Average Metabolic Power Research Articles

Human-Centered Coordination for Robot-Assisted Equipment Transport

Abstract This work explores how to use an unmanned ground vehicle (UGV) to offload the physical burdens of equipment from humans. This work formulates Dynamic Alignment Following and compares it to Position-Based Following techniques. We describe the control strategies of both following methods and implement them in a dynamic simulation and a physical prototype. We test the performance of the two following methods and show that Dynamic Alignment Following can reduce robot positional error and interaction force between the human and the robot. We then analyze the energetics and the performance of the human-UGV team for candidate transportation tasks. The presence of the robot can make some tasks take longer to perform. Nonetheless, the results show that for the candidate tasks, the robot can reduce human average metabolic power and average overall task energy.

Influence of Substitutions and Roles on Kinematic Variables in Professional Soccer Players.

In soccer, roles and substitutions can make it unclear how different physical capacities decrease over time and impact performance. This investigation aimed to analyze kinematic parameters and their changes over game time, and provide information to effectively prescribe training programs. Data from four professional teams were analyzed, and all the teams competed in the Italian First Division (Serie A). Average metabolic power and high-intensity activities associated with critical moments in the match were considered in the comparisons. The video analysis system STATS SportVU collected the data during official matches. Players were assigned to a specific group according to their time played, categorized as follows: 0-15', 15-30', 30-45', 45-60', 60-75', 75-90', and > 90 min. Different roles, including forwards and wingers (FW), midfielders (MF), center-backs (CB), and side-backs (SB) were also considered. Significant differences (p<0.05) were found in different roles and within roles at different times played. The results highlighted how MF performance decreased over time, whereas CB was unaffected by time. SB spent more time at very high velocity than other roles, independently from the time played. These findings provide valuable information about the physical demands of official soccer matches and could be used to review training prescriptions.

Performance in professional soccer players: normative data and benchmarks from official matches for metabolic power and high-intensity activities.

The opportunity to compare data among players using normative data and benchmarks may represent a helpful tool for coaches to assess the players' physical performance easily and quickly. This study aimed to create normative data and benchmarks that can be exploited to compare professional soccer players' physical capacity competing in the Premier Division Championship (series A). Match data from six professional soccer teams competing in the Premier Division championship (Serie A and Italy Cup matches) were collected during the entire season. Players (N.=112) were divided based on the role positioning as follows: forwards and wingers (FW), midfielders (MF), side-backs (SB), and center-backs (CB). All the teams analyzed competed with a 4-3-3 formation, and only players who played for the entire match (85-95 minutes) were considered. The video analysis system STATS SportVU was used to collect the data during official matches. Average metabolic power (AP) was considered to estimate the energy cost. The number of power events (PE), distance (m) covered at more than 25 W/kg (D25), and finally, the distance covered at v>25 km/h (VHS) were considered as high-intensity assessments. Standardized T-scores (scaled from 0 to 100) were calculated for each role and variable. T-score data was used to create performance bands combined with qualitative description (ranging from extremely poor to excellent), and a traffic light system approach was implemented to simplify the data's interpretation. The results could be used to compare different athletes' performance quickly and effectively, to detect symptoms of overtraining, and to give helpful insights to coaches on what the training should be focused on.

Average demands and most demanding passages of national-level female soccer matches: do small- and large-sided games replicate match demands?

