Investigating the internal and external load output across different drill classifications in semi-elite male Australian football players

"Monitoring athlete preparedness, including quantifying training and competition load and determining fatigue/training status, is used to complement training and recovery prescription in professional sport (Kenttä & Hassmén, 2002). The overall objective of this research was to investigate contemporary athlete monitoring practices in professional Australian football (AF). The aim of study 1 was to identify the relationship between external training load and session rating of perceived exertion (s-RPE) training load and the impact that playing experience, playing position and 2-km time-trial performance had on that relationship. Microtechnology devices provided external training load (distance, mean speed, high-speed running distance, Player loadTM (PL), and Player load slowTM (PLslow)). The external training load measures had moderate to very large associations with s-RPE training load. When controlling for external training load, the 4- to 5-year players had a small increase in s-RPE training load compared to the 0- to 1- and 2- to 3-year players. Furthermore, ruckmen had moderately higher s-RPE training load than midfielders, and there was a 0.2% increase in s-RPE training load per 1 s increase in time-trial time. The aim of study 2 was to profile weekly wellness within the context of the competitive season of professional AF. Each morning before any physical training, players completed a 5-item customised self-report questionnaire (sleep quality, fatigue, stress, mood, and muscle soreness), with the mean of the individual indices used to determine overall wellness. Internal match load (s-RPE), match-to-match micro-cycle length, stage of the season and internal training load were included in multivariate linear models in order to determine their effect on weekly wellness profile. There was a lower weekly training load on a 6-day micro-cycle (mean ± s = 1813 ± 291 au) compared to a 7- (1898 ± 327 au, likely small) and 8-day (1900 ± 271 au, likely small) micro-cycle. Match load had no significant impact on weekly wellness profile, whilst there was an interaction between micro-cycle and days-post-match. There was likely to be a moderate decrease in wellness Z-score 1 d post match for an 8-day micro-cycle compared to a 6- and 7- day cycle. There was possibly a small reduction in overall wellness Z-score in the second half of the season compared to the first half of the season. Finally, training load had no effect on wellness Z-score when controlled for days-post-match, micro-cycle and stage of the season. The aim of study 3 was to assess the application of athlete self-report measures to prompt modifications to training dose by exploring its association with subsequent activity profiles. The impact of perceived wellness on a range of external load parameters, RPE and external load: RPE ratios, was explored during skill-based training in AF. Mixed-effect linear models revealed significant effects of wellness Z-score on PL and PLslow. A negative wellness Z-score corresponded to a small reduction in PL and a moderate reduction PLslow, compared to those without reduced wellness. A small reduction was also observed in the PLslow: RPE ratio models, while a small increase was seen in mean speed: RPE ratio. The aim of study 4 was to corroborate the use of particular contemporary monitoring measures by examining their effect on individual match performances. The effects of internal load parameters, combined with athlete self-reported wellness, on subjective and objective measures of match performance in 20 rounds of professional AF was examined. Acute weekly internal load (s-RPE) was determined for each independent training modality. Chronic load was calculated as the rolling 4-week mean and a training-stress balance (TSB) was ascertained by dividing the acute load (1-weekly total) by the chronic load (4-week mean) expressed as a percentage. Load from every training modality was used to calculate an overall acute load, overall chronic load, and overall TSB and only outdoor skills and conditioning sessions were used to calculate a field-based acute load, a field-based chronic load and field-based TSB. Weekly wellness was quantified as the mean of the overall daily wellness scores. An iterative linear mixed modelling approach demonstrated that load and wellness variables had minimal impact on subjective performance ratings (coaches’ votes). Conversely, objective performance, measured via Champion Data© ranking points was positively associated with load, although the magnitude of this effect was greater for field-based loads compared to overall loads. Furthermore, athletes with high loads reporting low wellness, ranked better in objective performance than those reporting high wellness with high loads. Alternatively, an increase in wellness was associated with better objective performance when accompanying lower loads. This collection of studies suggests that s-RPE has a strong relationship with measures of external load, which is moderated by playing position, experience and time-trial performance in AF and that coaches and sport scientists should give consideration to these mediators of s- RPE. It was also revealed that the weekly profile of self-reported wellness in response to matches was influenced by the match-to-match micro-cycle and stage of the season in AF. However, when factoring in these conditions, training load had minimal influence on wellness profile. As such, determination of ‘red flags’ in self-reported measures should be made against comparative weeks. Furthermore, pre-training self-reported wellness was shown to be associated with accelerometer-derived external load measures, suggesting an altered movement pattern during diminished training states. Understanding the changes in external load that might be produced, relative to the pre-training self-reported wellness, provides coaches with an opportunity to adjust prescription if warranted. Finally, the use of internal load and athlete self-report measures can be corroborated based on their relationship with an objective measure of performance in AF and the importance of a mixed-method approach to comprehensively assess athlete status is emphasised."

