Lactate Threshold Speed Research Articles

Durability in recreational runners: effects of 90-min low-intensity exercise on the running speed at the lactate threshold.

Recent studies have suggested that the capability to resist deterioration of physiological characteristics could be an independent factor contributing to endurance performance. This study aimed at investigating whether prolonged low-intensity exercise induces shifts in the lactate threshold, and whether fatigue-induced changes differ between the sexes. A total of 31 (15 females) recreational runners performed an incremental treadmill test and a 90-min low-intensity exercise (LIT90) on two separate occasions. The LIT90 was performed at 90% of the first lactate threshold speed (LT1v), derived from the incremental treadmill test. The LT1v was determined from a 5-stage (3min) submaximal threshold test (SubmaxLT), performed before and after LIT90. The SubmaxLTs were followed by a 10/5 reactivity jump test. Respiratory gases, heart rate (HR), and HR-derived detrended fluctuation analysis alpha 1 (DFA-a1) were assessed every 15min during the LIT90. A significant decrease (p < 0.01) was observed in the LT1v in females (-5.8 ± 4.4%) and in males (-5.3 ± 6.4%). The HR increased (p < 0.001) similarly in females (5.9 ± 3.1%) and in males (5.5 ± 3.6%) during the LIT90, while energy expenditure increased (3.1 ± 4.5%, p = 0.013) in females but remained unchanged in males (0.9 ± 3.1%). Change in DFA-a1 during the LIT90 was the only marker that correlated significantly with the relative change of LT1v (r = 0.463, p = 0.013). LIT90 induced significant decreases in the LT1v, and the changes were comparable between sexes. DFA-a1 could be a potential intra-session marker of durability.

Technologically advanced running shoes reduce oxygen cost and cumulative tibial loading per kilometer in recreational female and male runners

Technologically advanced running shoes (TARS) improve performance compared to classical running shoes (CRS). Improved race performance has been attributed to metabolic savings in male runners, but it remains unclear if these same benefits are experienced among females and in recreational runners. The mechanisms behind these benefits are still not fully understood despite the need for optimisation, and their influence on injury mechanisms has not been explored. Here we combined biomechanical, physiological, and modelling approaches to analyse joint mechanics, oxygen uptake, and tibial load in nineteen male and female recreational runners running with CRS and TARS at their individual lactate threshold speed (12.4 ± 1.9 km/h). Oxygen uptake was 3.0 ± 1.5% lower in TARS than in CRS. Ankle dorsiflexion, joint moment and joint power were reduced in TARS compared to CRS at various phases of stance including midstance, while knee joint mechanics were mostly similar throughout. There were no significant differences for tibial bending moment during the stance phase but cumulative tibial damage per kilometre was 12 ± 9% lower in TARS compared to CRS. Our results suggest that running with TARS reduces oxygen cost in recreational female and male runners, which may partly be explained by differences in lower limb joint mechanics. The lower cumulative tibial bone load with TARS may allow runners to run longer distances in this type of shoe compared to CRS.

The Effect Of Synchronous And Asynchronous Music On Treadmill Running Performance Of Recreational Athletes

BACKGROUND: Running with synchronous music tempo is associated with positive physiological and psychological effects that improve running performance as expressed by time to exhaustion. Changes in the music tempo may increase physiological efficiency (slow tempo) or improve motivation and mood (fast tempo), but there is no conclusive evidence whether asynchronous music tempo can influence distance covered or time to exhaustion. PURPOSE: To investigate the effect of different music tempi on running performance, force and cadence profiles of recreational athletes. METHODS: Six college students (age = 21.2± 3yr; weight = 75.4± 12kg; height = 179.5± 10cm) participated in the study. The participants were tested five times over a period of three weeks. During the first visit, lactate threshold speed (LTS) was assessed via blood samples. During the second visit participants run at 5% above their LTS (3.5±0.4m/s) with no auditory stimuli until exhaustion. During the last three visits participants were randomly assigned to run on an instrumented treadmill in three different tempo conditions until exhaustion: slow, matched and fast. Time to exhaustion, vertical ground reaction forces (vGRF) and cadence were calculated through Matlab. RESULTS: A one-way repeated ANOVA (4 conditions) showed that there was a main effect of music, with the no music condition resulting in a decrease in time to exhaustion by 18-21% when compared to all the music conditions, but no significant differences among the 3 music conditions. The vGRF during running at slow tempo (2.58 BW) were significantly lower when compared to fast tempo (2.62 BW), whereas there was an increase in cadence between slow (167 steps/min) and fast (170 steps/min) tempo conditions. CONCLUSION: The findings indicate that music – in general – has a positive effect on running performance, while asynchronous tempi can only cause significant but subtle changes (less than 2%) in the force and cadence profiles.

