Deirdre E. McGhee

How do respiratory state and measurement method affect bra size calculations

Objectives: To investigate the effects of respiratory state and measurement method on bra size calculation. Methods: The bra sizes of 16 large-breasted women were measured during two respiratory states, end voluntary inspiration and relaxed voluntary expiration, and using two sizing methods, which were compared against subject-reported bra sizes. Results: Both respiratory state and measurement method significantly affected bra size estimations, whereby measuring chest circumference during inspiration increased both band and decreased cup size. However, whereas bra size calculated using the standard method differed significantly from subject-reported bra size, cup size calculated using the breast hemi-circumference method did not differ significantly from subject-reported cup size. Conclusions: As respiratory state significantly affects bra sizes, it should be standardised during bra size measurements. A more valid and reliable bra sizing method should be developed, possibly using the breast hemi-circumference method for cup size estimations and raw under-bust chest circumference values for band size.

Bra-breast forces generated in women with large breasts while standing and during treadmill running: implications for sports bra design

This study aimed to determine the bra-breast forces generated in women with large breasts while these women wore different levels of breast support during both upright standing and treadmill running. The mean bilateral vertical component of the bra-breast force in standing was 11.7 ± 4.6 N, whereas during treadmill running the mean unilateral bra-breast force was 8.7 ± 6.4 N and 14.7 ± 10.3 N in the high and low support conditions, respectively. Furthermore, breast mass was significantly correlated with vertical breast displacement (R(2) = 0.62) in the high support condition. The wide range of breast masses of women with large breasts is an important consideration for designers of sports bras to ensure these bras can reduce force generation and breast discomfort by providing a high level of breast support while these women participate in physical activity.

Does deep water running reduce exercise-induced breast discomfort?

Aim: To establish whether exercise-induced vertical breast displacement and discomfort in women with large breasts were reduced during deep water running compared to treadmill running. Methods: Sixteen women (mean age  = 32 years, range 19–43 years; mean mass  = 74.1 kg, range 61–114 kg; mean height  = 1.7 m, range 1.61–1.74 m), who were professionally sized to wear a C+ bra cup, were recruited as representative of women with large breasts. After extensive familiarisation, vertical breast motion of the participants was quantified as they ran at a self-selected stride rate on a treadmill and in 2.4 m deep water. Immediately after running, the subjects rated their breast discomfort and breast pain (visual analogue scale) and their perceived exertion (Borg scale). Breast discomfort, breast pain, perceived exertion, vertical breast displacement and vertical breast velocity were compared between the two experimental conditions. Results: Exercise-induced breast discomfort was significantly less and perceived exertion was significantly greater during deep water running relative to treadmill running. Although there was no significant between-condition difference in vertical breast displacement, mean peak vertical breast velocity was significantly (p<0.05) less during deep water (upward mean (SD): 29.7 (14.0) cm.s−1; downward: 31.1 (17.0) cm.s−1) compared to treadmill running (upward mean (SD): 81.4 (21.7) cm.s−1; downward: 100.0 (25.0) cm.s−1). Conclusion: Deep water running was perceived as a more strenuous but comfortable exercise mode for women with large breasts. Increased comfort was attributed to reduced vertical breast velocity rather than reduced vertical breast displacement.

Breast elevation and compression decrease exercise-induced breast discomfort

PURPOSE The aim of this study was to investigate whether a sports bra designed to both elevate and compress the breasts could decrease exercise-induced breast discomfort and bra fit discomfort experienced by women with large breasts relative to a standard encapsulation sports bra. METHODS Breast kinematic data, bra fit comfort, exercise-induced breast discomfort, and bra rankings in terms of preference to wear during running were compared in 20 women with large breasts who ran on a treadmill under three bra conditions: an experimental bra that incorporated both breast compression and elevation, an encapsulation sports bra, and a placebo bra. Subjective data were collected immediately before and after the treadmill running trials. RESULTS Exercise-induced breast discomfort (P < 0.01) and bra discomfort (P < 0.01) were significantly less for the experimental bra condition relative to the sports bra and placebo bra. This reduction in discomfort was achieved through greater breast elevation (P < 0.01) and compression, with no difference found in vertical breast displacement (P = 0.12) or vertical breast velocity (P = 0.06). CONCLUSIONS The design features of greater breast elevation and compression provided significantly increased breast and bra comfort compared with a standard encapsulation sports bra during physical activity for women with large breasts.

