The aim of this study was to investigate the effect of L-lactic acid on swimming endurance of mice. Mice (n = 50) were injected intraperitoneally with saline, then with L-lactic acid (either 25 mg/kg or 50 mg/kg body weight), then after 2 days with the same doses of glucose, and after another 2 days again with L-lactic acid at the same doses. Swimming times to exhaustion were determined at 30 min after each injection, in a tank filled with 25 cm of water maintained at 23 °C. After another week, mice were given either saline, L-lactic acid, or glucose (25 or 50 mg/kg) dissolved in saline and sacrificed after 30 min for biochemical analyses. The ratios of swimming times of L-lactic acid or glucose injections to saline injection were calculated as an index for endurance changes. Swimmingtime ratios for mice injected with L-lactic acid were significantly higher at either dose than for those injected with the corresponding doses of glucose (p < .05). The ratio of swimming time was greater in those given a dose of 50 mg/kg than in those given 25 mg/kg for mice in the L-lactic acid groups (p < .05) but not in the groups given glucose. There were no marked differences in biochemical parameters of plasma and muscle lactate, muscle and liver glycogen, or plasma glucose and nonesterified fatty acid between the L-lactic acid, glucose, and saline injection groups. These results suggest that L-lactic acid can enhance swimming endurance of mice and that this action is dose dependent.
Guihua Zhang, Nobuya Shirai and Hiramitsu Suzuki
Takeshi Kokubo, Yuta Komano, Ryohei Tsuji, Daisuke Fujiwara, Toshio Fujii and Osamu Kanauchi
protective effects of LC-Plasma through the expression of muscle degenerating genes. Method Preparation of Lactic Acid Bacteria LC-Plasma and Lactobacillus rhamnosus GG (ATCC 53103; LGG), representative probiotics strains, were prepared according to a previous study ( Jounai et al., 2012 ). Experimental
Ozgur Surenkok, Ayse Kin-Isler, Aydan Aytar and Zuhal Gültekin
This study sought to determine the effects of trunk-muscle fatigue and blood lactic acid elevation on static and dynamic balance.
Fatigue was induced by an isokinetic protocol, and static and dynamic balance were assessed during bilateral stance using a Kinesthetic Ability Trainer. Subjects participated in a fatigue protocol in which continuous concentric movements at 60°/s were performed until the torque output for both trunk flexion and extension dropped below 25% of the calculated peak torque for 3 consecutive movements.
Before and immediately after the fatigue protocol, blood lactic acid measurements and static- and dynamic-balance measurements were recorded.
An increase in lactic acid levels was detected in all subjects. According to a dependent-samples t test, significant differences in balance and lactic acid values were found after the fatigue protocol. There was no correlation between lactic acid accumulation (change between prefatigue and postfatigue levels) and balance-score differences.
Trunk-muscle fatigue has an adverse effect on static and dynamic balance.
Lee N. Burkett, Jack Chisum, Jack Pierce, Kent Pomeroy, Jim Fisher and Margie Martin
Twenty spinal-cord-injured subjects (4 quadriplegics and 16 paraplegics) were maximally stress tested on the Arizona State University wheelchair ergometer. Physiological data for each individual were collected as follows: (a) blood flow in the left leg by a photoelectric plethysmograph before exercise, during exercise, and postexercise, and (b) blood lactates before exercise and post-exercise. Eleven subjects had increased leg blood flow and vasodilation during exercise, but vasoconstriction postexercise. The lactate readings, in comparison to able-bodied individuals, were higher at rest but lower at maximal exercise.
Jacky J. Forsyth, Chris Mann and James Felix
In rowing ergometry, blood for determining lactate concentration can be removed from the toe tip without the rower having to stop. The purpose of the study was to examine whether sampling blood from the toe versus the earlobe would affect lactate threshold (Tlac) determination.
Ten physically active males (mean ± age 21.2 ± 2.3 y; stature 179.2 ± 7.5 cm; body mass 81.7 ± 12.7 kg) completed a multistage, 3 min incremental protocol on the Concept II rowing ergometer. Blood was sampled simultaneously from the toe tip and earlobe between stages. Three different methods were used to determine Tlac.
There were wider variations due to the method of Tlac determination than due to the sample site; for example, ANOVA results for power output were F(1.25, 11.25) = 11.385, P = .004 for method and F(1, 9) = 0.633, P = .45 for site. The greatest differences in Tlac due to sample site in rowing occurred when Tlac was determined using an increase in blood lactate concentration by >1 mmol/L from baseline (TlacΔ1).
The toe tip can be used as a suitable sample site for blood collection during rowing ergometry, but caution is needed when using the earlobe and toe tip interchangeably to prescribe training intensities based on Tlac, especially when using TlacΔ1 or at lower concentrations of lactate.
Carmelo Bazzano, Lee N. Cunningham, Giovanni Cama and Tony Falconio
The purpose of this study was to examine the relationship between selected physiological variables and lactate accumulation at the end of a l-mile walk test (MWT) in older women (mean ± SD: 64.6 ± 3.1 years). Seventeen women with a
Matthew W. Driller, Christos K. Argus and Cecilia M. Shing
To determine the reliability of a 30-s sprint cycle test on the Wattbike cycle ergometer.
