Estimation of lactate release from contracting muscles in man

Factors Influencing Running Velocity at Lactate Threshold in Male and Female Runners at Different Levels of Performance

BACKGROUND

The primary aim was to examine the relationship between lactate threshold (LT) expressed as percentage of maximal oxygen uptake (VO2max) and running velocity at LT (LTV). A secondary aim was to investigate to what extent VO2max, oxygen cost of running (CR), and maximal aerobic speed (MAS) determined LTV. A third aim was to investigate potential differences in LT and LTV between elite, national and recreational runners, as well as possible gender differences regarding VO2max, CR, LT, and LTV.

METHODS

Seventy-five competitive runners (37 males and 38 females) with an average VO2max of 63.0 ± 9.3 mL⋅kg-1⋅min-1, and an average LTV of 13.6 ± 2.3 km⋅h-1 were tested for VO2max, LT, LTV, MAS, and CR.

RESULTS

Lactate threshold did not correlate with LTV. With an r - value of 0.95 (p < 0.001) and a standard error of estimate of 4.0%, the product of MAS and individual LT determined 90% of LTV, outside a range of ±0.27 km⋅h-1. LTV increased with higher performance level. However, LT did not differ between elite, national and recreational runners. Female runners had 2.5% higher LT, 8% lower LTV, and 21% lower VO2max, but 9% better CR than male runners.

CONCLUSION

Lactate threshold did not correlate with LTV. The product of MAS and LT correlated strongly with LTV. There were no differences between elite, national and recreational runners regarding LT, but female runners had higher LT than the male runners. Female runners at the same relative performance level had lower LTV and VO2max, but better CR than male runners.

Influence of Interval Training Frequency on Time-Trial Performance in Elite Endurance Athletes

PURPOSE

To determine the impact of interval training frequency in elite endurance athletes. It was hypothesized that two longer sessions would elicit greater performance improvements and physiological adaptation than four shorter sessions at the same intensity.

METHODS

Elite cross-country skiers and biathletes were randomly assigned to either a high-frequency group (HF group) (5 M, 1 F, age 22 (19-26), VO_2max 67.8 (65.5-70.2) mL/kg/min) doing four short interval sessions per week or a low-frequency group (LF group) (8 M, 1 F, age 22 (18-23), VO_2max 70.7 (67.0-73.9) mL/kg/min) doing two longer interval sessions. All interval sessions were performed at ~85% of maximum heart rate, and groups were matched for total weekly training volume. Pre- and post-intervention, athletes completed an 8 km rollerski time-trial, maximal oxygen uptake (VO_2max) test, and an incremental, submaximal exercise test.

RESULTS

The LF group had a statistically significant improved time-trial performance following the intervention (p = 0.04), with no statistically significant changes in the HF group. Similarly, percentage utilization of VO_2max at anaerobic threshold (p = 0.04) and exercise economy (p = 0.01) were statistically significantly improved following the intervention in the LF group only. No statistically significant changes in VO_2max were observed in either group.

CONCLUSIONS

Two longer interval sessions appear superior to four shorter sessions per week in promoting endurance adaptations and performance improvements in elite endurance athletes. Despite matched training volume and exercise intensity, the larger, more concentrated exercise stimulus in the LF group appears to induce more favorable adaptations. The longer time between training sessions in the LF group may also have allowed athletes to recover more effectively and better "absorb" the training. These findings are in line with the "best practice" observed by many of the world's best endurance athletes.

Strength training in soccer with a specific focus on highly trained players

Background

Data concerning the physical demands of soccer (e.g., activity pattern) suggest that a high level of performance requires well-developed neuromuscular function (NF). Proficient NF may be relevant to maintain and/or increase players’ short- (intense periods of soccer-specific activity; accelerations, decelerations, and sprinting) and long-term performance during a match and throughout the season.

Objective

This review examines the extent to which distinct modes of strength training improve soccer players’ performance, as well as the effects of concurrent strength and endurance training on the physical capacity of players.

Data sources

A selection of studies was performed in two screening phases. The first phase consisted of identifying articles through a systematic search using relevant databases, including the US National Library of Medicine (PubMed), MEDLINE, and SportDiscus. Several permutations of keywords were utilized (e.g., soccer; strength; power; muscle function), along with the additional scanning of the reference lists of relevant manuscripts. Given the wide range of this review, additional researchers were included. The second phase involved applying six selection criteria to the articles.