Kinematics and shock attenuation during a prolonged run on the athletic track as measured with inertial magnetic measurement units

BackgroundTibial stress fractures are common running related injury and their etiology may include biomechanical factors like impact forces, shock attenuation, lower limb kinematics and how these factors are influenced by intense or prolonged running. Inertial-magnetic measurement units (IMUs) have recently emerged as an alternative to motion capture but their use to date was mostly limited to segmental and joint motion. Research questionThe present study sought to examine the effects of a prolonged run on shock attenuation, peak tibial and sacral acceleration (PTA, PSA), and lower limb kinematics using IMUs. MethodsTen trained male runners (31 +/− 5 yr, 183 +/− 3 cm, 76 +/− 9 kg) performed a twenty-minute prolonged run on an athletic track at estimated lactate threshold speed. Eight IMUs, positioned over the feet, lower and uppers legs, sacrum and sternum, were used to calculate joint kinematics, impact parameters and shock attenuation in the time domain (1-(PSA/PTA)*100). ResultsPTA increased while PSA and shock attenuation did not change following the prolonged run. Hip and knee flexion at midstance decreased. Vertical lower leg angle at initial contact did not change. ConclusionBy using IMUs, it was shown that a prolonged run at estimated lactate threshold speed had significant effects on kinematics and tibial acceleration parameters. By modifying hip and knee joint kinematics during stance, the body was able to maintain sacral acceleration possibly by shifting from active shock attenuation to more passive mechanisms. SignificanceThe present study shows that inertial sensors can be used in outdoor running to measure joint kinematics and kinetic parameters like PTA, PSA and shock attenuation simultaneously. The results of this study show new insights into how the body copes with impact during prolonged running.

Changes in Achilles tendon stiffness and energy cost following a prolonged run in trained distance runners.

During prolonged running, the magnitude of Achilles tendon (AT) length change may increase, resulting in increased tendon strain energy return with each step. AT elongation might also affect the magnitude of triceps surae (TS) muscle shortening and shortening velocity, requiring greater activation and increased muscle energy cost. Therefore, we aimed to quantify the tendon strain energy return and muscle energy cost necessary to allow energy storage to occur prior to and following prolonged running. 14 trained male (n = 10) and female (n = 4) distance runners (24±4 years, 1.72±0.09 m, 61±10 kg, 64.6±5.8 ml•kg-1•min-1) ran 90 minutes (RUN) at approximately 85% of lactate threshold speed (sLT). Prior to and following RUN, AT stiffness and running energy cost (Erun) at 85% sLT were determined. AT energy return was calculated from AT stiffness, measured with dynamometry and ultrasound and estimated TS force during stance. TS energy cost was estimated on the basis of AT force and assumed crossbridge mechanics and energetics. Following RUN, AT stiffness was reduced from 328±172 N•mm-1 to 299±148 N•mm-1 (p = 0.022). Erun increased from 4.56±0.32 J•kg-1•m-1 to 4.62±0.32 J•kg-1•m-1 (p = 0.049). Estimated AT energy return was not different following RUN (p = 0.99). Estimated TS muscle energy cost increased significantly by 11.8±12.3 J•stride-1, (p = 0.0034), accounting for much of the post-RUN increase in Erun (8.6±14.5 J•stride-1,r2 = 0.31). These results demonstrate that a prolonged, submaximal run can reduce AT stiffness and increase Erun in trained runners, and that the elevated TS energy cost contributes substantially to the elevated Erun.