The ability to maintain a high intensity of exercise over several repetitions depends on recovery from previous exercises. This study aimed to identify the effects of different recovery times on internal and external load during small-sided soccer games. An increase in recovery time will increase the external training load and decrease the internal exercise load, which will result in a greater physical impact of the exercise. Cross-sectional study. Level 2. Twenty male semiprofessional soccer players participated in the present study. They performed the same exercise (5-a-side game format) continuously (1 × 18 minutes) and repeatedly/fractionated (3 × 6 minutes) with different recovery times (30 seconds, 1 minute, 1.5 minutes, and 2 minutes). Their internal load (ie, average heart rate (HR) and maximum HR) and external load (ie, total distance, maximum speed, and ratio meters) were measured using an HR band and an inertial device equipped with a global positioning system, respectively. The manipulation of recovery times induced differences in the internal and external load. For the same total duration, the external and internal load indicators exhibited higher values during the fractionated method, particularly with short recovery periods. The application of small-sided soccer games with different recovery times induced varying responses in training load. To maintain high physical performance and high training load, the fractional method with short recovery periods (ie, 30 seconds) should be used. In contrast, to carefully manage players' efforts and decrease response to training load, continuous or fractional methods with longer recovery periods (ie, 1-2 minutes) should be used. The proper prescription of recovery time between exercises facilitates enhanced training efficiency and optimized performance.

To statistically evaluate the internal and external load metrics in different types of lacrosse drills. A total of 25 Division I collegiate female lacrosse players wore a heart rate monitor and a global positioning system during preseason training sessions. Seven measures determined training load, 2 internal measures and 5 external measures, across 5 different types of drills: stickwork, small-sided games, individual skills, conditioning, and team drills. Principal component analysis was used to determine which internal and external load variables were most associated with each drill type. Stickwork extracted 2 principal components, explaining 45% and 17% of the variance. Small-sided games extracted 1 principal component, explaining 51% of the variance. Individual skills extracted 2 components, explaining 39% and 22% of the variance. Conditioning extracted 2 components, explaining 44% and 24% of the variance. Team drills extracted 2 components, explaining 52% and 18% of the variance. In 4 out of 5 training modes, the inclusion of both internal and external training-load measures was necessary to accurately decipher training load. For most drills, the first component is related to measures of external load, and the second component described the balance between internal and external load measures. Small-sided games extracted only external measures including the following: accelerations, total distance, and average speed. These results show that a combination of internal and external load measures is required to determine training load during certain training modes. This information can help coaches make decisions about desired training load for practice sessions.

Diverse strategies for manipulating acute training load can be employed in small-sided games.However, the impact of different scoring methods on the internal and external training loads of young athletes during such games remains a topic of debate.The present study aimed to compare external and internal training loads and perceive recovery in small-sided games played with different scoring rules.The secondary objective was to analyse the correlation between internal and external training loads.On separate days, 13 young athletes (M age 14.7 0.4 years) participated in three different small-sided game models: ball possession, score zone, and small-sided games with small goals.Accelerometers worn by the players recorded raw acceleration values, which were later transformed into external training loads measured with PlayerLoad TM .Approximately 20 minutes after the conclusion of each small-sided game session, the participants' internal training loads were obtained, using the session rate of perceived exertion (session-RPE) method.Significant differences were found in external training load values (F (2.28) = 35.046,p < .001; = .78).Ball possession resulted in higher external training loads compared to the score zone and the small-sided games with small goals.Similarly, ball possession caused higher internal training loads compared to the score zone, and the small-sided games with small goals (F (2,28) = 19.549, p .001; = .62).In conclusion, ball possession led to higher external training loads and internal training loads, while small-sided games with small goals led to higher external and internal training loads than score zone.Coaches can opt to use ball possession in training intensifications and small-sided games with small goals in periods of reduced training loads.