This study aims to (1) determine the average and most demanding passage (MDP) load of national-level female soccer matches and (2) evaluate the relationship between average and MDP load during small-sided games (SSGs), large-sided games (LSGs), and matches. A total of 37 national-level female soccer players from a single club senior team and the U18 team participated. The average and 1-, 3-, and 5-min MDP external (total, high-speed, and very-high-speed running distances, acceleration and deceleration distances, average metabolic power, and high-metabolic load distance) and internal loads (average heart rate, rate of perceived exertion) of the 29 league matches, ten 4 vs. 4 + goalkeepers SSGs, and six 8 vs. 8 + goalkeepers LSGs were analyzed by the Polar Team Pro player tracking system. In matches, the external load variables during 1-, 3-, and 5-min MDPs were 167%-1,165%, 135%-504%, and 126%-359%, of match average values, respectively. In LSGs, all external load variables reached higher average values compared with those during matches, except for the very-high-speed running distance; however, no variable reached higher values of 1-min MDP compared with those during the matches. In SSGs, the average acceleration and deceleration distances were higher compared with those during the matches. The findings from the present study suggest that LSGs and SSGs can be used to overload the average values of the selected external load variables compared with those during the matches; however, other training options must be explored to overload 1-min match MDPs.

Large-Sided Games and Sport-Specific Training: Parameters of High Intensity in Professional Soccer Players

Study purpose. This study aimed to describe, analyze and compare the high intensity in internal and external load deriving from Large-Sided Games (LSG) exercises during the 4vs4 and 5vs5 formats, with goalkeepers. Materials and methods. The study participants were 22 professional soccer players (average age: 23.59±4.87 years, weight: 77.8±7.6 kg; height: 183.5±7.5 cm). The 4vs4 + 2 goalkeepers format was performed on a 60x54 m field (324 m2per player), while the 5vs5 + 2 goalkeepers format was performed on a 65 x 60 m field (325 m2 per player). During the two LSG exercises, the internal load and the external load were analyzed. The LSG exercises were performed in 4 sets of 5 minutes each, with 2 minutes of passive recovery between each set. Results. The data obtained show that the 4vs4 is the LSG exercise that succeeds in ensuring high exercise intensity: the time spent between 90-100% of the Heart Rate (HR) is significantly higher than in the 5vs5 (p &lt;.005). The average HR values (percentage and absolute) were also higher and significant (p &lt;.05) in the 4vs4 LSG. The peak speed (p &lt; .05), average metabolic power during exercise phases (p &lt; .05) and sprint distance (p &lt; .005) are higher in the 5vs5 LSG. Conclusions. By modulating the practice time, both formats can be used on the day after the match for those who did not play or on the match-day +3 for the whole team.

Shuttle Running Within a Small-Sided Game: Effects on Internal and External Workloads, in Young Elite Soccer Players.

To compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance. Ten young elite male soccer players (age 18.6 [1.9]y) performed two 5vs5 SSG formats (SSG-S and SSG-P) consisting of 4 × 4minutes with 1minute of passive recovery between bouts, 2 times each, once a week, and in a randomized order. Heart rate, blood lactate concentration, and rating of perceived exertion were assessed as indices of internal workload. Total and relative distances, distance at moderate and high speed, distances traveled in accelerations (≥2m·s-2) and decelerations (≤-2m·s-2; DDEC), and average metabolic power were chosen as indices of external workload and collected with a 10-Hz portable global positioning system device. Total distance, distances traveled in acceleration, distances traveled in deceleration, average metabolic power (always P < .01 and g > 1.62-large effect), and distance at moderate speed (P = .03 and g = 0.84-large effect) were significantly higher in SSG-S than in SSG-P. Moreover, the SSG-S showed higher blood lactate concentration (P = .0001, g = 12.58-large effect) and rating of perceived exertion (P = .03, g = 1.14-large effect) values than SSG-P. No significant differences in peak heart rate, relative distance, and distance at high speed were found. Our study showed, in young competitive male soccer players, the effectiveness of an SSG format that includes shuttle running within each bout in the development of more relevant internal and external workloads. These experimental data should encourage coaches to use this new SSG regimen within the traditional weekly training program.