The Effect of Cushioned Insoles on Tibial Acceleration During Running

Background: Running through fatigue has been found to place an excessive amount of stress to lower extrimities that may increase the risk of overuse injuries. Cushioned insoles are suggested to help attenuate shock and reduce impact forces caused by running. PURPOSE: To investigate the effect of implementing cushioned insoles on subjects before and after a fatigue protocol run to determine whether the insoles significantly lessened impacts. METHODS: Four male college students (age = 22.8± 4yr; weight = 80.2± 5kg; height = 187.3± 3cm) participated in the study. The participants were tested three times over a period of three weeks. During the first visit, lactate threshold speed (LTS) was assessed via blood samples (7.8±.5mph). During the second and third visits participants were randomly assigned to undergo incremental treadmill tests with and without insoles. The incremental runs included two rounds of seven 30-second bouts at stages -20% below to +40% above the LTS, with a 20 minute run at LTS in between the two trials. A triaxial accelerometer that was placed at each subject’s dominant tibial plateau recorded acceleration before and after the 20m run. Tibial acceleration (TA), stride length and frequency were calculated through Matlab. RESULTS: A two way repeated ANOVA (2 fatigue states by 2 insoles conditions) showed that there was a main effect of state (p=0.003) and a main effect of insole condition (p<0.001), as well as an interaction (p=0.044). Post hoc analysis revealed that TA was significantly lower during the non-fatigue control run with insoles when compared to the other conditions. Over the course of both pre- and post-fatigue incremental tests, stride length and frequency did not change. CONCLUSION: The findings indicate that insoles are an effective way to reduce tibial acceleration during running, but to a greater extent in the absence of fatigue (22% vs. 13%).

Do Seasonal Changes In Physiological Measures In An Incremental Running Test Track Peak Running Speed?

It is unclear whether physiological measures monitored in an incremental test during a training season provide useful diagnostic information about changes in distance running performance. PURPOSE: To quantify the relationship between changes in physiological measures and performance (peak running speed) over a winter training season. METHODS: Well-trained male distance runners (n=34, age 35.2 ± 1.1 y, VO2max 64.5 ± 6.2 ml.kg−1.min−1, training for 9.5 ± 0.9 h.wk−1, mean ± SD) completed four incremental treadmill tests over 17 wk. The test provided values of peak running speed, VO2max, running economy, and 4 mM lactate threshold (as speed and fraction of VO2max). The physiological measures were included in simple and multiple linear regression mixed models to quantify the effect of changes in these measures on changes in peak speed. RESULTS: The within-subject typical variation in peak speed from test to test was 1.9%, whereas those for physiological measures were: VO2max, 2.5%; economy, 2.6%; lactate threshold speed, 6.2%; lactate threshold fraction, 6.5%; and body mass, 1.6%. In simple models these typical changes in physiological variables predicted the following changes in performance: VO2max, 1.2% (90% confidence limits ±0.2%); economy, 0.5% (±0.3%); lactate threshold speed, 0.5% (±0.3%); lactate threshold fraction,−0.3% (±0.3%); and body mass,−0.4% (±0.3%). After adjustment for other predictors in a multiple linear regression, the effect of VO2max on peak speed was not diminished, but economy became a marginal predictor, while lactate threshold and body mass became ineffective. CONCLUSION: Change in VO2max in an incremental test during a running season is a good physiological predictor of change in peak running speed. Changes in running economy, lactate threshold and body mass provided little additional information about changes in performance.

