OVERLOAD AND HYPERPLASIA
Fig. 1. Percent changes in skeletal muscle mass (n 5 37), fiber area
(n 5 25), and fiber number (n 5 37).
, Outliers beyond 10th and 90th
Fig. 3. Percent increases in muscle fiber number according to
whether species was change calculated as
avian (n 5 20) or mammalian (n (treatment 2 control)/treatment
5 17). 100.
sum test. Differences between changes in muscle fiber num- ber partitioned according to potentially confounding vari- ables (fiber-counting technique, species used, fiber arrangement of muscles, and type of control) were also examined by using Mann-Whitney rank-sum tests. A one-way analysis of variance test (Kruskal-Wallis) was used to exam- ine the effect of different types of mechanical overload (stretch, exercise, and compensatory hypertrophy) on muscle fiber number. All data were reported as means 6 SD. The significance level was set at P # 0.05.
Literature search. A total of 17 studies yielding 37 data points (some studies had .1 group) and 360
subjects met the initial criteria for inclusion (1–7, 9, 15–19, 21, 28, 30–31). Two quantitative studies (27, 33) were excluded because of insufficient information needed to accurately calculate percent changes in muscle fiber number. Another eight studies (10–11, 13, 22–25, 32) were excluded because only qualitative information was provided on muscle fiber number.
Study characteristics. A summary of study character- istics is given in Table 1. More studies ( 53%) used chronic or intermittent stretch vs. exercise or compen- satory hypertrophy (ablation, tenotomy) as the form of mechanical overload. Approximately 47% of the studies
used the quail to examine
muscle fiber hyperplasia anterior latissimus dorsi
Fig. 2. Percent increases in muscle fiber number according to whether histological (Histo; n 5 15) or nitric acid digestion (n 5 22) method was used. Percent change calculated as (treatment2 control)/
Fig. 4. Percent increases in muscle fiber number according to whether mechanical overload consisted of stretch (n 5 20), compensa-
tory hypertrophy (CH; n 5 10), or exercise (n5 7). Percent
calculated as (treatment 2 control)/treatment
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