The purpose of the present study was to analyze the internal and external loads on regular and floater players during standardized small-sided games (SSGs) with different numbers of players (teams of 3, 5, or 7 players). Fifteen male semi-professional football players played different SSGs maintaining the same relative area per player. Total distance (TD), distance covered at different speeds (DC), the number of accelerations and decelerations, maximal (HR<inf>max</inf>) and mean (HR<inf>mean</inf>) heart rate and rate of perceived exertion (RPE) were registered. Regular players showed greater internal and external loads in SSGs with 3 and 5 players without floaters than with floaters (ES 0.60-to-1.27). Likewise, with floaters, regular players in the SSGs with 3 performed more accelerations (ES 1.40 and 1.17) and with 7 achieved higher TD, DC>14 km·h-1, HR<inf>max</inf> and HR<inf>mean</inf> (ES 0.66-to-2.79) than any other. During SSGs with 7 players the floaters showed a higher TD and decelerations than in other SSGs (ES 0.47-to-1.70), and a higher DC (0-6.9 km·h-1,14-17.9 km·h-1) and RPE than in SSGs with 3 players (ES 0.59-to-0.89). During SSGs with 5, the floaters showed a higher TD, HR<inf>max</inf>, HR<inf>mean</inf> and RPE than in SSGs with 3 (ES 0.86-to-1.45). In all SSGs, regular players showed higher TD, DC (14-17.9 km·h-1), accelerations, decelerations and HR<inf>mean</inf> than floaters (ES 1.24-to-6.23). Coaches must carefully design SSGs because the number of players and the presence or absence of floaters can affect the external-internal load expressed.

This study investigated the relationships between Rate of Perceived Exertion (RPE) and various objective internal and external training load measures across multiple drill types in youth academy soccer players, a comparative approach that has been rarely examined. Forty-six male outfield soccer players (16.3 ± 0.4 years) from two under-17 academy-level teams competing in a city-level league, training three times per week with weekend matches, were monitored over two weeks during regular training. Data included RPE (CR-10 scale), heart rate responses (HRaverage, HRmax), and external load variables (total distance per minute, average speed, distance in Z4 [15-19 km/h], and Z5 [>19 km/h]) via Polar Team Pro, measured across all drills (3v3, 6v6, 9v9, 11v11, 10x5 positional game, repeated sprint training, muscular endurance circuit training, and slalom exercise). Aerobic capacity (VIFT) was assessed separately using the 30-15 IFT. Results indicated that RPE consistently showed large positive correlations with HRaverage (e.g., 3v3: r = 0.977) and HRmax (e.g., 3v3: r = 0.778) across most drills, Conversely, relationships between RPE and the VIFT were varied, showing large negative correlations in larger-sided games (e.g., 11v11: r = -0.446; 9v9: r = -0.585), suggesting fitter players perceived less effort. Correlations between RPE and general distance/speed metrics were inconsistent, while distances covered in high-intensity speed zones (Z4, Z5) showed large positive correlations with RPE (e.g., 3v3 Z4: r = 0.830; 3v3 Z5: r = 0.710), particularly in drills like 3v3, 6v6, repeated sprint training, and slalom. In conclusion, RPE's relationship with training load is drill-specific. It possibly reflects physiological strain in small-sided games and conditioning drills, but shows more variable associations with external load and fitness in large-sided or tactical formats. Coaches should therefore combine RPE with objective metrics and interpret it in light of drill characteristics. These findings should be viewed cautiously given the short two-week monitoring period and absence of additional physiological markers.

This study aims to quantify and compare the external and internal training load demands of sided-game drills in professional team players during the competitive season. Twenty-four male professional soccer players of the same club were enrolled in this study. Drills were categorized as large-sided games (LSG): 10vs10 (84 × 60 m or 72 × 60 m), Hexagon possession 9vs9 + 3 (36 × 48 m), Possession gate 8vs8 + 2 (36 × 44 m), Possession 7vs7 + 3 (30 × 32 m) or as Small-sided games (SSG): 6vs6 (48 × 42 m), and Possession 6vs4 (30 × 60 m). A total of 7 drills and 279 individual data points were included in this analysis. Distance covered, high-speed running (HSR), and sprinting distance were all calculated in meters per minute (m.min−1) while total accelerations (>3 m.s−2) and total decelerations (− < 3 m.s−2) were calculated in number of actions per minute (n.min−1). All external load was measured with global navigation satellite systems (GNSS) STATSports Apex units. Players’ internal load was quantified using their rating of perceived exertion (RPE). We found that distance covered (p < 0.01, large), HSR (p < 0.01, large), and sprinting distance (p < 0.01, large) changed between drills (e.g., greater in LSG formats), acceleration (p < 0.01, large) and deceleration (p < 0.01, large) demands were greater in smaller formats (e.g., SSG 6vs6, and Possession 6vs4), while RPE was lower in the Possession gate 8vs8 + 2 format (p < 0.01, large). This study found that sided-games can replicate and sometimes exceed some match-specific intensity parameters, however, HSR and sprinting were consistently lower compared to official matches.