Nose-down saddle tilt improves gross efficiency during seated-uphill cycling.

here, we investigated if simply tilting the saddle nose down increases efficiency during uphill cycling, which would presumably improve performance. nineteen healthy, recreational cyclists performed multiple 5min trials of seated cycling at ~ 3Wkg-1 on a large, custom-built treadmill inclined to 8° under two saddle-tilt angle conditions: parallel to the riding surface and 8° nose down. We measured subjects' rates of oxygen consumption and carbon dioxide production using an expired-gas analysis system and then calculated their average metabolic power during the last two min of each 5 min trial. we found that, compared to the parallel-saddle condition, tilting the saddle nose down by 8° improved gross efficiency from 0.205 to 0.208-an average increase of 1.4% ± 0.2%, t = 5.9, p < 0.001, CI95% [0.9 to 1.9], dz = 1.3. our findings are relevant to competitive and recreational cyclists and present an opportunity for innovating new devices and saddle designs that enhance uphill-cycling efficiency. The effect of saddle tilt on other slopes and the mechanism behind the efficiency improvement remain to be investigated.

Small-Sided Game 훈련이 축구학과 학생들의 유·무산소성 능력과 경기 중 운동강도에 미치는 영향

The purpose of the study was to examine the effects of SSG on aerobic and anaerobic capacities and exercise intensity during games in college students. Thirty-two college students majoring in football-related subjects participated in an 8-week study, and they were randomly assigned to either group one playing 8vs.8 game(n=16) or group two playing 4vs.4 game(n=16). The assessments included aerobic and anaerobic capacities, running distances during games, and exercise intensity before and after 8 weeks of each training. Results show that both groups significantly improved VO2max and total distances covered. For anaerobic capacities, while both groups showed significant improvements in average metabolic power, the group played 4vs.4 games showed a statistically significant increase in maximal metabolic power(p＜.001). For the running outputs during the SSG, both groups showed similar improvements in jogging(p＜.001), while the group played 8vs.8 games improved walking capacity (p＜.05). Both groups showed significant changes in sprinting(p＜.001), only the group playde 4vs.4 games improved distances covered while running(p＜.05), high-intensity running(p＜.001), and high-speed running(p＜.001). Results indicated that the SSG training improved total distance coverde, anerobic and anaerobic capacities, and exercise intensity during games of college students. As the group played 4vs.4 games performed significantly better in high-intensity and speed running, compared to the other group, a small number of players of smaller pitches appear to influence the SSG trainging.

Influence of the Area per Player in Non-Professional Soccer Players: A Pilot Study Focused on Positional Roles.

This study analyses the influence of different area per player (AP; 75, 98 and 131 m2) on the average metabolic power (MP) and other soccer-related performance variables in relation to the positional roles. We recruited 19 non-professional male soccer players (25.2 ± 6.3 y; 23.7 ± 2.3 kg/m2; 16.4 ± 6.3 y soccer experience) to play three different small-sided games (SSGs): SSG1 (5 vs. 5; 30 × 30 m; 5 min), SSG2 (5 vs. 5; 35 × 45 m; 5 min) and SSG3 (7 vs. 7; 35 × 45 m; 8 min). Specific playing rules were applied. GPS-assessed soccer-related variables were: average MP (AMP), distance covered in 1 min (DIS); % time spent at high speed (v > 16 km/h; % hst) or MP (>20 W/kg; % hmpt); % distance covered at high positive/negative speed (2 < v < 4 m/s2, % ACC; −6 < v < −2 m/s2, % DEC); and number of actions at high MP (hmpa). All recorded variables differed when each SSG was compared to the others (p < 0.05), but for hmpa for attackers. Most performance variables were positively associated with increasing AP (p < 0.05), but for % ACC and % DEC, and differed among positional roles within the same SSG (p < 0.05). Here the general applicability of SSGs, regardless the physical/technical skills of the group of players, to enhance performance is confirmed; furthermore, quantitative advices on AMP and other performance variables are provided to achieve significant improvements in all soccer players of the team.

