Scientific Foundations

Adapta's plan follows the linear periodisation model: base → build → specific → taper. Each phase has a different physiological objective. The base phase develops fundamental aerobic capacity with moderate loads and high volume. The build phase introduces more intense sessions. The specific phase works on race-specific fitness. The taper phase reduces volume to allow full expression of fitness.

This scheme is well documented in the sports science literature (Matveev 1977; Bompa & Haff 2009) and is the reference model for most endurance coaches. Adapta's system automatically scales the duration of each phase based on the weeks available before the goal.

Research on elite endurance athletes consistently shows that around 80% of training volume occurs at low intensity (easy, aerobic zone) and only 20% at high intensity (threshold, VO₂max). This is known as the polarised model.

Stöggl & Sperlich (2014) demonstrated in a randomised study that polarised training produces superior adaptations compared to pure threshold training — greater improvements in VO₂max, running economy, and 10km performance. The "moderate intensity trap" (doing everything at moderate intensity) is one of the most common mistakes among amateur runners.

Adapta applies this principle by distributing weekly sessions with at most one quality session (interval or tempo) per week for runners with ≤4 available days, and the rest at controlled intensity.

RPE (Rate of Perceived Exertion) on a 1-10 scale is the tool Adapta uses to understand your internal load. No heart rate monitor, high-end GPS, or power meter needed: your perception of how hard you worked is a scientifically validated measurement tool.

The Session-RPE method, developed by Carl Foster et al. (2001), multiplies the RPE value by the session duration in minutes, yielding an "internal load" in arbitrary units (AU). This indicator correlates well with objective measures (TRIMP, HR, lactate) and works across any sport, with no additional equipment cost.

Adapta uses RPE to detect sessions that are too hard relative to the planned intensity (Rule 2), prolonged high-load periods (Rule 4), and phases of optimal fitness (Rule 5). Thresholds differ for standard athletes and adaptive profiles.

Physical improvement doesn't happen during effort — it happens during recovery. After a training stimulus the body adapts and becomes stronger: this phenomenon is called supercompensation. If the next stimulus comes too soon (before recovery is complete) fatigue accumulates; if it comes too late, the adaptation is lost.

Adapta monitors four daily indicators (sleep, energy, legs, motivation) to estimate recovery status. When the average score drops below threshold — indicating insufficient recovery — the engine automatically reduces the volume of subsequent sessions.

The literature (Meeusen et al. 2013, Halson 2014) indicates that multi-dimensional recovery monitoring is more reliable than any single metric. Functional overtraining is reversible within a few days; non-functional overtraining requires weeks or months. Prevention is far more efficient than recovery.

The risk of re-injury during return to training is high if load increases too quickly. Blanch & Gabbett (2016) showed that the ratio between acute load (current week) and chronic load (average of the previous 4 weeks) — called the A:C ratio — should stay between 0.8 and 1.3 during return. Rapid increases (>1.5) significantly raise the risk.

Adapta automatically applies a progressive ramp after injury resolution: load is reduced by a variable percentage based on severity (30%→55%→75% for severe injuries, 65%→85% for mild ones), with maximum intensity limited in the early phases. High-impact sessions (interval, threshold, technical trail) are automatically replaced with easy sessions until the ramp is complete.

Research shows that menstrual cycle phases influence aerobic performance, perceived effort, and recovery capacity. The follicular phase (post-menstruation) is characterised by high oestrogen levels: strength, power, and recovery tend to be optimal. The ovulatory phase represents the energy peak. The late luteal phase (pre-menstruation) brings elevated progesterone: higher body temperature, greater perceived effort at the same absolute load, slower recovery.

McNulty et al. (2020) — in a meta-analysis of 51 studies — found "small but potentially meaningful" effects of cycle phase on aerobic performance. Adapta's Cycle Sync function modifies volume and intensity of sessions based on the current phase: reduction during the menstrual and late-luteal phases (×0.75-0.85), slight amplification during the follicular and ovulatory phases (+5-10% on easy sessions).

