Authors: Katie M. Sell, Ph.D., CSCS, TSAC-F, ACSM EP-C
Department of Health Professions, Hofstra University, NY
Jamie Ghigiarelli, Ph.D., CSCS, USAW, CISSN
Department of Health Professions, Hofstra University, NY
Katie M. Sell, Ph.D., CSCS, TSAC-F, ACSM EP-C
Department of Health Professions, 101 Hofstra Dome, 220 Hofstra University, Hempstead, NY 11549
Comparison of Laboratory and Field-Based Predictors of 5-km Race Performance in Division I Cross-Country Runners
Purpose: The purpose of this study was to examine the predictive capabilities of laboratory- (VO2max, VO2@VT) versus field-based performance variables (2-mile trial time; 2-MTT) in determining 5-km performance time in collegiate cross-country runners. Methods: Twenty Division I college cross-country runners completed a 2-MTT on an outdoor track, a VO2max test under controlled laboratory settings, and a 5-km run under competitive conditions. All tests were completed within a 10-day timeframe. Oxygen uptake during the VO2max test was measured during treadmill running using open circuit spirometry. Oxygen consumption at ventilatory threshold (VO2@VT) was determined using the ventilatory equivalent method. Results: Significant correlations were observed between each predictor variable and 5-km performance time. Regression analyses revealed that 2-MTT and VO2@VT contributed significantly to predicting 5-km race performance (r2 = 0.90, p<0.05). Conclusions: For the highly trained runners in this study, 2-MTT and VO2@VT are among the variables best able to predict 5-km race performance, and accounted for a similar magnitude of variance in 5-km performance time. Applications in Sport: A 2-MTT is cheaper, quicker, and more feasible to administer than a VO2max test to determine VT during the short pre-season and intensive in-season inherent in collegiate cross-country schedules. Given the results of this study, the 2-MTT may present an attractive alternative to laboratory testing as a means to monitor cross-country runner’s progress throughout a season.
Keywords: Running, physical conditioning, athletes, physical fitness, college.
Purposeful conditioning practices and accurate feedback on fitness and training status throughout the competitive season are critical elements for a collegiate cross-country training program. A high level of aerobic fitness (maximal oxygen consumption; VO2max) is a necessary attribute for distance runners, however additional physiological variables such as ventilatory threshold (VT), lactate threshold, critical speed or velocity, and time over shorter distances, may further distinguish distance running performance amongst elite runners and assist cross-country coaches with training program design (9,12,15,17,20). However, coaches are often limited in their ability to use these gages of performance throughout a competitive season. The accurate measurement of these variables is limited to the research or laboratory setting, and VO2max testing can be both time-consuming and requires trained administrators. Furthermore, the pre-season for collegiate cross-country programs is rarely longer than 2-3 weeks, during which time training may take priority over exhaustive laboratory testing. Collegiate cross-country runners may have between 5-8 meets at 5-km and 8-km race distances over 7-9 weeks (mid-September to mid/late-November), which limits the feasibility of administering a VO2max test during the in-season without avoiding undue fatigue, and potentially interfering with the training program and competitive race performance.
Short duration treadmill tests (e.g., running economy tests) and alternative race times from both longer and shorter distances (e.g., 1-mile, 10-km times) have shown promise as predictors of race performance in elite and collegiate runners (2,4,7,8,11,12). Anaerobic and anthropometric measures conducted in the field have been significantly associated with 10-km performance (21), but minimal research exists for other middle-distance races. To the authors’ knowledge, no studies have compared the predictive capacity of field-based time trials to laboratory-determined predictors of 5-km performance in college cross-country runners. The results of such studies may serve to support the use of a surrogate predictive measure of training status or performance capacity for implementation in-season, when laboratory testing is not feasible or appropriate.
Therefore, the purpose of this study was to examine the predictive accuracy of two laboratory-determined physiological variables and a field-based time trial for 5-km performance time in collegiate cross-country runners. Given the current status of research examining physiological variables predictive of distance running performance and the popularity of cross-country running at the collegiate level (16), the results of this study may help identify measures that provide a practical and efficient performance assessment tool for coaches.
Twenty Division I cross-country runners volunteered to participate in this study. Eleven (2 women, 9 men) of these participants completed the measures in this study on two occasions during a 6-month period, for an accumulation of 31 total cases for data analysis. All participants were healthy at the time of data collection, currently on the university cross-country team, able to complete a maximal oxygen consumption test, and run a competitive 5-km distance race. Prior to participation, each participant completed an informed consent form and a medical health history questionnaire, and demonstrated that he or she did not have any health-related contraindications to physical activity. Additional clearance from the head athletic trainer for the cross-country team was also sought prior to study initiation and each data collection period. Approval from the university Institutional Review Board was obtained prior to study initiation.