Results and conclusions

After the two selection phases, 24 manuscripts involving a total sample of 523 soccer players were considered. Our analysis suggests that professional players need to significantly increase their strength to obtain slight improvements in certain running-based actions (sprint and change of direction speed). Strength training induces greater performance improvements in jump actions than in running-based activities, and these achievements varied according to the motor task [e.g., greater improvements in acceleration (10 m) than in maximal speed (40 m) running movements and in non-squat jump (SJ) than in SSC-based actions (countermovement jump)]. With regard to the strength/power training methods used by soccer players, high-intensity resistance training seems to be more efficient than moderate-intensity resistance training (hypertrophic). From a training frequency perspective, two weekly sessions of strength training are sufficient to increase a player’s force production and muscle power-based actions during pre-season, with one weekly session being adequate to avoid in-season detraining. Nevertheless, to further improve performance during the competitive period, training should incorporate a higher volume of soccer-specific power-based actions that target the neuromuscular system. Combined strength/power training programs involving different movement patterns and an increased focus on soccer-specific power-based actions are preferred over traditional resistance exercises, not only due to their superior efficiency but also due to their ecological value. Strength/power training programs should incorporate a significant number of exercises targeting the efficiency of stretch-shortening-cycle activities and soccer-specific strength-based actions. Manipulation of training surfaces could constitute an important training strategy (e.g., when players are returning from an injury). In addition, given the conditional concurrent nature of the sport, concurrent high-intensity strength and high-intensity endurance training modes (HIT) may enhance a player’s overall performance capacity.

Our analysis suggests that neuromuscular training improves both physiological and physical measures associated with the high-level performance of soccer players.

Electronic supplementary material

The online version of this article (doi:10.1186/s40798-015-0006-z) contains supplementary material, which is available to authorized users.

A time-saving method to assess power output at lactate threshold in well-trained and elite cyclists

The purpose of this study was to examine the relationship between lactate threshold (LT) as a percentage of maximal oxygen consumption (V[Combining Dot Above]O2max) and power output at LT (LTW) and also to investigate to what extent V[Combining Dot Above]O2max, oxygen cost of cycling (CC), and maximal aerobic power (MAP) determine LTW in cycling to develop a new time-saving model for testing LTW. To do this, 108 male competitive cyclists with an average V[Combining Dot Above]O2max of 65.2 ± 7.4 ml·kg·min and an average LTW of 274 ± 43 W were tested for V[Combining Dot Above]O2max, LT %V[Combining Dot Above]O2max, LTW, MAP, and CC on a test ergometer cycle. The product of MAP and individual LT in %V[Combining Dot Above]O2max was found to be a good determinant of LTW (R = 0.98, p < 0.0001). However, LT in %V[Combining Dot Above]O2max was found to be a poor determinant of LTW (R = 0.39, p < 0.0001). Based on these findings, we have suggested a new time-saving method for calculating LTW in well-trained cyclists. The benefits from this model come both from tracking LTW during training interventions and from regularly assessing training status in competitive cyclists. Briefly, this method is based on the present findings that LTW depends on LT in %V[Combining Dot Above]O2max, V[Combining Dot Above]O2max, and CC and may after an initial test session reduce the time for the subsequent testing of LTW by as much as 50% without the need for blood samples.

Nutrient intake and food habits of soccer players: analyzing the correlates of eating practice

Despite the impact and popularity of soccer, and the growing field of soccer-related scientific research, little attention has been devoted to the nutritional intake and eating habits of soccer players. Moreover, the few studies that have addressed this issue suggest that the nutritional intake of soccer players is inadequate, underscoring the need for better adherence to nutritional recommendations and the development and implementation of nutrition education programs. The objective of these programs would be to promote healthy eating habits for male and female soccer players of all ages to optimize performance and provide health benefits that last beyond the end of a player's career. To date, no well-designed nutrition education program has been implemented for soccer players. The design and implementation of such an intervention requires a priori knowledge of nutritional intake and other correlates of food selection, such as food preferences and the influence of field position on nutrient intake, as well as detailed analysis of nutritional intake on match days, on which little data is available. Our aim is to provide an up-to-date overview of the nutritional intake, eating habits, and correlates of eating practice of soccer players.

Physiological determinants of the cycling time trial

The purpose of this study was to examine the physiological determinants of endurance cycling time trial (TT) performance in a heterogeneous group of competitive male road cyclists. About 15 male cyclists who had all competed in cycling the preceding season were tested for the anthropometric variables height, body weight, leg length, ankle circumference, and body fat percentage. They were also tested for maximal oxygen consumption (VO2max), lactate threshold (LT), metabolic cost of cycling (CC), peak power output and average power output during a 30-second Wingate test, 1 repetition maximum and peak power in half squats, and a TT test on an ergometer. Heart rate and cadence (rounds per minute, RPM) were continuously measured during all cycle tests. Pearson Bivariate correlation tests and single linear regression tests were performed to obtain correlation coefficients (r), effect size (F), standard error of estimate (SEE), and 95% confidence interval. The single variable that correlated best with TT performance was power output at LT (r = 0.86, p < 0.01). Standard error of estimate was 7.5%. Lactate threshold expressed in %VO2max did not correlate significantly with TT performance. An equation representing both aerobic and anaerobic endurance capacity TT(w) = 0.95 ([VO2max/CC] TT%VO2max) + 0.05 (Wingate average) correlated strongly with TT laboratory performance (r = 0.93, p < 0.01, SEE = 5.7%). None of the strength, power, or anthropometric variables correlated significantly with TT laboratory performance.

