What are the limitations of our so far work?
The challenges of field work: Dr Matt Wilkes calibrating the Metamax on the hill, prior to a test flight in Chabre, France.
In Phase I, we showed that pilots had strikingly high heart rates on take off but that otherwise, paragliding was much more about mental rather than physical fitness, though G forces could be high enough to cause loss consciousness and our breathing patterns remain incompletely understood.
Many of these findings were quite obvious: take-off is stressful, paragliding isn’t a primarily physical sport, oxygen systems have a way to go and spiral dives can render us unconscious. We knew most of these things intuitively before we started. However, our aim in the first phase was to start quantifying these different elements of flight. We wanted to know how stressful, how physical, where the limits and tolerances lay. That way, we could start chasing down ways to make our sport safer.
Like every scientific study, our Phase I work had limitations. The most important was that we only studied a small number of pilots, making generalisations difficult. We were limited by the complexity of the measurements, time and funding. Because we could only study a few pilots we just looked at men, to try to reduce variation in our sample as much as possible. However, we would be much happier to study female and male pilots in future, reflecting the mixed gender nature of our sport. We also didn’t include any beginner pilots but we had to be sure that of all our measurement equipment could be used safely by experienced pilots first.
As ever though, we welcome any feedback on our work.
Equipment and sensor limitations we could not engineer away
Our Phase I instrumentation, while carefully chosen, brought its own constraints. The heart rate monitors we used were chest-strap units, which occasionally slipped or lost contact during harness adjustments and aggressive manoeuvres. In turbulent air, even a brief loss of signal left gaps in the data that we could not reliably interpolate. G-force logging depended on accelerometers mounted in the instrument pod, but body position changes meant the recorded axes did not always correspond cleanly to the pilot’s head-to-toe direction. A spiral dive, for example, produced a complex mix of lateral and vertical acceleration that was hard to interpret as a single “G load” figure.
Oxygen measurement was perhaps the most fragile link. We relied on fingertip pulse oximeters inside thin gloves, but cold fingers at altitude gave intermittent readings, and some pilots reported the sensor as distracting. Portable oxygen systems were tested in only a handful of flights, and the regulators behaved differently depending on altitude, temperature and moisture. These are not failures of the idea, but they are real limitations on what we can claim. We could show trends, not precise dose–response relationships. A reader should not imagine that our numbers were laboratory grade; they were field grade, which is the whole point but also the honest boundary.
Environmental variability and the impossibility of a control flight
No two paragliding flights share the same air. Even when we launched from the same hill in Chabre, the wind direction shifted, thermals formed and decayed unpredictably, and cloud cover changed the thermal structure within minutes. That made direct comparisons between pilots, or between flights by the same pilot, statistically messy. In a wind tunnel or a simulator you can hold conditions constant, but we deliberately chose not to. The cost of realism is a loss of experimental control, and we felt that cost every time we tried to compare a morning flight with an afternoon one.
Altitude also varied enormously across our test sessions. Some launches were at 1,400 metres, some at 2,100 metres, and pilots climbed or descended by hundreds of metres during a single task. Heart rate, oxygen saturation and perceived effort all respond to altitude, so the same manoeuvre flown at different heights produced different physiological readings for reasons unrelated to the manoeuvre itself. We attempted to correct for altitude in post-processing, but the corrections were crude. Weather windows in the Alps are short and unpredictable; logistics often forced us to fly when the air was workable rather than when it was scientifically ideal.
Who we measured — and who we did not
The small sample is the headline limitation, but within that sample there were further skews. All participants were experienced male pilots recruited through personal contacts and local clubs. They were predominantly from one region of Europe and shared similar training backgrounds. This is not a representative picture of global paragliding. Pilots who volunteer for physiological monitoring are also a self-selecting group: they tend to be comfortable with technology, physically active, and perhaps less anxious about being measured. We may have systematically missed pilots who find the equipment stressful or who fly less often, and those pilots might show very different heart rate or breathing patterns.
There was also an unavoidable observer effect. Pilots knew they were being recorded, and several told us afterwards that they flew more conservatively than usual, at least for the first few minutes. That alone could suppress the very extremes we were trying to capture — the spike on launch, the panic response in a collapse, the moment of near-loss of consciousness. Some of our most interesting data came from incidents that happened unexpectedly, but we cannot rely on accidents for science. The fact remains: a pilot wearing a chest strap and a finger probe is not flying exactly as they would on a normal Sunday afternoon.
The fuzzy boundary between physiology and experience
Heart rate and G-force are easy to put a number on. But the original question — how stressful is paragliding, and where do our limits lie — is partly a question about subjective experience, and that resisted quantification. We asked pilots to rate their perceived exertion and anxiety on simple scales after each flight, but memory is unreliable. A pilot who has just landed safely may retrospectively downplay how frightened they were at 2,000 metres. A pilot who felt calm throughout may still show a resting heart rate of 140, and we do not fully know whether that indicates hidden stress or simply physical effort and thermalling workload.
Breathing patterns remain one of our least understood measurements. We recorded respiratory rate from chest expansion, but this signal was noisy during harness movement and could not capture depth of breathing, breath-holding, or irregular sighing. Several pilots showed brief apnoeas during intense concentration, but we could not tell whether this was a conscious technique, a stress response, or an artefact. Loss of consciousness events were recorded only through pilot self-report, often with amnesia for the seconds immediately before and after. Without EEG or continuous cognitive testing, we cannot separate physical G-induced blackout from simple disorientation or decision overload. That boundary is exactly where future work should focus, but we accept that Phase I did not cross it.