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Latest Clinical Research Published by ACSM

Kiningham, Robert B. MD, FACSM

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Current Sports Medicine Reports: 11/12 2017 - Volume 16 - Issue 6 - p 375-376
doi: 10.1249/JSR.0000000000000427
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Cognitive Resilience and Psychological Responses Across a Collegiate Rowing Season

Collegiate athletes face the challenge of strenuous physical conditioning and competition while dealing with the academic and social stressors of attending college. The cumulative stress of this environment may have detrimental psychological and cognitive effects on athletes during their competitive season. The purpose of this cohort study of collegiate division 1 rowers was to measure psychological and cognitive indices during the course of a season (2). The authors of this November 2017 Medicine & Science in Sports & Exercise® (MSSE) article hypothesized that the physical and emotional stress that occurs during peak training and competition would induce a decrease in cognitive performance that is associated with increased negative mood states.

The study included objective and subjective measures of stress, psychologic state, and cognitive function. The Stroop color naming test was used to measure cognitive performance. Salivary cortisol was measured as an indicator of physiologic stress. Athletes indicated on visual analog scales (VAS) their perceived academic load and physical training load. Perception of cognitive functioning was assessed using the Perceived Deficits Questionnaire (PDQ). A total mood disturbance score (TMD) was obtained using the Profile of Mood States (POMS) questionnaire. Questionnaires also included the Perceived Stress Scale (PSS) and an assessment of daytime sleepiness (ESS).

Athletes completed all assessments at four testing time periods corresponding to the beginning of the semester and formal practice (time 1), mid-season (time 2), peak training and competition (time 3), and post season (time 4), which occurred on average 16 d after the last competition. Physically active college students not on a varsity team or otherwise competing in athletics, but involved in time-comparable extra-curricular activities, were recruited for the control group.

Forty-three varsity rowers (22 women and 21 men) participated in the study, with 23 college student controls (15 women, 8 men). There were no statistically significant differences between the athletes and control students at baseline (time 1) on any measure. The athletes had their highest scores on exercise VAS, PDQ, TMD, and ESS at time 3 during peak training, and these scores were significantly higher than the control group at time 3. TMD at peak training (time 3) was positively and significantly associated with perceived stress (PSS) and PDQ. PDQ was positively and significantly associated with PSS and TMD. Performance on the Stroop color naming test did not significantly change over the four testing times for athletes or controls. Salivary cortisol was highest at time 1 for both athletes and controls, and there were no significant differences between the groups.

In summary, the rowers had healthy mental health profiles at baseline that were comparable to physically active college students not participating in intercollegiate sports. There were significant increases in perceived stress and negative mood states among the athletes during their competitive season, and these changes were not seen in the student controls. This disparity suggests that it was physical training and competition that caused these changes and not the social and academic stressors of college. However, these changes did not affect cognitive function and returned quickly back to baseline after the season. Objective measures of cognitive function (Stroop color naming test) and physiological stress (salivary cortisol) did not significantly change during the season for either group. This finding indicates that either these tests are not sensitive enough to detect small changes in mood and cognition, or the impact of the increased perceived stress was not enough to alter cognitive performance or adrenal activity.

Bottom Line: The increased physical training and competition that occurs during intercollegiate rowing correlates with increased perceived stress and negative mood states, but these changes return to baseline quickly after the season and are not associated with changes in objective measures of cognitive performance and physiologic stress. The generalizability of these findings to athletes in other sports is unknown.

Effects of Two Years of Calorie Restriction on Aerobic Capacity and Muscle Strength

Epidemiologic studies have observed that caloric restriction without nutrient deficiency is associated with health benefits. However, while caloric restriction with weight loss decreases adipose tissue, it also causes a loss of lean body mass, and there is concern that it may decrease physical activity in humans. The Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study was a randomized controlled study designed to examine the impact of prolonged caloric restriction on body composition, strength, and aerobic fitness in nonobese adults. Phase I of the study enrolled middle aged (ages 50 to 60 yr) men and women and found that 1 yr of caloric restriction caused reductions in lean body mass, absolute muscle strength, and absolute maximal oxygen uptake (V˙O2max). However, these changes were not statistically significant when expressed relative to whole body mass, which also decreased during the study (3).

Phase II of the CALERIE is reported in the November 2017 issue of MSSE (1). In this 2-yr study, relatively young healthy men and women (ages 21 to 47 yr for women, 21 to 50 yr for men) with body mass index (BMI) between 22 and 28 were randomly assigned to a caloric restriction (CR) group or an ad libitum control group. The goal of the CR group was to reduce daily energy intake by 25% relative to daily energy expenditure assessed at baseline. There was not an exercise component to the study, although both groups were informed of the CDC physical activity guidelines. Dependent variables were measured at baseline, 1 yr, and 2 yr, and included lean body mass measured by DXA, physical activity energy expenditure, daily protein intake, maximum aerobic capacity (V˙O2 max), and knee extensor and flexor muscle strength and endurance.

The study enrolled 218 subjects (64.7% women; average age, 37.9 years), with data from 201 at 1 yr and 188 (117 CR, 71 controls) at 2 yr. At baseline, there were no significant differences in body mass measurements, physical activity level, aerobic fitness, or strength measurements between the CR group and control group. During the study, the CR group averaged 11.9% caloric reduction relative to baseline daily energy restriction, falling short of the target of 25%. The CR group lost an average of 8.5 kg in the first year with a slight weight gain of 0.8 kg in the second year, for a net loss of 7.7 kg over the 2-yr study. Lean body mass and lean leg mass also significantly decreased in the CR group. The control group's total and lean body mass did not change. Calculated physical activity level did not significantly change in either group. Absolute V˙O2 max significantly decreased in the CR group compared to the control group at one year but not after two years. However, V˙O2max relative to body mass and total treadmill time significantly increased in the CR group at both 1 and 2 yr, and these increases were significantly greater than the control group. In the CR group, there was a significant decrease in absolute knee extension and flexion strength, but an increase in strength relative to body mass, while strength in the control group was unchanged.

Results grouped by sex in the CR group revealed that men lost more total weight and lean body mass than women. Absolute V˙O2 max decreased in both sexes, but men increased V˙O2 max relative to body mass significantly more than women. Men actually gained absolute knee flexion and extension strength, while women significantly decreased in strength.

Bottom Line: Two years of caloric restriction (approximately 12% of energy expenditure) without nutrient deficiency in healthy, nonobese men and women resulted in significant total body and lean body weight loss. While absolute V˙O2 max and leg strength decreased, V˙O2 max and leg strength relative to body mass increased, and total work capacity as measured by treadmill time also increased. Women lost more strength and aerobic capacity than men in response to caloric restriction. It is important to remember that this study did not include an exercise component, which may have prevented the decrease in absolute strength and aerobic capacity. An aerobic and strength training program may be particularly important for women who are on a calorie deficit diet to prevent losses in aerobic fitness and strength.

The author declares no conflict of interest and does not have any financial disclosures.

References

1. Racette SB, Rochon J, Uhrich ML, et al. Effects of 2 years of calorie restriction on aerobic capacity and muscle strength. Med. Sci. Sports Exerc. 2017; 49:2240–9.
2. Shields MR, Brooks MA, Koltyn KF, et al. Cognitive resilience and psychological responses across a collegiate rowing season. Med. Sci. Sports Exerc. 2017; 49:2276–85.
3. Weiss EP, Racette SB, Villareal DT, et al. Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss. J. Appl. Physiol (1985). 2007; 102:634–40.
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