Declining glacier cover drives changes in aquatic macroinvertebrate biodiversity in the Cordillera Blanca, Perú.

Ongoing climate change threatens the biodiversity of glacier-fed river ecosystems worldwide through shifts in water availability and timing, temperature, chemistry, and channel stability. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. This study quantified aquatic biodiversity responses to decreasing glacier cover in the Cordillera Blanca range of the Peruvian Andes. Ten rivers were studied along a gradient of decreasing glacier cover in the Parón, Huaytapallana, and Llanganuco basins, with a specific focus on macroinvertebrates and physicochemical parameters in both the dry and wet seasons. We found higher temperatures, more stable and lower turbidity rivers as glacier cover decreased, which were related significantly to higher local diversity and lower ß-diversity. Analysis of similarity revealed significant differences in the macroinvertebrate community among rivers with high, medium, or low glacier cover, illustrating turnover from specialists to generalists as glacial influence decreased. Redundancy analysis demonstrated that there were more species found to prefer stable beds and water temperatures in medium and low glacier cover in a catchment rivers. However, certain taxa in groups such as Paraheptagyia, Orthocladiinae, Anomalocosmoecus, and Limonia may be adapted to high glacial influence habitats and at risk of glacier retreat. Although species composition was different to other biomes, the Cordillera Blanca rivers showed similar benthic macroinvertebrate biodiversity responses to glacier retreat, supporting the hypothesis that climate change will have predictable effects on aquatic biodiversity in mountain ranges worldwide.

Climate-driven spatial and temporal patterns in peatland pool biogeochemistry.

Peatland pools are freshwater bodies that are highly dynamic aquatic ecosystems because of their small size and their development in organic-rich sediments. However, our ability to understand and predict their contribution to both local and global biogeochemical cycles under rapidly occurring environmental change is limited because the spatiotemporal drivers of their biogeochemical patterns and processes are poorly understood. We used (1) pool biogeochemical data from 20 peatlands in eastern Canada, the United Kingdom, and southern Patagonia and (2) multi-year data from an undisturbed peatland of eastern Canada, to determine how climate and terrain features drive the production, delivering and processing of carbon (C), nitrogen (N), and phosphorus (P) in peatland pools. Across sites, climate (24%) and terrain (13%) explained distinct portions of the variation in pool biogeochemistry, with climate driving spatial differences in pool dissolved organic C (DOC) concentration and aromaticity. Within the multi-year dataset, DOC, carbon dioxide (CO2 ), total N concentrations, and DOC aromaticity were highest in the shallowest pools and at the end of the growing seasons, and increased gradually from 2016 to 2021 in relation to a combination of increases in summer precipitation, mean air temperature for the previous fall, and number of extreme summer heat days. Given the contrasting effects of terrain and climate, broad-scale terrain characteristics may offer a baseline for the prediction of small-scale pool biogeochemistry, while broad-scale climate gradients and relatively small year-to-year variations in local climate induce a noticeable response in pool biogeochemistry. These findings emphasize the reactivity of peatland pools to both local and global environmental change and highlight their potential to act as widely distributed climate sentinels within historically relatively stable peatland ecosystems.

A global agenda for advancing freshwater biodiversity research.

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

Extreme flood disturbance effects on multiple dimensions of river invertebrate community stability.

Multidimensional analysis of community stability has recently emerged as an overarching approach to evaluating ecosystem response to disturbance. However, the approach has previously been applied only in experimental and modelling studies. We applied this concept to an 18-year time series (2000-2017) of macroinvertebrate community dynamics from a southeast Alaskan river to further develop and test the approach in relation to the effects of two extreme flood events occurring in 2005 (event 1) and 2014 (event 2). Five components of stability were calculated for pairs of pre- or post-event years. Individual components were tested for differences between pre- and post-event time periods. Stability components' pairwise correlations were assessed and ellipsoids of stability were developed for each time period and compared to a null model derived from the permuted dataset. Only one stability component demonstrated a significant difference between time periods. In contrast, 80% of moderate and significant correlations between stability components were degraded post-disturbance and significant changes to the form of stability ellipsoids were observed. Ellipsoids of stability for all periods after the initial disturbance (2005) were not different to the null model. Our results illustrate that the dimensionality of stability approach can be applied to natural ecosystem time-series data. The major increase in dimensionality of stability observed following disturbance potentially indicates significant shifts in the processes which drive stability following disturbance. This evidence improves our understanding of community response beyond what is possible through analysis of individual stability components.

