Oliver Faude

Lactate threshold concepts: how valid are they?

During the last nearly 50 years, the blood lactate curve and lactate thresholds (LTs) have become important in the diagnosis of endurance performance. An intense and ongoing debate emerged, which was mainly based on terminology and/or the physiological background of LT concepts. The present review aims at evaluating LTs with regard to their validity in assessing endurance capacity. Additionally, LT concepts shall be integrated within the ‘aerobic-anaerobic transition’ — a framework which has often been used for performance diagnosis and intensity prescriptions in endurance sports.Usually, graded incremental exercise tests, eliciting an exponential rise in blood lactate concentrations (bLa), are used to arrive at lactate curves. A shift of such lactate curves indicates changes in endurance capacity. This very global approach, however, is hindered by several factors that may influence overall lactate levels. In addition, the exclusive use of the entire curve leads to some uncertainty as to the magnitude of endurance gains, which cannot be precisely estimated. This deficiency might be eliminated by the use of LTs.The aerobic-anaerobic transition may serve as a basis for individually assessing endurance performance as well as for prescribing intensities in endurance training. Additionally, several LT approaches may be integrated in this framework. This model consists of two typical breakpoints that are passed during incremental exercise: the intensity at which bLa begin to rise above baseline levels and the highest intensity at which lactate production and elimination are in equilibrium (maximal lactate steady state [MLSS]).Within this review, LTs are considered valid performance indicators when there are strong linear correlations with (simulated) endurance performance. In addition, a close relationship between LT and MLSS indicates validity regarding the prescription of training intensities.A total of 25 different LT concepts were located. All concepts were divided into three categories. Several authors use fixed bLa during incremental exercise to assess endurance performance (category 1). Other LT concepts aim at detecting the first rise in bLa above baseline levels (category 2). The third category consists of threshold concepts that aim at detecting either the MLSS or a rapid/distinct change in the inclination of the blood lactate curve (category 3).Thirty-two studies evaluated the relationship of LTs with performance in (partly simulated) endurance events. The overwhelming majority of those studies reported strong linear correlations, particularly for running events, suggesting a high percentage of common variance between LT and endurance performance. In addition, there is evidence that some LTs can estimate the MLSS. However, from a practical and statistical point of view it would be of interest to know the variability of individual differences between the respective threshold and the MLSS, which is rarely reported.Although there has been frequent and controversial debate on the LT phenomenon during the last three decades, many scientific studies have dealt with LT concepts, their value in assessing endurance performance or in prescribing exercise intensities in endurance training. The presented framework may help to clarify some aspects of the controversy and may give a rationale for performance diagnosis and training prescription in future research as well as in sports practice.

Injuries in female soccer players: a prospective study in the German national league.

Background In contrast to the high number of studies about soccer injuries in men, epidemiologic data in high-level female soccer players are scarce. Purpose Analysis of injury incidence in elite female soccer players. Study Design Descriptive epidemiology study. Methods There were 165 female soccer players (age, 22.4 ± 5.0 years) from 9 teams competing in the German national league, who were followed for one complete outdoor season. Their trainers documented the exposure to soccer on a weekly basis for each player, and the team physical therapists reported all injuries with regard to location, type, and circumstances of occurrence. An injury was defined as any physical complaint associated with soccer that limited sports participation for at least 1 day. Results There were 241 injuries sustained by 115 players (70%) reported; 39 injuries (16%) were owing to overuse, and 202 injuries (84%) were traumatic. Overall, 42% of the traumatic injuries occurred during training (2.8/1000 hours of training; 95% confidence interval, 2.2-3.4) and 58% during matches (23.3/1000 match hours; 95% confidence interval, 19.1-27.5); 102 of the traumatic injuries were caused by a contact situation, whereas 95 occurred without any contact. Most injuries (80%) were located at the lower extremities, concerning mainly the thigh (n = 44), knee (n = 45), and ankle (n = 43). Ankle sprain (n = 37) was the most often diagnosed injury. There were 51% minor injuries, 36% moderate injuries, and 13% major injuries. Eleven anterior cruciate ligament ruptures were observed during the season. Conclusion The results revealed a high injury incidence rate in games as well as a comparably low incidence rate during training. An important finding of this investigation was the frequent occurrence of anterior cruciate ligament ruptures. Preventive measures should thus focus on the high prevalence of anterior cruciate ligament tears, mostly occurring in noncontact situations.

