VO2 & blood lactate data obtained from a cycle ergometry test as a guide for physical capacity
Introduction
In the past, it was commonly believed that lactic acid was a waste product brought about by the process of glycolysis, involving the inadequate supply of oxygen to working muscles (Hill and Lupton 1923). This view has been greatly debated since then, with claims of anaerobic glycolysis and lactate processes ongoing even during resting levels (Gladden 2004). Attempts have been made to develop alternate parameters to analyse cardio-respiratory fitness. This has ranged from maximum oxygen consumption, blood lactate concentration (bLa) (Wasserman and Mcllroy 1964) and ventilatory efficiency (Hollman 2001), with the measurement of gas exchange becoming increasingly common along the way.
Studies on lactate threshold (LT) have increased till now, with the study of bLa during incremental exercise becoming a more significant method of diagnosing endurance performance. Examples include Faria’s (2005) study into the physiology of cycling training and Jones’ (2006) research on the physiology of the women’s marathon world record holder. Additionally, the blood lactate curve and lactate threshold (LTs) have turned out to be essential in the analysis of endurance performance. However, there is still ongoing debate surrounding the concept of LT and its physiological background. The aim of this report is to evaluate the incremental exercise LT concept and its usefulness in assessing physical endurance capacity. To note, this report will not conduct a comprehensive analysis of lactate metabolism and glycolysis.
Method
One male participant took part in this study. The participant was 52 years old and a competitive runner. Before the start of the experiment, the participant was asked to complete an informed consent and general health screening form. Their body mass was then measured to the nearest 0.1 kg while their stature was measured to the nearest 0.01 m. The participant weighed in at 72.75 kg while their stature was 1.81 m. A heart rate monitor (Polar monitor watch, Kempele, Finland) was fitted onto the participant, making sure that their heart rate was displayed on the device. Eight Douglas bags were evacuated, with a mouthpiece and tubing attached to the first bag. The ambient (room) temperature (°C) and pressure (mmHg) were then recorded. A resting capillary blood sample was then taken to identify their resting blood lactate concentration (Lactate Pro 2, Arkray, Japan). Height of the seat of the Monark cycle ergometer (Monark cycle ergometer, Vansbro, Sweden) was adjusted so that the participant could cycle comfortably, while maintaining a knee angle of ~160-170 degrees with a down stroke pedal. Recordings of all participant characteristics were recorded into table 1 shown below.
Table 1. Participant Characteristics.
First, the participant was made to carry out a light warm-up at 60 RPM with no added load for 5 minutes. The participant then began stage one, involving a load of 1.5 kg while cycling at a cadence of 60 rpm for 3 minutes. The weight was added bearing in mind the cradle’s weight of 1.0 kg. Resistance was gradually increased by 0.5 kg to the cradle of the cycle ergometer every 3 minutes. This continued until the participant indicated that they could manage only 1 more minute. It was agreed upon before the start of the warm up, between the participant and the researchers, that the indicator would be the participant raising one finger in the air. On completion of the exercise programme, the applied load was reduced to 1.5 kg, with the participant being asked to cycle for at least 5 more minutes before the seated rest period. The following measurements were obtained during the final minute of each stage as well as the final minute of the test:
• Expired air (Servomex 5200, Crowborough, UK)
• Flywheel count
• HR every 10 seconds in the final 30 seconds
• RPE in the final 15 seconds
• Blood lactate in the final 15 seconds.
Results
As work rate improved, increases were observed in both heart rate and lactate concentration. Increases in lactate concentration where minor in the first four stages, with stages 2 and 4 showing slightly lower concentrations compared to the stage before them (Stage 1 and 3, Figure 1). From stage 5 onwards, these increases grew progressively larger until the end of the exercise. The participant progressed from a resting lactate concentration of 1.2 mmol. L-1 to 12 mmol. L-1 at exercise termination. The largest increase in lactate concentration was observed from stage 7 to stage 8 (5.8 mmol. L-1 to 10.5 mmol. L-1). The applied weight for these stages were 5 kg and 5.5 kg.
With regards to heart rate, it was identified that the participant’s maximum heart rate (MHR) was 168 bpm (220 – 52). Comparing the heart rate results we obtained, the participant reached 90% of their MHR between stage 7 and 8.
Figure 1. Scatterplot of Heart Rate and Lactate Concentration over Power Output from data obtained by the participant
Discussion
Normally, an exponential rise in lactate concentration is observed during incremental exercise (Figure 1). Complications arise when interpreting the lactate curve to endurance capacity. It is commonly believed lactate curves shifting to the right (indicating a lower bLa at applied workload) can imply improvements in endurance capacity (Bosquet et al. 2002). To explain the downward curves at stage 2 and 4 of the lactate curve, Maasen and Busse (1989) state that ‘glycogen-depleted subjects’ are prone to this effect, leading to a ‘downward shift of the lactate curve’. They also stated it important to not falsely interpret this as an ‘enhancement in endurance capacity’. The participant also met both secondary criteria for 2 max, achieving a heart rate greater than 90% of MHR and a post-exercise bLa greater than 8 mmol. L-1. This makes the measurements for2 max more valid, which makes the study increasingly applicable and useful in understanding the relationship between this data and physical capacity.
Conclusion
Incremental exercise LT concepts are indeed useful, with the parameters for this study being shown to be valid and reliable in contributing to the assessment of physical endurance capacity.
tific studies on LTs has increased enormously up
to now and the sub-maximal course of bLa dur-
ing incremental exercise has probably become
one of the most important means in the diagnosis
of endurance performance in sports prac-
tice.
The number of scien-
tific studies on LTs has increased enormously up
to now and the sub-maximal course of bLa dur-
ing incremental exercise has probably become
one of the most important means in the diagnosis
of endurance performance in sports prac-
tice
References
Bosquet, L., Leger, L. and Legros, P. (2002). Methods to Determine Aerobic Endurance. Sports Medicine, 32(11), pp.675-700.
Faria, E., Parker, D. and Faria, I. (2005). The Science of Cycling. Sports Medicine, 35(4), pp.285-312.
Gladden, L. (2004). Lactate metabolism: a new paradigm for the third millennium. The Journal of Physiology, 558(1), pp.5-30.
Hill, A. and Lupton, H. (1923). Muscular Exercise, Lactic Acid, and the Supply and Utilization of Oxygen. QJM, os-16(62), pp.135-171.
Hollmann, W. (2001). 42 Years Ago: Development of the Concepts of Ventilatory and Lactate Threshold. Sports Medicine, 31(5), pp.315-320.
Jones, A. (2006). The Physiology of the World Record Holder for the Women's Marathon. International Journal of Sports Science & Coaching, 1(2), pp.101-116.
Maassen, N. and Busse, M. (1989). The relationship between lactic acid and work load: a measure for endurance capacity or an indicator of carbohydrate deficiency. European Journal of Applied Physiology and Occupational Physiology, 58(7), pp.728-737.
Wasserman, K. and McIlroy, M. (1964). Detecting the threshold of anaerobic metabolism in cardiac patients during exercise. The American Journal of Cardiology, 14(6), pp.844-852.
Word Count (excluding references): 999
Laboratory report assignment assessment form
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INTRODUCTION
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Student ID: B716706