Over 3 consecutive weeks, 11 highly trained cyclists (mean ± SD; age 31 ± 6 y, mass 74.6 ± 10.6 kg, height 180.5 ± 8.1cm) completed four 30-s maximal sprints on a Wattbike ergometer after a standardized warmup. The sprint test implemented a “rolling start” that consisted of a 60-s preload (at an intensity of 4.5 W/kg) before the 30-s maximal sprint. Variables determined across the duration of the sprint were peak power (Wpeak), mean power (Wmean), W/kg, mean cadence (rpm), maximum heart rate (n = 10), and postexercise blood lactate.
The average intraclass correlation coefficients between trials (2v1, 3v2, 4v3, 4v1) were Wpeak .97 (90%CI .94–.99), Wmean .99 (90%CI .97–1.00), W/kg .96 (90%CI .91–.98), mean cadence .96 (90%CI .92–.99), maximum heart rate .99 (90%CI .97–.99), and postexercise blood lactate .94 (90%CI .87–.98). The average typical error of measurement (expressed as a CV% and absolute value between trials—2v1, 3v2, 4v3, 4v1) was Wpeak 4.9%, 52.7 W; Wmean 2.4%, 19.2 W; W/kg 2.3%, 0.18 W/kg; mean cadence 1.4%, 1.6 rpm; maximum heart rate 0.9%, 1.6 beats/min; and postexercise blood lactate 4.6%, 0.48 mmol/L.
A 30-s sprint test on the Wattbike cycle ergometer is highly reproducible in trained cyclists.
Dawn T. Gulick and Iris F. Kimura
Muscle soreness, a familiar phenomenon to most athletes, has been differentiated into “acute” and “delayed onset.” The etiology of acute muscle soreness has been attributed to ischemia and the accumulation of metabolic by-products. However, the etiology of delayed onset muscle soreness (DOMS) is not so clear. Six theories have been proposed: lactic acid, muscle spasm, torn tissue, connective tissue, enzyme efflux, and tissue fluid theories. The treatment of DOMS has also been investigated. Studies in which anti-inflammatory medications have been administered have yielded varying results based on the dosage and the time of administration. Submaximal concentric exercise may alleviate soreness but does not restore muscle function. Neither cryotherapy nor stretching abates the symptoms of DOMS. Transcutaneous electrical stimulation has been shown to decrease soreness and increase range of motion, but the effect on the recovery of muscle function is unknown. Therefore, the treatment of DOMS remains an enigma.
Lauree M. Grubbs
Women, considering swimming as a form of exercise to lose weight, have been discouraged from doing so, since researchers suggest that swimming does not burn fat as efficiently as land exercise. The purpose of this study was to compare carbohydrate and fat utilization by women engaging in two different forms of exercise, walking and swimming, at the same intensity and duration. Subjects were 20 moderately trained female subjects, walkers (W) = 10 and swimmers (S) = 10; ages 18-40 years. Measurements of blood free fatty acids (FFA), glycerol, lactate, glucose, free fatty acid turnover (FFAT), respiratory quotient (RQ), and fat oxidation were made during 60 minutes of walking or swimming at the same exercise intensity. Multivariate analysis of variance determined no significant differences between groups in net energy expenditure (NEE), RQ, fat oxidation, blood FFA, glycerol, glucose, and FFAT(p > .05). There was a significant difference between groups in blood lactic acid levels (p < .01). Since it was found that swimming and walking at the same duration and intensity bum similar amounts of fat and carbohydrate as energy sources during exercise, women may find swimming to be a viable form of exercise for weight control.
In modern societies there is strong belief in scientific progress, but, unfortunately, a parallel partial regress occurs because of often avoidable mistakes. Mistakes are mainly forgetting, erroneous theories, errors in experiments and manuscripts, prejudice, selected publication of “positive” results, and fraud. An example of forgetting is that methods introduced decades ago are used without knowing the underlying theories: Basic articles are no longer read or cited. This omission may cause incorrect interpretation of results. For instance, false use of actual base excess instead of standard base excess for calculation of the number of hydrogen ions leaving the muscles raised the idea that an unknown fixed acid is produced in addition to lactic acid during exercise. An erroneous theory led to the conclusion that lactate is not the anion of a strong acid but a buffer. Mistakes occur after incorrect application of a method, after exclusion of unwelcome values, during evaluation of measurements by false calculations, or during preparation of manuscripts. Co-authors, as well as reviewers, do not always carefully read papers before publication. Peer reviewers might be biased against a hypothesis or an author. A general problem is selected publication of positive results. An example of fraud in sports medicine is the presence of doped subjects in groups of investigated athletes. To reduce regress, it is important that investigators search both original and recent articles on a topic and conscientiously examine the data. All co-authors and reviewers should read the text thoroughly and inspect all tables and figures in a manuscript.