Weaving, D, Jones, B, Till, K, Marshall, P, Earle, K, and Abt, G. Quantifying the external and internal loads of professional rugby league training modes: consideration for concurrent field-based training prescription. J Strength Cond Res 34(12): 3514-3522, 2020-Practitioners prescribe numerous training modes to develop the varied physical qualities that professional rugby league players must express during competition. The aim of this study was to determine how the magnitude of external and internal training load per minute of time differs between modes in professional rugby league players. These data were collected from 17 players across 716 individual sessions (mean [SD] sessions: 42 [13] per player) which were categorized by mode (conditioning [CON], small-sided games, skills, and sprint training). Derived from global positioning systems (5 Hz with 15 Hz interpolation), the distances covered within arbitrary speed and metabolic power thresholds were determined to represent the external load. Session rating of perceived exertion and individualized training impulse represented the internal load. All data were made relative to the session duration. The differences in time-relative load methods between each mode were assessed using magnitude-based inferences. Small-sided games and CON very likely to almost certainly produced the greatest relative internal and external loads. Sprint training provided players with the greatest sprinting and maximal-power distances without a concomitant increase in the internal load. The metabolic power method complements speed-based quantification of the external load, particularly during small-sided games and skills training. In practice, establishing normative loads per minute of time for each mode can be useful to plan future training by multiplying this value by the planned session duration.

BackgroundLimited research has investigated the association between training load and performance of basketball players during games. Little is known about how different indicators of player performance are affected by internal and external loads. The purpose of this study was to determine whether external and internal loads influence basketball players’ performance during games.MethodThis longitudinal study involved 20 professional male basketball players from a single team, classified as first-level athletes by the Chinese Basketball Association. During 34 games, external load was measured as PlayerLoad using micro-sensors, while internal load was assessed using session rating of perceived exertion (sRPE). Player performance was quantified using three metrics: Efficiency, Player Index Rating (PIR), and Plus-Minus (PM). Pearson correlation coefficients were calculated to assess the strength of the relationships between training loads and performance metrics. Linear mixed-effects models were applied to further analyze the influence of internal and external loads on basketball performance.ResultsPearson correlation analysis revealed moderate positive correlations between both sRPE and PlayerLoad with Efficiency and PIR. Specifically, sRPE (r = 0.52) and PlayerLoad (r = 0.54) were both significantly correlated with Efficiency. For PIR, sRPE (r = 0.50) and PlayerLoad (r = 0.56) also demonstrated moderate correlations. These correlations were further substantiated by linear mixed-effects models, which showed that sRPE (β = 2.21, p < 0.001) and PlayerLoad (β = 1.87, p = 0.004) had significant independent effects on Efficiency. Similarly, sRPE (β = 2.15, p < 0.001) and PlayerLoad (β = 2.36, p < 0.001) significantly predicted PIR. Additionally, a significant interaction effect between PlayerLoad and sRPE was found on Plus-Minus (β = -2.49, p < 0.001), indicating that the combination of high physical and psychological loads negatively impacted overall team performance. However, the correlation strengths for Plus-Minus were relatively low (sRPE: r = 0.16; PlayerLoad: r = 0.10).ConclusionBoth external and internal loads positively contribute to performance, the integration of objective (accelerometry) and subjective (sRPE) measures of load provides a comprehensive understanding of the physiological and psychological demands on athletes, contributing to more effective training regimens and performance optimization.

Running programs traditionally monitor external loads (eg, time and distance). Recent efforts have encouraged a more comprehensive approach to also account for internal loads (eg, intensity, measured as the session rating of perceived exertion [sRPE]). The combination of external and internal loads accounts for the possible interaction between these loads. Although weekly changes in training loads have been reported between external loads and the combination of external and internal loads during 2- and 4-week training cycles, no authors have indicated whether these differences occur during an entire cross-country season in high school runners. To compare changes in training loads, as measured by (1) external loads and (2) combined external and internal loads in high school runners during an interscholastic cross-country season. Case series. Community-based setting with daily online surveys. Twenty-four high school cross-country runners (females = 14, males = 10, age = 15.9 ± 1.1 years, running experience = 9.9 ± 3.2 years). Week-to-week percentage changes in training load were measured by external loads (time, distance) and combined external and internal loads (time × sRPE [timeRPE] and distance × sRPE [distanceRPE]). Overall, the average weekly change was 7.1% greater for distanceRPE than for distance (P = .04, d = 0.18). When the weekly running duration decreased, we found the average weekly change was 5.2% greater for distanceRPE than for timeRPE (P = .03, d = 0.24). When the weekly running duration was maintained or increased, the average weekly change was 10% to 15% greater when external and internal loads were combined versus external loads alone, but these differences were nonsignificant (P = .11-.22, d = 0.19-0.34). Progression in the training load may be underestimated when relying solely on external loads. The interaction between internal loads (sRPE) and external loads (distance or time) appears to provide a different measure of the training stresses experienced by runners than external loads alone.

