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The complex physiology of orienteering performance is not well understood but recent advances in technology allow for more in-depth investigation. The purpose of this study was to develop and validate physiological field tests for elite orienteers in Australia. Seven male and three female elite orienteers volunteered to take part in the study. Subjects completed an incremental fixed-distance (803m) trial in Australian forest terrain, paced by a bicycle equipped with a speedometer. This was replicated in the laboratory using a 4.5% grade for treadmill running. Subjects also completed four (males) or three (females) laps of a 1340m terrain loop incorporating uphill, track and downhill sections. Subjects then repeated this test in the laboratory, with treadmill grade manipulated to replicate the gradient profile of each section. Heart rate (HR) and oxygen uptake (VCh) were recorded continuously with telemetry during each stage/lap. Blood [La] and RPE were recorded after each stage/lap. In the incremental tests, no significant differences (p=0.05 level) were observed in HR, VO2, blood [La] or RPE between the Field test, and its Laboratory replication over the entire range of speeds tested. The actual speeds run during the Field tests were significantly faster than the Laboratory test at the slowest speed (8 kmh- 1 ) attempted, and slower at the fastest speed (18 km-h-1) attempted. In the time-trial tests, no significant differences were observed in HR, VO2, blood [La] or RPE between the Field test and its Laboratory replication. The running speeds in the Field tests were significantly slower than the Laboratory tests. Running speed appeared inversely related to the course profile and the terrain also affected the speeds that could be achieved. Despite the changes in the course profile, the physiological responses to the course were maintained within a narrow range at a high level (-95% of maximal heart rate, 80-90% of VO2max, blood [La] -10 mM) for the duration of the 20-25 minute test. The Field tests that were developed in this study for elite orienteers in Australian forest terrain were successfully validated by replicating the protocols in a Laboratory setting.

An accumulation of sudden unexpected cardiac deaths (SUCD) occurred in young Swedish orienteers, most of whom were elite athletes. From 1979 to 1992 the incidence in 18 to 34 year old male elite orienteers ranked on the national level the same year as death was calculated to 30 (per 100,000), which represents a 20 to 40 fold increase from the expected rate. From 1989 to 1992, the incidence was 50. There were, however, no indications on any similar clusters of SUCD in other sports. A special program to alter behaviour in orienteers was implemented in 1992-1993, after which there have been no more cases of SUCD in orienteers below 35 years of age. A histopathological re-evaluation of 16 cases of SUCD revealed myocarditis in 75% of these cases. In parallel, four of those cases also had changes mimicing arrhythmogenic right ventricular cardiomyopathy (ARVC). The combination of an increased incidence and myocarditis suggested that infection may be a pathogenetic factor. A broad search for different microorganisms in archival sera from five cases and tissues from the autopsies in two of those cases revealed the only common finding that all had antibodies to Chlamydia pneumoniae. DNA from C. pneumoniae was detected in the lung and heart in one of two cases. The intimate contact with nature of orienteers suggested possible zoonotic/vectorborne pathogens. Bartonella is such a pathogen and known to cross-react with C. pneumoniae. The use of PCR to test for DNA from the gltA gene of Bartonella in the two formerly mentioned cases of SUCD, and in three additional cases, gave positive bands from the hearts in four cases and the lung in a fifth case. The PCR products were sequenced and found to be identical to B. henselae in three cases and almost identical to B. quintana in the remaining two cases. Four of the five cases had antibodies to Bartonella when using micro immunofluorescence test with the antigens B. henselae, B. quintana, and B. elizabethae. The total prevalence of antibodies to Bartonella was 31% in 1,136 elite orienteers vs. 6.8% in 322 healthy blood donors (p<0.001), suggesting widespread exposure in the elite. It is hypothesized that subacute or reactivated Bartonella infection has a pathogenetic role in SUCD in orienteers, and may be involved in the development of ARVC-like disease.