Straight sprinting is the most frequent action in goal situations in professional football

Abstract The present study aimed to analyse the influence of speed and power abilities in goal situations in professional football. During the second half of the season 2007/08, videos of 360 goals in the first German national league were analysed by visual inspection. For the assisting and the scoring player the situations immediately preceding the goal were evaluated. The observed actions were categorised as: no powerful action, rotation (around the bodys centre-line), straight sprint, change-in-direction sprint, jump, or a combination of those categories. Two hundred and ninety-eight (83%) goals were preceded by at least one powerful action of the scoring or the assisting player. Most actions for the scoring player were straight sprints (n = 161, 45% of all analysed goals, P < 0.001) followed by jumps (n = 57, 16%), rotations and change-in-direction sprints (n = 22, 6% each). Most sprints were conducted without an opponent (n = 109, P < 0.001) and without the ball (n = 121, P < 0.001). Similarly, for the assisting player the most frequent action was a straight sprint (n = 137, P < 0.001) followed by rotations (n = 28), jumps (n = 22) and change-in-direction sprints (n = 18). The straight sprints were mostly conducted with the ball (n = 93, P = 0.003). In conclusion, straight sprinting is the most frequent action in goal situations. Power and speed abilities are important within decisive situations in professional football and, thus, should be included in fitness testing and training.

Risk factors for injuries in elite female soccer players

Objective: To describe risk factors for injuries in elite female soccer. Methods: A total of 143 female soccer players from the German national league participated in the study. Baseline information on player characteristics—for example, anthropometric measurements and playing position—and medical history were recorded at the start of the study. During one outdoor season, injuries and training and match exposure times were prospectively documented for each player. Results: The risk of a new anterior cruciate ligament (ACL) rupture was significantly increased in players with a previous rupture (odds ratio (OR)  =  5.24, p  =  0.01). This was not the case for ankle sprain (OR  =  1.39) or knee sprain (OR  =  1.50). In addition, no significantly increased risk of new sprains or ACL ruptures was found when the injured leg was the unit of analysis. Injury incidence was considerably higher in defenders (9.4 injuries per 1000 hours exposure) and strikers (8.4/1000 hours) than goalkeepers (4.8/1000 hours) and midfielders (4.6/1000 hours). Ten per cent of all players (n  =  14) sustained more than three injuries. Most of these were defenders (n  =  8) or strikers (n  =  4). Significantly more injuries occurred to the dominant leg (105 v 71, p  =  0.01); this was particularly true for contact injuries (52 v 29, p  =  0.01). Conclusions: Injury risk should be assessed on an individual basis. Therefore it seems appropriate to individualise preventive training programmes, as is recommended for other training content. Evaluating the existing rules of soccer and their appropriate application may also help to decrease injury risk, particularly in contact situations.

Exercise at given percentages of VO2max: Heterogeneous metabolic responses between individuals

PURPOSE Given percentages of VO(2max) are widely used for training and study purposes although they might not result in homogeneous metabolic strain. Therefore, the homogeneity of metabolic responses to prolonged exercise at fixed percentages of VO(2max) should be investigated. PROCEDURES Twenty-one healthy male subjects (29+/-5 years, 77+/-8 kg, VO(2max): 59.9+/-11.8 ml min(-1)kg(-1)) performed two incremental tests to exhaustion on a cycle ergometer to determine VO(2max). Subsequently, two 60 min tests at 60 and 75% VO(2max) were conducted in randomised order. VO(2) was kept constant by adjusting the work rate. Blood lactate (La) responses as primary outcome variable to quantify metabolic strain were assessed. FINDINGS Mean La was 2.1+/-1.1 mmol l(-1) (min-max: 0.7-5.6 mmol l(-1)) during the 60% VO(2max) test and 4.6+/-1.9 mmol l(-1) (min-max: 2.2-8.0 mmol l(-1)) during the 75% VO(2max) test. The coefficients of variation of La amounted for 52.4 and 41.3% during the 60 and 75% VO(2max) test, respectively. La responses did not differ significantly between three subgroups of the subjects (N=7 with VO(2max)<55 ml min(-1)kg(-1), N=7 with VO(2max) 55-65 ml min(-1)kg(-1), and N=7 with VO(2 max)>65 ml min(-1)kg(-1); P>or=0.08). CONCLUSION Altogether, prolonged exercise at given percentages of VO(2max) leads to inhomogeneous metabolic strain as indicated by the large variability of La responses. This holds true even in subgroups of similar aerobic capacity. Thus, intensity prescription for endurance training and study purposes should not be solely based upon percentages of VO(2max) when a comparable metabolic strain is intended.