This study aimed to assess the effect of playing different pick-and-roll (PnR) defensive tactical options during small-sided games (SSGs) on external and internal loads in female basketball players. Twelve female basketball players (age 28 [2]y; stature 175 [6]cm; body mass 65 [7]kg; playing experience 18 [4]y) belonging to a team competing in the Lithuanian second division were recruited for this study. Across 3 experimental sessions and in a randomized order, players performed 3 SSGs sharing the same features but using 3 defensive strategies on the middle PnR action: Switch, Trap, and Drop. External load was measured using PlayerLoad (PL); the number of accelerations, decelerations, and changes of direction, classified based on their intensities as low (<2.5m·s-2), medium (2.5-3.5m·s-2), and high (>3.5m·s-2); and jumps categorized as low (<40cm) and high (≥40cm). Internal load was measured via rating of perceived exertion (RPE). Higher PL values in SSGs including Trap defense were found compared with Drop (P < .001, ES = 0.69, moderate) and Switch (P = .001, ES = 0.60, moderate). Additionally, a higher number of accelerations was registered in Trap defense compared with Drop defense (P = .027, ES = 0.99, moderate). Trap defense also led to higher RPE compared with Switch (P = .003, ES = 1.49, large) and Drop (P = .004, ES = 1.42, large) defense. Different defensive strategies on the middle PnR can influence the external and internal loads during SSGs, and female basketball coaches should consider the high demand of the Trap defense when designing SSGs.

The purposes of this study were (1) to analyze between-session variations of external and internal load measures during small-sided games (SSGs) and (2) to test the relationships between the maximum speed reached (VIFT) during the last stage of the 30-15 Intermittent Fitness Test, hemoglobin levels, and training load measures during SSG intervals among professional soccer players. Sixteen professional soccer players (mean ± SD; age 27.2 ± 3.4 years, height 174.2 ± 3.6 cm, body mass 69.1 ± 6.4 kg, and body fat 10.4 ± 4.1%) participated in this study. Hemoglobin and aerobic performance were first tested, and then a 3-week SSG program was applied using a 3 vs. 3 format. During those 3 weeks, internal and external load of entire sessions were also monitored for all training sessions. Trivial-to-small, standardized differences were observed between sessions for external and internal measures during SSGs. Total distance (TD) and mechanical work (MW) were the only variables that indicated small changes. Large-to-very-large relationships were found between VIFT and external loads: TD (r range: 0.69; 0.87), high-intensity running (HIR; r range: 0.66; 0.75), and MW (r range: 0.56; 0.68). Moderate-to-large negative relationships were found between hemoglobin levels and internal loads: Edwards’ TRIMP (r range: −0.36; −0.63), %HRmax (r range: −0.50; −0.61), and red zone (r range: −0.50; −0.61). VIFT had unclear relationships with overall internal loads, while hemoglobin levels presented unclear relationships with overall external loads. In conclusion, no meaningful changes were found between sessions considering the format of play used. Additionally, the detected relationships indicate that VIFT and hemoglobin levels are good indicators of the performance capacity and physiological profile of players during SSGs. Also, the use of SSGs protocols as a monitoring complement of the 30-15IFT is suggested.