Changes in EMG and movement velocity during a set to failure against different loads in the bench press exercise.

This study examined changes in movement velocity and surface electromyographic (sEMG) activity of the pectoralis major (PM) and triceps brachii (TB) muscles during the bench press exercise to failure against different loads. Fourteen men performed a set to failure with maximum intended velocity, against low (40%-1 repetition maximum-RM), moderate (60%-1RM), and heavy loads (80%-1RM). Number of repetitions, volume load, mean and peak velocity, and total time increased with decreasing load (40% > 60% > 80%, p < 0.01). sEMG comparisons between different loads were performed by matching time under tension at the initial, middle, and last part of the set. sEMG was higher in the middle and last repetitions, compared with the initial, for all loads in both muscles (p < 0.001). sEMG activity of both muscles was higher in the 60% and 80%-1RM conditions compared with the 40%1-RM (p < 0.007). Also, sEMG of both muscles was similar for the 60%-1RM and 80%-1RM loads at the initial, middle, and last repetitions, with the exception of the last repetitions for the TB muscle. In contrast, sEMG integrated activity was higher for the 40% 1-RM and 60% 1-RM (p < 0.01) compared with the 80% 1-RM load. Mean velocity loss at exhaustion and drop in sEMG median frequency were greater in the 40% and 60%-1RM compared with the 80%-1RM condition (p < 0.05). It was concluded that performing a set to exhaustion with maximum intended velocity using a load of 60% 1-RM combines the characteristics of the high average sEMG activity of heavier loads, and the high total integrated sEMG observed at lighter loads.

Potentiation of Bench Press Throw Performance Using a Heavy Load and Velocity-Based Repetition Control.

ABSTRACT: Tsoukos, A, Brown, LE, Terzis, G, Veligekas, P, and Bogdanis, GC. Potentiation of bench press throw performance using a heavy load and velocity-based repetition control. J Strength Cond Res 35(2S): S72-S79, 2021-The acute effects of heavy load bench press exercise on subsequent bench press throw (BPT) performance and surface electromyographic (sEMG) activity were examined using movement velocity control. Eleven resistance-trained men completed 3 conditions in randomized and counterbalanced order. In 2 conditions, bench press was performed as fast as possible against a load of 80% of 1 repetition maximum, until mean velocity dropped to 90% (C90) or 70% (C70) of the fastest repetition. In the control condition, no bench press was performed. Single maximal BPT efforts were performed in all conditions after warm-up and throughout the 12 minutes of subsequent recovery. Mean propulsive velocity (MPV), peak velocity (PV), and sEMG activity of the prime mover muscles were measured during the BPT efforts. The total number of repetitions and volume load during bench press were significantly greater in C70 compared with C90 (6.5 ± 1.9 vs. 3.4 ± 0.9 repetitions and 557.8 ± 177.8 vs. 293.8 ± 95.7 kg, p < 0.01). In C90, MPV was increased 5.3-7.4% (p < 0.01) for a prolonged period (4-12 minutes), while in C70, MPV increased only at 10 minutes (+5.9%, p < 0.01) and 12 minutes (+4.3%, p < 0.01). Peak velocity was improved only in the C90 at 8-12th min by 3.6-4.7% (p ≤ 0.05). Surface electromyographic activity of the pectoralis major muscle was significantly greater than baseline at 10 minutes of recovery only in the C90 (p < 0.01). Performance gains may be optimized by taking into account the individual fatigue profiles, allowing a percentage drop of only 10% in movement velocity during the conditioning bench press exercise.

Trait-based ecology at large scales: Assessing functional trait correlations, phylogenetic constraints and spatial variability using open data.