Quantifying the Training and Match-Play External and Internal Load of Elite Gaelic Football Players

The current investigation quantified the training and match-play load of elite Gaelic football players across a two-season period using global positioning system technology (GPS), rating of perceived exertion (RPE) and sessional rating of perceived exertion (sRPE). Total weekly workload variables were collected across GPS, RPE, and sRPE across thirty-six elite Gaelic footballers (mean ± SD, age: 26 ± 5 years; height: 177 ± 8 cm; mass: 81 ± 7 kg) from one elite squad during a two-season observational period. External training load variables included: Total distance (m), High speed running (m; ≥ 17.1 km·h−1), Sprint distance (m; 22 km·h−1), Accelerations (n), Average metabolic power (W·kg−1), High-power distance (m; ≥ 25 W·kg−1). Internal load variables included: sRPE and RPE. Repeated measures ANOVA were used to understand the differences in loading patterns across phases, position, and week types when significant main effects were observed a Tukey’s post hoc test was applied and standardized effect sizes were calculated to understand the practical meaning of these differences. When total weekly loading across phases was considered total load was significantly greater in club 1 and provincial 1 with these phases showing the highest loading for players when compared to all other phases (p ≤ 0.001; ES: 2.95–7.22; very large). Furthermore, in-season 1 was greater for total loading when compared to in-season 2 and both championship phases (p ≤ 0.05; ES: 0.47–0.54; small). Total distance in training was greater during preseason 1 when compared to all other phases of the season (p ≤ 0.001; ES: 2.95–7.22; very large). During the in-season period, training based total distance was higher during provincial 1 when compared to other phases with similar trends across all measures (p ≤ 0.005). Finally, a positional profile for load measures was observed, with weekly context (match or non-match) having an impact on the internal and external loading players experienced across phases. The current data provide useful information for practitioners on the training periodization currently present within the elite Gaelic football training process. Specifically, the data provide positional profiles of loading across weekly and segmented phased of an elite Gaelic football season. These data can increase understanding as to the periods of increased and decreased loading across different phases of an elite Gaelic football season, while providing a framework for future analysis concerning Gaelic football periodization.

Is the metabolic power paradigm ecologically valid within elite Gaelic football?

To examine the association between the metabolic power paradigm during training and match-play and objective aerobic fitness measures within elite Gaelic football players. Twenty-five elite Gaelic football players completed objective physiological testing for VO2max, vVO2max, Peak treadmill Velocity (PTV), Running economy (RE) and selected blood lactate concentrations of 2 mmol L−1 (S2) and 4 mmol L−1 (S4). Aerobic testing was performed at the start of the season and at the halfway point of the season. Training and match-play running performances were recorded across the period with global positioning system technology (GPS; 4-Hz; VX Sport, Lower Hutt, New Zealand). Instantaneous raw velocity data were obtained from the GPS and exported to a customised spreadsheet which provided estimations of total distance (m), high-speed running distance (m; 17 km h−1), very-high-speed running distance (m; 22 km h−1), total accelerations (n), acceleration distance (m), peak and mean velocity (km h−1). Furthermore, changes in velocity were analysed which allowed for the assessment of the metabolic power paradigm during these training and match-play events. Players average metabolic power (Pmet; W Kg−1) observed to have a large association with VO2max (r = 0.76–0.88) and velocity at VO2max (r = 0.72–0.91) in training and match situations. Interestingly, peak treadmill velocity showed a moderate association with training and match-play high metabolic power distance (r = 0.56–0.76). Large associations were observed between high power distance during match and training categories and velocity at VO2max (r = 0.76–0.89). Furthermore, high power distance was observed to have a large association with peak treadmill velocity (r = 0.72–0.91) in training and match situations with lactate variables showing a small to moderate association with metabolic power variables. The current investigation is the first to provide evidence towards the ecological validity of the metabolic power paradigm to assess aerobic fitness within elite Gaelic football. Practitioners should consider the association between aerobic fitness and specific metabolic load paradigm variables within their monitoring system as a potential means to understand the impact of training plans within elite Gaelic football players.

Energetic Profiles of the Yo-Yo Intermittent Recovery Tests 1 and 2.

