Back Rack Barbell Walking Lunges 12-12-12-12 (6 ea. leg per set
or 12 total steps)



200m Run
10 T2B
20 KB Snatches (1.5/1)
30 Double Unders
20 Sit-ups

Interesting article from the CrossFit Journal archives:

A recent paper in the Journal of Bone and Mineral Research found that increased bone mineral content (BMC) and bone mineral density (BMD) in childhood are positively associated with time spent doing high-impact physical activities (PA), even for those with a genetic risk of low bone mass in adulthood (1).

A concern over BMC and BMD generally arises in those over 60 years old, when low bone mass and osteoporosis can occur. However, the time of maximal bone mineral accretion occurs as puberty begins reaching a maximal rate in females at 12.5 and males at 14.1 years old (2). This period also corresponds to a time of maximal height velocity (2). Therefore, actions that can affect this process during this window of opportunity are important to consider; indeed, “the magnitude of peak bone mass attained in young adulthood is an important predictor of osteoporosis later in life” (2).

The National Osteoporosis Foundation published a position statement in 2015 listing the factors that can influence peak bone-mass development throughout life (2). The most direct is an individual’s genes, explaining 60-80 percent of the measured differences (2). The remaining 20-40 percent include factors such as macronutrients, micronutrients, unhealthy habits (smoking, drinking, etc.) and PA (2). Despite years of research, the foundation concluded that only PA and calcium have a “strong” body of evidence behind their relationship with skeletal health; vitamin D is listed as “moderate” (2).

Mitchell et al. (1) investigated the relationship between PA and BMC as well as BMD in children from 5 to 19 years old. As many as 918 individuals were tracked for up to six years, responding to PA questionnaires and undergoing dual-energy X-ray absorptiometry (DXA) scans (1). Total PA time was positively associated with higher scores for BMC and BMD (1). In fact, the association was driven solely by time spent doing high-impact PA; low-impact PA showed no statistically significant relationships with skeletal health (1).

The questionnaires stated that low-impact PA included such activities as biking, bowling, climbing stairs, cross-country skiing, downhill skiing, gardening, golfing, hiking, hockey, kayaking, inline skating, rowing, sit-ups, skating, snowboarding, surfing, swimming, walking, waterskiing and yoga (1). Examples of high-impact PA were listed as aerobics/dancing, basketball, baseball, football, gymnastics, jogging/running, jump rope, lacrosse, martial arts, soccer, softball, squash, tennis, volleyball and weightlifting (1).

Read entire article here…