Analysis of fatigue development during elite male handball matches.

This study aimed at describing the physiological demands and fatigue development during elite male handball matches. Our hypothesis was that players perform multiple high-intensity activities during periods of the game and develop temporary and end-match neuromuscular fatigue. Time-motion analyses and heart rate (HR) recordings were performed in 40 players during 12 competitive matches. Blood samples were collected, and sprint, jump, and intermittent exercise performance (Yo-Yo Intermittent Endurance level 2 test [YYIE2]) was assessed for 18 players at baseline conditions and after 2 competitive matches, and additional blood sampling and testing were performed for 12 of these players during a friendly match. The time spent with high-intensity running (4.4 ± 2.0 to 3.1 ± 1.7%), the frequency of demanding actions (61 ± 5 to 54 ± 6), and the time with HR above 80% HRmax (62 ± 21 to 41 ± 17%) were lowered from the first to the second half. Average blood lactate during the match was 3.6 ± 2.1 (1.3-8.6) mM. Plasma free fatty acids (FFA), glycerol, glucose, and uric acid increased (p ≤ 0.05) during the first half and plasma FFA and glycerol increased further (p ≤ 0.05) during the second half. After an intense period in the second half, sprint performance was decreased by 3.9 ± 4.9%. After the match, YYIE2 (33.4 ± 8.7%), vertical jump (7.4 ± 6.5%), and 20-m sprint performance (1.6 ± 2.6%) was lower (p ≤ 0.05) than at baseline. This study showed that the intensity is high in certain periods during elite male handball games and that physical performance is impaired both temporarily during and toward the end of games confirming our hypothesis. These findings enables physical trainers and coaches to plan and design proper game-specific training exercises aiming at delaying both temporary and end-game fatigue and strengthen the physiological rationale for the need for substitutions in various stages of match-play.

Physiological demands of elite team handball with special reference to playing position.

This study aimed to analyze the physiological demands of match play for different playing positions in elite male team handball. Time motion (N = 30) and heart rate (HR; N = 70) data were recorded throughout 10 official matches. The mean distance covered by backcourt players (4.96 ± 0.64 km) was greater (p ≤ 0.02) than for wings and pivots (4.23 ± 0.52 and 3.91 ± 0.51 km, respectively). Backcourt players spent less time standing still and walking (∼76%) than wings and pivots (∼80%) (p ≤ 0.03), and wings spent more time sprinting than the other playing positions. Backcourt players (122.9 ± 17.0) and pivots (126.8 ± 33.0) performed more high-demanding actions per game than wings (54.6 ± 15.6) (p = 0.01). The time spent by pivots in high-intensity activities decreased from the first to the second half (4.1 ± 2.4 to 2.7 ± 0.9%; p ≤ 0.01), while backcourt players showed a decrease in high-demanding playing actions (p ≤ 0.05). Backcourt players and pivots had higher mean (84 ± 9 and 83 ± 9% vs. 79 ± 10%; p ≤ 0.03) and peak effective HR, and percentage of total time at intensities >80% maximal HR (HRmax) than wings. The fraction of total time spent at intensities >80% HRmax decreased for all outfield playing positions in the second half (from 39-76 to 30-46%). Competitive team handball involves position-specific differences in the physiological demands. Furthermore, exercise intensity decreases from the first to the second half for all outfield playing positions suggesting that these players experience neuromuscular fatigue. Training of elite handball players should comprise high-intensity position-specific exercises aiming at improving the ability to maintain a high exercise intensity throughout the game.

Physical and physiological demands of elite team handball.

This study aimed to analyze elite team handball physical and physiological demands during match play. Time-motion (N = 30) and heart rate (HR; N = 60) analyses were performed throughout 10 official matches. The defined locomotor categories were standing still, walking, jogging, fast running, sprinting, backwards movement, sideways medium-intensity movement, and sideways high-intensity movement, and playing actions studied were jumps, shots, stops when preceded by high-intensity activities, changes of direction and one-on-one situations. During matches, the mean distances covered were 4,370 ± 702.0 m. Around 80% of the total time was spent standing still (43.0 ± 9.27%) and walking (35.0 ± 6.94%) and only 0.4 ± 0.31% with sprinting. The most frequent high-intensity actions were stops, changes of direction, and one-on-one situations. Effective mean HR was 157 ± 18.0 b·min(-1) (82 ± 9.3% of HRmax), and total HR was 139 ± 31.9 b·min(-1) (72 ± 16.7% of HRmax). The HR, time spent in high-intensity activities, frequency of stops, changes of direction, one-on-one situations, and most intense periods of the game were higher during the first half than during the second half (p ≤ 0.05). The opposite was observed for the number of time outs and the time between each change of activity (p = 0.00). Handball is an intermittent exercise that primarily uses aerobic metabolism, interspersed by high-intensity actions that greatly tax anaerobic metabolism. Additionally, exercise intensity decreases from the first to the second half of the match, suggesting that neuromuscular fatigue may occur during the game. The training of elite handball players should comprise exercises targeting the ability to perform specific high-intensity actions throughout the game and to rapidly recover during the less intense periods.

Elite futsal refereeing: activity profile and physiological demands.

