Hair grows in cycles: Anagengrowth phase, Catagentransition phase, and Telogenrest and shedding phase. Disturbances shift this rhythm – more follicles slip into the telogen phase, making the hair appear thinner. Telogen effluviumdiffuse, temporary hair loss due to a shift into the resting phase often occurs after stress, illness, or nutrient deficiencies. Mechanical and thermal influences additionally damage the cuticleouter scale layer of the hair and undermine the cortexsupporting fiber layer with keratin bundles – the result is hair breakage, which visually resembles "hair loss." It is important to distinguish: hair breakage destroys the fiber; hair loss affects follicular activity. Understanding the causes allows targeted countermeasures: irritation reduction, nutrient sufficiency, protection of the fiber, and stress relief stabilize the cycle.

Excessive heat alters the keratin structure: disulfide bridges in hair proteins are disrupted, and the fiber loses integrity – a gateway situation for breakage and visibly thinner-looking hair. Studies show measurable protein changes after repeated heat exposure and a clear correlation between technical damage and human perception of "damaged" hair [Ref40708551; Ref40927888]. Care habits also count: aggressive brushing, especially when wet, leads to short and long-segment breakage due to friction, tangling, and impact loading [Ref22682401; Ref16832574; Ref18305876]. Chronic stress shifts the hair cycle: overactive sympathetic nerves release excessive norepinephrine, damaging sensitive transit-amplifying cells in the follicle – a biological pathway to telogen effluvium and immunological attacks on the follicle ^[1]. Tight hairstyles increase mechanical tension on the hair root; in the long term, this can lead to traction alopecia – partially irreversible in later stages ^[2]. For performance assessment, this means: subthreshold, cumulative damages accumulate – costing vitality signals, self-image, and mental energy.

Several lines of research complement each other. First: thermal stress. Laboratory work shows that heat reduces the tensile strength of individual hair fibers; based on this, a reproducible scale for heat damage has been developed, which correlates well with human damage perception – pragmatically relevant, as temperature and contact time are measurable variables ^[3]. Proteomic analyses also demonstrate that heat and UV chemically alter cysteine residues in keratins, breaking disulfide bridges and weakening the secondary structure – a plausible mechanism for brittle hair after frequent styling ^[4]. Second: mechanical stress. Studies on combing and brushing show that hair breakage occurs due to tangling, abrasion, and impact loading; wet-brushed, chemically treated, or highly curled hair breaks more often in longer segments – a pattern that explains why certain routines visibly "thin out" the hair without affecting the follicles [Ref22682401; Ref16832574; Ref18305876]. Third: stress biology. Experimental data suggest that acute stress can rapidly damage follicle cells through sympathetic activation and initiate autoimmune processes – a mechanistic link between stress spikes and sudden hair loss ^[1]. Taken together, the evidence outlines clear preventive paths: minimize heat and tension, manage friction intelligently, and interrupt stress cycles.

- Smart use of biotin: First, focus on biotin-rich foods (egg yolk, liver, nuts, seeds, legumes). High-quality studies find no clear benefit of biotin supplements for hair growth in healthy individuals; supplements are primarily beneficial in cases of proven deficiency or specific situations ^[5]. Tip: Dietary check, then possibly targeted supplementation in consultation with a doctor.
- Minimalistic heat: Blow-dry on low temperature, keep styling tools under 180°C, reduce contact time, and use heat protection. Repeated heat visibly damages keratin structures; less heat = measurably less damage [Ref40708551; Ref40927888].
- Mitigate mechanical stress: Brush dry hair with a wide-toothed comb from the tips upward. Avoid aggressive brushing, especially when wet, to reduce impact loading and abrasion [Ref22682401; Ref16832574; Ref18305876].
- Hairstyle with foresight: Loose braids, soft scrunchies, changing partings. Avoid prolonged tight hairstyles, extensions with tension, and very tight hair ties – this reduces the risk of traction alopecia ^[2].
- Manage stress as a follicle factor: Plan 10–15 minutes daily for nervous system hygiene (e.g., 4-7-8 breathing exercises, moderate endurance training, sleep routine). Acute stress can immediately disrupt the hair cycle; regular stress reduction stabilizes ^[1].
- Consider sun exposure: UV enhances structural damage. Protect hair with a hat or UV spray, especially during long outdoor training; UV-associated changes in hair proteins are documented ^[4].

Hair strength can be trained: less heat and tension, smarter care, stress buffers – and a diet that covers biotin instead of blindly overdosing. Start this week with three steps: lower the temperature when styling, adjust brushing routine to prevent tangles, and plan 10 minutes of stress hygiene daily. Your hair – and your energy level – will reflect it.