Education improves bra knowledge and fit, and level of breast support in adolescent female athletes: a cluster-randomised trial

QUESTIONS Can an education booklet handed out by a physiotherapist improve bra knowledge and fit, and level of breast support, of bras worn by adolescent female athletes? DESIGN Cluster-randomised trial with intention-to-treat analysis. PARTICIPANTS 115 adolescent females from four regional sporting academies aged 16 yr (SD 1) and with an average Australian bra size of 12B. INTERVENTION The experimental group received an education booklet on bra fit and breast support from a sports physiotherapist. The control group received no intervention. OUTCOME MEASURES The primary outcome was bra knowledge measured by a questionnaire. Secondary outcomes were a pass on the Bra Fit Assessment and the Level of Breast Support tests, and breast discomfort during exercise rated on a 10-cm visual analogue scale. RESULTS Four months after receiving the education booklet, the experimental group had improved their bra knowledge 19% (95% CI 14 to 25) more than the control group. In addition, 39% (95% CI 19 to 54) more of the experimental group passed the Bra Fit Assessment test and 30% (95% CI 11 to 47) more passed the Level of Breast Support test than the control group at 4 months. There was no difference in the level of breast discomfort during exercise. CONCLUSION Bra knowledge, bra fit, and level of breast support in adolescent female athletes were all poor but improved significantly after receiving an education booklet about breast support designed specifically for them. TRIAL REGISTRATION ACTRN12609000607279.

Does a drop landing represent a whole skill landing and is this moderated by fatigue

This study aimed to determine whether the landing phase of a drop landing (DL) differed with respect to a complete jumping and landing task, a spike jump (SJ), and whether fatigue altered the landing of these movements. Fourteen male volleyball players performed five DL and SJ in a counterbalanced order under two experimental conditions: non‐fatigued and fatigued. Fatigue, induced by repetitive jumping sets, was confirmed by decrements in vertical jump height >25% and increased blood lactate >6 mmol/L. Each landing task was characterized by the resultant ground reaction forces (GRF), sagittal plane kinematics and muscle recruitment patterns of six lower extremity muscles. Two‐way repeated analysis of variance results indicated a main effect of movement on many of the GRF, kinematic and electromyographic variables characterizing landing, indicating that the two tasks required substantially different lower limb biomechanics during landing. Although fatigue did not alter the GRF in either task, there were significant movement × fatigue condition interactions. The significant between‐task differences in the biomechanical variables characterizing landing and the differential effects of fatigue on each landing task, question the validity of using a DL as an experimental task to investigate lower limb landing mechanics of whole jumping and landing movements.

Dorsiflexion capacity affects achilles tendon loading during drop landings

PURPOSE Evidence suggests a link between decreased dorsiflexion range of motion (DROM) and injury risk during landings. The purpose of this study was to determine the effect of weight-bearing DROM on ankle mechanics during drop landings. METHODS Forty-eight men (mean ± SD = 22.5 ± 4.7 yr) were measured for DROM. Participants performed drop landings onto a force platform at two vertical descent velocities (2.25 ± 0.15 and 3.21 ± 0.17 m·s(-1)), while EMG activity of four shank muscles and three-dimensional ankle joint kinematics were recorded. Participants were classified into low (37.7° ± 2.5°) and high (48.4° ± 2.5°) DROM groups. RESULTS Ground reaction force, EMG, dorsiflexion angle, plantarflexion moment, and Achilles tendon force outcome variables were all equivalent for the two DROM groups during each landing condition. However, the low DROM group performed each landing condition at a significantly greater percentage of their DROM and displayed significantly more ankle eversion throughout most of the movement. The low and high DROM groups displayed DROM percentages of 27 ± 11 and 10 ± 11 (P = 0.013), 32 ± 9 and 23 ± 9 (P = 0.056), 60 ± 13 and 46 ± 13 (P = 0.004), and 66 ± 16 and 54 ± 9 (P = 0.003) when they encountered the peak plantarflexion moments, Achilles tendon force, eversion angles, and dorsiflexion angles, respectively. CONCLUSION Participants with a low DROM absorbed the landing impact forces with their plantarflexor muscle-tendon units in a more lengthened and everted position. Athletes with a low DROM may be more likely to regularly overload their plantarflexor muscle-tendon units, thereby potentially exposing themselves to a higher likelihood of incurring injuries such as Achilles tendinopathy.

Lower limb movement symmetry cannot be assumed when investigating the stop-jump landing.

