in vivo tendon mechanical properties but not systemic TGF-ß1 levels.

Modulators of loading-induced in vivo adaptations in muscle-tendon complex (MTC) mechanical properties remain unclear. Similarly contentious, is whether changes in MTC characteristics are associated with growth factor levels. Four groups were subjected to varying magnitudes of stress/strain: Group 1 trained with the MTC at a shortened position (MTCS; n = 10); Group 2 at a lengthened position (MTCL; n = 11; stress levels matched to MTCS); Group 3 over a wide range of motion (MTCX; n = 11); and Group 4 (n = 10) was the control population (no training). Patella tendon Stiffness (P < 0.001), Young's modulus, and quadriceps torque (P < 0.05) increments (only seen in the training groups), showed MTCL and MTCX groups responses to be superior to those of MTCS (P < 0.05). In addition, MTCL and MTCX better maintained adaptations compared to MTCS (P < 0.05) following detraining, with a pattern of slower loss of improvements at the early phase of detraining in all training groups. There were no significant changes (P > 0.05) in antagonist cocontraction, patella tendon dimensions or circulating transforming growth factor beta (TGF-ß1) levels following training or detraining in any of the groups. We conclude that chronically loading the MTC in a relatively lengthened position (which involves greater strains) enhances its mechanical properties, more so than loading in a shortened position. This is true even after normalizing for internal stress. The underlying endocrine mechanisms do not appear to be mediated via TGF-ß1, at least not at the systemic level. Our findings have implications with regard to the effectiveness of eccentric loading on improved tendon structural and mechanical properties.

Resting arterial diameter and blood flow changes with resistance training and detraining in healthy young individuals.

CONTEXT: Disruptions to habitual training routines are commonly due to injury or illness and can often lead to detraining adaptations. The implications of such adaptations to the human vasculature in a trained, asymptomatic population are not fully understood. OBJECTIVE: To determine the extent of local and systemic changes in arterial diameter and blood flow to resistance training and subsequent detraining in young adults. DESIGN: Randomized controlled clinical trial. SETTING: University physiology laboratory and fitness suite. PATIENTS OR OTHER PARTICIPANTS: Twenty-one healthy volunteers (aged 20.0 ± 2.8 years, 11 men and 10 women). INTERVENTION(S): Eight-week lower limb resistance training period and subsequent 4-week detraining period. MAIN OUTCOME MEASURE(S): Quadriceps and hamstrings concentric torque (strength), resting heart rate, arterial diameter, and blood flow velocity in the superficial femoral and carotid arteries were measured at 0, 8, 10, and 12 weeks. RESULTS: Resistance training increased quadriceps and hamstring strength (32% and 35%, respectively, P < .001), whereas strength decreased during detraining (24% and 27%, respectively, P < .05). Resting heart rate decreased after resistance training (16%, P < .01) and increased during detraining (19%, P < .001). Additionally, resistance training significantly increased superficial femoral and carotid resting arterial diameters (27% and 13%, respectively, P < .001) and mean blood flow (53% and 55%, respectively, P < .001). Detraining resulted in a significant decrease in superficial femoral and carotid resting diameter (46% and 10%, respectively, P < .001) and mean blood flow (61% and 38%, respectively, P < .05). CONCLUSIONS: Resistance training initiated both local and systemic changes to arterial diameter and blood flow; these changes appeared to reverse after detraining. The local changes in response to detraining showed a worsening (beyond pretraining values) of the vascular dimensional and blood flow characteristics.

On the application of multilevel modeling in environmental and ecological studies.

This paper illustrates the advantages of a multilevel/hierarchical approach for predictive modeling, including flexibility of model formulation, explicitly accounting for hierarchical structure in the data, and the ability to predict the outcome of new cases. As a generalization of the classical approach, the multilevel modeling approach explicitly models the hierarchical structure in the data by considering both the within- and between-group variances leading to a partial pooling of data across all levels in the hierarchy. The modeling framework provides means for incorporating variables at different spatiotemporal scales. The examples used in this paper illustrate the iterative process of model fitting and evaluation, a process that can lead to improved understanding of the system being studied.

Delineation and evaluation of hydrologic-landscape regions in the United States using geographic information system tools and multivariate statistical analyses.

Hydrologic-landscape regions in the United States were delineated by using geographic information system (GIS) tools combined with principal components and cluster analyses. The GIS and statistical analyses were applied to land-surface form, geologic texture (permeability of the soil and bedrock), and climate variables that describe the physical and climatic setting of 43,931 small (approximately 200 km2) watersheds in the United States. (The term "watersheds" is defined in this paper as the drainage areas of tributary streams, headwater streams, and stream segments lying between two confluences.) The analyses grouped the watersheds into 20 noncontiguous regions based on similarities in land-surface form, geologic texture, and climate characteristics. The percentage of explained variance (R-squared value) in an analysis of variance was used to compare the hydrologic-landscape regions to 19 square geometric regions and the 21 U.S. Environmental Protection Agency level-II ecoregions. Hydrologic-landscape regions generally were better than ecoregions at delineating regions of distinct land-surface form and geologic texture. Hydrologic-landscape regions and ecoregions were equally effective at defining regions in terms of climate, land cover, and water-quality characteristics. For about half of the landscape, climate, and water-quality characteristics, the R-squared values of square geometric regions were as high as hydrologic-landscape regions or ecoregions.

Toward a scientifically rigorous basis for developing mapped ecological regions.

Despite the wide use of ecological regions in conservation and resource-management evaluations and assessments, a commonly accepted theoretical basis for ecological regionalization does not exist. This fact, along with the paucity of focus on ecological regionalization by professional associations, journals, and faculties, has inhibited the advancement of a broadly acceptable scientific basis for the development, use, and verification of ecological regions. The central contention of this article is that ecological regions should improve our understanding of geographic and ecological phenomena associated with biotic and abiotic processes occurring in individual regions and also of processes characteristic of interactions and dependencies among multiple regions. Research associated with any ecoregional framework should facilitate development of hypotheses about ecological phenomena and dominant landscape elements associated with these phenomena, how these phenomena are structured in space, and how they function in a hierarchy. Success in addressing the research recommendations outlined in this article cannot occur within an ad hoc, largely uncoordinated research environment. Successful implementation of this plan will require activities--coordination, funding, and education--that are both scientific and administrative in nature. Perhaps the most important element of an infrastructure to support the scientific work of ecoregionalization would be a national or international authority similar to the Water and Science Technology Board of the National Academy of Sciences.