The guidelines published in 2019 by Tom Goom, Grainne Donnelly, and Emma Brockwell — the most cited reference for health professionals supporting postpartum women — identify two critical thresholds: 12 weeks as the absolute minimum before resuming running, and 26 weeks as the point at which the risk of pelvic floor dysfunction related to high-impact activity decreases significantly. Before 26 weeks, running can be resumed gradually but requires active symptom monitoring.

Signals to monitor during postpartum running include: sensation of pressure or heaviness at the perineum, urinary or faecal leakage during or after activity, pelvic or lower back pain. The presence of even one of these signals indicates the load exceeds the current capacity of the pelvic floor and requires volume reduction or physiotherapy assessment.

Adapta automatically adds safety notes to high-impact sessions (running, strides, intervals, hill repeats) for the first 26 weeks postpartum if the user has entered their postpartum weeks in their profile. The notes flag the symptoms to monitor and indicate stopping or reducing load if any signal is present.

The menopausal transition brings physiological changes relevant to training: reduction in oestrogen with impact on thermoregulation (greater difficulty dissipating heat), recovery (tends to be slower), body composition, and bone density. Perceived effort at the same absolute load tends to increase.

Stachenfeld (2008) documented how oestrogens influence body fluid regulation and thermal response: in menopause the sweating threshold rises and cutaneous vasodilatory response decreases, with greater risk of overheating during intense workouts or in a hot environment. Hydration becomes a particularly critical factor.

Enns & Tiidus (2010) documented how oestrogens modulate the muscular inflammatory response and eccentric exercise damage: post-menopausal reduction slows recovery between intense sessions. This doesn't mean reducing intensity indefinitely, but increasing recovery time between quality sessions.

Adapta recognises this phase: by activating menopause/perimenopause mode in the profile, the Cycle sync function is disabled (not applicable) and an informational note appears on the Recovery page. The adaptation engine operates with more conservative recovery thresholds during this phase.

Chronic systemic conditions — systemic lupus erythematosus, fibromyalgia, multiple sclerosis, chronic fatigue syndrome (ME/CFS), compensated heart conditions, and similar — share a common feature: variability in functional capacity. Good days and difficult days don't follow a predictable pattern. The standard linear load progression model isn't always safe or sustainable.

The pacing principle — adapting effort to the day's capacity rather than following a fixed plan — is recommended in fibromyalgia guidelines (Busch et al. 2011) and in ACSM guidelines for chronic disease populations (Garber et al. 2011). The most common mistake is training too intensely on good days, generating a boom-and-bust cycle that worsens the condition over the medium term.

Adapta implements this approach for the 'variable capacity' profile with: deload every 3rd week (instead of every 4th), maximum session duration of 75 minutes, 90/10 intensity distribution (instead of 80/20), more sensitive automatic adaptation thresholds. The 'Flare / symptoms' skip reason is dedicated to these users and helps the engine recognise flare patterns over time.

Strength training isn't optional for runners: it's a component that directly improves performance. Beattie et al. (2017) documented improvements in running economy, peak VO₂max velocity, and 5K performance of up to 5% in runners who added strength training to their programme.

Stability and mobility sessions in Adapta are integral parts of the plan — not fillers. Mobility is treated as active structured recovery: it doesn't increase the load, doesn't trigger intensity adaptation rules, and isn't counted in the average RPE calculation. This is how the system recognises its distinct recovery value separate from metabolic stress.

Trail running with significant elevation gain imposes a much higher energy cost than flat running at the same speed. Minetti et al. (2002) documented that at +15% gradient, metabolic cost is approximately 3 times that of flat terrain. Naismith's rule of thumb states that 1 metre of positive elevation gain is equivalent to approximately 7-8 horizontal metres.

Adapta manages trail running with dedicated session types (trail_easy, trail_technical, hill_short, hill_long) that reflect different physiological demands. Technical sessions on challenging terrain are treated differently from a road run of the same duration, because the energy cost — including the eccentric component on descents — is substantially higher.