The growing use of functional traits in ecological research has brought new insights into biodiversity responses to global environmental change. However, further progress depends on overcoming three major challenges involving (a) statistical correlations between traits, (b) phylogenetic constraints on the combination of traits possessed by any single species, and (c) spatial effects on trait structure and trait-environment relationships. Here, we introduce a new framework for quantifying trait correlations, phylogenetic constraints and spatial variability at large scales by combining openly available species' trait, occurrence and phylogenetic data with gridded, high-resolution environmental layers and computational modelling. Our approach is suitable for use among a wide range of taxonomic groups inhabiting terrestrial, marine and freshwater habitats. We demonstrate its application using freshwater macroinvertebrate data from 35 countries in Europe. We identified a subset of available macroinvertebrate traits, corresponding to a life-history model with axes of resistance, resilience and resource use, as relatively unaffected by correlations and phylogenetic constraints. Trait structure responded more consistently to environmental variation than taxonomic structure, regardless of location. A re-analysis of existing data on macroinvertebrate communities of European alpine streams supported this conclusion, and demonstrated that occurrence-based functional diversity indices are highly sensitive to the traits included in their calculation. Overall, our findings suggest that the search for quantitative trait-environment relationships using single traits or simple combinations of multiple traits is unlikely to be productive. Instead, there is a need to embrace the value of conceptual frameworks linking community responses to environmental change via traits which correspond to the axes of life-history models. Through a novel integration of tools and databases, our flexible framework can address this need.

Glacier shrinkage driving global changes in downstream systems.

Glaciers cover ∼10% of the Earth's land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how glacier shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that glacier-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by glacier shrinkage.

Caffeine's Effects on an Upper-Body Resistance Exercise Workout.

Salatto, RW, Arevalo, JA, Brown, LE, Wiersma, LD, and Coburn, JW. Caffeine's effects on an upper-body resistance exercise workout. J Strength Cond Res 34(6): 1643-1648, 2020-The purpose of this study was to examine the effects of caffeine on an upper-body resistance exercise workout. Fifteen men (mean ± SD: age, 23.1 ± 1.9 years; body mass, 89.1 ± 13.9 kg; height, 175 ± 6.1 cm) volunteered to come to the laboratory 3 times. During visit 1, 1-repetition maximum (RM) values were determined for the barbell bench press, incline barbell bench press, and dumbbell bench press exercises. For visit 2, subjects consumed either 800-mg caffeine or a placebo. Subjects then completed 3 sets to failure of each exercise using 80% of their 1RM. Visit 3 was the same as visit 2; however, participants consumed the opposite treatment as visit 2. Various perceptual measures were recorded before, during, and after the workouts. The results indicated that participants completed significantly more repetitions per set for the barbell bench press (4.80 ± 2.66) and incline barbell bench press (4.91 ± 2.29) in the caffeine condition compared with the placebo condition (4.42 ± 2.56 and 4.36 ± 2.11, respectively). Higher arousal scores were found in the caffeine condition. For vigor, participants reported higher scores with caffeine before warming up (caffeine = 10.20 ± 4.11, placebo = 6.20 ± 3.23) and mid workout (caffeine = 13.53 ± 2.29, placebo = 11.13 ± 2.79). These results suggest that caffeine has an ergogenic effect on strength workout performance due, at least in part, to positive effects on workout perception. Athletes and recreational lifters may want to consider the ingestion of caffeine before a resistance exercise workout.

Sediment deposition from eroding peatlands alters headwater invertebrate biodiversity.

Land use and climate change are driving widespread modifications to the biodiverse and functionally unique headwaters of rivers. In temperate and boreal regions, many headwaters drain peatlands where land management and climate change can cause significant soil erosion and peat deposition in rivers. However, effects of peat deposition in river ecosystems remain poorly understood. We provide two lines of evidence-derived from sediment deposition gradients in experimental mesocosms (0-7.5 g/m2 ) and headwaters (0.82-9.67 g/m2 )-for the adverse impact of peat deposition on invertebrate community biodiversity. We found a consistent negative effect of sediment deposition across both the experiment and survey; at the community level, decreases in density (1956 to 56 individuals per m2 in headwaters; mean 823 ± 129 (SE) to 288 ± 115 individuals per m2 in mesocosms) and richness (mean 12 ± 1 to 6 ± 2 taxa in mesocosms) were observed. Sedimentation increased beta diversity amongst experimental replicates and headwaters, reflecting increasing stochasticity amongst tolerant groups in sedimented habitats. With increasing sedimentation, the density of the most common species, Leuctra inermis, declined from 290 ± 60 to 70 ± 30 individuals/m2 on average in mesocosms and >800 individuals/m2 to 0 in the field survey. Traits analysis of mesocosm assemblages suggested biodiversity loss was driven by decreasing abundance of invertebrates with trait combinations sensitive to sedimentation (longer life cycles, active aquatic dispersal of larvae, fixed aquatic eggs, shredding feeding habit). Functional diversity metrics reinforced the idea of more stochastic community assembly under higher sedimentation rates. While mesocosm assemblages showed some compositional differences to surveyed headwaters, ecological responses were consistent across these spatial scales. Our results suggest short-term, small-scale stressor experiments can inform understanding of "real-world" peatland river ecosystems. As climate change and land-use change are expected to enhance peatland erosion, significant alterations to invertebrate biodiversity can be expected where these eroded soils are deposited in rivers.