To analyze the energetic profiles of the Yo-Yo Intermittent Recovery Tests 1 and 2 (YYIR1 and YYIR2). Intermittent running distance (IR1D and IR2D), time to exhaustion (IR1T and IR2T), and total recovery time between shuttles (IR1R and IR2R) were measured in 10 well-trained male athletes (age 24.4 [2.0] y, height 182 [1] cm, weight 75.8 [7.9] kg). Respiratory gases and blood lactate (BLC) were obtained preexercise, during exercise, and until 15 min postexercise. Metabolic energy, average metabolic power , and energy share (percentage of aerobic [WAER], anaerobic lactic [WBLC], and anaerobic alactic energy system [WPCr]) were calculated using the PCr-La-O2 method. Peak oxygen consumption was possibly higher in YYIR2 (60.3 [5.1]mL·kg-1·min-1) than in YYIR1 (P = .116, 57.7 [4.5]mL·kg-1·min-1, d = -0.58). IR1D, IR1T, and IR1R were very likely higher than IR2D, IR2T, and IR2R, respectively (P < .001, 1876 [391] vs 672 [132]m, d = -2.83; P < .001, 916 [175] vs 304 [57]s, d = -3.03; and P < .001, 460 [100] vs 150 [40]s, d = -2.83). Metabolic energy was most likely lower in YYIR2 than in YYIR1 (P < .001, 493.5 [118.1] vs 984.8 [171.7]kJ, d = 3.24). Average metabolic power was most likely higher in YYIR2 than in YYIR1 (P < .001, 21.5 [1.7] vs 14.5 [2.2]W·kg-1, d = 3.54). When considering aerobic phosphocreatine restoration during breaks between shuttles, WAER (P = .693, 49% [10%] vs 48% [5%], d = -0.16) was similar, WPCr (P = .165, 47% [11%] vs 42% [6%], d = -0.54) possibly higher, and WBLC (P < .001, 4% [1%] vs 10% [3%], d = 1.95) almost certainly lower in YYIR1 than in YYIR2. WAER and WPCr are predominant in YYIR1 and YYIR2 with almost identical WAER. Higher IR1D and IR1T in YYIR1 result in higher metabolic energy but lower average metabolic power and slightly lower peak oxygen consumption. Higher IR1R allows for higher reliance on WPCr in YYIR1, while YYIR2 requires a higher fraction of WBLC.

Metabolic power in hurling with respect to position and halves of match-play

The current investigation compared the metabolic power and energetic characteristics in team sports with respect to positional lines and halves of match-play. Global positioning system (GPS) technology data were collected from 22 elite competitive hurling matches over a 3-season period. A total of 250 complete match-files were recorded with players split into positional groups of full-back; half-back; midfield; half-forward; full-forward. Raw GPS data were exported into a customized spreadsheet that provided estimations of metabolic power and speed variables across match-play events (average metabolic power [Pmet], high metabolic load distance [HMLD], total distance, relative distance, high-speed distance, maximal speed, accelerations, and deceleration). Pmet, HMLD, total, relative and high-speed distance were 8.9 ± 1.6 W·kg-1, 1457 ± 349 m, 7506 ± 1364 m, 107 ± 20 m·min-1 and 1169 ± 260 m respectively. Half-backs, midfielders and half-forwards outperformed full-backs (Effect Size [ES] = 1.03, 1.22 and 2.07 respectively), and full-forwards in Pmet (Effect Size [ES] = 1.70, 2.07 and 1.28 respectively), and HMLD (full-backs: ES = -1.23, -1.37 and -0.84 respectively, and full-forwards: ES = -1.77, -2.00 and -1.38 respectively). Half-backs (ES = -0.60), midfielders (ES = -0.81), and half-forwards (ES = -0.74) experienced a second-half temporal decrement in HMLD. The current investigation demonstrates that metabolic power may increase our understanding of the match-play demands placed on elite hurling players. Coaches may utilize these findings to construct training drills that replicate match-play demands.