The purpose of this study was to determine the physiological demands and to establish the relationship between activity profile and endurance capacity of futsal referees. Eighteen elite futsal referees (33.0 ± 5.1 years, 173 ± 5 cm, and 73.2 ± 8.4 kg) were studied. Video filming (n = 18) and heart rate (HR) recordings were performed throughout games. Blood lactate (n = 14) was determined at rest and after the game. Endurance capacity was determined with the Yo-Yo IE2. The number of activity changes was as high as 1,395 ± 218 (± SD). Total distance covered, high-intensity running (HIR), sprinting (SPR), and sideways running were 5.89 ± 0.56, 0.96 ± 0.29, 0.09 ± 0.07, and 0.91 ± 0.46 km, respectively. The number of HIR and SPR bouts was 129 ± 41 and 9 ± 8, respectively, with a mean duration of ∼1.4 seconds. Blood lactate content was 1.0 ± 0.3 and 1.5 ± 0.5 mM before and after the game. The amount of HIR performed during the match correlated significantly (r = 0.77; p < 0.05) with the Yo-Yo IE2 performance. Considering the data obtained in the present study, the use of match-specific intermittent fitness tests to evaluate futsal referees seems to be required.

Individual match playing time during the season affects fitness-related parameters of male professional soccer players.

The purpose of this study was to analyze the effects of an entire season on physical fitness parameters (PFPs) in male professional soccer players (N = 18). Performance in 5- and 30-m sprint (T5 and T30), countermovement jump (CMJ), agility (T-test), knee extensor (KE) and knee flexor (KF) isokinetic strength, hamstrings/quadriceps strength ratio (H/Q) and bilateral differences (BDs), and Yo-Yo intermittent endurance test 2 (YYIE2) was evaluated in 4 moments (E1-E4) throughout the season. Individual match playing time was quantified. Significant improvements in CMJ and YYIE2 from E1 to E2 were observed (p < 0.05-0.01). The T30 improved from E2 to E3 (p < 0.01). The CMJ decreased from E2 to E3 and E4, and YYIE2 from E2 to E4 (p < 0.05). There were increments in the H/Q ratio and Agility from E1 and E2 to E3 and E4 (p < 0.05-0.01). Significant correlations were found in all evaluation points between different PFPs and between changes in strength parameters and agility, T5 and T30, CMJ, and YYIE2 (p < 0.05-0.001). Influence of individual match playing time was correlated to changes in T5 (E1 to E3; r = -0.705), KE nondominant leg (KEND; E2 to E3; r = 0.786), and KF (E3 to E4; r = 0.575-0.590). The interrelationship between muscle strength (e.g., KE), sprint (e.g., T5), and jump abilities (CMJ) suggests the importance of muscle strength and power training for soccer. This study suggests that the systematic participation of the players in soccer matches favors the increase and maintenance of soccer players KE and KF muscle strength and sprint ability (T5). Thus, given the unique demands of actual match play, coaches should try to incorporate a competitive friendly match in the weekly training cycle of nonstarter players.

Additive Effects of Intermittent Hypobaric Hypoxia and Endurance Training on Bodyweight, Food Intake, and Oxygen Consumption in Rats.

Cabrera-Aguilera, Ignacio, David Rizo-Roca, Elisa A. Marques, Garoa Santocildes, Teresa Pagès, Gines Viscor, António A. Ascensão, José Magalhães, and Joan Ramon Torrella. Additive effects of intermittent hypobaric hypoxia and endurance training on bodyweight, food intake, and oxygen consumption in rats. High Alt Med Biol. 19:278-285, 2018.-We used an animal model to elucidate the effects of an intermittent hypobaric hypoxia (IHH) and endurance exercise training (EET) protocol on bodyweight (BW), food and water intake, and oxygen consumption. Twenty-eight young adult male rats were divided into four groups: normoxic sedentary (NS), normoxic exercised (NE), hypoxic sedentary (HS), and hypoxic exercised (HE). Normoxic groups were maintained at an atmospheric pressure equivalent to sea level, whereas the IHH protocol consisted of 5 hours per day for 33 days at a simulated altitude of 6000 m. Exercised groups ran in normobaric conditions on a treadmill for 1 hour/day for 5 weeks at a speed of 25 m/min. At the end of the protocol, both hypoxic groups showed significant decreases in BW from the ninth day of exposure, reaching final 10% (HS) to 14.5% (HE) differences when compared with NS. NE rats also showed a significant weight reduction after the 19th day, with a decrease of 7.4%. The BW of hypoxic animals was related to significant hypophagia elicited by IHH exposure (from 8% to 12%). In contrast, EET had no effect on food ingestion. Total water intake was not affected by hypoxia but was significantly increased by exercise. An analysis of oxygen consumption at rest (mL O2/[kg·min]) revealed two findings: a significant decrease in both hypoxic groups after the protocol (HS, 21.7 ± 0.70 vs. 19.1 ± 0.78 and HE, 22.8 ± 0.80 vs. 17.1 ± 0.90) and a significant difference at the end of the protocol between NE (21.3 ± 0.77) and HE (17.1 ± 0.90). These results demonstrate that IHH and EET had an additive effect on BW loss, providing evidence that rats underwent a metabolic adaptation through a reduction in oxygen consumption measured under normoxic conditions. These data suggest that the combination of IHH and EET could serve as an alternative treatment for the management of overweight and obesity.

Back to the future: transgenerational transmission of xenobiotic-induced epigenetic remodeling.

Epigenetics, or regulation of gene expression independent of DNA sequence, is the missing link between genotype and phenotype. Epigenetic memory, mediated by histone and DNA modifications, is controlled by a set of specialized enzymes, metabolite availability, and signaling pathways. A mostly unstudied subject is how sub-toxic exposure to several xenobiotics during specific developmental stages can alter the epigenome and contribute to the development of disease phenotypes later in life. Furthermore, it has been shown that exposure to low-dose xenobiotics can also result in further epigenetic remodeling in the germ line and contribute to increase disease risk in the next generation (multigenerational and transgenerational effects). We here offer a perspective on current but still incomplete knowledge of xenobiotic-induced epigenetic alterations, and their possible transgenerational transmission. We also propose several molecular mechanisms by which the epigenetic landscape may be altered by environmental xenobiotics and hypothesize how diet and physical activity may counteract epigenetic alterations.