PURPOSE When investigating lower limb landing biomechanics, researchers often assume movement symmetry between a participants right and left lower limbs for the simplicity of data collection and analysis, although landing tasks often involve dual-limb motion. However, whether lower limb symmetry can be assumed when investigating dynamic, sport-specific movements such as the stop-jump has not been investigated. Therefore, this study aimed to determine whether there were any significant differences in selected kinetic, kinematic, and muscle activation patterns characterizing lower limb biomechanics displayed by the dominant limb compared with the nondominant limb of participants during a stop-jump task. METHODS Sixteen male athletes with normal patellar tendons on diagnostic imaging performed five successful stop-jump trials. Patellar tendon forces (FPT), ground reaction forces, three-dimensional kinematics, and EMG activity of seven lower limb muscles were recorded for the dominant and nondominant lower limbs during each trial. RESULTS During the horizontal landing phase, the dominant lower limb sustained a significantly higher FPT and peak net knee joint extension moment compared with the nondominant lower limb. Furthermore, during the vertical landing phase, the dominant lower limb sustained significantly lower vertical but higher posterior ground reaction forces compared with the nondominant lower limb. Other variables did not significantly vary as a function of lower limb dominance. CONCLUSIONS It is recommended that researchers clearly identify their primary outcome variables and ensure that their experimental design, particularly in terms of lower limb dominance, provides an appropriate framework to investigate possible mechanics underlying unilateral and bilateral knee joint injuries during dual-limb movements such as the stop-jump task.

Breast volume and bra size

Purpose – The purpose of this paper is to measure the breast volume of a large sample of women and their corresponding correctly fitted bra size, in order to demonstrate the range of volumes within each size and the variation amongst different bra sizes.Design/methodology/approach – Breast volume of 104 women was measured via water displacement and was compared to their professionally fitted bra size, in the one style and brand of bra.Findings – The mean breast volume of the left and right breast was 642 and 643 ml, ranging from 125 (size 10A) to 1,900 ml (size 24DD). The average professionally fitted bra band size was 12 (range size 10‐24; Australian sizing) and cup size was DD (range A‐G). A range of breast volumes was found to correspond to the same bra size and the volume of any one cup size was not homogenous amongst different band sizes.Practical implications – Appreciating the range of breast volumes that correspond to each bra size is important in terms of both bra structure and design in order to...

Passive dorsiflexion stiffness is poorly correlated with passive dorsiflexion range of motion

OBJECTIVES The purpose of this study was to determine the relationships among passive measures of weight-bearing dorsiflexion range of motion, non-weight-bearing dorsiflexion range of motion and dorsiflexion stiffness, thereby establishing whether they assess similar mechanical characteristics, as each measure has been implicated in injury risk during landings. DESIGN Cross-sectional study. METHODS Passive weight-bearing dorsiflexion range of motion, non-weight-bearing dorsiflexion range of motion and dorsiflexion stiffness were quantified for 42 males (22.8±5.0 years). The relationship between each data set was calculated using Pearson product-moment correlation coefficients. RESULTS Although weight-bearing dorsiflexion range of motion and non-weight-bearing dorsiflexion range of motion were significantly correlated, the strength of the relationship was poor (r(2)=0.18; p=0.004). Weight-bearing dorsiflexion range of motion (mean=43.0±5.0°) was significantly greater than non-weight-bearing dorsiflexion range of motion (29.8±5.9°; p<0.001) and weight-bearing dorsiflexion range of motion and non-weight-bearing dorsiflexion range of motion were also poorly correlated with passive dorsiflexion stiffness (1.48±0.55Nm°(-1); r(2)=0.04 and r(2)=0.14, respectively), despite the latter relationship being significant (p=0.017). CONCLUSIONS Passive dorsiflexion stiffness was not strongly associated with dorsiflexion range of motion, despite the significant correlation in the non-weight-bearing condition. It must be acknowledged that passive dorsiflexion stiffness was weakly associated with dorsiflexion range of motion, although the strength of the association suggests that it may not necessarily determine dorsiflexion range of motion. Furthermore, the functional dorsiflexion limits of the ankle during weight-bearing tasks may be underestimated or misrepresented by non-weight-bearing measures of dorsiflexion range of motion. Therefore, although ankle dorsiflexion range of motion and dorsiflexion stiffness have been implicated in injury risk during weight-bearing tasks such as landings, it may be due to different mechanisms.