Time Course of Neuromuscular Fatigue During Different Resistance Exercise Loadings in Power Athletes, Strength Athletes, and Nonathletes.

ABSTRACT: Kotikangas, J, Walker, S, Peltonen, H, and Häkkinen, K. Time course of neuromuscular fatigue during different resistance exercise loadings in power athletes, strength athletes, and nonathletes. J Strength Cond Res 38(7): 1231-1242, 2024-Training background may affect the progression of fatigue and neuromuscular strategies to compensate for fatigue during resistance exercises. Thus, our aim was to examine how training background affects the time course of neuromuscular fatigue in response to different resistance exercises. Power athletes (PA, n = 8), strength athletes (SA, n = 8), and nonathletes (NA, n = 7) performed hypertrophic loading (HL, 5 × 10 × 10RM), maximal strength loadings (MSL, 7 × 3 × 3RM) and power loadings (PL, 7 × 6 × 50% of 1 repetition maximum) in back squat. Average power (AP), average velocity (VEL), surface electromyography (sEMG) amplitude (sEMGRMS), and sEMG mean power frequency (sEMGMPF) were measured within all loading sets. During PL, greater decreases in AP occurred from the beginning of SET1 to SET7 and in VEL to both SET4 and SET7 in NA compared with SA (p < 0.01, g > 1.84). During HL, there were various significant group × repetition interactions in AP within and between sets (p < 0.05, ηp2 > 0.307), but post hoc tests did not indicate significant differences between the groups (p > 0.05, g = 0.01-0.93). During MSL and HL, significant within-set and between-set decreases occurred in AP (p < 0.001, ηp2 > 0.701) and VEL (p < 0.001, ηp2 > 0.748) concurrently with increases in sEMGRMS (p < 0.01, ηp2 > 0.323) and decreases in sEMGMPF (p < 0.01, ηp2 > 0.242) in all groups. In conclusion, SA showed fatigue resistance by maintaining higher AP and VEL throughout PL. During HL, PA tended to have the greatest initial fatigue response in AP, but between-group comparisons were nonsignificant despite large effect sizes (g > 0.8). The differences in the progression of neuromuscular fatigue may be related to differing neural activation strategies between the groups, but further research confirmation is required.

Two-week step-reduction has limited negative effects on physical function and metabolic health in older adults.

PURPOSE: This study determined the effects of a 2-week step-reduction period followed by 4-week exercise rehabilitation on physical function, body composition, and metabolic health in 70-80-year-olds asymptomatic for injury/illness. METHODS: A parallel-group randomized controlled trial (ENDURE-study, NCT04997447) was used, where 66 older adults (79% female) were randomized to either intervention or control group. The intervention group reduced daily steps to < 2000, monitored by accelerometer, for two weeks (Period I) and then step-reduction requirement was removed with an additional exercise rehabilitation 4 times per week for 4 weeks (Period II). The control group continued their habitual physical activity throughout with no additional exercise intervention. Laboratory tests were performed at baseline, after Period I and Period II. The primary outcome measure was leg lean mass (LLM). Secondary outcomes included total lean and fat mass, blood glucose and insulin concentration, LDL cholesterol and HDL cholesterol concentration, maximal isometric leg press force (MVC), and chair rise and stair climb performance. RESULTS: LLM remained unchanged in both groups and no changes occurred in physical function nor body composition in the intervention group in Period I. HDL cholesterol concentration reduced after Period I (from 1.62 ± 0.37 to 1.55 ± 0.36 mmol·L-1, P = 0.017) and returned to baseline after Period II (1.66 ± 0.38 mmol·L-1) in the intervention group (Time × Group interaction: P = 0.065). MVC improved after Period II only (Time × Group interaction: P = 0.009, Δ% = 15%, P < 0.001). CONCLUSION: Short-term step-reduction in healthy older adults may not be as detrimental to health or physical function as currently thought.

Acute Neuromuscular and Hormonal Responses to Power, Strength, and Hypertrophic Protocols and Training Background.