Periodized versus Non-periodized Stretch Training on Gymnasts Flexibility and Performance.

Static stretching (SS) can increase joint range of motion (ROM), due to neural, morphological, and physio-psychological factors. Periodized training programs (PD) (e. g., strength, power) are adopted to induce greater adaptations while avoiding overtraining. However, the effectiveness of periodized stretch training adaptations are unknown. Therefore, the objective of this study was to compare the effects of periodized and non-periodized (NP) stretching programs on flexibility, hamstrings stiffness and muscle performance. Sixteen gymnasts were allocated to either periodized or non-periodized SS training and tested pre- and post-8 weeks for countermovement jump height, hip flexors, hip extensors and dorsiflexors ROM, hamstrings stiffness and hamstrings and quadriceps peak torque. Both stretch training groups significantly and similarly increased hip extensor (33.2%), hip flexor (25.2%), and dorsiflexor (23.8%) ROM, hamstrings peak torque (7.9%) and jump height (8.1%) from pre - to post- training. Both groups decreased hamstrings stiffness across the last ten angles (32.1%). PD elicited consistently large magnitude flexibility effect size changes compared to small and moderate magnitude changes for the non-periodized. Therefore, 8-week PD and NP SS programs can decrease young gymnasts' muscle-tendon stiffness and increase muscle performance. However, effect sizes indicate that PD stretch training was more advantageous to increasing flexibility and improving performance.

Upper and Lower Body Power Are Strong Predictors for Selection of Male Junior National Volleyball Team Players.

Tsoukos, A, Drikos, S, Brown, LE, Sotiropoulos, K, Veligekas, P, and Bogdanis, GC. Upper and lower body power are strong predictors for selection of male junior National volleyball team players. J Strength Cond Res 33(10): 2760-2767, 2019-The purpose of this study was to determine whether a battery of anthropometric and lower and upper body strength and speed and power tests predicted selection of young volleyball players for a Junior National Team by expert coaches. Fifty-two male junior volleyball players (14.8 ± 0.5 years, height: 1.84 ± 0.05 m, body mass: 72.5 ± 7.1 kg) took part in a training camp and underwent a selection procedure by expert coaches' of the junior national team. Anthropometric data and fitness tests results were obtained and players were graded on a scale from 0 to 100 on the basis of their performance in a volleyball tournament. Selected players were superior in the majority of measured variables (p ≤ 0.017) and had higher grading scores compared with nonselected players (85.3 ± 4.1 vs. 70.5 ± 5.6, respectively, p < 0.01). The combination of spike jump and reach (SJR) test and 3-kg medicine ball throw (MB3) velocity explained 63.5% of the variance in expert coaches' grading (p < 0.001). A multivariate discriminant analysis yielded a significant discriminant function (Wilk's lambda = 0.55, χ = 29.324, p < 0.001, η = 0.82). Spike jump and reach and MB3 were the only variables that contributed to the discriminant function (standardized function coefficients: SJR = 0.68, MB3 = 0.67). Cross-validation results showed that selection was correctly predicted in 14 of the 16 selected players (predictive accuracy: 87.5%) and in 32 of the 36 nonselected players (predictive accuracy: 88.9%). The SJR and MB3 fitness tests can predict a large portion of the variance of expert coaches' grading and successfully discriminate elite young male volleyball players for selection vs. nonselection for a junior national team. This result is very important as performance testing during a selection process may be reduced to only 2 measurements.

Comparison Between Unilateral and Bilateral Plyometric Training on Single- and Double-Leg Jumping Performance and Strength.