Background: Moderate to very large correlation between internal training load, external training load, and recovery status have been reported in elite youth football. However, little is known about subelite youth football training environments. Objective: The purpose of this study was to assess the association between training load and recovery status in young subelite football players. Methods: Twenty under-15, twenty under-17, and twenty under-19 players were monitored over a 6-week period during the first month of the 2019-2020 competitive season. The global positioning system technology (GPS) was used to collect external training load variables. The internal training load variables were monitored using the rating of perceived exertion (RPE) scale and session RPE (sRPE). The recovery status was assessed by the total quality recovery (TQR). A total of 18 training sessions and 324 observation cases were collected. Results: Small to moderate correlation between internal and external load was observed (r = -0.316 to 0.136, p &lt; 0.05). Correlations between recovery status and external load were moderate for U15 (r = -0.326 to -0.240, p &lt; 0.05), U17 (r = -0.316 to 0.136, p &lt; 0.05) and U19 (r = -0.301 to 0.282, p &lt; 0.05). The association between perceived exertion and external training load is only significant for U19 subelite football players. Conclusion: Current research suggested that subelite youth football players were more likely to have lower capacity to judge training exertion. Additionally, recovery status was positively correlated with acceleration and deceleration movements. This study provides a new overview about training load and recovery in subelite youth training environment. Future researche should examine the between- and within-individual nonlinearity across training load and recovery variations.