This study investigated how two slightly different athlete groups would differ in acute neuromuscular and endocrine responses to specific resistance exercise loadings and recovery compared to untrained participants. Power athletes (PA, n = 8), strength athletes (SA, n = 8) and non-athletes (NA, n = 7) performed power (PL, 7 × 6 × 50% of 1RM), maximal strength (MSL, 7 × 3 × 3RM), and hypertrophic (HL, 5 × 10 × 10RM) loadings in Smith-machine back-squat. Neuromuscular performance, serum testosterone, growth hormone, and cortisol concentrations, and blood lactate (BL) were measured before (Pre), at Mid and after (Post) loading, and after recovery for 24 and 48 h. All loadings led to acute decreases in neuromuscular performance and elevations in hormone concentrations and BL. During PL, a significant group × time interactions occurred in maximal isometric force [F (4, 40) = 4.189, p = 0.006, η p 2 = 0.295] indicating a greater decrease in PA compared to SA from Pre to Mid (p < 0.05), and in countermovement jump height [F (4, 40) = 2.895, p = 0.034, η p 2 = 0.224] indicating a greater decrease in NA compared to SA from Pre to Mid (p < 0.05). During HL, growth hormone was higher in Mid and Post in SA compared to NA (p < 0.05). No significant interactions were found during recovery. The differences during PL and HL suggest that the training background may enhance acute responses during the present loadings, whereas it seemed to have a limited effect on the recovery.

Responses of coastal fishery resources to rapid environmental changes.

Coastal systems experience strong impacts of ongoing environmental change, affecting fish communities and subsequently fishery yields. In the Baltic Sea, the combined effects of climate-induced changes and eutrophication-related pressures constitute major threats to its living resources. Although much work has been devoted to uncovering environmental impacts on the commercially most valuable fish stocks, only little is known about community-wide responses of fished species and how environmental change may affect their yield. In this study, the authors use a joint species distribution modelling framework to disentangle environmental impacts on species-specific fishery yields of 16 fished species along the coast of Finland over four decades. The authors show that environmental covariates substantially contributed to variations in fishery yields and are likely to have strong impacts on fished resources also in the future. Salinity and near-bottom oxygen concentration emerged as the strongest environmental drivers of yields at the community level, whereas temperature was particularly important for cod (Gadus morhua) and sprat (Sprattus sprattus) yields. The authors found shore density to be an important predictor for fisheries resources especially for freshwater fish. The results of this study suggest that the changes in environmental conditions during the past four decades had a positive effect on the yields of freshwater and warm-affinity species, whereas yields of marine cold-affinity species have been mainly negatively affected by contracting favourable habitats, becoming warmer and less saline.

Power Loading-Induced Fatigue Is Influenced by Menstrual Cycle Phase.

PURPOSE: This study aimed to examine the effects of fatiguing power loading on neuromuscular properties, force production, and metabolic capacities during four phases of the menstrual cycle (MC): menstruation (M), midfollicular (mid FOL), ovulation (OV), and midluteal (mid LUT). METHODS: Sixteen eumenorrheic women performed sessions of maximal explosive leg press (2 × 10 at 60% one-repetition maximum load with 2-min recovery between sets). Serum hormones and neuromuscular responses were measured. RESULTS: The loading protocol significantly decreased power (between -14.2% and -12.5%; P < 0.001) and maximal force production (between maximum voluntary force (MVC); -15.0% and -7.8%; P < 0.001-0.05), while decreasing activation level (between AL; -6.9% and -2.2%; P < 0.001-0.05) in all MC phases. The decreases in AL were greater during mid LUT (P < 0.01) compared with OV. Changes in MVC and AL were associated (r2 = 0.53; P < 0.01) at all MC phases. The decrease in EMG during MVC did not differ between the MC phases; however, mean power frequency was higher during M (+7.7%; P < 0.05) and mid LUT (+3.1%; P < 0.05) compared with OV (-7.5%). Resting twitch force decreased during mid FOL (-6.9%; P < 0.05) and mid LUT (-16.2%; P < 0.001), and these values were significantly decreased (P < 0.05) compared with OV. In addition, resting twitch force at mid LUT was lower (P < 0.01) compared with M. Blood lactate levels increased more (P < 0.05) during M compared with mid LUT. Some serum hormone concentrations were associated with fatigue-induced changes in neuromuscular properties and force production, but these correlations behaved differently between the MC phases. CONCLUSIONS: OV may offer a more favorable hormonal milieu for acute neural responses, whereas mid FOL and mid LUT seem to be superior for acute muscular responses.