Effect of High-Intensity Resistance Training on Performance of Competitive Distance Runners

In a recent study competitive road cyclists experienced substantial gains in sprint and endurance performance when sessions of high-intensity interval training were added to their usual training in the competitive phase of a season. The current study reports the effect of this type of training on performance of 20 distance runners randomized to an experimental or control group for 5 to 7 weeks of training. The experimental group replaced part of their usual competitive-phase training with 10 x ?30-minute sessions consisting of 3 sets of explosive single-leg jumps (20 for each leg) alternating with 3 sets of resisted treadmill sprints (5 x ?30-second efforts alternating with 30-second recovery). Before and after the training period all runners completed an incremental treadmill test for assessment of lactate threshold and maximum running speed, 2 treadmill runs to exhaustion for prediction of 800- and 1500-m times, and a 5-km outdoor time trial. Relative to the control group, the mean changes (+/-90% confidence limits) in the experimental group were: maximum running speed, 1.8% (+/- 1.1%); lactate-threshold speed, 3.5% (+/-3.4%); predicted 800-m speed, 3.6% (+/- 1.8%); predicted 1500-m speed, 3.7% (+/- 3.0%); and 5-km time-trial speed, 1.2% (+/- 1.1%). We conclude that high-intensity resistance training in the competitive phase is likely to produce beneficial gains in performance for most distance runners.

Sea-level performance in runners using altitude tents: A field study

In this study of effects of simulated altitude exposure on sea-level performance, 10 competitive runners slept in a hypoxic environment achieved with tents for 9.8+/-1.3 h.d(-1) (mean+/-standard deviation) for 24 days-30 days at 2500-3500 m (PIO2=117-103 mmHg) above sea level. The altitude group and a control group of 10 runners performed usual training (PIO2=149 mmHg). At approximately 4-wk intervals before and after exposure both groups performed an incremental test for lactate threshold. The altitude group performed an additional test, a treadmill run to exhaustion lasting approximately 5 min. One week following exposure lactate threshold speed of the altitude group relative to the control group increased by 1.2% (90% likely limits +/-3.1%), but the effect became slightly negative after controlling for baseline differences in running speed between the groups. A 16% increase in time to exhaustion was observed in the altitude group, equivalent to a 1.9% (+/-1.4%) increase in speed in a time trial. Change in performance had an unclear relationship to total altitude exposure, genotype for angiotensin converting enzyme, and change in haemoglobin concentration. Our findings are consistent with little or no effect of use of altitude tents on sea-level performance.

Monitoring seasonal and long-term changes in test and competitive performance in elite swimmers

Purpose: To evaluate the utility of an incremental swimming test for monitoring seasonal changes in performance of elite swimmers. Methods: 40 elite swimmers (24 M, 16 F) performed a 7 x 200-m incremental swimming test several times throughout each 6-month season during 1998-2003. Each season concluded with a major competition. Log transformation and repeated measures mixed linear modeling were used to derive estimates of percent change in mean and within swimmercoefficient of variation for swim times between seasons and for the following test measures between phases and seasons: speed, stroke rate, stroke count, and HR at lactate threshold; time for the maximal (last) 200-m step; and maximal lactate. Ability to predict competition time changes was estimated as a within-subject correlation between each measure and performance. A reliability study of 12 swimmers also provided 3-d retest typical error of test measures. Results: Test measures directly related to swimming performance showed cyclical improvement (mean ~2%) from early to taper phases within each season. Within-swimmer variation had similar magnitude. These changes can be monitored confidently in individuals, because the typical error of the test measures was substantially smaller (e.g., lactate-threshold speed, 0.7%; 200-m time, 0.6%). Competition times improved slightly each season (0.7%) against a 1.1% within-swimmer variation between competitions. Only threshold speed, stroke rate and maximal lactate in the taper were moderately correlated (~0.4) with improvements in competition time. Conclusion: The swimming test tracks changes in training performance during a season, but is at best a moderate predictor of competitive performance only during the taper.