Chapter 1. Introduction: Eutrophication is one of the world's major water quality problems. Attempts to alleviate eutrophication of lakes have involved the control of phosphorus loadings. In such cases, an internal loading of phosphorus from the sediments may retard an improvement of the water quality. Chapters 2 - 5 deal specifically with the sediments of Lake Loosdrecht.Chapter 2. Distribution and forms of phosphorus in the sediments of the Loosdrecht Lakes (the Netherlands): The phosphorus loading entering the Dutch Lake Loosdrecht was reduced in 1984. A survey of the sediments of this lake indicated that an enrichment of these sediments with phosphorus was limited to the area near the former inlet of polluted water from the River Vecht. In most other areas the phosphorus accumulation in the upper 18 cm. was 10 - 15 g P m -2, equal to the external P loading of approximately one decade. This is probably due to the transport of phosphorus from the surficial sediments with the percolating. seepage water. A rough estimation indicates that the amount of phosphorus carried away with this seepage compensates for the external loading. Results of selective extractions, desorption experiments and bio-assays all indicate that 5 % or less of the phosphorus in the upper sediment layers is "available" for algal growth.Chapter 3. Unmasking the particulate organic matter in a lake ecosystem: origin and fate of POM in the shallow eutrophic Loosdrecht Lakes: The sediments of Lake Loosdrecht consist for over 50 % of organic matter. Pyrolysis mass spectroscopical analysis indicated that over 95% of this organic matter is old macrophyte debris, probably originating from the peat deposits in the lake area. In winter, this material also contributes significantly to the seston in the water column. In summer the seston consists almost entirely of algal material. However, only traces of this latter material could be detected even in the upper mm, of the sediments, suggesting that the influx of algal matter in the sediments is small or that a fast degradation of the material reaching the sediments takes place.Chapter 4. Phosphorus release from the peaty sediments of the Loosdrecht Lakes (the Netherlands): The release of phosphorus from the sediments of Lake Loosdrecht was studied in some detail using continuous flow reactors. The highest release rates, up to about 4 mg P m -2d -1, were found in summer and the lowest, less than 0.5 mg P m -2d -1, were measured in winter. Temperature and downward seepage are the two most important factors controlling release rates. pH of the water column, which many other researchers found to be an important controlling factor, did not play any role in Lake Loosdrecht. The influence of temperature and seepage were more pronounced in summer than in winter. The magnitude of the release rate and the influence of temperature and seepage could be largely, explained by a simple steady-state model based upon mineralization and precipitation processes. According to this model, the phosphorus release from the sediments of Lake Loosdrecht is mainly governed by mineralization processes. Retardation of phosphorus by precipitation plays only a minor role.Chapter 5. Ion concentrations in interstitial waters as indicators for phosphorus release processes and reactions: Processes governing the release of phosphorus in the sediments of Lake Loosdrecht were studied in more detail using pore water concentrations of phosphorus, ammonium, iron and DOC and pH. The local differences in pore water composition were much larger than those in sediment composition. So, pore water concentrations are much more sensitive indicators for processes in the sediments than sediment composition. From the close correlation between phosphorus and ammonium concentrations it was concluded that mineralization is the dominant process regulating phosphorus concentrations in the pore waters. Possibly, also precipitation of vivianite plays a role. Finally, several indications were found that the large amounts of refractory organic matter in the sediments of Lake Loosdrecht limit the availability of iron for binding of phosphorus.Chapter 6. The influence of pH on phosphate release from lake sediments: The release of phosphorus from the sediments is often believed to be increased by a high pH in the water column. This is usually attributed to a decreased adsorption capacity for phosphate of iron(III)oxyhydroxydes at the sediment-water interface. This mechanism is commonly studied in laboratory experiments in which the pH of the water column is manipulated by titration with NaOH. In nature, however, pH is increased by a reduced partial CO 2 pressure caused by uptake of CO 2 , by the phytoplankton. This process was simulated in the laboratory in continuous flow reactors by stripping the CO 2 , from the air which was lead through the water column. In the latter case the phosphorus release rate increased much less than when using the traditional experimental setup with NaOH. Measurements of pH gradients near the sediment-water interface showed that when using NaOH additions the high pH in the water column penetrated much deeper in the sediments than when using CO 2 , stripping. Addition of NaOH increases the alkalinity, and the transport of alkalinity from the sediments to the water reduces or even reverses in direction. By removing CO 2 , the alkalinity is not changed or eventually reduced by precipitation of calcite.Chapter 7. Lake restoration: estimation of internal phosphorus loading after reduction of external loading from sediment data: From literature data on a number of lakes with reduced external phosphorus loadings it was concluded that in most cases an annual net loading from the sediments takes place during several years. For the limited number of lakes for which sediment data were available, the internal loading rate was found to be highly significantly related to the phosphorus content and the P/Fe ratio in the sediment. These relationships can help to predict the internal loading rate, to be expected after reduction of the external loading.Chapter 8. Phosphorus fixation with iron (III)chloride: a new method to combat internal phosphorus loading in shallow lakes?: The traditional method to speed up the recovery of a lake with a significant internal loading is to remove the phosphorus rich upper sediment layers. However, this method is costly and time consuming. Treatment of the sediments with phosphorus binding compounds might be an alternative. Iron(III)chloride is a candidate, as it is a natural phosphorus-binding agent and non-toxic. Laboratory experiments indicated that addition of at least 100 g Fe m -2to lake sediments will strongly decrease the phosphorus release rate. The sediments of the shallow lake Groot Vogelenzang were treated with 100 g Fe m -2resulting in an immediate improvement of the water quality. This improvement lasted for only three months. A large external phosphorus loading, caused by rapid flushing with water from the surrounding lakes is held responsible for this failure. Nevertheless, release experiments and phosphorus budget calculations both indicated that the phosphorus retention in the sediments of lake Groot Vogelenzang had increased with about 3 mgP m -2d -1,Chapter 9. Changes in phosphorus cycling in a shallow lake due to foodweb manipulations: Biomanipulation is a recently developed method to improve water quality in lakes by removing undesired fish species and reintroducing other, desired but lacking species. 'Me goal of this lake restoration technique is to improve the predation on whitefish and thereby to decrease the predation of whitefish on zooplankton. Application of biomanipulation in small, shallow lakes usually results in a highly increased Secchi depth and strongly reduced algal biomass. In this chapter, the changes in the phosphorus cycling of the shallow lake Wolderwijd/Nuldernauw after biomanipulation were quantified. Before biomanipulation, most of the phosphorus in the food web is accumulated in fish, but a small portion is recycled rapidly in the water column. Sedimentation of detritus is the most important loss process. No evidence could be found for the hypothesis that the bottom stirring activities of fish enhance the phosphorus release.The availability of phosphorus for phytoplankton may decrease after biomanipulation for two reasons. The first is that the detritus formed from green algae is more refractory than the detritus from cyanobacteria. Therefore, the phosphorus content of cyanobacteria is recycled more rapidly. Cyanobacteria. will probably disappear after biomanipulation due to the improved light climate. The second reason is that the increased bottom area covered with submerged macrophytes enhances the net sedimentation of detritus from the water column and concomittantly the regeneration rate of phosphorus in the water column decreases. These changes in the phosphorus cycling in the lake may reinforce the success of biomanipulation.CONCLUSIONSUndoubtedly, the release of phosphorus from sediments forms an important part of the phosphorus cycling in shallow lakes. In the Loosdrecht Lakes, this release was found to be of the same magnitude as the external loading, although only a small proportion of the sediment phosphorus is "exchangeable". Mineralization of organic phosphorus reaching the sediments is the most important process for the phosphorus release. The availability of iron in the sediments of these lakes appeared to be an important factor in the retention of the phosphorus that is released by mineralization. The presence of large amounts of refractory organic matter in the sediments of the Loosdrecht Lakes seems to limit the potential of iron to bind phosphorus. The sources and fate of iron in aquatic sediments need further research. Probably, the availability of iron for the binding of phosphate is related to the cycling of other elements, such as sulfur, in the sediments.Just as important for the phosphorus cycling in a shallow lake is the settling to the sediments. The characterization of the particulate organic matter in the sediments of the Loosdrecht Lakes indicated that either the influx of algal matter into the sediments is very small or that this material is mineralized very rapidly. Possibly, the slow recovery of Lake Loosdrecht and other shallow, wind-exposed lakes is not only caused by internal phosphorus loading, but also by a poor sedimentation of particulate phosphorus from the water column.A quantification of the cycling of phosphorus through the food web revealed that changes in the sedimentation process may affect the availability of phosphorus to algae. In turn, the sedimentation is influenced by the presence of submersed macrophytes.Attention for the environmental conditions is necessary for a proper quantification of the internal loading rates. Some of the relevant conditions were discussed in this thesis. Resuspension of bottom material by benthivorous fish is not of any importance for the release of phosphorus from the sediments. The influence of the pH in the water column was found to be less important than reported by other researchers. Temperature and the sedimentation of particulate organic matter are two reasons for release maxima in summer.One of the most important questions in lake restoration is whether the improvement of the water quality will be delayed, following a reduction of the external loading. Although the results of the studies in Lake Loosdrecht indicate that the internal loading is of the same order of magnitude as the external loading, no direct proof of a delay of the recovery of the lake due to this internal loading could be found.From literature data on a number of shallow lakes with reduced external phosphorus loadings it could be concluded that indeed initially a net internal loading may take place upon restoration. The magnitude of this internal loading is related to the phosphorus content of the sediments and to the P/Fe ratio in the sediment. This latter may be a measure of the residual phosphorus binding capacity of the sediments. As long as no other methods to predict the occurrence of internal loading are available, the relations found between internal loading and sediment composition may be used. The question to what extent chemical extractions, bio-assays or laboratory release experiments can be used to predict the behavior of a lake after a reduction of the external loading is an important but still unanswered one.According to this study, upon restoration a net internal loading can be expected to take place already at a phosphorus content of the sediment of 1.4 mg P g -1. So, internal loading will take place in most of the Dutch lakes after a decrease of the external loading. To what extent this internal loading will delay the improvement of the water quality, depends on other characteristics of the lake, as the residual external loading and the residence time. Although internal loading will not last forever, in a number of cases additional "sediment restoration techniques" will be needed to recover lakes within an acceptable space of time. As dredging of the upper sediment layers is extremely costly and time consuming, alternatives for this sediment restoration technique are needed. Fixation of phosphorus in the sediments with phosphorus binding chemicals may be an alternative. In this study, the availability of iron was found to be an important factor in the immobilization of phosphorus in freshwater sediments and addition of iron compounds to the sediments may strengthen this natural Process. Although the method is promising, its suitability to reduce internal loading must still be proven. An important unanswered question is to what extent the added iron remains available for phosphorus binding.

