Intersexual and intrasexual selection for neck musculature in men: Attractiveness, dominance, and actual fighting success

Countless organisms are equipped with physiological armor that reduce damage from opponents. Because humans have sustained a long evolutionary history of hand-to-hand combat, selection would have been placed on morphological structures which reduce rotational acceleration to the head and increase the likelihood of victory. Grounded in over 60 years of sports performance theory and recent theoretical work in evolutionary biology, geometric morphometric analyses revealed that larger neck musculature in professional combatants (N = 715) was associated with greater real-world fighting success, after for adjusting for allometry (Study 1). Because sexual dimorphism emerges from selection on morphological structures that improve men’s fighting success, we then discovered that the human neck is the most sexually dimorphic feature of human anatomy when compared to 91 other anatomical features (N = 6,068; Study 2). This male-biased sexual dimorphism held after controlling for these 91 allometric measurements, and held across every world region (Africa, Asia, Europe, Oceania, and North, Central, and South America). Because human psychological systems consequently evolved to attend to men’s secondary sexual characteristics, we discovered that men (N = 564 stimuli) with larger neck musculature (Study 3: geometric morphometrics; Study 4: physiological neck strength; Study 5: photorealistic stimuli) are rated (N = 772 raters) as stronger, more masculine, and higher in fighting ability and short-term attractiveness, after accounting for allometry. Combined, our research introduced a new secondary sexual characteristic to the biological, anthropological, and psychological sciences: the human neck.

Associations of neck muscle strength and cervical spine mobility with future neck pain and disability: a prospective 16-year study

Background Neck pain has been associated with weaker neck muscle strength and decreased cervical spine range of motion. However, whether neck muscle strength or cervical spine mobility predict later neck disability has not been demonstrated. In this 16-year prospective study, we investigated whether neck muscle strength and cervical spine mobility are associated with future neck pain and related disability in women pain-free at baseline. Methods Maximal isometric neck muscle strength and passive range of motion (PROM) of the cervical spine of 220 women (mean age 40, standard deviation (SD) 12 years) were measured at baseline between 2000 and 2002. We conducted a postal survey 16 years later to determine whether any subjects had experienced neck pain and related disability. Linear regression analysis adjusted for age and body mass index was used to determine to what extent baseline neck strength and PROM values were associated with future neck pain and related disability assessed using the Neck Disability Index (NDI). Results The regression analysis Beta coefficient remained below 0.1 for all the neck strength and PROM values, indicating no association between neck pain and related disability. Of the 149 (68%) responders, mean NDI was lowest (3.3, SD 3.8) in participants who had experienced no neck pain (n = 50), second lowest (7.7, SD 7.1) in those who had experienced occasional neck pain (n = 94), and highest (19.6, SD 22.0) in those who had experienced chronic neck pain (n = 5). Conclusions This 16-year prospective study found no evidence for an association between either neck muscle strength or mobility and the occurrence in later life of neck pain and disability. Therefore, screening healthy subjects for weaker neck muscle strength or poorer cervical spine mobility cannot be recommended for preventive purposes.

Eight Weeks of Self-Resisted Neck Strength Training Improves Neck Strength in Age-Grade Rugby Union Players: A Pilot Randomized Controlled Trial

Background: Greater neck strength is associated with fewer head and neck injuries. Neck-strengthening programs are commonly burdensome, requiring specialist equipment or significant time commitment, which are barriers to implementation. Hypothesis: Completing a neck-strengthening program will increase isometric neck strength in age-group rugby players. Study Design: A pilot randomized controlled exercise intervention study. Level of Evidence: Level 2. Methods: Twenty-eight U18 (under 18) male regional age-group rugby union players were randomized (intervention n =15/control n = 13). An 8-week exercise program was supervised during preseason at the regional training center. Control players continued their “normal practice,” which did not include neck-specific strengthening exercises. The 3-times weekly trainer-led intervention program involved a series of 15-second self-resisted contractions, where players pushed maximally against their own head, in forward, backward, left, and right directions. Outcome Measure: Peak isometric neck strength (force N) into neck flexion, extension, and left and right side flexion was measured using a handheld dynamometer. Results: Postintervention between-group mean differences (MDs) in isometric neck strength change were adjusted for baseline strength and favored the intervention for total neck strength (effect size [ES] = 1.2, MD ± 95% CI = 155.9 ± 101.9 N, P = 0.004) and for neck strength into extension (ES = 1.0, MD ± 95% CI = 59.9 ± 45.4 N, P = 0.01), left side flexion (ES = 0.7, MD ± 95% CI = 27.5 ± 26.9 N, P = 0.05), and right side flexion (ES = 1.3, MD ± 95% CI = 50.5 ± 34.4 N, P = 0.006). Conclusion: This resource-efficient neck-strengthening program has few barriers to implementation and provides a clear benefit in U18 players’ neck strength. While the present study focused on adolescent rugby players, the program may be appropriate across all sports where head and neck injuries are of concern and resources are limited. Clinical Relevance: Greater neck strength is associated with fewer head and neck injuries, including concussion. Performing this neck exercise program independently, or as part of a whole-body program like Activate, an interactive guide for players and coaches, could contribute to lower sports-related head and neck injuries.