Integrating diverse model results into decision support for good environmental status and blue growth.

Sustainable environmental management needs to consider multiple ecological and societal objectives simultaneously while accounting for the many uncertainties arising from natural variability, insufficient knowledge about the system's behaviour leading to diverging model projections, and changing ecosystem. In this paper we demonstrate how a Bayesian network- based decision support model can be used to summarize a large body of research and model projections about potential management alternatives and climate scenarios for the Baltic Sea. We demonstrate how this type of a model can act as an emulator and ensemble, integrating disciplines such as climatology, biogeochemistry, marine and fisheries ecology as well as economics. Further, Bayesian network models include and present the uncertainty related to the predictions, allowing evaluation of the uncertainties, precautionary management, and the explicit consideration of acceptable risk levels. The Baltic Sea example also shows that the two biogeochemical models frequently used in future projections give considerably different predictions. Further, inclusion of parameter uncertainty of the food web model increased uncertainty in the outcomes and reduced the predicted manageability of the system. The model allows simultaneous evaluation of environmental and economic goals, while illustrating the uncertainty of predictions, providing a more holistic view of the management problem.

Influence of Menstrual Cycle or Hormonal Contraceptive Phase on Physiological Variables Monitored During Treadmill Testing.

Purpose: To examine the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on physiological variables monitored during incremental treadmill testing in physically active women (eumenorrheic, EUM = 16 and monophasic HC-users, CHC = 12). Methods: Four running tests to exhaustion were performed at bleeding, mid follicular (mid FOL)/active 1, ovulation/active 2, and mid luteal (mid LUT)/inactive. HC and MC phases were confirmed from serum hormones. Heart rate (HR), blood lactate (Bla), and V ˙ O2 were monitored, while aerobic (AerT) and anaerobic (AnaT) thresholds were determined. V ˙ O2peak, maximal running speed (RUNpeak), and total running time (RUNtotal) were recorded. Results: No significant changes were observed in V ˙ O2 or Bla at AerT or AnaT across phases in either group. At maximal effort, absolute and relative V ˙ O2peak, RUNpeak, and RUNtotal remained stable across phases in both groups. No significant fluctuations in HRmax were observed across phases, but HR at both AerT and AnaT tended to be lower in EUM than in CHC across phases. Conclusion: Hormonal fluctuations over the MC and HC do not systematically influence physiological variables monitored during incremental treadmill testing. Between group differences in HR at AerT and AnaT underline why HR-based training should be prescribed individually, while recording of MC or HC use when testing should be encouraged as phase may explain minor, but possibly meaningful, changes in, e.g., Bla concentrations or differences in HR response.

Resistance Training Induces Antiatherogenic Effects on Metabolomic Pathways.

INTRODUCTION: Arising evidence suggests that resistance training has the potential to induce beneficial modulation of biomarker profile. To date, however, only immediate responses to resistance training have been investigated using high-throughput metabolomics whereas the effects of chronic resistance training on biomarker profile have not been studied in detail. METHODS: A total of 86 recreationally active healthy men without previous systematic resistance training background were allocated into (i) a resistance training (RT) group (n = 68; age, 33 ± 7 yr; body mass index, 28 ± 3 kg·m) and (ii) a non-RT group (n = 18; age, 31 ± 4 yr; body mass index, 27 ± 3 kg·m). Blood samples were collected at baseline (PRE), after 4 wk (POST-4wk), and after 16 wk of resistance training intervention (POST-16wk), as well as baseline and after the non-RT period (20-24 wk). Nuclear magnetic resonance-metabolome platform was used to determine metabolomic responses to chronic resistance training. RESULTS: Overall, the resistance training intervention resulted in favorable alterations (P < 0.05) in body composition with increased levels of lean mass (~2.8%), decreased levels of android (~9.6%), and total fat mass (~7.5%). These changes in body composition were accompanied by antiatherogenic alterations in serum metabolome profile (false discovery rate < 0.05) as reductions in non-high-density lipoprotein cholesterol (e.g., free cholesterol, remnant cholesterol, intermediate-density lipoprotein cholesterols, low-density lipoprotein cholesterols) and related apolipoprotein B, and increments in conjugated linoleic fatty acids levels were observed. Individuals with the poorest baseline status (i.e., body composition, metabolome profile) benefitted the most from the resistance training intervention. CONCLUSIONS: In conclusion, resistance training improves cardiometabolic risk factors and serum metabolome even in previously healthy young men. Thus, suggesting attenuated risk for future cardiovascular disease.