All participants were asked to attend an initial consultation (during which time no study data was collected) to complete the informed consent and medical health history questionnaire. Participants were also given the opportunity to ask any questions regarding data collection and protocol during this meeting. Participants completed competitive 5-km races as part of the seasonal collegiate competitive meet schedule. The competitive race time from two of these events was used as the dependent variable for statistical analysis. Participants completed a maximal oxygen consumption (VO2max) test and a two-mile time trial (2-MTT) within ten days of the competitive race to which the VO2max and 2-MTT outcomes were compared.
Participants were asked to refrain from eating two hours (not more than eight hours) prior to the VO2max test, avoid any strenuous physical activity for 24 hours prior to each laboratory visit, and allow a minimum of 48 hours between data collection sessions. Additionally, participants were asked to abstain from alcohol ingestion 48 hours prior to participation and drink water liberally (two liters per day) one day prior to each testing session. During all data collection sessions each participant was asked to wear appropriate running attire – shorts, t-shirts and athletic shoes – to avoid differences in metabolic and thermoregulatory responses due to clothing. All data collection procedures were monitored and conducted by a trained exercise physiologist and the head cross-country coach. Ambient temperature was maintained at 22-240C for all testing conducted in the laboratory.
Height and weight. A standard scale and stadiometer (Seca Mechanical Beam Medical Scale – Model 700, Hanover, MD) was used to determine weight in kilograms and height in centimeters to the nearest tenth.
5-km performance time. The two 5-km race times used to generate the dependent variable in this study were conducted at an official cross-country meet on a dry, outdoor cross-country course, as part of the in-season race schedule for the Division I cross-country team. Performance in a competitive race as opposed to non-competitive or training race was used to optimize participant effort. Participants were encouraged to maintain an even pace throughout the race in order to produce the best result. The race time was the official time recorded by race organizers, and was recorded to the nearest 0.1 s.
Maximal oxygen consumption (VO2max) test. A graded treadmill exercise test was used to determine participants’ VO2max as a gauge of their maximal aerobic capacity. The VO2max test used in this study was chosen as it represented a valid protocol for elite level endurance athletes (13). Participants’ warmed-up by jogging for 10 minutes at 3.5 mph and 0% grade. During the first stage of the test, the participant ran at 7 mph and 0% grade for 2 minutes. Every two minutes thereafter the grade was increased by 2.5 percent. Following the warm-up, participants were fitted with a heart rate monitor, and mouthpiece and nose-clip for use with the open-circuit spirometry system. During each minute, oxygen consumption (VO2), respiratory exchange ratio (RER=VCO2/VO2: the ratio of carbon dioxide produced to oxygen consumed), and heart rate (HR) were recorded via open circuit spirometry (Parvo Medics Metabolic Measurement System MMS 2400, Salt Lake City, UT) and a Polar heart rate monitor (Polar Electro Inc., Lake Success, NY). Rating of perceived exertion (RPE) was also assessed at two minute intervals by asking the participant to point to the value on a written RPE scale (6-20 scale) (3) indicative of subjective effort. In accordance with recognized guidelines, VO2max was identified at the point when at least three (or more) of the following criteria were met: a) an RER of > 1.15, b) no further increase in HR with increasing intensity, c) a plateau of oxygen uptake with increasing workload (< 150 ml∙kg-1∙min-1), d) an RPE of > 17 (6-20 scale), and e) volitional fatigue (1,19). Ventilatory threshold (VT) was evaluated as the point of agreement at which 1) ventilation rate demonstrates inflection relative to VO2, and 2) a rise in the ventilatory equivalent for VO2 (VE/VO2) is observed without a concomitant increase in the ventilatory equivalent for VCO2 (VE/VCO2) (5). The VO2 data point at which VT was identified was recorded (VO2@VT). All VO2max testing was conducted by a certified exercise physiologist.
2-mile time-trial (2-MTT). The 2-MTT was conducted on an outdoor 400-meter running track. Participants were asked to complete a 2-mile paced run at near maximal effort, but maintain and even pace in order to produce the most consistent trial time. The 2-MTT was administered twice during the 6 month timeframe of this study as part of the conditioning program for the entire cross-country team. Therefore, the head cross-country coach was present to assist with the administration of the 2-MTT and assist each athlete with the pacing element inherent in this 2-MTT. The 2-MTT was conducted within 10 days of the VO2max and 5-km race to which it was being compared.
