General Nutrition Centers Inc. flexed its sales muscles across the board in the second quarter.

For the quarter ended June 30, GNC, No. 227 in the Internet Retailer Top 500 Guide, reported:

• Web sales of $19.4 million, a 42.8% increase from $13.6 million in the second quarter of 2010.
• Total retail sales of $384.3 million, up by 12.1% from $342.8 million.
• Total sales, including franchise and wholesale segments, of $518.5 million, up by 13.8% from $455.7 million.
• Comparable-store sales, which include e-commerce, increased 10.7% in domestic company-owned stores (including e-commerce).
• Net income of $36.0 million, up by 41.7% from net income of $25.4 million for the second quarter of 2010.

Internet Retailer calculates the web accounted for 5% of total retail sales for the quarter, compared with 4% in Q2 of 2010.

“We saw strength in our core merchandise categories and accelerated growth in our e-commerce business,” says Joe Fortunato, president and CEO.

For the first six months GNC reported:

• Online sales of $39.6 million, up by 38.5% from $28.6 million for the same period in 2010.
• Total retail sales of $768.0 million, a 10.7% increase from $693.6 million.
• Total sales of $1.024 billion, up by about 11.3% from $920.7 million.
• Comparable-store sales increased 9% in domestic company-owned stores (including e-commerce).
• Net income of $45.9 million, a 10.1% decrease from net income of $51.1 million in the first six months of 2010.

Internet Retailer calculates the web accounted for 5.2% of total retail sales for the period, compared with 4.1% in the first half of 2010.