Increased rate of force development during periodized maximum strength and power training is highly individual.

Maximum strength training induces various improvements in the rate of force development (RFD) on a group level, but no study has investigated inter-individual adaptations in RFD. Fourteen men (28 ± 6 years old) performed the same 10-week maximum strength and then a 10-week power training program. Maximal force and RFD were recorded during maximal isometric leg extension voluntary contractions repeatedly before every 7th training session (2 sessions/week). After the intervention, subjects were retrospectively divided into three groups based on their RFD improvements: (1) improved only during the maximum strength period (MS-responders, + 100 ± 35%), (2) improved only during the power period (P-responders, + 53 ± 27%) or (3) no improvement at all (non-responders, + 3 ± 9%). All groups increased dynamic 1RM equally, but baseline 1RM was greater (p < 0.05) in responder vs non-responder groups. MS-responders had higher electrical stimulation-induced torque at baseline and they improved (+ 35 ± 28%) power production at 50% 1RM load more than P- (- 7 ± 20%, p = 0.052) and non-responders (+ 3 ± 6%, p = 0.066) during the maximum strength training period. MS-responders increased vastus lateralis cross-sectional area (+ 12 ± 9%, p < 0.01) as did P-responders (+ 10 ± 7%, p = 0.07), whereas non-responders were unchanged. Free androgen index (FAI) in responders was higher (+ 34%, p < 0.05) compared to non-responders at baseline. The maximum strength period decreased testosterone (- 17 ± 12; 17 ± 22%), FAI ratio (- 12 ± 14; - 21 ± 23%) and testosterone/cortisol ratio (- 17 ± 25; - 31 ± 20%) in MS and P-responders, respectively. During the P-period hormonal levels plateaued. To conclude, periodized strength training induced different inter-individual physiological responses, and thus RFD development may vary between individuals. Therefore, RFD seems to be a useful tool for planning and monitoring strength training programs for individual neuromuscular performance needs.

Inflammation status of healthy young men: initial and specific responses to resistance training.

Our primary aim was to study the effects of a 4-week preparatory resistance-training (RT) period followed by 12 weeks of 2 specific RT protocols (either hypertrophic-strength (HS) or strength-hypertrophy-power training) on inflammation markers and the possible relationship of the changes in abdominal fat and lean mass to the changes in inflammation status. A total of 82 healthy men were included in the study. Maximal concentric leg press strength (1-repetition maximum), total body lean mass, total body and abdominal fat mass, circulating high-sensitivity C-reactive protein, interleukin-6, interleukin-1 receptor antagonist (IL-1ra), monocyte chemoattractant protein 1 (MCP-1), and selected adipocytokines (resistin, adiponectin, and leptin) concentrations were measured before and after 4 (wk4) and 16 weeks (wk16) of RT. After the initial phase of RT, on wk4, abdominal and total fat mass as well as plasma leptin concentrations were significantly reduced (p < 0.05), whereas muscle mass, IL-1ra, resistin, and MCP-1 concentrations were significantly increased (p < 0.05). During specialized training phase, at wk16, only HS led to further reduction in abdominal and total fat mass, resistin, and leptin (p < 0.05), whereas both training modes led to lower MCP-1 concentrations (p < 0.05). Abdominal fat mass and circulating leptin were reduced already after 4 weeks of RT. Simultaneously, circulating MCP-1 and resistin concentrations increased, possibly as markers of muscle adaptation and regeneration. The present findings also suggest that RT with hypertrophic focus is beneficial for further reductions in abdominal fat mass and to decrease circulating inflammatory markers.