Bogdanis, GC, Tsoukos, A, Kaloheri, O, Terzis, G, Veligekas, P, and Brown, LE. Comparison between unilateral and bilateral plyometric training on single- and double-leg jumping performance and strength. J Strength Cond Res 33(3): 633-640, 2019-This study compared the effects of unilateral and bilateral plyometric training on single- and double-leg jumping performance, maximal strength, and rate of force development (RFD). Fifteen moderately trained subjects were randomly assigned to either a unilateral (U, n = 7) or bilateral group (B, n = 8). Both groups performed maximal effort plyometric leg exercises 2 times per week for 6 weeks. The B group performed all exercises with both legs, whereas the U group performed half the repetitions with each leg, so that total exercise volume was the same. Jumping performance was assessed by countermovement jumps (CMJs) and drop jumps (DJs), whereas maximal isometric leg press strength and RFD were measured before and after training for each leg separately and both legs together. Countermovement jump improvement with both legs was not significantly different between U (12.1 ± 7.2%) and B (11.0 ± 5.5%) groups. However, the sum of right- and left-leg CMJ only improved in the U group (19.0 ± 7.1%, p < 0.001) and was unchanged in the B group (3.4 ± 8.4%, p = 0.80). Maximal isometric leg press force with both legs was increased similarly between groups (B: 20.1 ± 6.5%, U: 19.9 ± 6.2%). However, the sum of right- and left-leg maximal force increased more in U compared with B group (23.8 ± 9.1% vs. 11.9 ± 6.2%, p = 0.009, respectively). Similarly, the sum of right- and left-leg RFD0-50 and RFD0-100 were improved only in the U group (34-36%, p < 0.01). Unilateral plyometric training was more effective at increasing both single- and double-leg jumping performance, isometric leg press maximal force, and RFD when compared with bilateral training.

Declining glacier cover threatens the biodiversity of alpine river diatom assemblages.

Climate change poses a considerable threat to the biodiversity of high altitude ecosystems worldwide, including cold-water river systems that are responding rapidly to a shrinking cryosphere. Most recent research has demonstrated the severe vulnerability of river invertebrates to glacier retreat but effects upon other aquatic groups remain poorly quantified. Using new data sets from the European Alps, we show significant responses to declining glacier cover for diatoms, which play a critical functional role as freshwater primary producers. Specifically, diatom α-diversity and density in rivers presently fed by glaciers will increase with future deglaciation, yet ß-diversity within and between sites will reduce because declining glacier influence will lower the spatiotemporal variability of glacier cover and its associated habitat heterogeneity. Changes in diatom assemblage composition as glacier cover declined were associated strongly with increasing riverbed stability and water temperature. At the species level, diatoms showed a gradation of responses; for example, Eunotia trinacria, found exclusively at river sites with high (≥52%) catchment glacier cover, may be affected negatively by ice loss. Conversely, seven taxa confined to sites with no glacier cover, including Gomphonema calcareum, stand to benefit. Nineteen (22%) taxa were noted as threatened, endangered, rare or decreasing on the Red List of Algae for Germany, with most at sites ≤26% glacier cover, meaning further ice loss may benefit these diatoms. However, six taxa found only in rivers ≥28% glacier cover may require reclassification of their Red List conservation status, as this habitat is threatened by deglaciation. Our identification of clear links between decreasing glacier cover and river diatom biodiversity suggests there could be significant reorganization of river ecosystems with deglaciation, for example, through alterations to primary production, biogeochemical cycles, and the shifting resource base of alpine freshwater food webs which lack significant allochthonous energy inputs.

Muscle health and performance in monozygotic twins with 30 years of discordant exercise habits.

