November 2024

Where Goes Muscle Mass With Cardio Exercise?

Did you ever notice that cardio athletes tend to be lean but not mean? It’s been an accepted scientific conclusion that our bodies respond to the stimuli they are provided such that aerobic exercise builds the heart muscle but not the muscles that do the exercise. For the most part, most studies support this except when cycling is the exercise modality: cyclists tend to build more and stronger quadriceps whereas walkers/joggers do not. But many of these studies increased dietary intake to meet activity caloric expenditure.

Thus, when a group of Canadian researchers undertook to test this generally-accepted factoid, they provided dietary guidance to all of the 238 obese subjects, 175 of whom were in the exercise cohort (Ex), and 63 in the control group of non exercisers (C), from a pool of subjects from prior studies. This study estimated caloric intake based on initial, pre-exercise weight, allowing more accurate assessment of skeletal muscle mass (SMM) changes that resulted solely from the exercise program. The Ex did 4-5 sessions of supervised walking or jogging at 50%-75% of their maximal aerobic capacity for 12 -24 weeks. A balanced diet of ~50% carbs, ~20% protein, and ~30% fat was prescribed. MRI was used to determine total and regional – arms, legs – SMM pre and post-training.

As expected, Ex increased aerobic capacity and reduced weight (~11+/-8 lbs), waist circumference, and total and visceral fat; C did not change. Neither group nor sex had significant changes in total, leg, or arm SMM. However, those who lost the most weight (~9%) lost the most total and arm SMM; leg SMM didn’t change across all tertiles of Ex. At best, Ex simply maintained leg SMM. While a positive for the aging population, if you want to build SMM, you gotta do weight training.          

MSSE May 2024

Does Knee or Hip Replacement Improve Overall Activity?

Nearly everyone with knee or hip osteoarthritis (OA) claims that they will be more active once they get a joint replacement. But few studies have done objectively measured assessments of patients’ physical activity after surgery. A British study of joint replacement patients, from 2013-2016, used wrist-worn accelerometry to assess step count, cadence, overall acceleration (intensity), and activity behaviors between non-arthritic controls, end-stage OA patients, and postoperative patients.

End-stage hip or knee OA was associated with taking 1,129 fewer steps/day and having almost 6 minutes/day less  moderate-to-vigorous activity compared to non-arthritic controls, understandably. Those who had had a unilateral joint replacement took 877 (hip) to 893 (knee) more steps/day than end-stage OA patients. As one might expect, since hip replacement is an easier and shorter recovery compared to knee replacement surgery, post-operative hip patients had daily step counts and moderate-to-vigorous activity levels similar to the non-arthritic controls.

Sadly, though, no differences were found in physicalint activity levels between any of the cohorts in this study so far as overall acceleration, time spent in light activity, sedentary behavior, or sleep. This finding suggests that older adults have lots of room to improve their healthful lifestyles regardless of which cohort they started from. So, while it’s good news that those who get a lower body joint replaced resumed levels of activity similar to those without OA, perhaps a higher standard to strive towards is called for for all older adults.                   

MSSE Dec. 2023

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