Isometric parameters in the monitoring of maximal strength, power, and hypertrophic resistance-training.

This study monitored strength-training adaptations via isometric parameters throughout 2 × 10 weeks of hypertrophic (HYP I-II) or 10 weeks maximum strength (MS) followed by 10 weeks power (P) training with untrained controls. Trainees performed bilateral isometric leg press tests analyzed for peak force (maximal voluntary contraction (MVC)) and rate of force development (RFD) every 3.5 weeks. These parameters were compared with dynamic performance, voluntary and electrically induced isometric contractions, muscle activity, and cross-sectional area (CSA) in the laboratory before and after 10 and 20 weeks. RFD increased similarly during the first 7 weeks (HYP I, 44% ± 53%; MS, 48% ± 55%, P < 0.05), but RFD continued to increase up to 65% ± 61% from baseline (P < 0.01) only during P. These increases were concomitant with enhanced dynamic performances of 1-repetition maximum (1RM) (HYP I, 8% ± 6%; MS, 11% ± 6%, P < 0.001), and explosive repetitions during P (11% ± 15%, P < 0.05). Time to reach peak RFD differed (P < 0.001) between HYP (mean 42 ± 20 ms) and MS-P (mean 31 ± 12 ms) groups because of training. The changes in MVC correlated with the changes in CSA during weeks 1-20 (HYP I-II, r = 0.664; MS-P, r = 0.595, P ≤ 0.05), as well as changes in 1RM (r = 0.724, P < 0.05) during weeks 11-20 (HYP II). Muscle activity increased during MS and P only. Both MVC and RFD improvements reflected combinations of central and peripheral adaptations. RFD parameters may be effective tools to evaluate adaptations, particularly during maximal strength/power training, while MVC cannot distinguish between strength or muscle mass changes. Monitoring RFD provided important information regarding plateaus in RFD improvement, which were observed in dynamic explosive performances after HYP II compared with P.

Resistance training status modifies inflammatory response to explosive and hypertrophic resistance exercise bouts

The purpose of the present study was to examine the immediate and prolonged immune response in circulating cytokine and adipocytokine concentrations after two different resistance exercise bouts: hypertrophic (HYP1, 5 × 10, 80% of 1RM) and maximal explosive (POW1, 10 × 5, 60% of 1RM) resistance exercise bouts and how 12 weeks of resistance training (RT) modifies these responses (HYP2, POW2). Eight men completed the study. RE-induced interleukin-6 (IL-6), interleukin-1 Beta (IL-1Beta), interleukin-1 receptor antagonist (IL-1ra), monocyte-chemoattractant protein-1 (MCP-1), leptin, resistin, and adiponectin were measured before (PRE) and immediately (POST0), 24 (POST24) and 48 (POST48) hours after RE bouts before and after RT. In the untrained state, IL-6 increased immediately after RE in HYP1 (p = 0.002) and in POW1 (p = 0.003) whereas no changes were observed after RT. Similar results were observed in IL-1Beta, whereas conversely, IL-1ra increased only after RT in HYP2 and POW2 (p < 0.05). Resistin increased before RT in HYP1 and in POW1 (p = 0.011 and p = 0.003, respectively), but after RT, significant responses were not observed. Interestingly, in HYP2, MCP-1 increased significantly at POST24 (p = 0.009) and at POST48 (p = 0.032) only following RT. The present study shows that RT modifies RE-induced cytokine responses towards an anti-inflammatory direction

Resistance training status modifies inflammatory response to explosive and hypertrophic resistance exercise bouts.