INTRODUCTION: Physical health and function depend upon both genetic inheritance and environmental factors (e.g., exercise training). PURPOSE: To enhance the understanding of heritability/adaptability, we explored the skeletal muscle health and physiological performance of monozygotic (MZ) twins with > 30 years of chronic endurance training vs. no specific/consistent exercise. METHODS: One pair of male MZ twins (age = 52 years; Trained Twin, TT; Untrained Twin, UT) underwent analyses of: (1) anthropometric characteristics and blood profiles, (2) markers of cardiovascular and pulmonary health, and (3) skeletal muscle size, strength, and power and molecular markers of muscle health. RESULTS: This case study represents the most comprehensive physiological comparison of MZ twins with this length and magnitude of differing exercise history. TT exhibited: (1) lower body mass, body fat%, resting heart rate, blood pressure, cholesterol, triglycerides, and plasma glucose, (2) greater relative cycling power, anaerobic endurance, and aerobic capacity (VO2max), but lower muscle size/strength and poorer muscle quality, (3) more MHC I (slow-twitch) and fewer MHC IIa (fast-twitch) fibers, (4) greater AMPK protein expression, and (5) greater PAX7, IGF1Ec, IGF1Ea, and FN14 mRNA expression than UT. CONCLUSIONS: Several measured differences are the largest reported between MZ twins (TT expressed 55% more MHC I fibers, 12.4 ml/kg/min greater VO2max, and 8.6% lower body fat% vs. UT). These data collectively (a) support utilizing chronic endurance training to improve body composition and cardiovascular health and (b) suggest the cardiovascular and skeletal muscle systems exhibit greater plasticity than previously thought, further highlighting the importance of studying MZ twins with large (long-term) differences in exposomes.

Different Muscle Action Training Protocols on Quadriceps-Hamstrings Neuromuscular Adaptations.

The aim of this study was to compare three specific concentric and eccentric muscle action training protocols on quadriceps-hamstrings neuromuscular adaptations. Forty male volunteers performed 6 weeks of training (two sessions/week) of their dominant and non-dominant legs on an isokinetic dynamometer. They were randomly assigned to one of four groups; concentric quadriceps and concentric hamstrings (CON/CON, n=10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n=10), concentric quadriceps and eccentric hamstrings (CON/ECC, n=10), or no training (CTRL, n=10). Intensity of training was increased every week by decreasing the angular velocity for concentric and increasing it for eccentric groups in 30°/s increments. Volume of training was increased by adding one set every week. Dominant leg quadriceps and hamstrings muscle thickness, muscle quality, muscle activation, muscle coactivation, and electromechanical delay were tested before and after training. Results revealed that all training groups similarly increased MT of quadriceps and hamstrings compared to control (p<0.05). However, CON/ECC and ECC/ECC training elicited a greater magnitude of change. There were no significant differences between groups for all other neuromuscular variables (p>0.05). These findings suggest that different short-term muscle action isokinetic training protocols elicit similar muscle size increases in hamstrings and quadriceps, but not for other neuromuscular variables. Nevertheless, effect sizes indicate that CON/ECC and ECC/ECC may elicit the greatest magnitude of change in muscle hypertrophy.

Delayed Effects of a Low-Volume, Power-Type Resistance Exercise Session on Explosive Performance.

Tsoukos, A, Veligekas, P, Brown, LE, Terzis, G, and Bogdanis, GC. Delayed effects of a low-volume, power-type resistance exercise session on explosive performance. J Strength Cond Res 32(3): 643-650, 2018-This study examined the delayed effects of a power-type training session on explosive performance. Seventeen well-trained male power and team sport athletes (age: 22.7 ± 5.5 years, height: 181 ± 8 cm, body mass: 80.7 ± 8.6 kg, body fat: 9.2 ± 1.7%, 1 repetition maximum (1RM) half-squat: 163 ± 29 kg) performed 4 sessions (2 experimental and 2 control) 1 week apart in a randomized and counterbalanced order. Explosive performance was assessed before, 24 and 48 hours after a low-volume, power-type training session (5 × 4 jump squats at 40% 1RM with 3 minutes rest), as well as before and after 24 and 48 hours of rest (control). Dependent variables were as follows: countermovement jump (CMJ), reactive strength index (RSI) during a drop jump, leg press maximum isometric force, and rate of force development (RFD) at 3 time windows: 0-100, 0-200, and 0-300 milliseconds. Analysis of variance revealed no changes in the control conditions. In contrast after training, CMJ was improved by 5.1 ± 1.0% and 3.0 ± 1.0% at 24 and 48 hours, respectively, compared with baseline. The RSI improved by 10.7 ± 2.1% only at 24 hours. The RFD increased at all time windows at 24 hours (range of improvement: 9.7 ± 3.4% to 18.3 ± 4.1%, p < 0.01). However, at 48 hours, improvement was only seen in RFD0-100 (9.8 ± 3.1%, p < 0.01). These findings suggest that a low-volume, power-type training session results in delayed enhancement of explosive muscle performance, which is greatest at 24 hours after the activity. Athletes are advised to perform power-type training 1 day before competition or a high-quality training session to improve their performances.

