two days after the performance of an eccentric exercise ... Dolan 1987; Jones et al. ... formed cycling exercise at the same time of day on both occasions.
Eur J Appl Physiol (1998) 77: 292±295
Ó Springer-Verlag 1998
SHORT COMMUNICATION
Michael Gleeson á Andrew K. Blannin á Neil P. Walsh Christine N.E. Field á Jeanette C. Pritchard
Effect of exercise-induced muscle damage on the blood lactate response to incremental exercise in humans
Accepted: 27 September 1997
Abstract Eccentric muscle actions are known to induce temporary muscle damage, delayed onset muscle soreness (DOMS) and muscle weakness that may persist for several days. The purpose of the present study was to determine whether DOMS-inducing exercise aects blood lactate responses to subsequent incremental dynamic exercise. Physiological and metabolic responses to a standardised incremental exercise task were measured two days after the performance of an eccentric exercise bout or in a control (no prior exercise) condition. Ten healthy recreationally active subjects (9 male, 1 female), aged 20 (SD 1) years performed repeated eccentric muscle actions during 40 min of bench stepping (knee high step; 15 steps á min)1). Two days after the eccentric exercise, while the subjects experienced DOMS, they cycled on a basket loaded cycle ergometer at a starting work rate of 150 W, with increments of 50 W every 2 min until fatigue. The order of the preceding treatments (eccentric exercise or control) was randomised and the treatments were carried out 2 weeks apart. Two days after the eccentric exercise, all subjects reported leg muscle soreness and exhibited elevated levels of plasma creatine kinase activity (P < 0.05). Endurance time and peak V_ O2 during cycling were unaected by the prior eccentric exercise. Minute volume, respiratory exchange ratio and heart rate responses were similar but venous blood lactate concentration was higher (P < 0.05) during cycling after eccentric exercise compared with the control condition. Peak blood lactate concentration, observed at 2 min post-exercise was also higher [12.6 (SD 1.4) vs 10.9 SD (1.3) mM; P < 0.01]. The higher blood lactate concentration during cycling exercise after M. Gleeson (&) á A. K. Blannin á N. P. Walsh C. N. E. Field á J. C. Pritchard School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK
prior eccentric exercise may be attributable to an increased rate of glycogenolysis possibly arising from an increased recruitment of Type II muscle ®bres. It follows that determination of lactate thresholds for the purpose of ®tness assessment in subjects experiencing DOMS is not appropriate. Key words Lactate á exercise á muscle damage
Introduction Repeated eccentric muscle actions, during which the muscle lengthens during activation, are known to induce delayed onset muscle soreness (DOMS) which is ®rst felt 6±10 hours post-exercise and peaks between 24 and 48 hours post-exercise. The symptoms most often reported are muscular stiness, tenderness and pain, especially when performing active movements. Associated with DOMS, there is evidence of in¯ammation and damage of the aected muscles, with muscle ®bre swelling (Friden et al. 1988), elevated serum activities of muscle speci®c enzymes such as creatine kinase (CK, Newham et al. 1983), muscle weakness (Sargeant and Dolan 1987; Jones et al. 1989) and a prolonged decrease in muscle glycogen concentration (O'Reilly et al. 1987). These factors could be expected to have an eect on metabolic and physiological responses to subsequent concentric exercise. We have recently reported increased blood lactate concentration, rating of perceived exertion, heart rate and ventilation during submaximal cycling at 80% V_ O2 max when subjects performed exercise with DOMS compared with the normal condition (Gleeson et al. 1995). In the present study we chose to investigate the physiological and metabolic responses to an incremental exercise test in order to determine if DOMS in¯uences peak V_ O2 , time to exhaustion and peak blood lactate concentration.
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Materials and methods Subjects Ten healthy recreationally active subjects volunteered to take part in the study, which was approved by the local Ethics Committee. Their mean (SD) physical characteristics were as follows: age 20 (1) years; height 1.79 (0.07) m; body mass 74.6 (8.9) kg; V_ O2 max 3.92 (0.59) l á min)1. None of the subjects took any form of medication during the study period. All subjects were required to refrain from alcohol consumption and strenuous physical activity for two days before each cycling exercise session. All exercise bouts were performed in the post-absorptive state, 4±6 hours after the last meal which consisted of cereal and milk. Methods In this study the eect of 40 min eccentric exercise on muscle soreness and physiological responses to incremental cycling exercise was investigated. This involved each subject performing a standardised incremental cycle ergometer exercise test 2 days following bench stepping (involving eccentric exercise) as described by Newham et al. (1983) or without any strenuous exercise in the preceding 2 days (control condition). Each subject's maximal oxygen uptake (V_ O2 max ) was measured 1±2 weeks before the experiment during an incremental ride to exhaustion on a basket loaded cycle ergometer (Monark 814E, Cranlea, UK). Respiratory gas exchange was monitored throughout the ride using Douglas bag collection of expired gas which was analysed using oxygen and carbon dioxide analysers (Servomex, Crowborough, UK) and a dry gas meter (Harvard Apparatus, Edenbridge, UK). Heart rate was measured throughout the ride using short range radiotelemetry (Polar SportsTester 3000, Polar Electro, Kempele, Finland).