The purpose of the present study was to examine the immediate and prolonged immune response in circulating cytokine and adipocytokine concentrations after two different resistance exercise bouts: hypertrophic (HYP1, 5 × 10, 80% of 1RM) and maximal explosive (POW1, 10 × 5, 60% of 1RM) resistance exercise bouts and how 12 weeks of resistance training (RT) modifies these responses (HYP2, POW2). Eight men completed the study. RE-induced interleukin-6 (IL-6), interleukin-1ß (IL-1ß), interleukin-1 receptor antagonist (IL-1ra), monocyte-chemoattractant protein-1 (MCP-1), leptin, resistin, and adiponectin were measured before (PRE) and immediately (POST0), 24 (POST24) and 48 (POST48) hours after RE bouts before and after RT. In the untrained state, IL-6 increased immediately after RE in HYP1 (p = 0.002) and in POW1 (p = 0.003) whereas no changes were observed after RT. Similar results were observed in IL-1ß, whereas conversely, IL-1ra increased only after RT in HYP2 and POW2 (p < 0.05). Resistin increased before RT in HYP1 and in POW1 (p = 0.011 and p = 0.003, respectively), but after RT, significant responses were not observed. Interestingly, in HYP2, MCP-1 increased significantly at POST24 (p = 0.009) and at POST48 (p = 0.032) only following RT. The present study shows that RT modifies RE-induced cytokine responses towards an anti-inflammatory direction.

Heterogeneity in resistance training-induced muscle strength and mass responses in men and women of different ages.

Physical activity recommendations for public health include typically muscle-strengthening activities for a minimum of 2 days a week. The range of inter-individual variation in responses to resistance training (RT) aiming to improve health and well-being requires to be investigated. The purpose of this study was to quantify high and low responders for RT-induced changes in muscle size and strength and to examine possible effects of age and sex on these responses. Previously collected data of untrained healthy men and women (age 19 to 78 years, n = 287 with 72 controls) were pooled for the present study. Muscle size and strength changed during RT are 4.8 ± 6.1 % (range from -11 to 30 %) and 21.1 ± 11.5 % (range from -8 to 60 %) compared to pre-RT, respectively. Age and sex did not affect to the RT responses. Fourteen percent and 12 % of the subjects were defined as high responders (>1 standard deviation (SD) from the group mean) for the RT-induced changes in muscle size and strength, respectively. When taking into account the results of non-training controls (upper 95 % CI), 29 and 7 % of the subjects were defined as low responders for the RT-induced changes in muscle size and strength, respectively. The muscle size and strength responses varied extensively between the subjects regardless of subject's age and sex. Whether these changes are associated with, e.g., functional capacity and metabolic health improvements due to RT requires further studies.

The effects of whey protein with or without carbohydrates on resistance training adaptations.

BACKGROUND: Nutrition intake in the context of a resistance training (RT) bout may affect body composition and muscle strength. However, the individual and combined effects of whey protein and carbohydrates on long-term resistance training adaptations are poorly understood. METHODS: A four-week preparatory RT period was conducted in previously untrained males to standardize the training background of the subjects. Thereafter, the subjects were randomized into three groups: 30 g of whey proteins (n = 22), isocaloric carbohydrates (maltodextrin, n = 21), or protein + carbohydrates (n = 25). Within these groups, the subjects were further randomized into two whole-body 12-week RT regimens aiming either for muscle hypertrophy and maximal strength or muscle strength, hypertrophy and power. The post-exercise drink was always ingested immediately after the exercise bout, 2-3 times per week depending on the training period. Body composition (by DXA), quadriceps femoris muscle cross-sectional area (by panoramic ultrasound), maximal strength (by dynamic and isometric leg press) and serum lipids as basic markers of cardiovascular health, were analysed before and after the intervention. RESULTS: Twelve-week RT led to increased fat-free mass, muscle size and strength independent of post-exercise nutrient intake (P < 0.05). However, the whey protein group reduced more total and abdominal area fat when compared to the carbohydrate group independent of the type of RT (P < 0.05). Thus, a larger relative increase (per kg bodyweight) in fat-free mass was observed in the protein vs. carbohydrate group (P < 0.05) without significant differences to the combined group. No systematic effects of the interventions were found for serum lipids. The RT type did not have an effect on the adaptations in response to different supplementation paradigms. CONCLUSIONS: Post-exercise supplementation with whey proteins when compared to carbohydrates or combination of proteins and carbohydrates did not have a major effect on muscle size or strength when ingested two to three times a week. However, whey proteins may increase abdominal fat loss and relative fat-free mass adaptations in response to resistance training when compared to fast-acting carbohydrates.