Does prolonged cycling of moderate intensity affect immune cell function

Background: Prolonged exercise may induce temporary immunosuppression with a presumed increased susceptibility for infection. However, there are only few data on immune cell function after prolonged cycling at moderate intensities typical for road cycling training sessions. Methods: The present study examined the influence on immune cell function of 4 h of cycling at a constant intensity of 70% of the individual anaerobic threshold. Interleukin-6 (IL-6) and C-reactive protein (CRP), leukocyte and lymphocyte populations, activities of natural killer (NK), neutrophils, and monocytes were examined before and after exercise, and also on a control day without exercise. Results: Cycling for 4 h induced a moderate acute phase response with increases in IL-6 from 1.0 (SD 0.5) before to 9.6 (5.6) pg/ml 1 h after exercise and CRP from 0.5 (SD 0.4) before to 1.8 (1.3) mg/l 1 day after exercise. Although absolute numbers of circulating NK cells, monocytes, and neutrophils increased during exercise, on a per cell basis NK cell activity, neutrophil and monocyte phagocytosis, and monocyte oxidative burst did not significantly change after exercise. However, a minor effect over time for neutrophil oxidative burst was noted, tending to decrease after exercise. Conclusions: Prolonged cycling at moderate intensities does not seem to seriously alter the function of cells of the first line of defence. Therefore, the influence of a single typical road cycling training session on the immune system is only moderate and appears to be safe from an immunological point of view.

Is lactic acidosis a cause of exercise induced hyperventilation at the respiratory compensation point

Objectives: The respiratory compensation point (RCP) marks the onset of hyperventilation (“respiratory compensation”) during incremental exercise. Its physiological meaning has not yet been definitely determined, but the most common explanation is a failure of the body’s buffering mechanisms which leads to metabolic (lactic) acidosis. It was intended to test this experimentally. Methods: During a first ramp-like exercise test on a cycle ergometer, RCP (range: 2.51–3.73 l*min–1 oxygen uptake) was determined from gas exchange measurements in five healthy subjects (age 26–42; body mass index (BMI) 20.7–23.9 kg*m–2; Vo2peak 51.3–62.1 ml*min–1*kg–1). On the basis of simultaneous determinations of blood pH and base excess, the necessary amount of bicarbonate to completely buffer the metabolic acidosis was calculated. This quantity was administered intravenously in small doses during a second, otherwise identical, exercise test. Results: In each subject sufficient compensation for the acidosis, that is, a pH value constantly above 7.37, was attained during the second test. A delay but no disappearance of the hyperventilation was present in all participants when compared with the first test. RCP occurred on average at a significantly (p = 0.043) higher oxygen uptake (+0.15 l*min–1) compared with the first test. Conclusions: For the first time it was directly demonstrated that exercise induced lactic acidosis is causally involved in the hyperventilation which starts at RCP. However, it does not represent the only additional stimulus of ventilation during intense exercise. Muscle afferents and other sensory inputs from exercising muscles are alternative triggering mechanisms.

Pre-cooling and sports performance: a meta-analytical review.

Pre-cooling is used by many athletes for the purpose of reducing body temperature prior to exercise and, consequently, decreasing heat stress and improving performance. Although there are a considerable number of studies showing beneficial effects of pre-cooling, definite conclusions on the effectiveness of pre-cooling on performance cannot yet be drawn. Moreover, detailed analyses of the specific conditions under which pre-cooling may be most promising are, so far, missing. Therefore, we conducted a literature search and located 27 peer-reviewed randomized controlled trials, which addressed the effects of pre-cooling on performance. These studies were analysed with regard to performance effects and several test circumstances (environmental temperature, test protocol, cooling method, aerobic capacity of the subjects).Eighteen studies were performed in a hot (>26°C) environment and eight in a moderate. The cooling protocols were water application (n=12), cooling packs (n=3), cold drinks (n=2), cooling vest (n=6) and a cooled room (n=4). The following different performance tests were used: short-term, high-intensity sprints (n=2), intermittent sprints (n=6), time trials (n= 10), open-end tests (n=7) and graded exercise tests (n=2). If possible, subjects were grouped into different aerobic capacity levels according to their maximal oxygen consumption (

Reliability of gait parameters during treadmill walking in community-dwelling healthy seniors.

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Effects of slackline training on balance, jump performance & muscle activity in young children.

O2max): medium 55–65mL/kg/min (n= 11) and high >65 mL/kg/min (n=6). For all studies the relative changes of performance due to pre-cooling compared with a control condition, as well as effect sizes (Hedges’g) were calculated. Mean values were weighted according to the number of subjects in each study.Pre-cooling had a larger effect on performance in hot (+6.6%, g=0.62) than in moderate temperatures (+1.4%, g = 0.004). The largest performance enhancements were found for endurance tests like open-end tests (+8.6%, g=0.52), graded exercise tests (+6.0%, g=0.44) and time trials (+4.2%, g=0.44). A similar effect was observed for intermittent sprints (+3.3%, g = 0.43), whereas performance changes were smaller during short-term, high-intensity sprints (−0.5%, g = 0.03). The most promising cooling methods were cold drinks (+15.0%, g= 1.68), cooling packs (+5.6%, g = 0.70) and a cooled room (+10.7%, g = 0.49), whereas a cooling vest (+4.8%, g = 0.31) and water application (+1.2%, g = 0.21) showed only small effects. With respect to aerobic capacity, the best results were found in the subjects with the highest