whilst lightly palpating their own muscles when in a standing posture. Soreness was rated on a scale of 1 (normal) to 10 (very, very, sore) for overall muscle soreness in the back lower leg and front thigh. Muscle soreness was also rated at three speci®c sites in each area using the same scale. The mean soreness rating for each area from both legs was then calculated and these were averaged for the criterion score. Blood sampling and analysis On each occasion, 4 ml of blood was collected using a dry syringe and dispensed into tubes containing lithium heparin. Duplicate aliquots (100 ll) were immediately deproteinised in 1.0 ml of icecooled 0.3 M perchloric acid which was then centrifuged, stored at )70°C, and the supernatant subsequently analysed for lactate using a standard enzymatic spectrophotometric method using lactate dehydrogenase and NAD (Sigma, Poole, UK). Plasma creatine kinase (CK) activity was measured at 30°C using a kit (Sigma, Poole, UK). Statistics Preliminary statistical evaluation of the results was carried out by analysis of variance with repeated measures, with further post-hoc analysis using the Schee test where appropriate. The results for the muscle soreness rating were also analysed using Wilcoxon's signed rank test which con®rmed the parametric analysis reported in the Results. Paired t tests were used to examine dierences in endurance time, peak V_ O2 and peak blood lactate concentration between the DOMS and control condition. The accepted level of signi®cance was P < 0.05. All values in the text and tables are means and SD.
Eccentric exercise and control condition
Results
Subjects performed eccentric muscle actions during 40 min of bench stepping (knee height step )50 cm on average ± at a rate of 15 steps á min)1). Subjects began using the right leg as the leading leg and changed the leading leg every 10 min. Heart rate during stepping, monitored using short range radio telemetry, averaged 140 beats á min)1. Forty eight hours after the eccentric exercise the subjects performed the standardised cycle ergometer test. Subjects also performed the incremental cycle test in the normal (control) condition without any strenuous exercise in the preceding 48 hours. The cycle tests were performed 2 weeks apart and the order of the treatments (DOMS or control) was randomised. Subjects performed cycling exercise at the same time of day on both occasions. All exercise bouts were performed between 11:00±15:00 h.
Two days after the eccentric exercise, all subjects reported leg muscle soreness (mean rating 3.1 SD 2.0) whereas in the control condition they were not sore (mean rating 1.0 SD 0.0). Plasma CK activity was signi®cantly higher 2 days after the eccentric exercise compared with the control condition: 371 (175) U á l)1 vs 253 (67) U á l)1, respectively (P < 0.05). Endurance time, peak heart rate and peak V_ O2 were not signi®cantly dierent for the two conditions (Table 1). During cycling, oxygen uptake, minute volume, heart rate and RER were not signi®cantly dierent for the two experimental conditions at any time during the exercise (data not shown). Blood lactate concentration was similar for the two experimental treatments at rest prior to the cycle exercise bout, but was higher during exercise in the post-eccentric (DOMS) condition (Fig. 1). The peak blood lactate
Cycle ergometer exercise test Each subject cycled to exhaustion on the same basket loaded cycle ergometer. The starting work rate was 150 W and was increased by 50 W every 2 min until volitional fatigue. Subjects were required to maintain a pedal cadence of 90 rpm. Room temperature was 18± 20°C and relative humidity was 45±55%. Respiratory gas exchange and heart rate were monitored throughout the ride as described above. Expired gas was collected during the last 40 s of each 2 min period. Blood samples (4 ml) were taken from a butter¯y needle cannula inserted into a super®cial forearm vein at rest and every 2 min during the exercise; further samples were obtained immediately post-exercise and at 2 min post-exercise. Muscle soreness rating Subjective assessments of muscle soreness were made just prior to the cycle ergometer exercise test. Subjects rated their soreness
Table 1 Mean (SD) peak V_ O2 , peak heart rate (HR), endurance time and peak blood lactate (La) concentration for incremental cycle exercise in the DOMS and control conditions
Peak V_ O2 (l á min ) Peak HR (beats.min)1) Endurance time (min) Peak blood La (mM) )1
Control
DOMS
P
3.98 185 8.50 10.9
4.18 186 8.05 12.6
NS NS NS