Medium-intensity, high-volume "hypertrophic" resistance training did not induce improvements in rapid force production in healthy older men.

The aim of the study was to determine whether it is possible to improve both maximum and rapid force production using resistance training that is typically used to induce muscle hypertrophy in previously untrained older men. Subjects (60-72 years) performed 20 weeks of "hypertrophic" resistance training twice weekly (n = 27) or control (n = 11). Maximum dynamic and isometric leg press, as well as isometric force over 0-100 ms, and maximum concentric power tests were performed pre- and post-intervention. Muscle activity was assessed during these tests by surface electromyogram of the vastus lateralis and medialis muscles. Muscle hypertrophy was assessed by panoramic ultrasound of the vastus lateralis. The intervention group increased their maximum isometric (from 2268 ± 544 to 2538 ± 701 N) and dynamic force production (from 137 ± 24 to 165 ± 29 kg), and these changes were significantly different to control (isometric 12 ± 16 vs. 1 ± 9 %; dynamic 21 ± 12 vs. 2 ± 4 %). No within- or between-group differences were observed in rapid isometric force or concentric power. Relative increases in vastus lateralis cross-sectional area trended to be statistically greater in the intervention group (10 ± 8 vs. 3 ± 6 %, P = 0.061). It is recommendable that resistance training programs for older individuals integrate protocols emphasizing maximum force/muscle hypertrophy and rapid force production in order to induce comprehensive health-related and functionally important improvements in this population.

PCDD/Fs, PCBs and PBDEs in zooplankton in the Baltic Sea - spatial and temporal shifts in the congener-specific concentrations.

In the marine food-webs, zooplankton is a key element in the transfer of persistent organic pollutants to higher trophic levels. We determined the congener-specific concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in offshore zooplankton (size from 0.2 to 20mm) collected in 2001, 2002 and 2010 in the northern and central Baltic Sea. Of the PCDD/Fs, the concentrations of 2378-TCDF were from 18 to 47 and of 23478-PeCDF from 7.9 to 29 pg g(-1)fat and showed little temporal differences. However, 1234678-HpCDF and OCDF were abundant in 2001-2002 especially in the eastern Gulf of Finland (average concentrations 50 and 89 pg g(-1)fat, respectively). In 2010 the concentrations of these two congeners were lower, 29 and 30 pg g(-1)fat, respectively, but still substantially higher than in the other surveyed areas. The principal components analysis (PCA) supported that area-specific patterns in pollution strongly contributed to the congener profiles particularly in surface sediment and in sediment trap material, but even in zooplankton. The concentrations of the PCBs were highest in the Gulf of Finland and in the Bothnian Bay. The concentrations of most PCBs were somewhat lower in 2010 than in 2001-2002. Of the dioxin-like PCBs, the concentrations of PCB-77 were highest (271-572 pg g(-1)fat) but PCB-126 (32-113 pg g(-1)fat) contributed from 85% to 91% of the total toxicity of PCBs due to its higher toxic potency. Of the PBDEs, the BDE47 and BDE99 were the most abundant (concentrations from 1.2 to 4.6 and from 0.4 to 3.3 ng g(-1) fat, respectively). The concentrations of most PBDEs were lower in 2010 than in 2001/2002 except in the eastern Gulf of Finland.

Neuromuscular fatigue to power loading using a weight-stack device fitted with or without additional rubber band resistance.