Zhang, S, Li, M, Xing, W, Zheng, W, and Zhai, Z. Effects of player characteristics and periodization strategies on external and internal loads, wellness, and recovery in collegiate male basketball players. J Strength Cond Res 40(5): e472-e478, 2026-This study investigated the effects of playing time, player role, player position, and training cycles-both microcycles (the six days leading up to a match) and mesocycles (the four weeks preceding competition)-on PlayerLoad (PL), rating of perceived exertion (RPE),well-being (WB), and total quality recovery (TQR) in highly trained collegiate male basketball players. A total of 18 highly trained collegiate male basketball players were monitored across a continuous 2-month, resulting in a total of 804 training session observations. External load was quantified as PL using wearable tracking devices, while internal load was assessed through RPE. Well-being and TQR were measured using digital self-report questionnaires. The key findings showed that high-minute players (>26 minutes) exhibited significantly higher PL ( p < 0.05, effect sizes [ES] = 0.34) and RPE ( p < 0.05, ES = 0.33) compared with low-minute players (<26 minutes). Positional differences were also reported, with centers reporting significantly lower RPE than forwards ( p < 0.05, ES = -0.67) and higher WB than guards ( p < 0.05, ES = -0.88). In the microcycle analysis, the highest PL and RPE were observed 5 to 6 days before official matches. Mesocycle analysis showed a significant increase in PL and RPE during week 2, accompanied by a concurrent decrease in TQR. These results demonstrate that playing time, player role, player position, and training cycles significantly influence PL, RPE, WB, and TQR, underscoring the importance of individualized load management within microcycle and mesocycle structures to optimize performance and recovery in collegiate male basketball players.