A modified TRIMP to quantify the in-season training load of team sport players

The aims of the study were to modify the training impulse (TRIMP) method of quantifying training load for use with intermittent team sports, and to examine the relationship between this modified TRIMP (TRIMP(MOD)) and changes in the physiological profile of team sport players during a competitive season. Eight male field hockey players, participating in the English Premier Division, took part in the study (mean+/-s: age 26+/-4 years, body mass 80.8+/-5.2 kg, stature 1.82+/-0.04 m). Participants performed three treadmill exercise tests at the start of the competitive season and mid-season: a submaximal test to establish the treadmill speed at a blood lactate concentration of 4 mmol . l(-1); a maximal incremental test to determine maximal oxygen uptake ([V]O(2max)) and peak running speed; and an all-out constant-load test to determine time to exhaustion. Heart rate was recorded during all training sessions and match-play, from which TRIMP(MOD) was calculated. Mean weekly TRIMP(MOD) was correlated with the change in [V]O(2max) and treadmill speed at a blood lactate concentration of 4 mmol x l(-1) from the start of to mid-season (P<0.05). The results suggest that TRIMP(MOD) is a means of quantifying training load in team sports and can be used to prescribe training for the maintenance or improvement of aerobic fitness during the competitive season.

Food habits and nutritional status assessment of adolescent soccer players. A necessary and accurate approach

The aim of this study was to assess the food habits and nutritional status of high level adolescent soccer players (N = 33; ages 14-16 yrs) living in their home environment. Body composition (height, mass, skinfolds), biochemical and hematological parameters, performance in soccer-specific tests (sprinting, jumping, intermittent endurance), and dietary intake (weighed food intake method) and related behaviors (nutrient supplement use, daily activity profile) were assessed. Daily energy expenditure and energy intake were 12.5 MJ and 12.6 MJ, respectively. Protein (16% of energy intake; 1.9 g/kg of body mass), lipid (38%), and cholesterol (385 mg) intake were above recommendations, while carbohydrates (45%) were below. The food intake of these adolescents was based on cereals and derivates; meat, fish, and eggs; milk and dairy products; biscuits and confectionery; and oil, butter and margarine, which provided 78% of total energy intake, 85% of proteins, 64% of carbohydrates, 90% of lipids, and 47% of fiber. Although diet provided sufficient iron, 48% of individuals showed iron deficiency without anemia. Based on these results, a well designed nutrition intervention would be advisable for optimizing performance, and especially for promoting healthy eating habits in adolescent soccer players.

Lactate release, concentration in blood, and apparent distribution volume after intense bicycling

To study the release of lactate from muscle and its relationship to the blood lactate concentration during and after intense bicycling, young men cycled at 5.5 W kg(-1) body mass for 2 min to exhaustion or stopped after 1 min (nonexhaustive ride). The leg's release of lactate during and after each ride was taken from the measured blood flow and lactate concentrations in arterial and femoral-venous blood. Muscle biopsies were taken in separate experiments and analyzed for lactate. During the bicycling, 6 to 10% of the lactate produced was released to the blood. During exercise and for the first few minutes after, the rate of lactate release did not differ between 2 min exhaustive and 1 min nonexhaustive bicycling. The integrated release (exercise plus recovery) for the 1 min bicycling was 60 to 80% of the corresponding value of the 2 min exhaustive bicycling. In the late recovery, the blood lactate concentration was 3 to 5 times higher after 2 min exhaustive bicycling than after the 1 min nonexhaustive bicycling. There was thus a mismatch between the amount of lactate released and measured concentration in blood, reflecting a smaller distribution volume after the exhaustive bicycling. The blood lactate concentration may therefore not be a good measure of the lactate production and anaerobic energy release during bicycling.

Energetics of high-intensity exercise (soccer) with particular reference to fatigue

Soccer entails intermittent exercise with bouts of short, intense activity punctuating longer periods of low-level, moderate-intensity exercise. High levels of blood lactate may sometimes be observed during a match but the active recovery periods at submaximal exercise levels allow for its removal on a continual basis. While anaerobic efforts are evident in activity with the ball and shadowing fast-moving opponents, the largest strain is placed on aerobic metabolism. On average, competitive soccer corresponds to an energy expenditure of about 75% maximal aerobic power. The energy expenditure varies with playing position, being highest among midfield players. Muscle glycogen levels can be reduced towards the end of a game, the level of reduction being reflected in a decrease in work rate. Blood glucose levels are generally well-maintained, although body temperature may rise by 2 degrees C even in temperate conditions. The distance covered by players tends to under-reflect the energy expended. Unorthodox modes of motion-running backwards and sideways, accelerating, decelerating and changing direction-accentuate the metabolic loading. These are compounded by the extra requirements for energy associated with dribbling the ball and contesting possession. The overall energy expended is extreme when players are required to play extra-time in tournaments. Training, nutritional and tactical strategies may be used to reduce the effects of fatigue that may occur late in the game.