The addition of a rubber band (RB) to traditional weight-based resistance may be beneficial regarding the deceleration phase common during explosive power actions with light weights. This would lead to greater force and muscle activity during the latter part of the movement, but this may influence the distribution of neuromuscular fatigue. Fifteen men performed 2 knee extension power loadings (5 × 5 × 40% of 1 repetition maximum [1RM]) using a typical weight-stack device without (WS) and with the addition of a RB (WS + RB) in a crossover design. Concentric contractions were performed as fast as possible, and analyzed for torque, velocity, power, and vastus lateralis and medialis surface electromyography (EMG) parameters over 20° segments (range of motion, 60-180°) from throughout the loading. Additionally, maximum isometric knee extension was analyzed preloading and postloading for torque and EMG parameters, and for voluntary activation level using the twitch interpolation technique. Peak concentric power occurred at 100-120° on both devices but was greater during WS + RB (p ≤ 0.05). Electromyographic amplitude was greater in WS at 80-120°, p ≤ 0.05-0.01. Loading-induced reductions in peak concentric power (-12 ± 8 vs. -4 ± 10 kW, p ≤ 0.05) and voluntary activation level (-5.5 ± 7 vs. -1.1 ± 5%, p ≤ 0.05) were greater when using WS + RB. However, a greater reduction in root mean square of electromyography over 0-100 milliseconds was observed after WS (-31 ± 22 vs. 10 ± 26%, p < 0.05) accompanied by a large reduction in torque over 0-100 milliseconds. It seems that activation strategies, and consequently neuromuscular fatigue, during power loading could be modified through the addition of RB resistance.

Neuromuscular responses to different resistance loading protocols using pneumatic and weight stack devices.

The purpose of this study was to examine single repetition characteristics and acute neuromuscular responses to typical hypertrophic (HL), maximal strength (MSL), and power (PL) loadings performed with two of the most common resistance modes; pneumatic and weight stack. Acute responses were assessed by measuring maximal voluntary contraction (MVC), corresponding quadriceps-EMG and resting and superimposed twitch torques. Activation level was calculated from the twitch torques. Decreases in MVC were greater during HL and MSL than during PL. During HL, resting twitch force decreased 8% (P < 0.05) more on the weight stack than on the pneumatic device. Furthermore, loading using the weight stack caused reduced resting twitch force, activation level, and EMG-amplitude after MSL and PL (P < 0.05-0.01). PL on the pneumatic device decreased MVC and rapid force production, while the respective PL on the weight stack device was specific to decreased rapid force production only. However, mean angular velocities and power of the repetitions were higher on the pneumatic device when using light loads. The present study showed that, at least in untrained subjects, the weight stack device induced greater levels of peripheral fatigue during HL. It also led to large central fatigue during MSL and PL. On the other hand, on the pneumatic device contraction velocity with low loads was higher compared to the weight stack device. Therefore, it is recommended that the resistance mode should be chosen according to the specific training goal.

Neuromuscular fatigue in young and older men using constant or variable resistance.

The purpose of the present study was to determine: (1) if different acute neuromuscular responses occur between constant versus variable external resistance machines, two commonly used resistance machines and (2) whether the potential differences in fatigability between young and older men influence the magnitude of acute response between these resistance machines. Twelve young men (28 ± 5 year) and 13 older men (65.4 ± 4 year) performed 15 × 1 repetition maximum and 5 × 10 repetitions isotonic knee extension resistance loadings with both constant and variable resistance (four loadings in total). Maximum isometric knee extension torque, superimposed twitch, resting twitch torque, maximal M wave properties, electromyograph, and blood lactate concentration measured the effects of loading. Concentric torque reduced to a greater extent during variable 15 × 1 versus constant loading in young men only (P < 0.05). While three out of the four loadings caused decreased voluntary activation in young men, only 15 × 1 using variable resistance caused reductions in older men (P < 0.05). 5 × 10 variable resistance loading significantly increased M wave duration and decreased EMG median frequency, which was not observed following constant resistance loading in both age groups. Acute decreases in force production were significantly greater in young men following all loading protocols (P < 0.05). Both young and older men showed indications of greater fatigue from variable resistance loadings. Differing muscle properties may have led to different magnitudes of fatigue between groups, and older subjects may benefit from specifically tailored training programs.