Bone mass and structure, constituting bone strength, adapt to habitual mechanical loading environments. Exercise and physical activity provide natural forms of mechanical loading to the bones, contributing to their strength. However, not all types of exercise are equally effective in enhancing the strength, and the effectiveness also varies depending on the anatomical site. Discovering the effective exercise types for the hip bone – proximal femur – is crucial due to the rapidly increasing socioeconomic burden caused by hip fracture.
Hip fractures are a major public health problem, as they increase morbidity, disability, and even mortality among the older population. Within one year after the fracture, only half of the hip fracture patients regain their pre-fracture mobility. Globally, it is estimated that the annual number of hip fractures and associated financial costs will reach over 6 million fractures and $130 billion by 2050, respectively, due to the aging population worldwide.
Over 90 % of hip fractures are caused by falls. Moreover, with advancing age, some parts of proximal femur bone become thinner and more prone to fracture in a fall event where the side of the hip is hit on the ground. Therefore, if certain types of exercise or sports can increase or maintain proximal femur bone strength, the risk of hip fractures may be reduced.
The effect of exercise was confirmed by simulation
To identify effective exercise types, Abe explored the effect of various exercise loading histories on proximal femur bone strength in falling events in his doctoral dissertation. This was performed by comparing the proximal femur bones of young adult female athletes with distinct exercise loading histories to those of nonathletic control females.
In his study, Abe utilized computer simulations of these bones in falling events. He found that compared to controls, the proximal femora were stronger in falling events when the person had done exercises that were high-impact (e.g., triple/long and high jumping exercises), odd-impact (e.g., experiencing ground impact from unusual directions, typical in squash/tennis and football) or repetitive impact (e.g., long-distance running). Therefore, the present finding suggests that these impact exercise types can lead to the lower risk of hip fracture due to falling.
In contrast, the bone strength of athletes with a history of high-magnitude exercise (e.g., powerlifting – squat and deadlift) or repetitive, non-impact exercise loading (e.g., swimming) did not increase compared to the control group.
Exercises that contain jumping, hopping, and running make proximal femur stronger
Compared to high-impact exercise types, odd-impact exercises and repetitive-impact exercises (perhaps also jogging and vigorous walking) are likely to provide a safer and more feasible form of exercise for sedentary adults and older population.
“This is due to the relatively more moderate ground impacts involved in odd- and repetitive-impact loading exercises compared to high-impact exercises”, says he.
For young, physically active, and/or fit individuals, high-impact and jumping exercises as well as any excercises involving high ground impact (e.g., volleyball, basketball, gymnastics) can also be added to their exercise routines to increase proximal femur bone strength and reduce the risk of hip fractures.
Considering the loading characteristics of the exercise types examined in the doctoral research, it seems that moderate-to-high loading magnitude alone is insufficient. Exercise-induced mechanical loading needs to be generated at a high loading rate and/or frequency to effectively enhance proximal femur bone strength.
“This implies that effective exercise types need to involve ground impacts (e.g., common in jumping, hopping, running movements). Therefore, in addition to the high-impact, odd-impact, and repetitive-impact exercise loading types, other exercise or sport types that meet this condition may also be effective in increasing or maintaining proximal femur bone strength, thereby reducing the risk of fall-induced hip fractures,” says Shinya Abe.
Public defence on Friday 15 December
The doctoral dissertation of MSc (Tech) Shinya Abe in the field of biomedical/biomechanical engineering titled Exercise and Proximal Femur Bone Strength to Reduce Fall-Induced Hip Fracture will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12 o’clock on Friday, 15 December 2023 at Hervanta campus, Rakennustalo, Lecture Hall RG202 (Korkeakoulunkatu 5, Tampere). The Opponent will be Professor Emeritus Jukka Jurvelin from University of Eastern Finland. The Custos will be Professor Reijo Kouhia from Tampere University.
Photograph: Nelli Jokelainen