Data was reported as means and standard deviations and all identifying information was removed prior to study initiation. Pearson product moment correlations were used to analyze the strength and direction of the relationship between VO2max values, VO2@VT, 2-MTT, and 5-km race time. A multiple linear regression analysis was conducted to examine the predictive capacity of the physiological variables on 5-km race time. The statistical assumptions inherent in linear regression were satisfied with the exception of multicolinearity, however a stepwise regression approach was used which retained independent variables that did not exceed correlation coefficients of 0.9 (18). All statistical analyses were conducted using the IBM SPSS Statistics 22 for Windows (IBM Corp., Armonk, NY). Unless specified otherwise, p<0.05 was used as an acceptable level of significance for all analyses. RESULTS
The participants’ demographic and variable data is presented in Table 1. Results showed a strong significant correlation between 5-km race time and VO2max (r = -0.901), VO2@VT (r = -0.911), and 2-MTT (r = 0.903) (p<0.05). The multiple regression model with all three predictors produced R2 = .90, F(3, 27) = 45.67, p<0.001. Multiple regression using a stepwise approach yielded a significant model [R2 = 0.90, F(2, 28) = 125.40, p<0.001] that excluded VO2max and decreased the model SEE slightly (0.75 versus 0.73, respectively). The VO2@VT and 2-MTT were able to explain 90% of the variance in 5-km race performance. When VO2@VT and 2-MTT were entered independently as predictor variables, they were able to explain 83% and 82% of the variance in 5-km time, respectively. Sex differences were not analyzed due to the relatively small sample of women in the study.
The purpose of this study was to compare field- and laboratory-based predictors of 5-km performance in collegiate cross-country runners. Previous research has explored the predictive capacity of each of the variables used in this study, but has not compared their effectiveness in the same study using a NCAA collegiate cross-country population.
This study found that VO2max, VO2@VT and 2-MTT were significantly correlated with 5-km performance time. However VO2@VT and 2-MTT were stronger predictors of 5-km race performance than VO2max. These findings are consistent with previous research suggesting that measures taken at ventilatory threshold (e.g., VO2, velocity) and during track runs using a known distance may be stronger predictors of distance running performance than VO2max in well-trained runners (10,12,14). The achievement of ventilatory threshold corresponds to a substantial increase in lactic acid accumulation. Previous research has demonstrated a strong relationship between rises in lactic acid and ability to sustain running pace without additional fatigue-inducing lactic acid accumulation and consequently distance race performance (22). In the current study the ability to offset lactic acid accumulation is likely related to the ability to maintain efficient pace for the duration of a 5-km run.
Kranenburg and Smith (12) have suggested that track-based field tests are a suitable approach for evaluating conditioning status of middle-distance runner and predicting 10-km performance times. Running to a state of volitional fatigue (i.e., a laboratory-based VO2max test) requires considerable motivation to maintain effort not knowing the ultimate distance or duration that will be needed to complete the test. Whereas Kranenburg and Smith (12) suggest when runners are aware of the distance they need to complete or given a specific goal, they may be able to manage their work effort more accordingly in order to achieve a maximal performance that is reflective of their current training status. Elite runners are often experienced in pace or tempo-running approaches, making the learning curve with a test such as the 2-MTT very small. The utility of predicting performance times in one distance from times in another distance has been well established (6,7,20), although typically requires performance times in two alternative distances.
The present study revealed that 2-MTT accounted for the same variance in 5-km time as VO2@VT. This finding has important and potentially very useful implications for cross-country coaches looking for approaches that will accurately track the progress their runners are making, without having to rely on laboratory-based testing that may put undue stress on the body, increase risk of injury or interfere with pre- or in-season training schedules.
For collegiate cross-country runners in the US, the competitive season typically runs from August or September to November, and typically includes competitive runners every 7 to 14 days in the lead up to conference or regional competitions. As a result, runners have a restricted amount of time to recover between races and tweak performance variables. This need for ongoing conditioning with special consideration for adequate recovery and injury risk reduction practices often makes VO2max testing inappropriate or simply not feasible during the competitive season and challenging to incorporate during the short pre-season given the intense training schedule often present. Furthermore, a VO2max test requires an administrator with specialized training and expensive equipment which must also be calibrated accordingly, in addition to being physiologically very demanding (which may necessitate a break from regular scheduled training in order to recover sufficiently). The 2-MTT is easier, cheaper and possibly quicker to conduct that a VO2max test to determine VO2@VT (or other VT-related variables) in motivated runners. A track may also be more sport-specific for runners (although typically not a race-setting for cross-country runners) than a treadmill, and, as has been suggested by other researchers and practitioners, allow for field-based tests to be more easily built into the training schedule of elite level runners2.
APPLICATIONS IN SPORT
The 2-MTT is a field-based test and is cheaper and easier to administer than a VO2max test, making it an attractive marker from which to evaluate progress throughout the course of a competitive season, and a more feasible alternative to time-consuming laboratory-based testing. However, further research is needed to examine if other field- or track-determined variables (e.g., track-determined critical speed) have a greater predictive capacity than the laboratory or 2-MTT variables included in this study, and whether the relationships highlighted in this study are consistent across other running populations and courses, and similar for both male and female athletes.
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