Effect of Three Different Muscle Action Training Protocols on Knee Strength Ratios and Performance.

Ruas, CV, Brown, LE, Lima, CD, Costa, PB, and Pinto, RS. Effect of three different muscle action training protocols on knee strength ratios and performance. J Strength Cond Res 32(8): 2154-2165, 2018-Hamstring to quadriceps (H:Q) ratios are often used to assess strength imbalances. The aims of this study were to compare 3 different muscle action training protocols on H:Q strength balance and functional performance. Forty untrained men (age: 22.87 ± 2.28 years, mass: 70.66 ± 11.049 kg, ht: 174.29 ± 6.90 cm) performed 6 weeks of training on an isokinetic dynamometer. They were randomly assigned to one of 4 groups; concentric quadriceps and concentric hamstring (CON/CON), eccentric quadriceps and eccentric hamstring (ECC/ECC), concentric quadriceps and eccentric hamstring (CON/ECC), or no training. Mixed Factor analyses of variance were used to compare interactions for variables pretest and posttest between groups (p ≤ 0.05). The ECC/ECC group showed significant increases in H:Q functional ratio (pre = 0.73 ± 0.092, post = 0.87 ± 0.098), ECC peak torque (PT) (pre = 226.44 ± 67.80 N·m, post = 331.74 ± 54.44 N·m), isometric PT (IPT) (pre = 173.69 ± 41.41 N·m, post = 203.091 ± 30.82 N·m), countermovement jump (CMJ) (pre = 52.73 ± 6.95 cm, post = 58.16 ± 6.10 cm), and drop jump (DJ) (pre = 52.91 ± 6.080 cm, post = 58.20 ± 7.72 cm), whereas the CON/CON group increased the rate of torque development (pre = 152.19 ± 65.0074 N·m·s, post = 225.26 ± 88.80 N·m·s). There were no differences between groups for CON PT, squat jump, conventional ratio or 40 m sprint. Our findings suggest that ECC/ECC training may be the most effective at increasing functional H:Q strength ratios, as well as ECC PT, IPT, CMJ, and DJ performance. Eccentric training increases ECC PT, thereby increasing the functional H:Q ratio. Eccentric training also improves vertical jumping involving ECC actions. CON/CON training may be more effective at increasing explosive muscle strength.

The Multitrophic Effects of Climate Change and Glacier Retreat in Mountain Rivers.

Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-melt inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. Glacier-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric-cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing glacier cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to glacier retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the potential to identify and protect a wider range of sensitive and threatened species.

Antagonistic effects of biological invasion and environmental warming on detritus processing in freshwater ecosystems.

Global biodiversity is threatened by multiple anthropogenic stressors but little is known about the combined effects of environmental warming and invasive species on ecosystem functioning. We quantified thermal preferences and then compared leaf-litter processing rates at eight different temperatures (5.0-22.5 °C) by the invasive freshwater crustacean Dikerogammarus villosus and the Great Britain native Gammarus pulex at a range of body sizes. D. villosus preferred warmer temperatures but there was considerable overlap in the range of temperatures that the two species occupied during preference trials. When matched for size, G. pulex had a greater leaf shredding efficiency than D. villosus, suggesting that invasion and subsequent displacement of the native amphipod will result in reduced ecosystem functioning. However, D. villosus is an inherently larger species and interspecific variation in shredding was reduced when animals of a representative size range were compared. D. villosus shredding rates increased at a faster rate than G. pulex with increasing temperature suggesting that climate change may offset some of the reduction in function. D. villosus, but not G. pulex, showed evidence of an ability to select those temperatures at which its shredding rate was maximised, and the activation energy for shredding in D. villosus was more similar to predictions from metabolic theory. While per capita and mass-corrected shredding rates were lower in the invasive D. villosus than the native G. pulex, our study provides novel insights in to how the interactive effects of metabolic function, body size, behavioural thermoregulation, and density produce antagonistic effects between anthropogenic stressors.