Respiratory Frequency as a Marker of Physical Effort During High-Intensity Interval Training in Soccer Players.

Variables currently used in soccer training monitoring fail to represent the physiological demand of the player during movements like accelerations, decelerations, and directional changes performed at high intensity. We tested the hypothesis that respiratory frequency (fR) is a marker of physical effort during soccer-related high-intensity exercise. A total of 12 male soccer players performed a preliminary intermittent incremental test and 2 shuttle-run high-intensity interval training (HIIT) protocols, in separate visits. The 2 HIIT protocols consisted of 12 repetitions over 9 minutes and differed in the work-to-recovery ratio (15:30 vs 30:15s). Work rate was self-paced by participants to achieve the longest possible total distance in each HIIT protocol. Work-phase average metabolic power was higher (P < .001) in the 15:30-second protocol (31.7 [3.0]W·kg-1) compared with the 30:15-second protocol (22.8 [2.0]W·kg-1). Unlike heart rate and oxygen uptake, fR showed a fast response to the work-recovery alternation during both HIIT protocols, resembling changes in metabolic power even at supramaximal intensities. Large correlations (P < .001) were observed between fR and rating of perceived exertion during both 15:30-second (r = .87) and 30:15-second protocols (r = .85). Our findings suggest that fR is a good marker of physical effort during shuttle-run HIIT in soccer players. These findings have implications for monitoring training in soccer and other team sports.

Monitoring Fatigue During Intermittent Exercise With Accelerometer-Derived Metrics.

The aim of this study was to assess the sensitivity of accelerometer-derived metrics for monitoring fatigue during an intermittent exercise protocol. Fifteen university students were enrolled in the study (age 20 ± 1 years). A submaximal intermitted recovery test (Sub-IRT) with a duration of 6 min and 30 s (drill 1) was performed. In order to increase the participants’ fatigue, after that, a repeated sprint protocol (1×6 maximal 20 m sprints) was performed. Following that, participants repeated the Sub-IRT (drill 2) to evaluate the external and internal training load (TL) variations related to fatigue. Apex 10 Hz global navigation satellite system (GNSS) units were used to collect the variables total distance (TD), high metabolic distance (HMD), relative velocity (RV), average metabolic power (MP), heart rate maximal (HRmax) and mean (HRmean), muscular (RPEmus) and respiratory rating of perceived exertion (RPEres), dynamic stress load (DSL), and fatigue index (FI). A Bayesian statistical approach was used. A likelihood difference (between drill 1 and drill 2) was found for the following parameters: TD (BF10 = 0.33, moderate per H0), HMD (BF10 = 1.3, anecdotal), RV (BF10 = 0.29, moderate per H0), MP (BF10 = 1.3, anecdotal), accelerations (BF10 = 1.6, anecdotal ), FI (BF10 = 4.7, moderate), HRmax (BF10 = 2.2, anecdotal), HRmean (BF10 = 4.3, moderate), RPEmus (BF10 = 11.6, strong), RPEres (BF10 = 3.1, moderate), DSL (BF10 = 5.7, moderate), and DSL•m−1 (BF10 = 4.3, moderate). In conclusion, this study reports that DSL, DSL•m−1, and FI can be valid metrics to monitor fatigue related to movement strategy during a standardized submaximal intermittent exercise protocol.

Positional demands for various-sided games with goalkeepers according to the most demanding passages of match play in football.