Continuous training increase on the lactate threshold improves soccer players’ performance

It has been described that the continuous training at the lactate threshold improves performance leading to a decrease of the lactate concentrations or at the threshold of intensity. Here we measured changes in soccer athletes' performance that were submitted to a continuous training at the lactate threshold speed, in addition to soccer conventional training. Soccer athletes (n=17) aged 18 and 20 years old were randomly divided into two groups. The former received both continuous and conventional trainings (EG, n=10), whereas the latter just conventional training (CG, n=7). The lactate threshold speed increased after the two fi rst training weeks in both groups. In EG the lactate threshold's speed increased during the following four weeks. Our results showed a decrease in the lactate concentration in the EG at the same velocity. These data indicate that the soccer players' performance can be improved by a combination of both training methods.

MONITORING LONG-TERM CHANGES IN TEST AND COMPETITIVE PERFORMANCE IN ELITE SWIMMERS

PURPOSETo evaluate the utility of an incremental swimming test for monitoring seasonal changes in performance of elite swimmers. METHODSOlympic representative 100- to 400-m swimmers (10 males, 9 females) performed a 7 × 200-m incremental swimming step test several times throughout each 6-month season during 1998–2002. Each season concluded with a national or international competition. Log transformation and repeated measures mixed linear modeling were used to derive estimates of percent change in the mean and within-swimmer coefficient of variation (CV) for swim times between seasons and for the following test measures between phases and seasons: speed, stroke rate, stroke count and heart rate at lactate threshold; speed for the maximal (last) 200-m step; and maximal lactate. Change in competition time was modeled as a linear function of change in each of the step-test measures between season. We also determined the 3-day retest typical error for the test measures in a reliability study of 12 of the swimmers.RESULTS Test measures directly related to swimming performance showed cyclical improvement (mean ~2%) from early through to taper phases within each season, and within-swimmer variation was of similar magnitude. These changes can be monitored confidently in individuals, because the typical error of the test measures was substantially smaller (e.g. lactate-threshold speed, 0.7%; maximal speed 0.6%). Competition times improved slightly each season (0.2%) against a within-swimmer variation of 1.0% between competitions, but typical (1 × CV) changes in test measures between seasons predicted worthwhile changes in competition time (> 0.4%) only for tests in the taper and only for speed (0.8%) and stroke rate (0.6%) at lactate threshold and for maximum lactate (0.5%).CONCLUSIONThe step test can track changes in a swimmer's performance during a season, but it appears to be useful for predicting competitive performance only during the taper.

Comparison of physiological responses to morning and evening submaximal running

The aim of this study was to assess the effect of time of day on physiological responses to running at the speed at the lactate threshold. After determination of the lactate threshold, using a standard incremental protocol, nine male runners (age 26.3 - 5.7 years, height 1.77 - 0.07 m, mass 73.1 - 6.5 kg, lactate threshold speed 13.6 - 1.6 km· h -1 ; mean - s ) completed a standardized 30 min run at lactate threshold speed, twice within 24 h (07:00- 09:00 h and 18:00-21:00 h). Core body temperature, heart rate, minute ventilation, oxygen uptake, carbon dioxide expired, respiratory exchange ratio and capillary blood lactate were measured at rest, after a warm-up and at 10, 20 and 30 min during the run. In addition, the rating of perceived exertion was reported every 10 min during the run. Significant diurnal variation was observed only for body temperature (36.9 - 0.9°C vs 37.3 - 0.3°C) and respiratory exchange ratio at rest (0.86 - 0.01 vs 0.89 - 0.07) ( P ≪ 0.05). Diurnal variation persisted for body temperature throughout the warm-up (37.1 - 0.2°C vs 37.5 - 0.3°C) and during exercise (36.2 - 0.6°C vs 38.6 - 0.4°C), but only during the warm-up for the respiratory exchange ratio (0.85 - 0.05 vs 0.87 - 0.02) ( P ≪ 0.05). The rating of perceived exertion was significantly elevated during the morning trial (12.7 - 0.9 vs 11.9 - 1.2) ( P ≪ 0.05). These findings suggest that, despite the diurnal variation in body temperature, other physiological responses to running at lactate threshold speed are largely unaffected. However, a longer warm-up may be required in morning trials because of a slower increase in body temperature, which could have an impact on ventilation responses and ratings of perceived exertion.