The main aim was to determine the differences between four training games and competitive matches (CM) according to position and compared to the most demanding passages (MDP) of competitive match play. Global Positioning System data were obtained from 21 football players belonging to the reserve squad of a Spanish La Liga club during the 2015/16 season. The training games were small-sided games (SSGs) with 5 and 6 and large-sided games with 9 and 10 outfield players per team. The players were categorized based on positional groups: full back (FB), central defender (CD), midfielder (MF), offensive midfielder (OMF), and forward (FW). The variables recorded were the distance covered (DIS), DIS at high speed (HSR; >19.8 km·h-1), DIS at sprint (SPR; >25.2 km·h-1), high metabolic load distance (HMLD; >25.5 W·kg-1) all in m·min-1, average metabolic power (AMP; W·kg-1) and number of high-intensity accelerations (ACC; >3 m·s-2) and decelerations (DEC; <-3 m·s-2), both in n·min-1. The MDP was analysed using a rolling average method for AMP as a criterion variable, where maximal values were calculated for time windows of 5 and 10 minutes of CM and after that compared with the training game formats. As the SSG format increases, all the rest of the variables increase and the number of cases with significant interposition differences also increases (effect size [ES]: DIS: 0.7-2.2; HSR: 0.7-2.1; SPR: 0.8-1.4; HMLD: 0.9-2.0; AMP: 0.8-1.9; ACC: 0.8-1.7; DEC: 0.5-1.7). The large-sided game 10v10 + 2 goalkeepers over-stimulates sprint values relative to MDP (all: 121.0% of MDP, ES=0.5-1.8). This study provides useful information for coaching staff on the heightened impact of different training game formats on physical load, considering positional differences in relation to the MDP of competitive match play.

The most demanding passages of play in football competition: a comparison between halves.

The purpose of this investigation was to determine the differences between halves in the most demanding passages of play in football players according to playing position and duration-specific activity. Global positioning system data were collected from twenty-three football players from a reserve squad of the Spanish La Liga. A total of 265 individual match half data were analysed across the competitive season. Players were categorised based on positional groups: full-back (FB), central defender (CD), midfielder (MF), offensive midfielder (OMF) and forwards (FW). The most demanding passage of match play was analysed using a rolling average method, where maximal values were calculated for five different time durations (1, 3, 5, 10 min and half completed) using distance (m·min-1), high metabolic load distance (HMLD; m·min-1) and average metabolic power (AMP; W·kg-1) as variables of interest. The differences between the first and second half increased as the rolling duration increased, reaching the greatest difference between halves in the complete half (45 min) in all the variables studied (ES = 0.54 ± 0.15, 0.75 ± 0.15 and 0.76 ± 0.15 in distance, HMLD and AMP). The CDs were the players that presented the greatest differences, and it was in the AMP variable where the greatest differences between the first and second half were found. Large decreases in AMP were found for CD (ES = -1.30 ± 0.36) and moderate decreases were found in AMP for FB (ES = -0.84 ± 0.30) and OMF (ES = -0.78 ± 0.37). These results provide insight into the most demanding passages of play to inform training practices for specific football playing positions.

The metabolic cost of in vivo constant muscle force production at zero net mechanical work.

The metabolic cost per unit force is generally thought to increase with the mechanical work done by the muscle fibres. It is currently unclear how the metabolic cost of doing alternating positive and negative muscle fibre mechanical work relates to the metabolic cost of doing zero muscle fibre mechanical work at similar muscle force. The current study aimed to investigate this issue by comparing in vivo metabolic power between a dynamic and an isometric near-constant force production task. In both tasks, participants performed periodic movement about the knee joint in the gravitational field. Therefore, net external mechanical work was constrained to be zero. The tasks mainly differed from each other in average positive knee joint mechanical power, which was 4.3±0.5 W per leg during the dynamic task and 0.1±0.1 W per leg during the isometric task. Knee extension torque was near-constant around 15.2±1.7 N m during the dynamic task and around 15.7±1.7 N m during the isometric task. Owing to near-constant knee extension torque, quadriceps tendon length was presumably nearly constant during both tasks. Therefore, knee joint mechanical work was predominantly done by the muscle fibres in both tasks. Average gross metabolic power was 3.22±0.46 W kg-1 during the dynamic task and 2.13±0.36 W kg-1 during the isometric task. Because tasks differed mainly in the amount of positive muscle fibre mechanical work, these results imply that the metabolic cost of near-constant force production in vivo at zero net mechanical work can be reduced by minimizing positive muscle fibre mechanical work.

Effectively Quantifying the Performance of Lower-Limb Exoskeletons Over a Range of Walking Conditions.

Exoskeletons and other wearable robotic devices have a wide range of potential applications, including assisting patients with walking pathologies, acting as tools for rehabilitation, and enhancing the capabilities of healthy humans. However, applying these devices effectively in a real-world setting can be challenging, as the optimal design features and control commands for an exoskeleton are highly dependent on the current user, task and environment. Consequently, robust metrics and methods for quantifying exoskeleton performance are required. This work presents an analysis of walking data collected for healthy subjects walking with an active pelvis exoskeleton over three assistance scenarios and five walking contexts. Spatial and temporal, kinematic, kinetic and other novel dynamic gait metrics were compared to identify which metrics exhibit desirable invariance properties, and so are good candidates for use as a stability metric over varying walking conditions. Additionally, using a model-based approach, the average metabolic power consumption was calculated for a subset of muscles crossing the hip, knee and ankle joints, and used to analyse how the energy-reducing properties of an exoskeleton are affected by changes in walking context. The results demonstrated that medio-lateral centre of pressure displacement and medio-lateral margin of stability exhibit strong invariance to changes in walking conditions. This suggests that these dynamic gait metrics are optimised in human gait and are potentially suitable metrics for optimising in an exoskeleton control paradigm. The effectiveness of the exoskeleton at reducing human energy expenditure was observed to increase when walking on an incline, where muscles aiding in hip flexion were assisted, but decrease when walking at a slow speed. These results underline the need for adaptive control algorithms for exoskeletons if they are to be used in varied environments.

Decrements in Neuromuscular Performance and Increases in Creatine Kinase Impact Training Outputs in Elite Soccer Players

Malone, S, Mendes, B, Hughes, B, Roe, M, Devenney, S, Collins, K, and Owen, A. Decrements in neuromuscular performance and increases in creatine kinase impact training outputs in elite soccer players. J Strength Cond Res 32(5): 1342-1351, 2018-The aim of the current investigation was to understand the impact of pretraining neuromuscular performance and creatine kinase (CK) status on subsequent training performance in elite soccer players. Thirty soccer players (age: 25.3 ± 3.1 years; height: 183 ± 7 cm; mass: 72 ± 7 kg) were involved in this observational study. Each morning before training, players completed assessments for neuromuscular performance (countermovement jump; CMJ) and CK levels. Global positioning technology provided external load: total distance, high-speed distance, sprint distance, accelerations, decelerations, average metabolic power, explosive distance, and high metabolic power distance (>25.5 W·kg). Mixed-effect linear models revealed significant effects for CK and CMJ Z-score on total high-speed distance, very high-speed distance, accelerations, decelerations, explosive distance, and maximal velocity. Effects are reported with 90% confidence limits. A CK Z-score of +1 corresponded to a -5.5 ± 1.1, -3.9 ± 0.5, -4.3 ± 2.9%, -4.1 ± 2.9%, -3.1 ± 2.9%, and -4.6 ± 1.9%, reduction in total high-speed distance, very high-speed distance, accelerations, decelerations, explosive distance, and maximal velocity, respectively. Countermovement jump Z-score of -1 corresponded to a -3.5 ± 1.1, -2.9 ± 0.5, -2.1 ± 1.4, -5.3 ± 2.9%, -3.8 ± 2.9%, -1.1 ± 2.9%, and -5.6 ± 1.2% reduction in these external load measures. Magnitude-based analysis revealed that the practical size of the effect of a pretraining CMJ Z-score of -1 and CK Z-score of +1 would have on total high-speed distance, very high-speed distance, high metabolic power distance (>25.5 W·kg), accelerations, decelerations, explosive distance, and maximal velocity was likely negative. The results of this study suggest that systematic pretraining monitoring of neuromuscular and muscle stress within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session.